Co-reporter:Cheng Lian, Kun Liu, Honglai Liu, and Jianzhong Wu
The Journal of Physical Chemistry C July 6, 2017 Volume 121(Issue 26) pp:14066-14066
Publication Date(Web):June 8, 2017
DOI:10.1021/acs.jpcc.7b04869
Room-temperature ionic liquids (RTILs) have been widely used as electrolytes to enhance the capacitive performance of electrochemical capacitors also known as supercapacitors. Whereas impurities are ubiquitous in RTILs (e.g., water, alkali salts, and organic solvents), little is known about their influences on the electrochemical behavior of electrochemical devices. In this work, we investigate different impurities in RTILs within the micropores of carbon electrodes via the classical density functional theory (CDFT). We find that under certain conditions impurities can significantly change the charging behavior of electric double layers and the shape of differential capacitance curves even at very low concentrations. More interestingly, an impurity with a strong affinity to the nanopore can increase the energy density beyond a critical charging potential. Our theoretical predictions provide further understanding of how impurity in RTILs affects the performance of supercapacitors.
Co-reporter:Cheng Lian, Cheng Zhan, De-en Jiang, Honglai Liu, and Jianzhong Wu
The Journal of Physical Chemistry C July 6, 2017 Volume 121(Issue 26) pp:14010-14010
Publication Date(Web):June 9, 2017
DOI:10.1021/acs.jpcc.7b02827
Capacitive double-layer expansion is a promising technology to harvest energy arising from the salinity difference between freshwater and seawater. Its optimal performance requires a careful selection of the operation potentials and electrode materials. While carbonaceous materials such as graphene and various forms of activated carbons are routinely used as the electrodes, there is little knowledge on how the quantum capacitance and the electric double-layer (EDL) capacitance, which are on the same order of magnitude, affect the capacitive performance. Toward understanding that from a theoretical perspective, here we study the capacitive energy extraction with graphene electrodes as a function of the number of graphene layers. The classical density functional theory is joined with the electronic density functional theory to obtain the EDL and the quantum capacitance, respectively. The theoretical results show that the quantum capacitance contribution plays a dominant role in extracting energy using the single-layer graphene, but its effect diminishes as the number of graphene layers increases. The overall extracted energy is dominated by the EDL contribution beyond about four graphene layers. Electrodes with more graphene layers are able to extract more energy at low charging potential. Because many porous carbons have nanopores with stacked graphene layers, our theoretical predictions are useful to identify optimal operation parameters for capacitive energy extraction with porous electrodes of different wall thickness.
Co-reporter:Sijia Wang, Xia Han, Danyang Liu, Mengya Li, Shouhong XuHonglai Liu
Langmuir February 14, 2017 Volume 33(Issue 6) pp:
Publication Date(Web):January 18, 2017
DOI:10.1021/acs.langmuir.6b04080
A zipper-structured lipopeptide is expected to play a role of “intelligent valve” in the lipid bilayer. In this paper, a series of zipper-structured lipopeptides have been designed for preparing thermocontrollable hybrid liposomes. Their conformational transition as a function of temperature in lipid bilayer has been investigated for understanding the influences of molecular structure and bilayer property on biofunction. The melting temperatures Tm of the lipopeptides have been found to depend on their molecular structures. When the lipopeptides have been doped in bilayer, an increase of size of alkyl chain increases the stability of the α-helix resulting in a decrease in fluidity of lipid bilayer. However, an increase of amino groups at N-terminal is found to decrease the stability of the spatial structure. The thermocontrollability of the “valve” in lipid bilayer is confirmed by drug release experiments under different temperatures. Meanwhile, effects of bilayer properties on the thermosensitivity of lipopeptides have also been investigated. Results show the Tm of lipopeptide doped in bilayer decreases with the increase of membrane fluidity. Furthermore, the reversibility of the thermocontrolled “valve” is also proven by release drug under intermittent temperatures. It could be concluded that the molecular structure of the lipopeptide, as well as the property of bilayer, give great influence on the biofunction of the hybrid liposomes.
Co-reporter:Lu Peng, Fangyuan Guo, Cui Zhang, Jian Xu, Sheng Xu, Changjun Peng, Jun Hu, and Honglai Liu
Industrial & Engineering Chemistry Research April 19, 2017 Volume 56(Issue 15) pp:4319-4319
Publication Date(Web):March 24, 2017
DOI:10.1021/acs.iecr.6b04873
Porous poly(ionic liquids) (PPILs) with both advantages of ionic liquids (ILs) activities and porous properties have caused great interests in adsorptive desulfurization. High density of active functional groups and large surface area in PPILs are two critical factors for enhancing the desulfurization performance; however, there is usually a trade-off between them. In this work, a novel PPIL of poly(bipropargyl-imidazolium chloride) (P[BPPIM]) was fabricated through a single-step cyclotrimerization homopolymerization. Through this full-atomic utilization method, the mass density of active imidazolium groups were maximized; meanwhile, the introduction of rigid benzene rings within imidazolium rings propped up the porous structure in P[BPPIM], with a surface area of 160.8 m2·g–1 and pore volume of 0.39 cm3·g–1. On the basis of the density function theory calculation, the binding energies of dibenzothiophene (DBT) over P[BPPIM] were significantly increased due to the synergistic effect of the imidazolium ring and benzene ring, resulting in an enhanced saturated DBT adsorption capacity of 37.13 mgS·g–1, which was the best one among all the reported PILs according to our knowledge.
Co-reporter:Chenchen Meng, Yujie Sheng, Qibin Chen, Huiling Tan, Honglai Liu
Journal of Membrane Science 2017 Volume 526() pp:25-31
Publication Date(Web):15 March 2017
DOI:10.1016/j.memsci.2016.12.019
•The fabricated Glu-modified GO (Glu-GO) membranes were used into chiral separations.•Glu-GO membranes exhibited high flux with a 1–2 orders of magnitude enhancement.•Glu-GO membranes exhibited high selectivity (the maximum exceeds 2.0).•This is the first report on GO-based membranes for chiral separations.The primary aim of this investigation was to achieve chiral separations via fabricating graphene oxide (GO) based membranes with high separation performances, derived from incorporating a chiral selector (L-Glutamic acid) into GO flakes, based on considerations of GO membranes having the inherently high throughput nature. The GO membrane was fabricated via a simple vacuum filtration method, in which L-Glutamic acid not only provided the stacked GO nanosheets with the necessary stability to overcome their inherent dispensability in water environment but also finely tuned spacing of the GO nanosheets and the resulting performance. The corresponding membrane structure together with GO and amino acid modified GO nanosheets was systematically characterized by SEM, TEM, AFM, XPS, XRD, FT-IR and so on. Finally, enantioseparation performances of amino acid modified GO membranes toward 3, 4-Dihydroxy-D, L-phenylalanine were detected. Results show that such membranes exhibit extraordinary chiral resolution properties, which are 1−2 orders of magnitude higher in the flux and greater in selectivity, compared to common chiral separation membranes. Our findings demonstrate that the modified GO membranes might provide another general approach to simultaneously facilitate high-flux and high-selectivity for a host of enantio- and bio-separations.Chemical modification of graphene oxide (GO) flakes by incorporating chiral selectors can offer GO membranes extraordinary chiral separation performances, which exhibit a higher flux and a competitive selectivity, compared with the conventional membrane separation method. GO-based membranes show a great potential in the application of chiral separation.
Co-reporter:Xiang Zhu;Tian Jin;Chengcheng Tian;Chenbao Lu;Xiaoming Liu;Min Zeng;Xiaodong Zhuang;Shize Yang;Lin He;Honglai Liu;Sheng Dai
Advanced Materials 2017 Volume 29(Issue 47) pp:
Publication Date(Web):2017/12/01
DOI:10.1002/adma.201704091
AbstractAn in situ coupling approach is developed to create a new highly efficient and durable cobalt-based electrocatalyst for the oxygen evolution reaction (OER). Using a novel cyclotetramerization, a task-specific bimetallic phthalocyanine-based nanoporous organic framework is successfully built as a precursor for the carbonization synthesis of a nonprecious OER electrocatalyst. The resultant material exhibits an excellent OER activity with a low overpotential of 280 mV at a current density of 10 mA cm−2 and high durability in an alkaline medium. This impressive result ranks among the best from known Co-based OER catalysts under the same conditions. The simultaneous installation of multiple diverse cobalt-based active sites, including FeCo alloys and Co4N nanoparticles, plays a critical role in achieving this promising OER performance. This innovative approach not only enables high-performance OER activity to be achieved but simultaneously provides a means to control the surface features, thereby tuning the catalytic property of the material.
Co-reporter:Xiang Zhu;Yihua Zhu;Chengcheng Tian;Tian Jin;Xuejing Yang;Xianbo Jin;Chunzhong Li;Hualin Wang;Honglai Liu;Sheng Dai
Journal of Materials Chemistry A 2017 vol. 5(Issue 9) pp:4507-4512
Publication Date(Web):2017/02/28
DOI:10.1039/C6TA09604B
Developing new techniques for the synthesis of N-doped carbon nanotubes (N-CNTs) with high porosities and abundant N-doped active sites is significant for energy conversion and utilization. We report herein a novel non-CVD methodology that exploits a conjugated-nanoporous-polymer-driven, self-templated route toward a new family of highly N-doped carbon nanotubes. The utilization of a task-specific tubular nanoporous polycarbazole as a template maintains both high porosity and density of N-doped active sites, while simultaneously affording a hollow nanotube-like morphology of the final N-doped carbons. Attributed to these unique functionalities, the resultant N-CNT-based electrocatalyst exhibits a superior oxygen reduction reaction (ORR) activity with a half-wave potential of 0.88 V (vs. the reversible hydrogen electrode), higher long-term stability, and better methanol tolerance than commercial 20% Pt/C in alkaline media. More importantly, the ORR performance in an acidic medium exceeds that of the most previously reported non-precious carbonaceous catalysts. These findings could provide an alternative approach towards highly efficient non-precious N-CNT-based electrocatalysts for the ORR.
Co-reporter:Yi Guo;Xiuyan Dong;Wenjing Ruan;Yazhuo Shang;Honglai Liu
Colloid and Polymer Science 2017 Volume 295( Issue 2) pp:327-340
Publication Date(Web):2017 February
DOI:10.1007/s00396-016-4006-4
The interactions between poly(2-(2-methoxyethoxy)ethyl methacrylate90-co-oligo(ethylene glycol) methacrylate10) (P(MEO2MA90-co-OEGMA10)) and sodium dodecyl sulfate (SDS) or dodecyltrimethyl ammonium bromide (DTAB) in aqueous solutions with and without salt are explored. The influence rule of surfactant on thermo-sensitive behavior of polymer and the corresponding mechanism is revealed. The results have suggested that both surfactants have moderate interactions with P(MEO2MA90-co-OEGMA10), which result in the formation of P(MEO2MA90-co-OEGMA10)/surfactant complexes. Meanwhile, the self-aggregation of polymer chains is hindered causing the lower critical solution temperatures (LCSTs) increase due to the electrostatic repulsion and “locking water” effect caused by surfactant head groups. Tetra-n-butylammonium bromide (Bu4NBr) and tetra-n-propylammonium bromide (Pr4NBr) can associate with SDS and form mixed micelles. Interestingly, the formed mixed micelles apt to attach on the polymer chain and the polymer-bound necklace-like structure forms in the ternary polymer/salt/surfactant system. The structure of the complexes formed in the ternary system is confirmed by 2D NOESY NMR and the interaction mode is proposed. The relations between LCST of different systems and surfactant concentrations are also established quantitatively.
Co-reporter:Yi Guo, Meng Li, Xinrui Li, Yazhuo Shang, Honglai Liu
Reactive and Functional Polymers 2017 Volume 116(Volume 116) pp:
Publication Date(Web):1 July 2017
DOI:10.1016/j.reactfunctpolym.2017.04.013
A series of star-shaped block copolymers (CDPDPM) of 2-(dimethylamino)ethyl methacrylate (DMAEMA) and 2-(2-methoxyethoxy)ethyl methacrylate (MEO2MA) with tunable stimuli-responsive behavior are synthesized via sequential atom transfer radical polymerization (ATRP) with the 2-bromoisobutyryl-terminated β-cyclodextrin (β-CD) as a core. The properties of these star-shaped copolymers are characterized by FT-IR, NMR and GPC analyses. Meanwhile, the thermo-sensitive behaviors of CDPDPM with different compositions and pH values are investigated by dynamic light scattering (DLS) and UV–vis measurements. The results have shown that the synthesized polymer CDPDPM exhibits both pH- and thermo-responsive behaviors in aqueous solutions. The star-shaped copolymers with the nearly equal mole fraction of DMAEMA and MEO2MA show two-step thermo-induced aggregation behavior in water at a pH near the isoelectric point (IEP), which corresponds to the formation of branch aggregates and large aggregates consisting of clustered branch aggregates, respectively. The mole fraction of DMAEMA and MEO2MA in polymer affects the thermal-responsive behaviors of polymer itself. Moreover, the micellar behaviors of the synthesized copolymers in aqueous solution are explored. The aggregation process of the copolymer can be generalized into intramolecular aggregation of the hydrophobic chains (corresponding to CI), formation of premicelles, the aggregation and rearrangement of the premicelles (namely CMC), as well as the formation of multicore structures. The CI and CMC values depend on both the MEO2MA molar fraction and the carbon backbone length of polymers. The aggregation number (N) and the sizes of polymer micelles (Dh) vary with the polymer composition, polymer concentration and ambient environment.
Co-reporter:Cheng Lian;Alejandro Gallegos;Honglai Liu;Jianzhong Wu
Physical Chemistry Chemical Physics 2017 vol. 19(Issue 1) pp:450-457
Publication Date(Web):2016/12/21
DOI:10.1039/C6CP07124D
Ionic transport through nanopores is of fundamental importance for the design and development of nanofiltration membranes and novel electrochemical devices including supercapacitors, fuel cells and batteries. Recent experiments have shown an unusual variation of electrical conductance with the pore size and the electrolyte parameters that defies conventional scaling relations. Here ionic transport through voltage-gated nanopores was studied by using the classical density functional theory for ion distributions in combination with the Navier–Stokes equation for the electroosmotic flow. We identified a significant influence of the gating potential on the scaling behavior of the conductance with changes in the pore size and the salt concentration. For ion transport in narrow pores with a high gating voltage, the conductivity shows an oscillatory dependence on the pore size owing to the strong overlap of electric double layers.
Co-reporter:Haiying Li, Bo Meng, Song-Hai Chai, Honglai Liu and Sheng Dai
Chemical Science 2016 vol. 7(Issue 2) pp:905-909
Publication Date(Web):13 Nov 2015
DOI:10.1039/C5SC04034E
A hyper-crosslinked β-cyclodextrin porous polymer (BnCD-HCPP) was designed and synthesized facilely by β-cyclodextrin benzylation and subsequent crosslinking via a Friedel–Crafts alkylation route. The BnCD-HCPP shows an extremely high BET surface area, large pore volume, and high thermal stability, making it a highly efficient adsorbent for removal of aromatic pollutants from water. The adsorption efficiency in terms of distribution coefficient, defined as the ratio of adsorption capacity to equilibrium adsorbate concentration, ranged from 103 to 106 mL g−1 within a concentration of 0–100 ppm, one order of magnitude higher than that of other β-cyclodextrin-based adsorbents reported previously. The molar percentage of adsorbate to β-cyclodextrin exceeded 300%, suggesting that the adsorption occurred not only in the cyclodextrin cavities via a 1:1 complexation, but also in the nanopores of the BnCD-HCPP created during the hyper-crosslinking. The BnCD-HCPP can be further functionalized by incorporation of gold nanoparticles for catalytic transformation of adsorbed phenolic compounds such as 4-nitrophenol to 4-aminophenol.
Co-reporter:Tian Jin, Yan Xiong, Xiang Zhu, Ziqi Tian, Duan-Jian Tao, Jun Hu, De-en Jiang, Hualin Wang, Honglai Liu and Sheng Dai
Chemical Communications 2016 vol. 52(Issue 24) pp:4454-4457
Publication Date(Web):03 Feb 2016
DOI:10.1039/C6CC00573J
We present a rational design and synthesis of a novel porous pyridine-functionalized polycarbazole for efficient CO2 capture based on the density functional theory calculations. The task-specific polymer, generated through a one-step FeCl3-catalyzed oxidative coupling reaction, exhibits a superior CO2 uptake at 1.0 bar and 273 K (5.57 mmol g−1).
Co-reporter:Sijia Wang, Yinxing Shen, Junqi Zhang, Shouhong Xu and Honglai Liu
Physical Chemistry Chemical Physics 2016 vol. 18(Issue 15) pp:10129-10137
Publication Date(Web):11 Mar 2016
DOI:10.1039/C6CP00378H
Thermo-sensitive drug carriers are receiving increasing attention for use with localized hyperthermia at abnormal tissue sites or to easily implement hyperthermia. In this study, a thermo-sensitive lipopeptide was designed, consisting of a carbon chain and a leucine zipper with an amino acid sequence CH3-(CH2)4-CO-NH-VAQLEVK-VAQLESK-VSKLESK-VSSLESK-COOH. They could form dimers by the hydrophobic force at body temperature and separate into single random coils above the melting temperature (Tm). The lipopeptide was mixed with phospholipids to form a hybrid liposome (Lipo-LPe). The Tm of the free lipopeptide and lipopeptide in Lipo-LPe was found to be 48.0 °C and 42.5 °C from circular dichroism data, respectively. Compared with the pure liposome, the phase-transition temperature (Ttr) of Lipo-LPe, which was obtained by differential scanning calorimetry, was increased by about 5 °C, showing an improvement of thermal stability. The drug release rate of Lipo-LPe was slightly decreased at body temperature but greatly increased at mild hyperthermia in vitro. Drug release under intermittent heating was performed, and the reversibility of thermo-sensitive on/off switch was confirmed. Furthermore, Lipo-LPe achieved the maximum amount of cell death under mild hyperthermia. We concluded that Lipo-LPe, as a novel thermo-sensitive drug carrier, provides a promising opportunity for controlling drug release.
Co-reporter:Shengwei Deng, Sanal Sebastian Payyappilly, Yongmin Huang and Honglai Liu
RSC Advances 2016 vol. 6(Issue 48) pp:41734-41742
Publication Date(Web):20 Apr 2016
DOI:10.1039/C6RA08231A
Mechanical properties of polymer blends are not only determined by characteristics of individual polymer but also depend significantly on processing such as shear fields. A sequential mesoscopic simulation method was adopted to study the influence of shear processing on morphology orientation and mechanical responses. This method utilizes mesoscopic dynamic simulation (MesoDyn) for structural evolution and lattice spring model (LSM) for correlating the structure and mechanical behaviour. The dispersed phase in meso-structures moves from spherical to elliptical and then to columnar structure with the increase of shear rates. The morphology orientation leads to the anisotropy of elastic modulus. During the tensile test, different fracture processes were observed with two kinds of toughness relationship in blends which correspond to brittle phases dispersed in a ductile matrix and in reverse ductile phases dispersed in a brittle matrix. The tensile strength along shear processing direction increases with the increase of shear rates when the dispersed phase is ductile, while the strength decreases when the dispersed phase is brittle. The strength perpendicular to shear processing direction is mainly related to the soft matrix and interfacial strength. The morphologies of polymer blends at different shear rates and their corresponding mechanical behavior are well correlated by the mesoscopic simulation. The simulation results also yield guidelines to manufacture desired polymer blends with shearing process, e.g. extrusion or injection molding.
Co-reporter:Feng Jiang, Tian Jin, Xiang Zhu, Ziqi Tian, Chi-Linh Do-Thanh, Jun Hu, De-en Jiang, Hualin Wang, Honglai Liu, and Sheng Dai
Macromolecules 2016 Volume 49(Issue 15) pp:5325-5330
Publication Date(Web):July 27, 2016
DOI:10.1021/acs.macromol.6b01342
Controlled synthesis of efficient CO2 adsorbents with high porosities and CO2 binding affinities remains a challenge. Herein, we report the use of a substituent effect to develop a novel family of porous organic polymers for enhanced carbon capture. Based on the in silico-aided design strategy, the task-specific polymeric adsorbent derived from a 2,6-carbazole-substituted pyridinic scaffold exhibits a superior uptake of CO2, which reaches as high as 5.76 mmol g–1 at 273 K and 1 bar and ranks among the best by porous polymeric CO2 adsorbents. This approach not only enables us to achieve a very high CO2 capture for porous polymers but also provides tunable control of polymeric architectures and, in turn, their properties.
Co-reporter:Shuangliang Zhao, Bicai Zhan, Yaofeng Hu, Zhaoyu Fan, Marc Pera-Titus, and Honglai Liu
Langmuir 2016 Volume 32(Issue 49) pp:12975-12985
Publication Date(Web):November 4, 2016
DOI:10.1021/acs.langmuir.6b03046
Pickering emulsions combining surface-active and catalytic properties offer a promising platform for conducting interfacial reactions between immiscible reagents. Despite the significant progress in the design of Pickering interfacial catalysts for a broad panel of reactions, the dynamics of Pickering emulsions under reaction conditions is still poorly understood. Herein, using benzene hydroxylation with aqueous H2O2 as a model system, we explored the dynamics of benzene/water Pickering emulsions during reaction by dissipative particle dynamics. Our study points out that the surface wettability of the silica nanoparticles is affected to a higher extent by the degree of polymer grafting rather than an increase of the chain length of hydrophobic polymer moieties. A remarkable decline of the oil-in-water (O/W) interfacial tension was observed when increasing the yield of the reaction product (phenol), affecting the emulsion stability. However, phenol did not alter to an important extent the distribution of immiscible reagents around the nanoparticles sitting at the benzene/water interface. A synergistic effect between phenol and silica nanoparticles on the O/W interfacial tension of the biphasic system could be ascertained.
Co-reporter:Haiying Li, Bo Meng, Shannon M. Mahurin, Song-Hai Chai, Kimberly M. Nelson, David C. Baker, Honglai Liu and Sheng Dai
Journal of Materials Chemistry A 2015 vol. 3(Issue 42) pp:20913-20918
Publication Date(Web):18 Aug 2015
DOI:10.1039/C5TA03213J
Recently, microporous organic polymers, especially those hyper-crosslinked from functionalized aromatic monomers, have been shown to be effective for CO2 capture and storage with considerable capacity and selectivity. Herein, a class of novel microporous hyper-crosslinked polymers (HCPs), based on green and renewable carbohydrates, was synthesized by Friedel–Crafts alkylation for carbon capture and storage by hydrogen bonding and dipole–quadrupole interactions. These carbohydrate polymers, which have BET surface areas around 800 m2 g−1, can absorb a considerable amount of CO2 with the CO2/N2 selectivity up to 42 at 273 K, and 96 under 100 kPa in the mixed gases (0.15 mol CO2 and 0.85 mol N2). Furthermore, we experimentally and computationally studied the structures of carbohydrate backbones and determined several features that govern their CO2 absorption ability, which sheds light on understanding the structure/function relationship for designing better CO2 separation materials.
Co-reporter:Fei Gao, Yankai Li, Zijun Bian, Jun Hu and Honglai Liu
Journal of Materials Chemistry A 2015 vol. 3(Issue 15) pp:8091-8097
Publication Date(Web):03 Mar 2015
DOI:10.1039/C4TA06645F
For the real industrial process of CO2 capture, it is still a great challenge for adsorbents to exhibit excellent CO2 adsorption capacity in the presence of water. By combining a pre-seeding process and a two-step temperature controlling crystallization, a zeolitic imidazolate framework (ZIF-8) shell is introduced on the commercial zeolite adsorbent (5A) core to produce a series of 5A@ZIF-8 composites with an enhanced surface hydrophobicity. Each 5A@ZIF-8 composite exhibits a dynamic hydrophobic hindrance effect for the separation of CO2 from the simulated humid flue gas (15% CO2 and 90% humidity at 298 K). Among these, the CO2 adsorption capacity and the CO2/H2O selectivity of 5A@ZIF-8(I) can be as high as 2.67 mmol g−1 and 6.61, respectively, at the optimized adsorption time of 10 min. More importantly, over 10 adsorption–desorption cycles, there is almost no degradation of the adsorption performance. Therefore, the novel strategy of utilizing the dynamic hydrophobic hindrance effect through a core–shell structure would be a good solution for improving the CO2 separation performance in practical applications.
Co-reporter:Shanshan Liu, Qibin Chen, Yujie Sheng, Jincheng Shen, Changjun Peng and Honglai Liu
Polymer Chemistry 2015 vol. 6(Issue 21) pp:3926-3933
Publication Date(Web):23 Mar 2015
DOI:10.1039/C5PY00163C
Developing supramolecular helical assemblies with a controlled helix sense and revealing the forming mechanism of hierarchical helices for mimicking biological self-organization and physiological processes remain major challenges. In this work, a bottlebrush-like supramolecular polymer is prepared through the formation of a hydrogen bond between the keto group of polyvinylpyrrolidone (PVP) and the phenolic hydroxyl group of p-dodecylphenol (PDP), characterized by 1H NMR and FT-IR spectroscopy. CD spectra show an unsplit Cotton effect, suggesting the emergence of a helical structure in this supramolecular polymer brush (PVP–PDP). In particular, straightforward experimental evidence for the formation of hierarchical helices is obtained via TEM and AFM methods. We propose a detailed structural transition of the hierarchical helix or superhelix of PVP–PDP from primary to secondary, tertiary and even quaternary structures, resulting from the incorporation of bulky pendant PDP into the PVP backbone and the binding site of the hydrogen bond at ortho-position.
Co-reporter:Tian Jin, Zhichao Xiong, Xiang Zhu, Nada Mehio, Yajing Chen, Jun Hu, Weibing Zhang, Hanfa Zou, Honglai Liu, and Sheng Dai
ACS Macro Letters 2015 Volume 4(Issue 5) pp:570
Publication Date(Web):May 1, 2015
DOI:10.1021/acsmacrolett.5b00235
A facile template-free strategy for the synthesis of mesoporous phenolic polymers with attractive porosities, nitrogen-containing functionalities, and intrinsic hydrophilic skeletons is presented. The resultant polymer has a high BET surface area (548 m2 g–1) and mesopore size (13 nm) and exhibits superior glycopeptide-capturing performance, thus, revealing the potential application of mesoporous polymers in highly selective glycopeptide enrichment. This general capture protocol may open up new opportunities for the development of glycoproteomes.
Co-reporter:Xia Han, Zhiying Xiong, Xuxia Zhang and Honglai Liu
Soft Matter 2015 vol. 11(Issue 11) pp:2139-2146
Publication Date(Web):19 Jan 2015
DOI:10.1039/C5SM00025D
Intelligent polymers, due to their sensitive stimuli response to changes in the environment, have gained increasing amounts of attention over recent years and have become a popular topic in polymer materials science. In this study, the aggregation behaviors and stimuli responses of the stimuli-responsive diblock polyampholyte poly(2-(dimethylamino)ethyl methacrylate)-b-poly(acrylic acid) (PDMAEMA-b-PAA) are conveniently tunable by introducing pH changes, temperature changes, salt addition and surfactant neutralization. Under different pH values, either globular or fractal self-assemblies can be observed in which the latter have crystal properties. Salts and alkalis can promote the fractal aggregation growth because their deposited crystals can act as nucleation sites for the polyampholyte chains. A combination of fluorescence spectroscopy, atom force microscopy and transmission electron microscopy revealed that the presence of anionic surfactants in the PDMAEMA-b-PAA solutions promoted the solubility of the polyampholyte, consequently leading to a more homogeneous distribution of the polymer chains on the solid substrate upon drying the mixtures. The fractal formation was suppressed for the studied Gemini surfactants, and a higher surfactant hydrophobicity results in an earlier start of the formation of the fractal pattern.
Co-reporter:Hui Shi;Dr. Zhaoyu Fan;Dr. Virginie Ponsinet;Remi Sellier; Honglai Liu;Dr. Marc Pera-Titus;Dr. Jean-Marc Clacens
ChemCatChem 2015 Volume 7( Issue 20) pp:
Publication Date(Web):
DOI:10.1002/cctc.201501070
Co-reporter:Hui Shi;Dr. Zhaoyu Fan;Dr. Virginie Ponsinet;Remi Sellier; Honglai Liu;Dr. Marc Pera-Titus;Dr. Jean-Marc Clacens
ChemCatChem 2015 Volume 7( Issue 20) pp:3229-3233
Publication Date(Web):
DOI:10.1002/cctc.201500556
Abstract
Polystyrene-grafted silica nanoparticles bearing sulfonic acid centers and with tunable amphiphilic properties were designed to perform the biphasic etherification reaction of glycerol with dodecanol at the interface of Pickering emulsions. By optimizing the hydrophobic properties of the particles, double Pickering emulsions could be generated allowing a facilitated diffusion of glycerol and dodecanol into the microenvironment near the acid centers.
Co-reporter:Xiang Zhu, Chengcheng Tian, Tian Jin, Jitong Wang, Shannon M. Mahurin, Wenwen Mei, Yan Xiong, Jun Hu, Xinliang Feng, Honglai Liu and Sheng Dai
Chemical Communications 2014 vol. 50(Issue 95) pp:15055-15058
Publication Date(Web):07 Oct 2014
DOI:10.1039/C4CC07255C
Thiazolothiazole-linked porous organic polymers have been synthesized from a facile catalyst-free condensation reaction between aldehydes and dithiooxamide under solvothermal conditions. The resultant porous frameworks exhibit a highly selective uptake of CO2 over N2 under ambient conditions.
Co-reporter:Xiang Zhu, Shannon M. Mahurin, Shu-Hao An, Chi-Linh Do-Thanh, Chengcheng Tian, Yankai Li, Lance W. Gill, Edward W. Hagaman, Zijun Bian, Jian-Hai Zhou, Jun Hu, Honglai Liu and Sheng Dai
Chemical Communications 2014 vol. 50(Issue 59) pp:7933-7936
Publication Date(Web):02 May 2014
DOI:10.1039/C4CC01588F
A porous triazine and carbazole bifunctionalized task-specific polymer has been synthesized via a facile Friedel–Crafts reaction. The resultant porous framework exhibits excellent CO2 uptake (18.0 wt%, 273 K and 1 bar) and good adsorption selectivity for CO2 over N2.
Co-reporter:Quanyi Yin, Xia Han, Virginie Ponsinet, Honglai Liu
Journal of Colloid and Interface Science 2014 Volume 431() pp:97-104
Publication Date(Web):1 October 2014
DOI:10.1016/j.jcis.2014.05.047
•Plasmonic nanoparticle assemblies are induced using electrostatic complexation.•The complex formation is triggered by a change in ionic strength.•Quantities of polymer and nanoparticles in the suspension tune the complex size.•The complex formation is reversible and complete.In this study, our aim was to control the assembly of plasmonic nanoparticles by using the electrostatic assembly of oppositely charged colloidal species. Gold nanoparticles (Au NPs) were modified with a carboxyl-terminated polymeric ligand, O-(2-carboxyethyl)-O′-(2-mercaptoethyl) heptaethylene glycol (SH-PEG7-COOH), so that they are negatively charged on the pH range 5–10 and they stand elevated ionic strength (up to 1 M NaCl) without loss of colloidal stability. Block copolymers poly[(ethylene glycol) methyl ether-block-(N,N-dimethylamino-2-ethyl methacrylate)] (mPEG–PDMAEMA), with a neutral mPEG block and a pH-sensitive positively charged PDMAEMA block were synthesized by atom transfer radical polymerization (ATRP). The formation of complexes, driven by the electrostatic attraction between opposite charges and by the release of the condensed counter ions, was investigated using dynamic light scattering and spectrophotometry. The relative quantities of polymer chains and nanoparticles in the suspension were shown to affect the size of the formed complexes. In this report, it is also shown that the complex formation is reversible. Stable complexes of typical size 400 nm were formed, which could be used as building blocks for new optical materials.
Co-reporter:Jianhai Zhou, Xiang Zhu, Jun Hu, Honglai Liu, Ying Hu and Jianwen Jiang
Physical Chemistry Chemical Physics 2014 vol. 16(Issue 13) pp:6075-6083
Publication Date(Web):03 Feb 2014
DOI:10.1039/C3CP55498H
A fully atomistic simulation study is reported to provide mechanistic insight into the superior performance experimentally observed for a polymer membrane (Carta et al., Science, 2013, 339, 303–307). The membrane namely PIM-EA-TB is produced by a shape-persistent ladder polymer of intrinsic microporosity (PIM) with rigid bridged bicyclic ethanoanthracene (EA) and Tröger's base (TB). The simulation reveals that PIM-EA-TB possesses a larger surface area, a higher fraction free volume and a narrower distribution of torsional angles compared to PIM-SBI-TB, which consists of less rigid spirobisindane (SBI). The predicted surface areas of PIM-EA-TB and PIM-SBI-TB are 1168 and 746 m2 g−1, close to experimental values of 1120 and 745 m2 g−1, respectively. For five gases (CO2, CH4, O2, N2 and H2), the solubility and diffusion coefficients from simulation match well with experimental data, except for H2. The solubility coefficients decrease in the order of CO2 > CH4 > O2 > N2 > H2, while the diffusion coefficients increase following CH4 < CO2 < N2 < O2 < H2. In terms of the separation for CO2/N2, CO2/CH4 and O2/N2 gas pairs, PIM-EA-TB exhibits higher permselectivities than PIM-SBI-TA, in good agreement with experiment. From a microscopic perspective, this simulation study elucidates that the presence of bridged bicyclic units in PIM-EA-TB enhances the rigidity of polymer chains as well as the capability of gas permeation and separation, and the bottom-up insight could facilitate the rational design of new high-performance membranes.
Co-reporter:Shengwei Deng, Yongmin Huang, Shouhong Xu, Shaoliang Lin, Honglai Liu and Ying Hu
RSC Advances 2014 vol. 4(Issue 108) pp:63586-63595
Publication Date(Web):18 Nov 2014
DOI:10.1039/C4RA10016F
The incorporation of nanoparticles into elastomeric block copolymers affords engineers an opportunity to obtain polymer nanocomposites that potentially rival the most advanced materials in nature. A computationally efficient simulation method that utilized MesoDyn for the morphologies and the lattice spring model (LSM) for the mechanical properties was adopted in this work. The simulation results show that the selective distribution of nanoparticles in hard or soft segment microdomains of block copolymers will narrow the phase domain size in bicontinuous structures. The Zener model was incorporated into pure elastic LSM to capture the stress relaxation behavior. Mechanical tests reveal that the stress transfer between the polymer matrix and nanoparticles in different composites is critical to the stiffness enhancement. In dispersed structures, adding nanoparticles in a hard microdomain can increase the elastic modulus and maintain high extensibility without impairing its viscosity dramatically. The methods developed in this work yield guidelines for formulating elastomeric nanocomposites with desired macroscopic mechanical responses.
Co-reporter:Shengwei Deng, Yongmin Huang, Cheng Lian, Shouhong Xu, Honglai Liu, Shaoliang Lin
Polymer 2014 Volume 55(Issue 18) pp:4776-4785
Publication Date(Web):2 September 2014
DOI:10.1016/j.polymer.2014.07.039
•An efficient method for correlating the complex morphologies to mechanical response.•Two kinds of fracture process were shown to explain novel experimental findings.•Stiffness is closely related to the hard phase rather than the molecular architecture.•The relation between the fracture strain and molecular architecture.Multiblock copolymers containing a large number of blocks have distinct microstructures and mechanical responses that are different from that of conventional diblock and triblock copolymers. A combined simulation method that utilized MesoDyn for morphologies and probabilistic lattice spring model (LSM) for mechanical properties was adopted in this work. Simulation results show that tensile strength increases dramatically with an increase in the number of blocks within “hard-soft” multiblock copolymers. This phenomenon can be described by the occurrence of bridging and looping chain conformations in experiment. One-dimensional lamellae were built to provide an ideal morphology for studying the influence of lamellar orientation on multiblock copolymer mechanical properties. During tensile tests different failure processes were observed with two kinds of interface strength that corresponded to a difference in chain structures (diblock, triblock or multiblock copolymers). These studies provide an efficient method for correlating the complex morphologies to the mechanical response of multiblock copolymers.
Co-reporter:Cheng Lian, Le Wang, Xueqian Chen, Xia Han, Shuangliang Zhao, Honglai Liu, and Ying Hu
Langmuir 2014 Volume 30(Issue 14) pp:4040-4048
Publication Date(Web):2017-2-22
DOI:10.1021/la5003429
A key problem in designing thermoresponsive polymer brushes on a solid surface is to find a relation between the targeted thermoresponsive properties and controllable conditions. Usually, a temperature-thickness curve showing the heating-induced swelling behavior of polymer brushes is chosen as the relation by either experimental or theoretical investigation. In this work, a lattice density functional theory (LDFT) developed previously is employed to investigate the temperature-thickness curves for five different types of polymer brushes, where the density profiles of polymer brushes calculated by LDFT are compared directly with simulation. It is found that the thermoresponsive behavior of a polymer brush can be characterized by the bulk phase behaviors of its corresponding polymer solution, including UCST, LCST, both UCST and LCST, closed LOOP and hourglass-shaped, which implies that the bulk phase diagram of polymer solutions can help us to find an appropriate polymer brush for a targeted thermoresponsive behavior. As an example, we show that the swelling behavior of a thermoresponsive polymer brush found in the experiment could be predicted by our LDFT results with the bulk phase diagram of real polymer solution only.
Co-reporter:Fei Gao, Cheng Lian, Lihui Zhou, Honglai Liu, and Jun Hu
Langmuir 2014 Volume 30(Issue 38) pp:11284-11291
Publication Date(Web):2017-2-22
DOI:10.1021/la501648j
The mixed micelle template approach is one of the most promising synthesis methods for hierarchical porous materials. Although considerable research efforts have been made to explore the formation mechanism, explicit theoretical guidance for appropriately choosing templates is still not available. We found that the phase separation occurring in the mixed micelles would be the key point for the synthesis of hierarchical porous materials. Herein, the pseudophase separation theory for the critical micelle concentration (cmc) combined with the Flory–Huggins theory for the chain molecular mixture were employed to investigate the properties of mixed surfactant aqueous solutions. The cmc values of mixed surfactant solutions were experimentally determined to calculate the Flory–Huggins interaction parameter between two surfactants, χ. When χ is larger than the critical value, χc, the phase separation would occur within the micellar phase, resulting in two types of mixed micelles with different surfactant compositions, and hence different sizes, which could be used as the dual-template to induce bimodal pores with different pore sizes. Therefore, the Flory–Huggins theory could be a theoretical basis to judge whether the mixed surfactants were the suitable templates for inducing hierarchical porous materials. We chose cetyltrimethylammonium bromide (CTAB) and n-octylamine (OA) as a testing system. The phase separation behavior of the mixed solutions as well as the successful synthesis of hierarchical porous materials by this dual-template indicated the feasibility of preparing hierarchical porous materials based on the concept of phase separation of the mixed micelles.
Co-reporter:Xiang Zhu, Chi-Linh Do-Thanh, Christopher R. Murdock, Kimberly M. Nelson, Chengcheng Tian, Suree Brown, Shannon M. Mahurin, David M. Jenkins, Jun Hu, Bin Zhao, Honglai Liu, and Sheng Dai
ACS Macro Letters 2013 Volume 2(Issue 8) pp:660
Publication Date(Web):July 16, 2013
DOI:10.1021/mz4003485
A 3D Tröger’s-base-derived microporous organic polymer with a high surface area and good thermal stability was facilely synthesized from a one-pot metal-free polymerization reaction between dimethoxymethane and triaminotriptycene. The obtained material displays excellent CO2 uptake abilities as well as good adsorption selectivity for CO2 over N2. The CO2 storage can reach up to 4.05 mmol g–1 (17.8 wt %) and 2.57 mmol g–1 (11.3 wt %) at 273 K and 298 K, respectively. Moreover, the high selectivity of the polymer toward CO2 over N2 (50.6, 298 K) makes it a promising material for potential application in CO2 separation from flue gas.
Co-reporter:Xiang Zhu;Songhai Chai;Chengcheng Tian;Pasquale F. Fulvio;Kee Sung Han;Edward W. Hagaman;Gabriel M. Veith;Shannon M. Mahurin;Suree Brown;Honglai Liu;Sheng Dai
Macromolecular Rapid Communications 2013 Volume 34( Issue 5) pp:452-459
Publication Date(Web):
DOI:10.1002/marc.201200793
Abstract
A porous, nitrogen-doped carbonaceous free-standing membrane (TFMT-550) is prepared by a facile template-free method using letrozole as an intermediate to a triazole-functionalized-triazine framework, followed by carbonization. Such adsorption/diffusion membranes exhibit good separation performance of CO2 over N2 and surpassing the most recent Robeson upper bound. An exceptional ideal CO2/N2 permselectivity of 47.5 was achieved with a good CO2 permeability of 2.40 × 10−13 mol m m−2 s−1 Pa−1. The latter results arise from the presence of micropores, narrow distribution of small mesopores and from the strong dipole–quadrupole interactions between the large quadrupole moment of CO2 molecules and the polar sites associated with N groups (e.g., triazine units) within the framework.
Co-reporter:Xia Han;Xuxia Zhang;Quanyi Yin;Jun Hu;Honglai Liu;Ying Hu
Macromolecular Rapid Communications 2013 Volume 34( Issue 7) pp:574-580
Publication Date(Web):
DOI:10.1002/marc.201200785
Co-reporter:Baoliang Peng, Xia Han, Honglai Liu, Kam C. Tam
Journal of Colloid and Interface Science 2013 Volume 412() pp:17-23
Publication Date(Web):15 December 2013
DOI:10.1016/j.jcis.2013.09.012
•Binding interactions between surfactants and thermo-responsive polymers are investigated.•Interactions are driven by electrostatic and hydrophobic forces.•Physical mechanism for the interaction is proposed.The binding interactions between cationic surfactants and a statistical thermo-sensitive copolymer based on oligo(ethylene glycol) methacrylates were studied by isothermal titration calorimetry (ITC), surfactant selective electrode (SSE) and dynamic light scattering (DLS). Strong binding interactions were observed between this copolymer and cationic surfactants. The binding is driven by the hydrophobic effect, occurring on the hydrophobic backbone instead of the ethylene–glycol side chains. The surfactant saturation concentration C2 depended on the polymer concentration, but was not affected by temperature. Three types of cationic alkyltrimethylammonium bromide surfactants (RTAB with R equal to C12, C14, and C16), namely, dodecyltrimethylammonium bromide (DoTAB), tetradecyltrimethylammonium bromide (TTAB), and cetyltrimethylammonium bromide (CTAB), were examined, and the results confirmed that the binding affinity followed the sequence: CTAB > TTAB > DoTAB.
Co-reporter:Shouhong Xu;Xiangye Li;Ruting Chen;Xiaoxiao Lin;Honglai Liu;Ying Hu
Journal of Chemical Technology and Biotechnology 2013 Volume 88( Issue 8) pp:1561-1567
Publication Date(Web):
DOI:10.1002/jctb.4005
Abstract
BACKGROUND
In some disease therapy, it is necessary to release multiple drugs continuously and orderly. This paper describes a technique for preparing a microparticle that can load two kinds of substances and release them at two different rates.
RESULTS
A core–shell structural microparticle was designed using liposome as core and hyaluronan/poly(N-isopropylacrylamide) (HA/PNIPAM) gel as shell. The core liposome keeps its vesicle structure after undergoing the whole crosslinking process. The microparticles are injectable at room temperature and become sticky when heated. The fluorescent loaded in the shell released 80% in 1 h, while that in the core kept releasing for 35 h.
CONCLUSION
The stability and function of liposomes are improved after being coated with a gel shell. Two kinds of fluorophores were successfully loaded into microparticles and released at two different rates. The main factors controlling the tracer diffusion are the microparticle properties, e.g. crosslink density and shell thickness. These microparticles can be used as injectable or implantable drug carriers by minimally invasive techniques. © 2012 Society of Chemical Industry
Co-reporter:Yao-Feng Hu, Wen-Jie Lv, Ya-Zhuo Shang, Hong-Lai Liu, Hua-Lin Wang, and Soong-Hyuck Suh
Industrial & Engineering Chemistry Research 2013 Volume 52(Issue 19) pp:6550
Publication Date(Web):April 19, 2013
DOI:10.1021/ie303006d
Configurational, energetic, and dynamical properties of dimethyl sulfoxide (DMSO) transport across the water/hexane interface are investigated by molecular dynamics simulations. It is shown that the interface accumulation caused by the interface activity of DMSO dominates the diffusion process. In this case the underlying transport process can be divided into two steps by different energy landscapes and kinetic motions of solute molecules. In addition, interface deformation caused by solutes also influences the process and its impact on solutes is different on each side. A transfer of DMSO from the hexane phase to the interface (step I) is facilitated by free energy gradient and the interface deformation does not hinder its motion toward the interface, whereas its escape from the interface to the water phase (step II) will be obstructed by high free energy gradient and the interface deformation also plays a negative role. Consequently, step II dictates the whole transport process. However, the solute concentration in the interface is much higher than that in the bulk, and it is deduced that a larger interface area can lead to higher capacity of DMSO with higher extractions. For such systems observed in our simulation studies, the distribution of dispersed phase can be a key factor for the efficient extraction process.
Co-reporter:Yazhuo Shang, Chengzhi Min, Jun Hu, Tianmiao Wang, Honglai Liu, Ying Hu
Solid State Sciences 2013 Volume 15() pp:17-23
Publication Date(Web):January 2013
DOI:10.1016/j.solidstatesciences.2012.09.002
Gold nanoparticles were prepared in surfactant solutions by reduction of HAuCl4 under UV irradiation without adding extra reductants or other organic substances. The effect of the structure and the property of surfactant on the size and the optical properties of prepared gold nanoparticles were studied. It was found that the longer the alkyl chain of the surfactant, the larger gold particles are obtained. On the other hand, lengthen the geminis spacer benefits the formation of smaller gold particles. The formation of adduct micelles composed of the charged surface active portion of the surfactant molecule and the (AuIIICl4)− ion in cationic surfactant solution serves as the gold source and favors the formation of gold particles with larger sizes. While the repulsion between the (AuIIICl4)− ion and the negative charged surface of anionic surfactant micelle is in favor of the formation of gold nanoparticles with smaller sizes. The nonionic surfactants can also assist the formation of dispersed gold nanoparticles.Highlights► The properties of surfactants determine the sizes of synthesized god nanoparticles. ► The surfactant act as soft template, controller of gold source as well as stabilizer. ► The adduct micelles favor the formation of gold nanoparticles with bigger sizes. ► The anionic surfactants can assist the formation of smaller gold nanoparticles.
Co-reporter:Baoliang Peng, Xia Han, Honglai Liu, Richard C. Berry, Kam C. Tam
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2013 Volume 421() pp:142-149
Publication Date(Web):20 March 2013
DOI:10.1016/j.colsurfa.2012.12.059
The interactions between surfactants and nanocrystalline cellulose (NCC) grafted with a 600 Da polypropylene glycol (M600) were investigated by isothermal titration calorimetry (ITC) and nuclear magnetic resonance spectroscopy (NMR). The M600-grafted NCC prepared by reacting carboxylated NCC with amine-terminated M600 via a peptide coupling reaction, which was confirmed by infrared spectroscopy and transmission electron microscopy (TEM). Three types of surfactants with dodecyl alkyl chain and different head groups, namely cationic dodecyltrimethylammonium bromide (DoTAB), anionic sodium dodecyl sulfate (SDS), and nonionic poly (ethylene glycol) dodecyl ether (Brij 30) were studied. Strong electrostatic interaction was only observed between M600-grafted NCC and DoTAB, due to the binding of opposite charges. Hydrophobic interaction was displayed for the M600-grafted NCC/SDS system, and negligible interaction between M600-grafted NCC and Brij 30 was observed. Physical mechanisms describing the interactions of cationic, anionic and nonionic surfactants and M600-grafted NCC are proposed.Highlights► A thermo-responsive nanocrystalline cellulose (NCC) was synthesized. ► A 600 Da polypropylene glycol was grafted to NCC. ► Strong electrostatic interaction was observed between M600-grafted NCC and DoTAB. ► Binding is driven by electrostatic forces. ► Physical mechanisms for binding interaction were proposed.
Co-reporter:Xia Han, Xuxia Zhang, Hongfan Zhu, Quanyi Yin, HongLai Liu, and Ying Hu
Langmuir 2013 Volume 29(Issue 4) pp:1024-1034
Publication Date(Web):January 5, 2013
DOI:10.1021/la3036874
A series of poly(2-(dimethylamino) ethyl methacrylate) (PDMAEMA) homopolymers and poly(2-(dimethylamino)ethyl methacrylate)-b-poly(acrylic acid) (PDMAEMA-b-PAA) diblock copolymers were synthesized by atomic transfer radical polymerization. Thanks to a fine-tuning of the hydrophobic–hydrophilic balance by varying the molecular weight of the polymers and the pH of the aqueous solutions, as well as the composition for the block copolymers, the lower critical solution temperature (LCST) and the aggregation–dissolution kinetics of PDMAEMA homopolymers and PDMAEMA-b-PAA block copolymers can be adjusted. For the block copolymers, the results show that larger relative size of the PDMAEMA blocks leads to an increasing tendency to form micellar aggregates and a decrease of the LCST of the aqueous solution, which is consistent with the increasing copolymer hydrophobicity. A significant difference of the stimuli-responsive behavior between PDMAEMA-rich and PAA-rich copolymers is observed, because the former exhibit thermo-responsive behavior in a broad temperature range of 40–60 °C in basic media, while the pH-responsive behavior is dominant, and only a weak thermo-responsive behavior is exhibited around the specific isoelectric point (IEP) in the latter case. The aggregation rate is strongly influenced by temperature, molecular weight, structure, and composition of the polymer. Specifically, temperature has a stronger effect than the molar ratio of the PDMAEMA segment in the copolymer (related to its hydrophobicity) and the chain molecular weight, although the PDMAEMA-b-PAA copolymers show faster aggregation rate than do the PDMAEMA homopolymers.
Co-reporter:Baoliang Peng, Nathan Grishkewich, Zhaoling Yao, Xia Han, Honglai Liu, and Kam C. Tam
ACS Macro Letters 2012 Volume 1(Issue 5) pp:632
Publication Date(Web):April 24, 2012
DOI:10.1021/mz300135x
A well-defined random copolymer containing 2-(2-methoxyethoxy) ethyl methacrylate (MEO2MA, Mn = 188 g/mol) and poly(ethylene glycol) methyl ether methacrylate (PEGMA, Mn = 2080 g/mol) (poly(MEO2MA-co-PEGMA2080)), Mn = 17300 g/mol) was synthesized using the atom transfer radical polymerization (ATRP) process, and its thermoresponsive behaviors in aqueous solution were investigated. In comparison to other temperature-sensitive random copolymers based on oligo(ethylene glycol) methacrylates, this copolymer exhibited an unusual thermally induced two-stage aggregation process. The copolymer chains associate at the first thermal transition followed by a rearrangement process at the second thermal transition to produce a stable core–shell micellar structure. The morphology of the micelle comprises of a methacrylate core stabilized by the longer ethylene glycol segments (Mn = 2080 g/mol) shell.
Co-reporter:Yu Liu, Yazhuo Shang, Honglai Liu, Ying Hu and Jianwen Jiang
Physical Chemistry Chemical Physics 2012 vol. 14(Issue 44) pp:15400-15405
Publication Date(Web):24 Sep 2012
DOI:10.1039/C2CP42138K
A molecular thermodynamic model is developed to examine crowding effect on DNA melting. Each pair of nucleotides in double-stranded DNA and each nucleotide in single-stranded DNA are represented by two types of charged Lennard-Jones segments, respectively. Water molecules are mimicked explicitly as spherical particles, embedded in a dielectric continuum. Crowders with varying concentration, size, interaction strength, and chain length are considered. For DNA with a sequence of A20, the melting temperature is predicted to increase by 1 K in the presence of Ficoll70 and by 7.5 K in the presence of Ficoll70–polyvinyl pyrrolidone360 mixture. The predictions agree well with experimental data. Furthermore, the melting temperature is found to increase with increasing crowder size, but reduce with increasing interaction strength and crowder length. The predicted changes of Gibbs energy, entropy and enthalpy are consistent with experimentally measured values. The study reveals that DNA melting in a crowded environment is influenced by both entropic and enthalpic effects.
Co-reporter:Qibin Chen, Xueli Kang, Rong Li, Xuezhong Du, Yazhuo Shang, Honglai Liu, and Ying Hu
Langmuir 2012 Volume 28(Issue 7) pp:3429-3438
Publication Date(Web):January 19, 2012
DOI:10.1021/la204089u
The properties of the complex monolayers composed of cationic gemini surfactants, [C18H37(CH3)2N+-(CH2)s-N+(CH3)2C18H37],2Br– (18-s-18 with s = 3, 4, 6, 8, 10 and 12), and ds-DNA or ss-DNA at the air/water interface were in situ studied by the surface pressure–area per molecule (π–A) isotherm measurement and the infrared reflection absorption spectroscopy (IRRAS). The corresponding Langmuir–Blodgett (LB) films were also investigated by the atomic force microscopy (AFM), the Fourier transform infrared spectroscopy (FT-IR), and the circular dichroism spectroscopy (CD). The π–A isotherms and AFM images reveal that the spacer of gemini surfactant has a significant effect on the surface properties of the complex monolayers. As s ≤ 6, the gemini/ds-DNA complex monolayers can both laterally and normally aggregate to form fibril structures with heights of 2.0–7.0 nm and widths of from several tens to ∼300 nm. As s > 6, they can laterally condense to form the platform structure with about 1.4 nm height. Nevertheless, FT-IR, IRRAS, and CD spectra, as well as AFM images, suggest that DNA retains its double-stranded character when complexed. This is very important and meaningful for gene therapy because it is crucial to maintain the extracellular genes undamaged to obtain a high transfection efficiency. In addition, when s ≤ 6, the gemini/ds-DNA complex monolayers can experience a transition of DNA molecule from the double-stranded helical structure to a typical ψ-phase with a supramolecular chiral order.
Co-reporter:Xiang Zhu;Dr. Patrick C. Hillesheim;Shannon M. Mahurin; Congmin Wang;Chengcheng Tian;Suree Brown;Dr. Huimin Luo;Dr. Gabriel M. Veith;Dr. Kee Sung Han;Dr. Edward W. Hagaman; Honglai Liu; Sheng Dai
ChemSusChem 2012 Volume 5( Issue 10) pp:1912-1917
Publication Date(Web):
DOI:10.1002/cssc.201200355
Abstract
The search for a better carbon dioxide (CO2) capture material is attracting significant attention because of an increase in anthropogenic emissions. Porous materials are considered to be among the most promising candidates. A series of porous, nitrogen-doped carbons for CO2 capture have been developed by using high-yield carbonization reactions from task-specific ionic liquid (TSIL) precursors. Owing to strong interactions between the CO2 molecules and nitrogen-containing basic sites within the carbon framework, the porous nitrogen-doped compound derived from the carbonization of a TSIL at 500 °C, CN500, exhibits an exceptional CO2 absorption capacity of 193 mg of CO2 per g sorbent (4.39 mmol g−1 at 0 °C and 1 bar), which demonstrates a significantly higher capacity than previously reported adsorbents. The application of TSILs as precursors for porous materials provides a new avenue for the development of improved materials for carbon capture.
Co-reporter:Jun Hu, Feng Gao, Yazhuo Shang, Changjun Peng, Honglai Liu, Ying Hu
Microporous and Mesoporous Materials 2011 Volume 142(Issue 1) pp:268-275
Publication Date(Web):June 2011
DOI:10.1016/j.micromeso.2010.12.011
Based on the micro-phase separation of the dual templates consisting of an alkyl imidazole ionic liquid [Cnmim]Br and a surfactant cetyltriethylammonium bromide (CTAB), the micro/mesoporous silicate materials were synthesized. At room temperature, the cations [C4mim]+ and CTA+ aggregated into mixed micelles and acted as co-templates for synthesis of mesoporous materials which possessed an extremely large BET surface area of 1719 m2 g−1. While at a hydrothermal temperature of 373 K, the mixed micelles separated into CTA+ mesoscale micelles and [C4mim]+ micro scale aggregates which were served as mesoporous templates and microporous templates, respectively. With a total BET surface area of 1016 m2 g−1, the resulted materials had distinctly different micropore range and mesopore range of pores of 0.6 and 2.7 nm, respectively. The formation mechanism was tentatively elucidated by studying the interaction between CTAB and [C4mim]Br based on the measurement of the cmc of the CTAB/[C4mim]Br mixture aqueous solutions at different compositions and temperatures.Graphical abstractThe micro-phase separation triggered between [C4mim]Br and CTAB at higher hydrothermal temperature to form suitable molecular and supermolecular aggregations which successfully template the micro/mesoporous composites.Research highlights► We first introduce the micro-phase separation (MPS) concept to select dual templates. ► We select IL of [C4 mim]Br and CTAB as the dual templates to produce micro/mesoporous materials. ► At room T, IL and CTAB aggregate together to induce the materials with extremely large surface area. ► At high temperature, MPS occurs between IL and CTAB, which induce the micro/mesoporous materials. ► IL can act as different function roles at different compositions and temperatures.
Co-reporter:Jian Feng, Xiutao Ge, Yazhuo Shang, Lihui Zhou, Honglai Liu, Ying Hu
Fluid Phase Equilibria 2011 Volume 302(1–2) pp:26-31
Publication Date(Web):15 March 2011
DOI:10.1016/j.fluid.2010.07.016
The transport of biomolecules such as DNA, RNA and proteins in organism is important for life processes. The translocation of these biomolecules through a nanopore in the biomembrane is one of the key steps. In this work, the fast-driven process of a homopolymer translocated through a nanopore has been studied by dissipative particle dynamics (DPD) with two different dissipative radii in three dimensions and compared with the results of Langevin dynamics (LD) method. The results show that the scaling relationship between translocation time (τ) and the polymer chain length (N) is τ ∼ N0.94 by DPD method with small dissipative radius, and τ ∼ N0.98 with large dissipative radius. However, LD method gives the scaling relationship τ ∼ N1.27. In addition, the translocation time by LD method is larger than that by DPD method for the same chain. During the translocation process, the size of subchain of a polymer on the trans side is larger than the size of subchian on the cis side. Moreover, the gyration radius (Rg) of the subchain with the subchain length (L) has a good scaling relationship on the trans side. The scaling relationship is Rg ∼ L0.79 by DPD method with small dissipative radius, Rg ∼ L0.64 with large dissipative radius, and Rg ∼ L0.37 by LD method. The fluctuation of the force resulted from the thermostat decays in the order of LD, DPD with large dissipative radius, and DPD, LD with small dissipative radius. It is shown that the results are different using different simulation methods. Model parameters have also effect on the simulation results. The reasons for the difference are preliminarily analyzed.
Co-reporter:Xuezhe Zhao;Shengwei Deng;Yongmin Huang;Honglai Liu
Frontiers of Chemistry in China 2011 Volume 6( Issue 3) pp:
Publication Date(Web):2011 September
DOI:10.1007/s11458-011-0248-3
The wrinkling of phase-separated binary polymer blend film was studied through combining the Monte Carlo (MC) simulation for morphologies with the lattice spring model (LSM) for mechanical properties. The information of morphology and structure obtained by use of MC simulation is input to the LSM composed of a three-dimensional network of springs, which allows us to determine the wrinkling and the mechanical properties of polymer blend film, such as strain, stress, and Young’s modulus. The simulated results show that the wrinkling of phase-separated binary polymer blend film is related not only to the structure of morphology, but also to the disparity in elastic moduli between polymers of blend. Our simulation results provide fundamental insight into the relationship between morphology, wrinkling, and mechanical properties for phase-separated polymer blend films and can yield guidelines for formulating blends with the desired mechanical behavior. The wrinkling results also reveal that the stretching of the phase-separated film can form the micro-template, which has a wide application prospect.
Co-reporter:Xiang Zhu, Yunxiang Lu, Changjun Peng, Jun Hu, Honglai Liu, and Ying Hu
The Journal of Physical Chemistry B 2011 Volume 115(Issue 14) pp:3949-3958
Publication Date(Web):March 17, 2011
DOI:10.1021/jp111194k
In recent years, several novel halogenated liquids with characteristics of ionic liquids (ILs) were reported. To explore their performance in the absorption of CO2, in this work, quantum chemical calculations at DFT level have been carried out to investigate halogen bonding interactions between experimentally available brominated ion pairs and CO2 molecules. It is shown that, as compared to B3LYP, the functional PBE yields geometrical and energetic data more close to those of MP2 for cation−CO2 systems. The cation of brominated ILs under study can interact with CO2 molecules through Br···O interactions, possibly making an important impact on the physical solubility of CO2 in brominated ILs. The optimized geometries of the complexes of the ion pair with CO2 molecules are quite similar to those of the corresponding complexes of the cation, especially for the essentially linear C—Br···O contacts. However, much weaker halogen bonds are predicted in the former systems, as indicated by the longer intermolecular distances and the smaller interaction energies. Charges derived from NBO analysis reveal the origin of the different optimized conformations and halogen bonding interactions for the CO2 molecule. Based on the electrostatic potential results, the substitution of hydrogen atoms with fluorine atoms constituting the cation is then applied to enhance halogen bond strength. The QTAIM analysis further validates the existence of halogen bonding interaction in all complexes. The topological properties at the halogen bond critical points indicate that the Br···O interactions in the complexes are basically electrostatic in nature and belong to conventional weak halogen bonds. This study would be helpful for designing new and effective ILs for CO2 physical absorption.
Co-reporter:Shengwei Deng, Xuezhe Zhao, Yongmin Huang, Xia Han, Honglai Liu, Ying Hu
Polymer 2011 Volume 52(Issue 24) pp:5681-5694
Publication Date(Web):10 November 2011
DOI:10.1016/j.polymer.2011.09.050
The mechanical behavior of binary polymer blends polystyrene/polypropylene were studied by a continuous mesoscopic simulation method. The dynamic density functional theory approach embodied in MesoDyn method was adopted to obtain the meso-structures of polymer blends. The output of MesoDyn serves as the input of a micromechanical lattice spring model (LSM), which consists of a three-dimensional network of springs. Mechanical properties, such as young’s modulus and stress distribution can be obtained through applying strain in LSM. Subsequently, a stress-related probabilistic method was applied in LSM to study the fracturing process of materials. The fracture positions were shown in detail which have close relationship with the meso-structures. Due to the significance of interface which has a notable influence on the global mechanical properties of immiscible blends, we proposed a new method to define the stiffness in the interfacial area to study the global stiffness (young’s modulus) of materials. The results show a good agreement with the existing experiments. Besides, we varied the minimum fracture stress (related to toughness) of the interface to investigate the strength of polymer blends. A graphic representation was shown in this work, it indicates that the system with continuous interface perpendicular to the applied strain are more likely to exhibit catastrophic failure. The methods developed in this work provide important tools to predict the mechanical properties of real polymer blends.
Co-reporter:Yu Liu, Yazhuo Shang, Honglai Liu, Ying Hu, and Jianwen Jiang
The Journal of Physical Chemistry B 2011 Volume 115(Issue 8) pp:1848-1855
Publication Date(Web):February 7, 2011
DOI:10.1021/jp108415x
A reaction density functional theory (R-DFT) is developed for chemical reactions in confined space by integrating reaction thermodynamics and DFT for chain fluids. The theory is applied to investigate DNA melting in slit pores, with nucleotides represented by coarse-grained charged Lennard-Jones particles. Three types of slit pores are considered for DNA melting: repulsive pore, attractive pore, and under electric field. In repulsive pores, the melting temperature increases slightly with reducing pore width, and the increase magnitude is nearly the same for DNA of different chain lengths. The double-strand DNA (dsDNA) and single-strand DNA (ssDNA) are located in the slit center, particularly for long DNA due to the effect of configuration entropy. In attractive pores, the melting temperature increases with increasing wall−fluid interaction. The DNA chains are preferentially adsorbed near the slit walls with a strong wall−fluid interaction. Under electric field, the melting temperature increases slightly and is more distinct for shorter DNA.
Co-reporter:Lifei Chen, Yazhuo Shang, Honglai Liu, Ying Hu
Materials & Design (1980-2015) 2010 Volume 31(Issue 4) pp:1661-1665
Publication Date(Web):April 2010
DOI:10.1016/j.matdes.2009.05.047
In the water-in-oil (W/O) microemulsion stabilized by the cationic gemini surfactant alkanediyl-α, ω (dimethydodecyl-ammonium bromide) (12–3-12, 2Br−1), CuS nanorod, tube-like, and star sheet-like structures are successfully prepared. The effect of the concentration ratio of S2− to Cu2+, molar ratio (ω0) of water to surfactant in solution, incubation time, and absolute reactant concentration on the morphology and size of CuS nanocrystal have been investigated. The properties of the products and their morphologies are characterized by X-ray powder diffraction (XRD), UV–vis absorption spectrum and transmission electron microscopy (TEM). The growth mechanics of the nanocrystal with different morphology is also supposed.
Co-reporter:Jun Hu, Hongpei Cai, Huiqing Ren, Yongming Wei, Zhengliang Xu, Honglai Liu, and Ying Hu
Industrial & Engineering Chemistry Research 2010 Volume 49(Issue 24) pp:12605-12612
Publication Date(Web):November 9, 2010
DOI:10.1021/ie1014958
Metal−organic framework (MOF) crystals of Cu3(BTC)2 with a high surface area (1396 m2·g−1) were synthesized and mixed with polyimide (PI) to prepare mixed-matrix membranes (MMMs) for gas separations. The PI−Cu3(BTC)2 blend was successfully spun into MMM hollow fiber by the dry/wet-spinning method. SEM images of the fiber cross sections revealed significant plastic deformation of the polymer matrix owing to the strong affinity between Cu3(BTC)2 and PI. The H2 permeance and the selectivity of H2 with respect to other gases such as N2, CO2, O2, and CH4 both increased markedly with increased Cu3(BTC)2 loading. At a loading of 6 wt % Cu3(BTC)2, the permeance of H2 increased by 45%, and the ideal selectivity increased by a factor of 2−3 compared to the corresponding values for pure PI.
Co-reporter:Shouhong Xu;Aiping Liu;Xiaoxiao Lin;Honglai Liu;Masakastu Yonese
Chinese Journal of Chemistry 2010 Volume 28( Issue 9) pp:1565-1574
Publication Date(Web):
DOI:10.1002/cjoc.201090266
Abstract
A 3-dimensional and multi-layered network nanostructure of collagen assembled on the poly(L-lactic) acid (PLLA) substrate was reported. Collagen adsorption layers were prepared by dipping PLLA substrates into collagen solutions with various pH. The influences of adsorption interval, pH of collagen solutions and properties of PLLA substrate on the adsorption behavior of collagen were investigated by using atomic force microscopy and ellipsometry measurements. It was found that the multiple association degrees of collagen molecules in solution at a certain pH value seemed to play an important role in the adsorption process. The distinct adsorption behavior determined a specific 3-dimensional structure formed at the interface. Furthermore, calcium carbonate (CaCO3) can be biomimetically crystallized by the inducement of biomineralization on these collagen layers.
Co-reporter:Y. Liu, F. Kermanpour, H. L. Liu, Y. Hu, Y. Z. Shang, S. I. Sandler and J. W. Jiang
The Journal of Physical Chemistry B 2010 Volume 114(Issue 30) pp:9905-9911
Publication Date(Web):July 12, 2010
DOI:10.1021/jp104121q
A molecular thermodynamic model is developed to predict DNA melting in ionic and crowded solutions. Each pair of nucleotides in the double-stranded DNA and each nucleotide in the single-stranded DNA are respectively represented by two types of charged Lennard-Jones spheres. The predicted melting curves and melting temperatures Tm of the model capture the general feature of DNA melting and match fairly well with the available simulation and experimental results. It is found that the melting curve is steeper and Tm is higher for DNA with a longer chain. With increasing the fraction of the complementary cytosine−guanine (CG) base pairs, Tm increases almost linearly as a consequence of the stronger hydrogen bonding of the CG base pair than that of adenine−thymine (AT) base pair. At a greater ionic concentration, Tm is higher due to the shielding effect of counterions on DNA strands. It is observed that Tm increases in the presence of crowder because the crowder molecules occupy a substantial amount of system volume and suppress the entropy increase for DNA melting. At a given concentration, a larger crowder exhibits a greater suppression for DNA melting and hence a higher Tm. At the same packing fraction, however, a smaller crowder leads to a higher Tm.
Co-reporter:Yu Liu, Honglai Liu, Ying Hu and Jianwen Jiang
The Journal of Physical Chemistry B 2010 Volume 114(Issue 8) pp:2820-2827
Publication Date(Web):February 9, 2010
DOI:10.1021/jp9104932
In this work, a recently developed density functional theory in three-dimensional space was extended to the adsorption of gas mixtures. Weighted density approximations to the excess free energy with different weighting functions were adopted for both repulsive and attractive contributions. An equation of state for hard-sphere mixtures and a modified Benedict−Webb−Rubin equation for Lennard-Jones mixtures were used to estimate the excess free energy of a uniform fluid. The theory was applied to the adsorption of CO2/CH4 and CO2/N2 mixtures in two metal−organic frameworks: ZIF-8 and Zn2(BDC)2(ted). To validate the theoretical predictions, grand canonical Monte Carlo simulations were also conducted. The predicted adsorption and selectivity from DFT were found to agree well with the simulation results. CO2 has stronger adsorption than CH4 and N2, particularly in Zn2(BDC)2(ted). The selectivity of CO2 over CH4 or N2 increases with increasing pressure as attributed to the cooperative interactions of adsorbed CO2 molecules. The composition of the gas mixture exhibits a significant effect on adsorption but not on selectivity.
Co-reporter:Xia Han;Yuan Zhou;Jun Hu ;Honglai Liu
Journal of Polymer Science Part B: Polymer Physics 2010 Volume 48( Issue 21) pp:2262-2273
Publication Date(Web):
DOI:10.1002/polb.22109
Abstract
The surface morphologies and compositions of the asymmetric films of polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS) prepared by in situ and ex situ oxidization with the KMnO4 aqueous solution and KMnO4/H2SO4 mixed solution were investigated by using scanning electron microscope, atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance infrared spectroscopy (ATR-FTIR). The effect of the oxidization reagents on morphological changes and the influence of in situ and ex situ preparation methods on surface compositions were discussed. Different from the in situ oxidation by degrading the copolymers to form a gradient film, the ex situ oxidation preferentially degraded the uppermost layer of the film. Although both the KMnO4 oxidation and the KMnO4/H2SO4 oxidation gave hierarchical structures, distinctive differences were found that large ridges and smaller granules were fabricated in the former film and the latter produced large and deep ravines and fine sponge-like morphologies. Additionally, the oxygen concentration and the oxo-species implanted by these oxidation treatments were characterized and evaluated to provide a quantitative comparison. Oxygen, as well as manganese was found to be implanted in the surface layer of the oxidized film, forming predominantly OC and OCO groups, as well as a small fraction of OH and MnO compounds. Changes in contact angle of water on these films and total surface oxygen content are related but not directly. The hystereses of water contact angle at a value of 119 ± 3° due primarily to surface roughness and at a value of 63 ± 3° due primarily to chemical heterogeneity are led by different oxidation degrees and oxidation methods. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010
Co-reporter:Shengchi Zhuo, Yongmin Huang, Changjun Peng, Honglai Liu, Ying Hu and Jianwen Jiang
The Journal of Physical Chemistry B 2010 Volume 114(Issue 19) pp:6344-6349
Publication Date(Web):April 27, 2010
DOI:10.1021/jp910253b
A molecular dynamics simulation study is reported to investigate a CO2-induced microstructure transition of surfactant AOT4 in aqueous solution. The lamellar bilayer changes into a spherical micelle induced by CO2 at ambient temperature, while a thermotropic aggregate transition occurs in the absence of CO2 above 140 °C. In the lamellar bilayer, AOT4 shows a bimodal density distribution. The bilayer thickness and the average area per AOT4 are estimated to be 19.2 Å and 83.3 Å2. The AOT4 bilayer possesses a sandwich structure and consists of a hydrophobic region in the center and a hydrated layer on both sides. Upon CO2 dissolving, the lamellar bilayer is swollen and becomes loose and unstable. CO2 molecules in the lamellar bilayer are initially near the ester groups of AOT4 and then accumulate in the center of the hydrophobic region. With increasing amounts of CO2, the AOT4 bilayer expands gradually and the density distribution of each leaflet becomes broader. Driven by surface tension, the lamellar bilayer tends to reduce the surface area. The lamellar bilayer changes into a 3D cubic network in a small simulation box, attributed to the influence of neighboring images. In a sufficiently large box, the lamellar bilayer transforms into spherical micelles. CO2-active surfactants such as fluorinated surfactants and oxygenated AOT analogues are proposed to substitute CO2-inactive AOT and may reduce the critical pressure in microstructure transition.
Co-reporter:Houyang Chen, Xueqian Chen, Zhencheng Ye, Honglai Liu and Ying Hu
Langmuir 2010 Volume 26(Issue 9) pp:6663-6668
Publication Date(Web):December 8, 2009
DOI:10.1021/la904001h
By employing off-lattice Monte Carlo simulations, the competitive adsorption and assembly of block copolymer blends on a nanopatterned surface were investigated. The segment distributions and polymer configurations are examined by varying the chemical structures of polymers, the interactions between segments and adsorbing stripe domains of the nanopatterned surface, and the width of stripe domains in the nanopatterned surface. The simulation results show that by modulating the affinities between a copolymer and the adsorbing stripe domain, one can adjust the density distributions and adsorption properties of block copolymer blends. With decorating the chemical structure of a surface, the targeted molecules would be actively recognized and separated. This offers a versatile way for novel separation materials and for the fabrication of nanomaterials.
Co-reporter:Xiaochun Xu, Changjun Peng, Honglai Liu and Ying Hu
Industrial & Engineering Chemistry Research 2009 Volume 48(Issue 24) pp:11189
Publication Date(Web):October 13, 2009
DOI:10.1021/ie9011722
The cations or anions of ionic liquids (ILs) usually have long alkyl chains or chainlike structures. Therefore, ILs can be reasonably considered as fluids containing neutral chainlike molecules. Lattice-based molecular thermodynamic models generally used for polymer systems can be applied to describe the thermodynamic properties and phase behavior of IL systems. In our previous work, a new lattice-fluid equation of state (LF EoS) was developed and successfully applied to normal fluid systems (Xu et al., Fluid Phase Equilib. 2008, 265, 112.). In this work, this LF EoS is further extended to model the pVT properties and phase equilibria of IL systems. The molecular parameters of ILs in this EoS were determined by correlating the experimental pVT data of pure ILs. It is shown that the pVT behavior of IL mixtures can be fairly well predicted by these parameters. The vapor−liquid equilibria (VLE) of binary IL−solvent systems were calculated by using an adjustable binary parameter, κ12. For liquid−liquid equilibria (LLE) of binary IL systems, a parameter Cr describing the effect of the mixture composition on the chain-length parameter r is further used, and satisfactory correlation is obtained. The upper critical solution temperature (UCST) can be predicted successfully. Moreover, the EoS reproduces the solubility data for carbon dioxide (CO2) in various ILs covering a wide range of pressures (0−100 MPa), and it describes the global behavior of trifluoromethane (CHF3) and IL mixtures. The results reveal that the LF EoS is well-suited for the calculation or prediction of the thermodynamic properties of systems containing ILs.
Co-reporter:Tengfang Wang, Changjun Peng, Honglai Liu, Ying Hu
Journal of Molecular Liquids 2009 Volume 146(Issue 3) pp:89-94
Publication Date(Web):30 June 2009
DOI:10.1016/j.molliq.2009.02.007
The phase behavior and microstructure of the system consisting of ionic liquid BmimPF6, copolymer F127, H2O and short-chain alcohols including ethanol, n-propanol or n-butanol were investigated at 30 °C. Large areas of single-phase microemulsion were observed in all the three systems. Specially, lyotropic liquid crystal appeared in the n-butanol system while it disappeared when the other two alcohols were used. The water-in-BmimPF6, bicontinuous, and BmimPF6-in-water regions of the microemulsions were identified by the usual electrical conductivity measurement. As an attempt, UV–vis spectroscopy was successfully used to distinguish different type of microemulsions using methyl orange as solvatochromic probe. Furthermore, dynamic light scattering (DLS) measurements were also skillfully introduced to vividly track the structural variation of different microemulsions. On the other hand, the hydrodynamic diameter of the BmimPF6-in-water microemulsion was accurately obtained. An unusual phenomenon was demonstrated that Z-average size of BmimPF6-in-water microemulsions decreases with increasing BmimPF6 (oil) concentration at fixed (F127 + n-propanol) concentration.
Co-reporter:Xiaochun Xu, Changjun Peng, Guiping Cao, Honglai Liu and Ying Hu
Industrial & Engineering Chemistry Research 2009 Volume 48(Issue 16) pp:7828
Publication Date(Web):July 20, 2009
DOI:10.1021/ie900676n
In our previous work, a new lattice-fluid equation of state (LF-EoS) was developed and successfully applied to normal fluid systems and ionic liquid systems. In this work, this LF-EoS is further extended to describe thermodynamic properties of polymer systems. First, the model parameters for polymers were determined by fitting experimental pVT data of polymers over a wide temperature and pressure range. Then, the LF-EoS was applied for calculating vapor−liquid equilibrium (VLE) of polymer−solvent systems using one adjustable binary parameter κ12. The solubility of gas in polymer can be calculated up to a high pressure. Moreover, a new parameter Cr was introduced to describe the effect of composition of mixtures on chain length parameter r, and several typical liquid−liquid equilibrium behaviors of polymer solutions can be successfully reproduced.
Co-reporter:Jinlong Li, Haihua He, Changjun Peng, Honglai Liu, Ying Hu
Fluid Phase Equilibria 2009 Volume 286(Issue 1) pp:8-16
Publication Date(Web):25 November 2009
DOI:10.1016/j.fluid.2009.07.019
An equation of state (EOS) for square-well chain molecules with variable range developed on the basis of statistical mechanics for chemical association in our previous work is employed for the calculations of pVT properties and vapor–liquid equilibria (VLE) of pure non-associating fluids. The molecular parameters for 73 normal substances and 46 polymers are obtained from saturated vapor pressure and liquid molar volume data for normal fluids or pVT data for polymers. Linear relations are found for the molecular parameters of normal fluids with their molecular weight of homologous compounds. This indicates that the model parameters of homologous series, subsequently pVT and VLE, can be predicted when experimental data are not available. The predicted saturated vapor pressures and/or liquid volumes are satisfactory through the generalized model parameters. The calculated VLE and pVT for normal fluids and polymers by this EOS are compared with those from other engineering models, respectively.
Co-reporter:Abdulaziz Mohammed Al-Hakimi;Yazhuo Shang;Honglai Liu
Journal of Solution Chemistry 2009 Volume 38( Issue 10) pp:
Publication Date(Web):2009 October
DOI:10.1007/s10953-009-9449-5
The effect of added salts (NaCl, KCl and NaBr) on the aqueous two-phase system (ATPS) formed in mixtures of Gemini(12-3-12, 2Br−)/sodium dodecyl sulfate/polyethylene glycol has been investigated. Phase diagrams of the aqueous systems containing Gemini(12-3-12, 2Br−), sodium dodecyl sulfate (SDS), polyethylene glycol(PEG) and a salt have been determined experimentally at 313.15 K. The results indicate that the addition of salts not only induces the appearance of ATPS-A (in which anionic surfactant is in excess), shortens the phase separation time, enlarges the regions of ATPS-C (in which cationic surfactant is in excess), and decreases the minimum concentration required for forming an ATPS, but also alters the matching between anionic and cationic surfactants. Extractive experiments also showed that these salts notably enhance the extraction ability of ATPS; the Gemini-rich phase exhibits prominent cohesive action with xylenol orange, regardless of whether or not it is the upper phase or the lower phase.
Co-reporter:Yu Liu, Honglai Liu, Ying Hu and Jianwen Jiang
The Journal of Physical Chemistry B 2009 Volume 113(Issue 36) pp:12326-12331
Publication Date(Web):August 19, 2009
DOI:10.1021/jp904872f
A density functional theory (DFT) is developed in three-dimensional nanoconfined space and applied for H2 storage in metal−organic frameworks. Two different weighting functions based on the weighted density approximation (WDA) are adopted, respectively, for the repulsive and attractive contributions to the excess free energy. The Carnahan−Starling equation and a modified Benedicit−Webb−Rubin equation are used to calculate the excess free energy of uniform fluid. To compare with DFT predictions, grand canonical Monte Carlo simulations are carried out separately. For H2 adsorption in MOF-5 and ZIF-8, the isotherms predicted from the DFT agree well with simulation and experiment results, and the DFT is found to be superior to the mean-field-approximation (MFA)-based theory. The adsorption energies and isosteric heats predicted are also in accord with simulation results. From the predicted density contours, the DFT shows that the preferential adsorption sites are the corners of metal clusters in MOF-5 and the top of organic linkers in ZIF-8, consistent with simulation and experimental observations.
Co-reporter:Shouhong Xu, Aiping Liu, Qibin Chen, Mingyu Lv, Masakastu Yonese, Honglai Liu
Colloids and Surfaces B: Biointerfaces 2009 Volume 70(Issue 1) pp:124-131
Publication Date(Web):1 April 2009
DOI:10.1016/j.colsurfb.2008.12.023
The self-assembly nano-structures of type I collagen adsorbed on anionic Gemini surfactant LB monolayer were observed by using atomic force microscopy (AFM) images. It was found that the adsorption behavior and self-assembly structure of collagen could be controlled by the concentration of the collagen solution, adsorption interval and the properties of substrates. With the increase of the adsorption interval and concentration of collagen, the strands size of collagen changed. The self-assembly structures of collagen were also influenced by the interaction between collagen molecules and Gemini surfactant monolayer substrates. Finally, the adsorption behaviors of collagen molecules on cationic Gemini monolayer were compared with those on anionic Gemini monolayer.
Co-reporter:Qin Xin, Changjun Peng, Honglai Liu and Ying Hu
Industrial & Engineering Chemistry Research 2008 Volume 47(Issue 23) pp:9678-9686
Publication Date(Web):October 31, 2008
DOI:10.1021/ie800924r
The molecular thermodynamic model of polymer solutions based on a close-packed lattice model presented in a previous work has been generally extended to multicomponent chainlike fluid mixtures. The Helmholtz function of mixing contains three terms, i.e., the contribution of athermal mixing of polymer chains, which is calculated by Guggenheim’s theory; the contribution of nearest-neighbor interactions between monomers, which is calculated by Yang et al.’s model of the Helmholtz function of mixing for a multicomponent Ising lattice; and the contribution of the formation of polymer chains from monomers, which is obtained according to the sticky-point theory of Cummings, Zhou, and Stell. The liquid−liquid phase equilibria of ternary chainlike mixtures predicted by this model are in good agreement with Monte Carlo simulation results and superior to the results calculated by Flory−Huggins (FH) theory and revised Freed theory (RFT) obviously. This model not only can describe types 1−3 phase separations of Treybal classification satisfactorily, but can also correlate well the coexistence curves of binary polymer blends systems with an upper critical solution temperature (UCST) or a lower critical solution temperature (LCST). Meanwhile, model parameters correlated from the binary system can be further extended to predict the corresponding liquid−liquid equilibrium of ternary mixtures, including systems of ionic liquids.
Co-reporter:Yanfang Geng, Siliu Chen, Tengfang Wang, Dahong Yu, Changjun Peng, Honglai Liu, Ying Hu
Journal of Molecular Liquids 2008 Volume 143(2–3) pp:100-108
Publication Date(Web):20 October 2008
DOI:10.1016/j.molliq.2008.06.014
Densities, viscosities and electrical conductivities of ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim][PF6]) in monoethanolamine (MEA) and N, N-dimethylethanolamine (DMEA) have been determined from (288.15 to 323.15) K. The results show that the densities of both binary mixtures linearly decrease with increasing temperature. The dependence of temperature on the viscosity has been fitted to the Arrhenius equation with high precision. A viscosity model based on the equation of state for chain-like fluids and a solute aggregation model were used to calculate the viscosity of binary mixture. The dependence of temperature on the electrical conductivity has also been fitted in the form of Arrhenius equation. The effect of concentration of ionic liquid on the electrical conductivity has been examined using the Walden rule. Excess molar volumes and viscosity deviations from a mole fraction average have been obtained and fitted to the Redlich–Kister equation.
Co-reporter:Hui Xu, Tengfang Wang, Yongmin Huang, Honglai Liu and Ying Hu
Industrial & Engineering Chemistry Research 2008 Volume 47(Issue 17) pp:6368-6373
Publication Date(Web):June 4, 2008
DOI:10.1021/ie701776r
Microphase separation and morphology evolution of polystyrene and polybutadiene blends are quantitatively studied by the dynamic density functional theory that is based on the equation of state (EOS-based DDFT). The structure parameters of coarse-grained beads are regressed from the experimental pressure−volume−temperature data of pure components. The comparisons between simulated and experimental results are presented as illustrations. Notably, in the region near the critical composition, the deviation of the order−disorder transition temperature between simulation and experiment is <10 °C. Considering the fact that EOS-based DDFT is a unique simulation method that can predict the morphologies of blends in the different temperatures and compositions and match the simulated and experimental results in the same time, which is beyond the capabilities of the phase equilibrium theory and other simulation methods, such a deviation is obvious, but definitely acceptable. The factors that affect the accuracy of the simulation results are discussed.
Co-reporter:Yanjin Jia, Jian Xu, Lihui Zhou, Honglai Liu, Ying Hu
Materials Letters 2008 Volume 62(8–9) pp:1336-1338
Publication Date(Web):31 March 2008
DOI:10.1016/j.matlet.2007.08.041
Multipod-like γ-MnOOH and rod-like β-MnO2 nanocrystals are synthesized by oxidization of manganese sulphate hydrate (MnSO4·H2O) using sodium chlorate (NaClO3) as an oxidizing agent in a simple hydrothermal reaction system in the absence of any templates, catalysts, or organic reagents. The powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) are used to characterize the as-prepared products. Based on the results of XRD and SEM, multipod-like γ-MnOOH can be transformed into rod-like β-MnO2 nanocrystals via one step synthetic route by simply increasing the reaction time while other conditions are kept constant. And a possible transfer mechanism via a nucleation–dissolution–anisotropic growth–recrystallization process is presented.
Co-reporter:Jian Feng;Honglai Liu;Ying Hu;Jianwen Jiang
Macromolecular Theory and Simulations 2008 Volume 17( Issue 4-5) pp:163-170
Publication Date(Web):
DOI:10.1002/mats.200800005
Co-reporter:Xiaochun Xu, Honglai Liu, Changjun Peng, Ying Hu
Fluid Phase Equilibria 2008 Volume 265(1–2) pp:112-121
Publication Date(Web):25 March 2008
DOI:10.1016/j.fluid.2008.01.011
In previous work, we have developed a close-packed lattice model for binary solutions of chain-like molecules. As a continuation, considering the effect of volume change, we present here a new molecular-thermodynamic model based on lattice fluid theory. The resulting equation of state shows good performance in describing thermodynamic properties such as pVT behavior, vapor pressure and liquid volume of pure normal fluids. Equation-of-state parameters are obtained by correlation of experimental data. The model is extended to calculate vapor–liquid equilibria of binary mixtures with only one binary interaction parameter. Comparison between the present model and other theories is also presented.
Co-reporter:Qin Xin, Changjun Peng, Honglai Liu, Ying Hu
Fluid Phase Equilibria 2008 Volume 267(Issue 2) pp:163-171
Publication Date(Web):25 May 2008
DOI:10.1016/j.fluid.2008.03.001
A new Helmholtz energy model of mixing for random copolymer solutions based on a close-packed lattice has been developed. The model contains three terms: the contribution of the athermal mixing of polymer chain and solvent, the Helmoltz energy of mixing in a multi-component Ising lattice where the interactions between segments is accounted for, and the contribution of the dissociation of the polymer and the association of monomers. The Guggenheim model, Yang et al.'s model and the sticky-point model of Cummings, Zhou and Stell are used respectively, for the above three contributions. Comparisons between Monte Carlo simulated coexistence curves with those predicted by various theories for random copolymer solutions with various chain lengths, chain compositions and inter-segment interaction parameters show that the agreement between simulations and the predictions of this work is nearly perfect. The model can be used satisfactorily to correlate the liquid–liquid equilibria of practical random copolymer solutions.
Co-reporter:Qibin Chen, Dazhi Zhang, Rong Li, Honglai Liu, Ying Hu
Thin Solid Films 2008 Volume 516(Issue 23) pp:8782-8787
Publication Date(Web):1 October 2008
DOI:10.1016/j.tsf.2008.06.082
Surface properties of the insoluble cationic bis-(quaternary ammonium halide) surfactants (Gemini) with polymethylene spacer at the air/water interface were investigated. The monolayers were transferred onto mica by the Langmuir–Blodgett (LB) technique and the corresponding LB films were characterized by the atomic force microscopy (AFM) and the contact angle of water. For the Gemini surfactants with the different spacer length, it was found that the surface pressure-molecular area isotherms resemble to each other. The limiting area increases rapidly and almost linearly with the increase of spacer length for the short spacers, but reaches a maximum at s = 10 and decreases slightly at s > 10. The AFM images show that the surface micelles and the multilayer aggregates gradually appear with the increase of surface pressure. No matter what the surface pressures are, the main structure of the monolayer almost keeps the same, which suggested that the major molecules lie nearly flat on the water surface, while the increase of surface pressure forces the minor alkyl chains to turn only partly or completely vertical to the water surface and even to overturn. This is the cause that the contact angle of water on LB film increases slightly with the surface pressure.
Co-reporter:Houyang Chen, Jun Cai, Zhencheng Ye, Changjun Peng, Honglai Liu, Ying Hu and Jianwen Jiang
The Journal of Physical Chemistry B 2008 Volume 112(Issue 32) pp:9568-9573
Publication Date(Web):July 23, 2008
DOI:10.1021/jp802633p
A hybrid density functional theory (DFT) is developed for adsorption of copolymers in a selective nanoslit. The DFT incorporates a single-chain simulation for the ideal-gas free energy functional with two weighted density approximations for the residual free energy functional. The theory is found to be insensitive to the width parameter used in the weighted density. Theoretical predictions are in excellent agreement with simulation results in the segment density profiles and the adsorption configurations including tail, loop, and train for copolymers with various sequences over a wide range of surface affinity. The bridge conformation is also observed in multiblock copolymers. Ordered assembly is facilitated in copolymers with longer chain/block and at stronger attraction between segment B and the slit wall. While diblock copolymer shows the longest tail, alternating copolymer has the shortest. As the attraction between segment B and the slit wall increases, the average size and fraction decrease for tail, but increase for loop and train.
Co-reporter:Shengchi Zhuo, Yongmin Huang, Jun Hu, Honglai Liu, Ying Hu and Jianwen Jiang
The Journal of Physical Chemistry C 2008 Volume 112(Issue 30) pp:11295-11300
Publication Date(Web):July 4, 2008
DOI:10.1021/jp803428n
Adsorption of pure and mixed CO 2 and N 2 is simulated in a mimetic MCM-41. The full-atom MCM-41 model is constructed by caving cylindrical pores from an amorphous silica matrix and energetically optimized. Dreiding force field is used for the dispersive interaction with the atomic charges estimated from the density-functional theory calculations. The optimized MCM-41 maintains a hexagonal array of the mesoscopic pores as evidenced by the three characteristic peaks in the XRD pattern. The pore surface of MCM-41 is corrugated and coated with hydroxyls and defects. The pore size exhibits a Gaussian distribution with an average radius of 14.38 Å close to the experimental value. Simulated adsorption isotherms and isosteric heats of CO 2 match well with the experimental data. CO 2 adsorbs preferentially at the active sites near the pore surface, while N 2 tends to adsorb homogeneously on the pore surface. In CO 2 and N 2 mixture as a flue gas, CO 2 is more adsorbed than N 2. The selectivity of CO 2 over N 2 drops rapidly with increasing temperature and depends weakly on pressure. At temperatures higher than 400 K, the selectivity approaches a constant and pressure has no discernible effect.
Co-reporter:Li-Hui Zhou;Ying-Hua Tao;Jun Hu;Xia Han
Journal of Porous Materials 2008 Volume 15( Issue 6) pp:653-659
Publication Date(Web):2008 December
DOI:10.1007/s10934-007-9146-y
Immobilization of hemoglobin (Hb) in SBA-15 with various pore sizes by physical adsorption was studied. The structure changes of mesoporous SBA-15 before and after the immobilization of Hb were characterized by N2 adsorption isotherms, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Ultraviolet-visible spectroscopy (UV). The results indicate that SBA-15 is a good support for the immobilization of Hb due to its regular structure, large pore diameter, and high surface area. After immobilization of Hb, the regular structure of SBA-15 is still kept, but the pore diameter, pore volume and surface area decrease. With the increase of pore size, the binding amount and leaching amount of Hb increase. There is a maximum binding amount of Hb up to 355.2 mg/g SBA-15 when pore size is 8.9 nm. It is suggested that the immobilization of Hb depends significantly on the pore size of SBA-15.
Co-reporter:Jun Hu, Lihui Zhou, Jian Feng, Honglai Liu, Ying Hu
Journal of Colloid and Interface Science 2007 Volume 315(Issue 2) pp:761-767
Publication Date(Web):15 November 2007
DOI:10.1016/j.jcis.2007.06.077
The micellization properties of aqueous solutions of the mixed Gemini surfactant homologues GEM16-6-16 and GEM16-12-16 with various compositions were investigated. The measured critical micelle concentration (CMC) deviated significantly from the ideal mixing model. Good agreement was found with a nonideal mixing model, the Margules model, which has two optimal parameters, A12=−3.611A12=−3.611 and A21=−6.318A21=−6.318. It was shown that the properties of mixed micelles were not sensitive to the compositions, and most of the GEM16-12-16 molecules were aggregated into the micelles. Dynamic laser light-scattering measurements revealed that the mixed micelles had almost the same size and similar zeta potential. When the mixed micelles were used as templates, a series of highly ordered cubic MCM-48 mesoporous materials, characterized by XRD and TEM, were produced through self-assembly. The N2 adsorption–desorption measurements suggested that the pores of these materials had similar average diameters of 2.2–2.5 nm. This further demonstrated the nonideal behavior of the homologue mixture.Gemini surfactant homologues GEM16-6-16 and GEM16-12-16 are nonideal mixed micelles and have template approaches for ordered mesoporous materials MCM-48.
Co-reporter:Qibin Chen, Shouhong Xu, Rong Li, Xiaodong Liang, Honglai Liu
Journal of Colloid and Interface Science 2007 Volume 316(Issue 1) pp:1-9
Publication Date(Web):1 December 2007
DOI:10.1016/j.jcis.2007.07.059
Elucidating the assembly mechanism of the collagen at interfaces is important. In this work, the structures of type I collagen molecules adsorbed on bare mica and on LB films of propanediyl-bis(dimethyloctadecylammonium bromide) transferred onto mica at zero surface pressure was characterized by AFM. On mica, the granular morphologies randomly distributed as elongated structures were observed, which were resulted from the interlacement of the adsorbed collagen molecules. On the LB films, the topographical evolution of the adsorbed collagen layers upon the increasing adsorption time was investigated. After 30 s, the collagen assembled into network-like structure composed of the interwoven fibrils, called as the first adlayer, which was attributed to its adsorption on the LB film by means of a limited number of contact points followed by the lateral association. One minute later, the second adlayer was observed on the top of the first adlayer. Up to 5 min, collagen layers, formed by inter-twisted fibrils, were observed. Under the same conditions after 1 min adsorption on LB film, the AFM image of the layer obtained in the diluted hydrochloric acid solution is analogous to the result of the sample dried in air, indicating that it is the LB film that leads to the formation of the network structure of collagen and the formation of the network structures of collagen layers is tentatively ascribed to the self-assembly of type I collagen molecules on LB film, not to the dewetting of the collagen solution during drying.After the adsorption of 30 s in the diluted collagen acidic solution, the hole-like structures with the diameter of several hundred nm could be observed, as shown in figure, occasionally. The height of the patterns in the holes, indicated by the arrows, is approximately 0.4 nm and the height of the network structure varies from 1.4 to 2.9 nm, while the rims of the hole-like structures are ranged from 3.0 to 6.5 nm higher compared to the network structure.
Co-reporter:Yingying Pi, Yazhuo Shang, Honglai Liu, Ying Hu, Jianwen Jiang
Journal of Colloid and Interface Science 2007 Volume 306(Issue 2) pp:405-410
Publication Date(Web):15 February 2007
DOI:10.1016/j.jcis.2006.10.020
The effect of alkali halides (NaBr, NaCl, KCl) on the interactions between the cationic gemini surfactant hexylene-1,6-bis(dodecyldimethylammonium bromide) (12-6-12) and the anionic polyelectrolyte sodium polyacrylate (NaPAA) in aqueous solution has been investigated by fluorescence emission spectroscopy, UV transmittance, zeta potential, and transmission electron microscopy (TEM). With increased addition of NaBr, a counterbalancing salt effect on the critical aggregation concentration (CAC) is observed. At low concentrations, NaBr facilitates the formation of micelle-like structures between surfactant and polyelectrolyte and results in a smaller CAC. At high concentrations, NaBr screens the electrostatic attraction between surfactant and polyelectrolyte and leads to a larger CAC. Upon the formation of micelle-like structures at high surfactant concentrations, the addition of NaBr is favorable for larger aggregates. The microstructure detected by TEM show that a global structure is generally formed in the presence of NaBr. The interactions also depend on ion species. Compared to NaBr, the addition of NaCl or KCl yields a smaller CAC.Microstructure of 12-6-12/NaPAA solution in the presence of NaBr.
Co-reporter:Xia Han, Lihui Zhou, Honglai Liu, Ying Hu
Polymer Degradation and Stability 2007 Volume 92(Issue 1) pp:75-85
Publication Date(Web):January 2007
DOI:10.1016/j.polymdegradstab.2006.09.006
The morphologies of the asymmetric membranes of polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) prepared and simultaneously oxidized with different substrate solutions were investigated with atomic force microscopy (AFM), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance infrared spectroscopy (ATR-FTIR). We used the KMnO4 aqueous solution and KMnO4/H2SO4 mixture solution as solvent-casting substrates, as well as oxidized reagents. The surface composition and functional groups of membranes were also measured. The effect of casting substrates on morphological changes was discussed through possible chemical reactions. It was found that the SEBS membranes were transformed from an ordered microphase-separated structure to disordered nodular or sponge-like structures. The former might be contributed to MnO2 depositions while the latter was caused by the bond interruption, after KMnO4 or KMnO4/H2SO4 oxidizing.
Co-reporter:Hui Xu;Ying Hu;Honglai Liu
Macromolecular Theory and Simulations 2007 Volume 16(Issue 3) pp:262-268
Publication Date(Web):27 MAR 2007
DOI:10.1002/mats.200600078
The effect of pressure on the microphase separation of diblock copolymer melts was investigated by dynamic density functional theory based on equation of state. The results correspond well with experiment data. With the application of high pressure, all of the phase regions corresponding to the different ordered morphologies become narrower. However, the pressure dependence of the order-disorder transition temperature (TODT) relies on the symmetry of the diblock copolymer. In the very non-symmetrical case when f is small, TODT decreases with increasing pressure, while in the symmetrical case when f = 0.5, TODT increases with increasing pressure. For the latter case, the increase in the total bead number of the system at the ODT is found, which is in good accordance with the experimental phenomenon that there is an increase in volume accompanying with the transition from ordered to disordered state. In contrast to the temperature, the pressure does not influence the starting time and the duration of microphase separation.
Co-reporter:Yongmin Huang;Han Xia;Honglai Liu;Ying Hu
Macromolecular Theory and Simulations 2007 Volume 16(Issue 1) pp:93-100
Publication Date(Web):22 JAN 2007
DOI:10.1002/mats.200600055
The morphologies of triblock copolymer/homopolymer blend films confined between two neutral hard walls were studied via MC simulations on a simple cubic lattice. For ABA/A and ABA/B blend films, the effects of φh (the volume fraction of the homopolymer) and Mh/Mb (the ratio of the molecular mass of the homopolymer to that of the corresponding blocks) on the morphologies were investigated in detail. For both ABA/A and ABA/B blend films, a higher φh or Mh/Mb would result in stronger macrophase separation between the triblock copolymer and homopolymer. For ABA/C blend films, Mh/Mb hardly influences the morphologies of homopolymer domains regardless of whether the homopolymer C is more compatible with block A or with block B. Compared to AB/A and AB/C blend films, the morphologies of ABA/A (or ABA/B) and ABA/C blend films are much more irregular. The simulated results in this work show good consistency with experiments and other simulations.
Co-reporter:Xingqing Xiao;Yongmin Huang;Honglai Liu;Ying Hu
Macromolecular Theory and Simulations 2007 Volume 16(Issue 2) pp:166-177
Publication Date(Web):26 FEB 2007
DOI:10.1002/mats.200600064
Monte Carlo simulations were used to identify the microphase morphologies of ABA triblock copolymer melts confined in a cylindrical nanotube. The influences of the volume fraction of mid-block B (fB), the radius of nanotube (R) and the asymmetry of ABA triblock copolymer chain were discussed in detail. When fB varies, a series of double-continuous, three-layer concentric cylinder barrel, porous net, double helixes and the new multiplex structures were observed under different conditions. In addition, the stacked disk, catenoid-cylinder and multi-layer concentric cylinder barrel structures occur in turns at changing R. The relation between circular lamellae period L and layer number Nlayer of concentric cylinder barrel with the increase of R was investigated to further explain the put-off phenomenon of microphase transition of the multi-layer concentric cylinder barrel structures. As for the increase of the asymmetry of ABA triblock copolymer chain, it was concluded that the short AI segments tend to site at the interface between rich A and B circular lamellae.
Co-reporter:Honglai Liu;Xingqing Xiao;Yongmin Huang;Ying Hu
Macromolecular Theory and Simulations 2007 Volume 16(Issue 8) pp:732-741
Publication Date(Web):17 OCT 2007
DOI:10.1002/mats.200700041
The morphology transitions in AB diblock and ABA triblock copolymers confined between flat and curved surfaces were investigated by MC simulations. Upon variation of the extent of frustration between thickness d and bulk lamellae period L0, parallel and vertical or distorted vertical lamellar structures appear in both flat and curved confinements. With increasing curvature, the compatibility of d and L0 becomes more perturbed so that perfectly parallel lamellae are formed with increasing difficulty. Owing to the smaller L0 of ABA as compared to AB, the transformation frequency of the incompatible region of d/L0(ABA) is more notable for ABA and the corresponding transformation period is larger than that of AB.
Co-reporter:Yazhuo Shang, Honglai Liu, Ying Hu, John M. Prausnitz
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2007 Volume 294(1–3) pp:203-211
Publication Date(Web):15 February 2007
DOI:10.1016/j.colsurfa.2006.08.012
Phase behavior and microstructures have been investigated for aqueous mixtures of cationic Gemini surfactant (12-3-12,2Br−) and anionic surfactant sodium dodecyl sulfate (SDS) using freeze-etching and negative-staining and with transmission electron microscopy (TEM). The phase diagram shows different regions characterized by different microstructures. Most of the regions are occupied by multi-lamellar phases in which vesicles coexist with micelles when the solutions are dilute. The multi-lamellar vesicles have higher stability because of their special structures. The ratio of vesicles to micelles varies with concentration and composition of the mixed-surfactant solutions. At higher surfactant concentrations, we observe other phases: the lamellar phase, anisotropic phase, aqueous two-phase system (ATPS), rod-like micelle phase, as well as other unique microstructures such as cylindrical micelles formed by short rod-like micelles, and porous morphology. Observations are reported for the transformation among different phases, especially from rod-like to spherical micelles.
Co-reporter:Hui Xu;Honglai Liu;Ying Hu
Frontiers of Chemical Science and Engineering 2007 Volume 1( Issue 1) pp:26-34
Publication Date(Web):2007 February
DOI:10.1007/s11705-007-0006-8
The effect of steady shear on multi-axial texture of symmetric diblock copolymer was investigated by using dynamic density functional theory. Through modifying the periodic boundary condition, the parallel-transverse biaxial texture and perpendicular-parallel-transverse triaxial texture have been observed. In the formation of the multi-axial texture, there are two critical velocities uper-par* and upar-tra*, at which the transition between the perpendicular and the parallel lamellar morphology, and the transition between the parallel and the transverse lamellar morphology occur, respectively. The two critical velocities increase as the interaction parameter increases, but they almost remain constant at different shear rates. Furthermore, the rotation from the transverse lamellae to the parallel lamellae induced by the shear strain, and the increase of lamellar spacings of the three lamellae after removing the shear, have also been observed by the time evolution of the morphologies. These phenomena are consistent with experimental work.
Co-reporter:Jian Feng;Yongmin Huang;Honglai Liu
Frontiers of Chemical Science and Engineering 2007 Volume 1( Issue 2) pp:132-139
Publication Date(Web):2007 May
DOI:10.1007/s11705-007-0025-5
Diblock copolymers with ordered mesophase structures have been used as templates for nano-fabrication. Unfortunately, the ordered structure only exists at micromete rscale areas, which precludes its use in many advanced applications. To overcome this disadvantage, the diblock copolymer confined in a restricted system with a patterned surface is proved to be an effective means to prohibit the formation of defects and obtain perfect ordered domains. In this work, the morphologies of a thin film of diblock copolymer confined between patterned and neutral surfaces were studied by dissipative particle dynamics. It is shown that the morphology of the symmetric diblock copolymer is affected by the ratio of the pattern period on the surface to the lamellar period of the symmetric diblock copolymer and by the repulsion parameters between blocks and wall particles. To eliminate the defects in the lamellar phase, the pattern period on the surface must match the lamellar period. The difference in the interface energy of different compartments of the pattern should increase with increasing film thickness. The pattern period on the surface has a scaling relationship with the chain length, which is the same as that between the lamellar period and the chain length. The lamellar period is also affected by the polydispersity of the symmetric diblock copolymer. The total period is the average of the period of each component multiplied by the weight of its volume ratio. The morphologies of asymmetric diblock copolymers are also affected by the pattern on the surface, especially when the matching period of the asymmetric diblock copolymer is equal to the pattern period, which is approximately equal to the lamellar period of a symmetric diblock copolymer with the same chain length.
Co-reporter:Lifei Chen, Yazhuo Shang, Honglai Liu, Ying Hu
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2007 Volume 305(1–3) pp:29-35
Publication Date(Web):15 September 2007
DOI:10.1016/j.colsurfa.2007.04.037
The middle-phase microemulsion (Winsor III) induced by salt in the low surfactant + cosurfactant (S + A) region of n-butanol/n-octane/water/alkanediyl-α,ω(dimethydodecyl-ammonium bromide) (12-3-12) system was investigated by salinity scan. It is shown that the original water-in-oil single phase cannot form Winsor III even when the NaCl aqueous solution added reaches saturation. However, the original coexisting multi-phase and oil-in-water single phase can form Winsor III easily in a wide concentration range of salt, which is favorable to the application of Winsor III. The super low salinity for the initial formation of Winsor III (S1) attributes to the special structure of geminis. The water content, salinity, and temperature have great effect on the volume fraction of Winsor III and the temperature induces different phase transition from Winsor II to Winsor III. The condition for the formation of stable Winsor III was obtained by the interfacial tension (IFT) measurements. The multi-phase microemulsion was also studied by fluorescence, and the information, which was used to determine the microstructure of single-phase microemulsion. The results agree well with that obtained from the conductivity measurement carried out in our previous work.
Co-reporter:Jian Xu;Weijun Liu;Honglai Liu;Ying Hu
Frontiers of Chemical Science and Engineering 2007 Volume 1( Issue 3) pp:221-227
Publication Date(Web):2007 July
DOI:10.1007/s11705-007-0040-6
A simple solution-phase approach has been demonstrated for the large-scale synthesis of silver nanowires with diameters in the range of 15–25 nm, and lengths usually in the range of tens of micrometers. In the presence of gemini surfactant 1,3-bis(cetyldimethylammonium) propane dibromide (16-3-16), the growth of silver could be directed into a highly anisotropic mode to form uniform nanowires with aspect ratios up to about 2,000. X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), X-ray powder diffraction (XRD), electron diffraction (ED), and UV-vis absorption spectroscopy, were used to characterize the as-prepared silver nanowires, indicating the formation of a highly pure phase, good crystallinity, as well as a uniform diameter.
Co-reporter:Xia Han;Honglai Liu;Ying Hu
Journal of Polymer Science Part B: Polymer Physics 2007 Volume 45(Issue 5) pp:532-543
Publication Date(Web):17 JAN 2007
DOI:10.1002/polb.21071
Surface morphologies formed by the phase segregation of poly(styrene-b-ethylene/butylene-b-styrene) (SEBS)/poly(methyl methacrylate) (PMMA) blend films prepared via spin coating on mica substrates were studied with atomic force microscopy accompanied by a solvent extraction treatment, X-ray photoelectron spectroscopy, and contact-angle measurements. Three kinds of surface structures of films were observed. Besides the ribbonlike morphology and the dispersed domains in a continuous matrix that are common in this field, we found a special interlocking layer structure characterized by a smooth SEBS layer as the cover on the top and a layer composed of hill-like PMMA dispersed in the SEBS matrix at the bottom when the composition of the film was around 50:50 SEBS and PMMA. A series of blend films with different thicknesses were then prepared to investigate the interfacial structure, and the formation process of the interlocking layer, which could be elucidated by a schematic diagram, was discussed. The interlocking bilayer film with SEBS on the top possessed high thermal stability and the best surface roughness in comparison with other structures. It might find important technical applications in fields such as adhesion, lubrication, and protective coatings. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 532–543, 2007.
Co-reporter:Yan-Qing Nan, Hong-Lai Liu, Ying Hu
Journal of Colloid and Interface Science 2006 Volume 293(Issue 2) pp:464-474
Publication Date(Web):15 January 2006
DOI:10.1016/j.jcis.2005.06.054
Interfacial tensions in two aqueous phase-separated cationic/anionic surfactant mixtures, CTAB/AS and 12-3-12/AS, without and with NaBr added were determined by the spinning drop method at 318.15 K. CTAB, 12-3-12 and AS are the abbreviations for cetyltrimethylammonium bromide, 1,3-propanediyl-bis(dodecyldimethylammonium bromide) and sodium dodecyl sulfonate, respectively. The interfacial tension σ was found to be in the range of 0.06–21 μNm−1. Toward a better understanding of the influence of the concentration difference between the separated phases in aqueous two-phase systems (ATPS) to interfacial tension, compositions of equilibrium phases were determined by elemental analysis coupled with material balance and electroneutrality. The investigation indicates that the concentration differences of surfactant ions between the separated phases and the adsorption of surfactant ions at the interface are the decisive factors determining the magnitude of interfacial tension.Interfacial tensions in two aqueous phase-separated cationic/anionic surfactant mixtures were determined and the decisive factors for the magnitude of interfacial tension were discussed.
Co-reporter:Yingying Pi, Yazhuo Shang, Changjun Peng, Honglai Liu, Ying Hu, Jianwen Jiang
Journal of Colloid and Interface Science 2006 Volume 299(Issue 1) pp:410-415
Publication Date(Web):1 July 2006
DOI:10.1016/j.jcis.2006.01.035
The phase behavior of aqueous mixtures of gemini surfactant hexylene-1,6-bis(dodecyldimethylammonium bromide) (12-6-12) and oppositely charged polyelectrolyte sodium polyacrylate (NaPAA) has been studied experimentally. Compared to the mixtures of the traditional surfactant dodecyltrimethylammonium bromide (DTAB) and NaPAA, the gel phase region in the 12-6-12/NaPAA solution is larger. Element analysis reveals that NaPAA in the gel phase tends to replace the counterions of surfactant micelle and to release its own counterions. Spherical aggregates are observed in either top or bottom gel phase as detected by transmission electron microscopy. The addition of sodium bromide (NaBr) leads to a decrease in the gel phase region and the occurrence of a new cream phase.Phase diagrams of (A) 12-6-12/NaPAA and (B) DTAB/NaPAA aqueous solution.
Co-reporter:Yingying Pi, Yazhuo Shang, Changjun Peng, Honglai Liu, Ying Hu, Jianwen Jiang
Journal of Colloid and Interface Science 2006 Volume 301(Issue 2) pp:631-636
Publication Date(Web):15 September 2006
DOI:10.1016/j.jcis.2006.05.043
Interactions between cationic gemini surfactant alkanediyl-α,ωα,ω-bis(dodecyldimethylammonium bromide) (12-n -12, n=3,4,6n=3,4,6) and oppositely charged polyelectrolyte sodium polyacrylate (NaPAA) in aqueous solution have been investigated by measuring fluorescence, conductivity, UV–vis transmittance, dynamic lighting scattering, and transmission electron microscopy. Micelle-like structure and 12-n-12/NaPAA complex are observed to form due to the electrostatic and hydrophobic interactions, and the effective diameter of the complex reduces with increasing 12-n-12 concentration. The microstructures of 12-n-12/NaPAA solution determined from fluorescence and electron microscopy measurements are in good agreement. The spacer length is found to play an important role in the interactions of 12-n-12 with NaPAA.
Co-reporter:Xia Han;Jian Xu;Ying Hu
Chinese Journal of Chemistry 2006 Volume 24(Issue 1) pp:149-152
Publication Date(Web):17 JAN 2006
DOI:10.1002/cjoc.200690013
The image contrast inversion was investigated in detail when soft polymeric materials were imaged with tapping mode atomic force microscopy (TM-AFM). Solvent cast film of polystyrene-block-poly(ethylene/butylene)-block-polystyrene (SEBS) triblock copolymers was used as a model system in this study, which showed phase separation domains with a size of several tens of nanometers. AFM contrast reversal process, through positive image, to an intermediary and till negative image, could be clearly seen in height images of the soft block copolymer using different tapping force. The higher tapping force would lead to not only contrast inversion, but also the different size of the microdomains and different roughness of the images. Moreover, contrast inversion was explained on the basis of attractive and repulsive contributions to the tip-sample interaction and indentation of the soft domains.
Co-reporter:Jianyong Yang, Changjun Peng, Honglai Liu, Ying Hu, Jianwen Jiang
Fluid Phase Equilibria 2006 Volume 244(Issue 2) pp:188-192
Publication Date(Web):20 June 2006
DOI:10.1016/j.fluid.2006.04.012
A generic molecular thermodynamic model is developed for linear and branched polymer solutions in a cubic lattice. The long-range correlations beyond the nearest-neighbor interaction sites are incorporated, which account for arbitrary coordination number of lattice and arbitrary degree of branching. A significant improvement is found from our model over Flory–Huggins theory and lattice-cluster theory in the predictions of phase equilibria. The model correctly predicts a reduced critical temperature, an increased critical composition, and a lower miscibility with enhanced degree of branching, as observed in simulation and experimental studies. The model also satisfactorily predicts the phase behavior of branched polystyrenes with different molecular weights and architectures in cyclohexane.
Co-reporter:Yongmin Huang;Honglai Liu;Ying Hu
Macromolecular Theory and Simulations 2006 Volume 15(Issue 2) pp:117-127
Publication Date(Web):3 FEB 2006
DOI:10.1002/mats.200500043
Summary: The morphologies and conformations of triblock copolymer (ABA and ABC) thin films confined between two identical walls were investigated by Monte Carlo simulation using bond length fluctuation and cavity diffusion algorithm on cubic lattice. Effects of the wall-block interactions, copolymer chain composition and film thickness on morphologies, as well as on the fraction of chain “bridge” conformation fbridge are presented in detail. In ABA thin film, column, parallel, perforated and perpendicular lamellas were discriminated, furthermore, the transition of morphology and the variation of fbridge of ABA film along with the increase of thickness were revealed. In ABC thin film, lamella especially perpendicular lamella morphologies are predominant in varying the wall-block interactions and the thickness. The results are consistent with some theoretical predictions such as DDFT and simulations reported in literature.
Co-reporter:Yongmin Huang;Honglai Liu;Ying Hu
Macromolecular Theory and Simulations 2006 Volume 15(Issue 4) pp:321-330
Publication Date(Web):2 MAY 2006
DOI:10.1002/mats.200500085
Summary: Using bond length fluctuation and cavity diffusion algorithm, the morphologies of diblock copolymer/homopolymer blend films, AB/C and AB/A, confined between two hard walls are studied via Monte Carlo (MC) simulation on a cubic lattice. For the AB/C film, the C homopolymer is supposed to be more compatible with the A block than with the B block, while A and B are mutually incompatible. Effects of the composition of the diblock copolymer/homopolymer mixture, the symmetry of the diblock copolymer chain, the film thickness and the selective wall field on morphologies are studied in detail. Furthermore, the simulated results are compared with that of corresponding ABA and ABC triblock copolymer thin films. Comparisons with experiments and SCF theory also show good agreement. The results indicate that both the AB/C and AB/A can be used to prepare porous AB diblock copolymer membranes, the size of the pore channel can be controlled by the volume fraction of homopolymer C or homopolymer A.
Co-reporter:Jian Feng;Ying Hu;Honglai Liu
Macromolecular Theory and Simulations 2006 Volume 15(Issue 9) pp:
Publication Date(Web):23 NOV 2006
DOI:10.1002/mats.200690016
Co-reporter:Jian Feng;Honglai Liu;Ying Hu
Macromolecular Theory and Simulations 2006 Volume 15(Issue 9) pp:674-685
Publication Date(Web):13 NOV 2006
DOI:10.1002/mats.200600042
Summary: The morphologies of diblock copolymers confined in a cylindrical tube have been investigated by the dissipative particle dynamics (DPD) method. Results indicate that the morphology depends on the volume ratio of the immiscible blocks, the diameter of the cylindrical tube and the interactions between the blocks and between the confinement wall and blocks. For symmetric diblock copolymers, when the tube wall is uniform toward the two blocks, perpendicular lamellae or a stacked disk morphology are generally formed except when the diameter of the cylindrical tube is very small; in that case, a special bi-helix morphology forms because of the entropy effect. When the tube wall is non-uniform, as the diameter of the tube increases, perpendicular lamellae are first formed, then changing to parallel lamellae and, finally, back to perpendicular lamellae again. An intermediate morphology characterizing the transition between perpendicular and parallel lamellae is observed. If the non-uniformity of the wall is further enhanced, only parallel lamellae can be found. In the case of asymmetric diblock copolymers, more complex morphologies can be obtained. Multi-cylindrical micro-domains and a multilayer helical phase as well as other complex pictures are observed. Generally, the morphologies obtained could find their counterparts from experiments or Monte Carlo simulations; however, differences do exist, especially in some cases of asymmetric diblock copolymers.
Co-reporter:Yingying Pi;Yazhuo Shang;Changjun Peng;Honglai Liu;Ying Hu;Jianwen Jiang
Biopolymers 2006 Volume 83(Issue 3) pp:
Publication Date(Web):7 JUN 2006
DOI:10.1002/bip.20552
Interactions between bovine serum albumin (BSA) and cationic gemini surfactant alkanediyl-α,ω-bis(dimethyldodecyl-ammonium bromide) (12-n-12, n = 3, 4, 6) in aqueous solution have been investigated by measuring fluorescence, UV-vis transmittance, dynamic lighting scattering, and circular dichroism. Compared to a traditional surfactant dodecyltrimethylammonium bromide (DTAB), 12-n-12 interacts with BSA more strongly. With increasing concentration, 12-n-12 first binds specifically onto BSA leading to the unfolding and aggregation of BSA, and the decrease in α-helix content; and then forms micelle-like complexes along the unfolded BSA chains. A gemini surfactant with a longer spacer has a larger effect on BSA unfolding due to a stronger hydrophobic interaction. © 2006 Wiley Periodicals, Inc. Biopolymers 83:243–249, 2006
This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Co-reporter:Yan-Qing Nan, Hong-Lai Liu, Ying Hu
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2006 Volume 277(1–3) pp:230-238
Publication Date(Web):5 April 2006
DOI:10.1016/j.colsurfa.2005.11.095
Aqueous systems containing 1,3-propanediyl bis(dodecyl dimethylammonium bromide) (12-3-12) and sodium dodecyl sulfonate (AS) can separate into a concentrated phase and a dilute phase at certain conditions. The composition analysis demonstrates that the 12-3-12/AS/water system must be treated as a quaternary with four independent components, the equality relations between 2m12−3−122+2m12−3−122+ and mBr−mBr−, mAS−mAS− and mNa+mNa+, are not held in general for the two separated phases. Tie lines are only possible to be described in a three-dimensional phase diagram. Microstructures of some concentrated phases in the phase-separated systems were determined by negative stained TEM method. For the concentrated bottom phase in aqueous two-phase system (ATPS) with water or 0.10 mol kg−1 NaF brine as solvent, vesicles are easy to form. Whereas in 0.10 mol kg−1 NaCl brine, irregular aggregates appear in the concentrated top phase of ATPS. The rheological behavior was examined indicating that the systems studied exhibit thixotropic, antithixotropic, or mixed thixotropic and antithixotropic depending on the compositions and microstructures. Effects of added sodium halide have also been studied.
Co-reporter:Xia Han;Jian Xu;Ying Hu;Honglai Liu
Macromolecular Rapid Communications 2005 Volume 26(Issue 22) pp:1810-1813
Publication Date(Web):3 NOV 2005
DOI:10.1002/marc.200500440
Summary: A unique and simple method to prepare films with various ordered nanoscopic cylindrical patterns on the surface is reported. Various solutions of gemini surfactants with different spacers were used as a nanotemplate, on which thick polymer films were fabricated by the supramolecular assembly of a native or chemically modified polystyrene-block-poly(ethylene/butylene)-block-polystyrene (SEBS) triblock copolymer. At the air/polymer surface, normal oriented cylindrical nanodomains formed by poly(ethylene/butylene) (PEB) block associates surrounded by polystyrene (PS) blocks are exhibited. While at the polymer/surfactant solution interface, parallel cylindrical nanodomains formed by PEB block stripes alternating with PS block stripes are observed. The ordered structure of the surface can be adjusted by changing the surfactant and the chemical nature of the polymer. In a special case using Gemini 16-1-Ph-1-16 and SEBS chemically modified with 2 wt.-% maleic anhydride, a nearly perfect hexagonal ordered structure is obtained.
Co-reporter:Changjun Peng;Jiankang Li;Honglai Liu;Ying Hu
Macromolecular Theory and Simulations 2005 Volume 14(Issue 3) pp:172-180
Publication Date(Web):30 MAR 2005
DOI:10.1002/mats.200400071
Summary: We have performed Monte Carlo simulations to study the bridging of symmetrical or asymmetrical triblock copolymers confined between two similar or different solid surfaces based on a simple lattice model. The influence of the molecular structure, surface separation, adsorption energy, chain composition, and the chain concentration on the fractions of chains with bridge, loop and dangling configurations are reported in detail. The results show that the largest bridging fraction is given only when symmetrical triblock copolymers are confined between two parallel surfaces with the same adsorption energy. The bridge fraction is decreased so long as the asymmetry of the copolymers or the difference between the two surfaces is enhanced. It was found also that the bridging fraction increases as the adsorption energy increases. The bridging fraction Ωbridge under different separations, Lz, can be expressed as in various situations. On the other hand, by introducing a symmetry index ν, the influence of molecular structure of copolymers on the bridges can be illustrated approximately by a relation when the two surfaces are similar and the adsorption energy is not too high. Combining the two expressions, data of the bridge fractions for copolymers of different symmetries confined between surfaces with different separations can be described with a single equation, which, in some occasion, can be used for prediction.
Co-reporter:Changjun Peng;Honglai Liu;Jiankang Li;Ying Hu
Macromolecular Theory and Simulations 2004 Volume 13(Issue 8) pp:711-723
Publication Date(Web):18 OCT 2004
DOI:10.1002/mats.200400028
Summary: Monte Carlo simulation on a simple lattice model has been used to study the adsorption of asymmetrical triblock copolymers from a non-selective solvent at the solid-liquid interface. The size distributions of train, loop and tail configurations for those copolymers are obtained as well as other details of the adsorption layer microstructure. Also the influence of adsorption energy and the role of molecular symmetry are investigated. A segment-density profile, the adsorption amount, the surface coverage, and the adsorption layer thickness have been determined. Finally, it is shown that the adsorption behavior of an asymmetrical copolymer can be predicted from the symmetrical copolymer.
Co-reporter:Ting Chen;Honglai Liu;Ying Hu;Lian Guo
Macromolecular Theory and Simulations 2003 Volume 12(Issue 2‐3) pp:153-162
Publication Date(Web):10 APR 2003
DOI:10.1002/mats.200390010
Thorough investigations on the adsorption of diblock copolymers from a non-selective solvent on solid surface have been performed by using Scheutjens-Fleer mean-field lattice theory. One main objective of this work is to make an in-depth comparison between the Scheutjens-Fleer theory (SF) and our previous simulation work. Although our study shows that there are some systematic deviations between theory and simulation, we still find that the calculations are in qualitative agreement with Monte Carlo (MC) simulation results. The theory can reproduce main features of diblock copolymer's adsorption as compared to the simulation. For instance, both theory and simulation correctly predict the appearance of a maximum in adsorption amount as a function of the adsorbing segment fraction in a chain when the total chain length is fixed. When the adsorption of diblock copolymer is relatively weak, the predictions made by the theory agree better with the simulation results. Being the first paper of a series, this article will focus on studying the adsorption information like segment density profiles, adsorption amount and isotherms, and adsorption layer thickness. The influence of adsorption energy, chain composition and bulk concentration on these adsorption properties was inspected by self-consistent-field theory and were further compared to MC simulation results. Also discussed are some other theoretical, simulation, and experimental results in the literature and their relationships with the conclusions derived from this work.
Co-reporter:Lian Guo;Ying Hu;Honglai Liu;Ting Chen
Macromolecular Theory and Simulations 2003 Volume 12(Issue 2‐3) pp:163-173
Publication Date(Web):22 APR 2003
DOI:10.1002/mats.200390019
Following our previous Monte Carlo simulation work on the adsorption of diblock copolymer from a non-selective solvent, the well-established Scheutjens-Fleer (SF) mean field theory is employed in this work to investigate the same system. Extensive comparisons between the Monte Carlo simulation and the SF theory are presented in two consecutive papers. In this second paper, the microstructure of adsorbed chains will be examined and discussed. After carefully inspecting various microstructure information including bound fraction, surface coverage, density profiles of the adsorbed segments corresponding to tails, loops and trains, and size distributions of these individual adsorption configurations, we observe that a systematic deviation between the theory and the simulation exists despite qualitative agreements between them. An in-depth investigation and discussion on the source and the degree of this kind of deviation has been presented after we inspected the effect of adsorption energy, chain composition f and bulk concentration on the adsorption layer properties. Our results further corroborate that the deviation between the SF theory and Monte Carlo simulation can be attributed to two major factors: the allowance of the direct chain back-folding and the random mixing approximation.
Co-reporter:Honglai Liu;Jie Feng;Ying Hu
Macromolecular Theory and Simulations 2002 Volume 11(Issue 5) pp:556-565
Publication Date(Web):28 JUN 2002
DOI:10.1002/1521-3919(20020601)11:5<556::AID-MATS556>3.0.CO;2-4
Microphase separation and morphology of asymmetric diblock copolymer (f = 0.4) thin films confined in a slit with surfaces neutral or attractive towards block A or block B were studied by the cell dynamic system method (CDS). The size effect in CDS calculations was carefully investigated. For asymmetric copolymers, the size effect is important even in the case of attractive walls. Not only must we use boxes with larger sizes in the X- and Y-directions, the size is also dependent on the film thickness. In contrast, for symmetric copolymers, the size effect is not serious when we adopt attractive plates. Various microdomain morphologies including regular lamellae adjacent to the surfaces, mesh-like layers with nanosized spheres dispersed in a matrix of block A, and flexuous cylindrical phases are found in this work. A series of conditions we can control, such as the chemical composition of the copolymer, the thickness of the film, the selective interactions between plates and blocks as well as their strength, all make the potential technology more adaptable. To test the reliability of the CDS method, the results are compared with those from dynamical density functional theory and Monte Carlo simulation.
Co-reporter:Jie Feng;Ying Hu;Honglai Liu
Macromolecular Theory and Simulations 2002 Volume 11(Issue 5) pp:549-555
Publication Date(Web):28 JUN 2002
DOI:10.1002/1521-3919(20020601)11:5<549::AID-MATS549>3.0.CO;2-X
The microphase separation and morphology of symmetric diblock copolymer thin films confined in a slit with neutral or attractive surfaces were studied by the cell dynamic system method (CDS) and Monte Carlo simulation. The size effect, especially in CDS, was carefully investigated indicating that excessively small sizes in the X- and Y-directions will give incorrect results although periodic boundary conditions are imposed. When the walls are neutral, parallel ordered lamella structure only exists over a short range, while irregular microdomain morphology occurs over the whole region. When directional quenching is applied, or the walls are attractive to one of the blocks, a periodical lamellar structure of alternating A-rich and B-rich layers occurs over the whole region of the film. Changing the slit width and the strength of interaction will influence the period and arrangement of lamellae. Agreement between the results from CDS and those from simulation is satisfactory indicating the reliability of the CDS method. Comparisons with corresponding experimental results are also discussed.
Co-reporter:Jun Li, Honglai Liu, Ying Hu
Fluid Phase Equilibria 2001 Volumes 187–188() pp:193-208
Publication Date(Web):15 September 2001
DOI:10.1016/S0378-3812(01)00535-0
A mutual-diffusion-coefficient model based on local-composition concept is developed. An expression for the calculation of concentration-dependent intra-diffusion coefficients is also established by considering the formation of clusters. With the import of diffusion coefficients at infinite dilution, self-diffusion coefficients and viscosities of pure components and mixtures, mutual-diffusion-coefficients of binary fluid mixtures can be predicted. The total average relative deviation of predicted values with respect to experimental data is 6.0% for 45 binary systems including those containing associative component. Results indicate that this model is superior to some currently used methods.
Co-reporter:Yujun ZHU, Jianhai ZHOU, Jun HU, Honglai LIU, Ying HU
Chinese Journal of Chemical Engineering (October 2011) Volume 19(Issue 5) pp:709-716
Publication Date(Web):1 October 2011
DOI:10.1016/S1004-9541(11)60047-5
Covalent organic framework (COF) is a porous material with low density and large BET (Brunauer-Emmett-Teller) surface area. They have great potential in gas adsorption and separation. In this work, the adsorption of pure CO2 and CO2/CH4 mixture on modified COF-102 was simulated by using GCMC (grand canonical Monte Carlo). Metal Li was incorporated into COF-102 through three doping methods, including charge exchange, O−-Li+ dipolar interaction and O−-Li+ chemical bonding. The influence of Li doping on the adsorption of CO2 was studied. The results showed that among the three methods, the dipole doping is the best way to improve CO2 adsorption performance. Further, the ligands of COF-102 were replaced by extended aromatic moieties, such as diphenyl and pyrene. The adsorption capacity of CO2 and CH4, and the selectivity of CO2/CH4 on the ligand-replaced COF-102 were studied. The capacity of CO2 and CH4 on the ligand-replaced COF-102 had obvious changes; hence the selectivity of CO2/CH4 can be adjusted accordingly.
Co-reporter:Yi XU, Jian FENG, Yazhuo SHANG, Honglai LIU
Chinese Journal of Chemical Engineering (August 2007) Volume 15(Issue 4) pp:560-565
Publication Date(Web):1 August 2007
DOI:10.1016/S1004-9541(07)60124-4
AbstractInteraction of anionic polyelectrolyte with cationic gemini surfactant has been investigated by coarse-grained molecular dynamics simulation. Polyelectrolyte facilitates the oppositely charged ionic surfactants to aggregate by suppressing the electrostatic repulsion between ionic head groups leading to the formation of micellar complex. With addition of surfactant, the conformation of polyion chain changes from stretched to random coiled to spherical, and at the same time more free micelles are formed by surfactants in mixtures. Increasing the length of spacer or tail chain in gemini surfactant will weaken its interaction with polyelectrolyte and simultaneously strengthen its tendency to self-assemble. The simulation results are consistent with experimental observations and reveal that the electrostatic interaction plays an important role in the interaction of polyelectrolyte with gemini surfactant.
Co-reporter:Jian FENG, Yazhuo SHANG, Lihui ZHOU, Honglai LIU, Ying HU
Chinese Journal of Chemical Engineering (April 2012) Volume 20(Issue 2) pp:231-238
Publication Date(Web):1 April 2012
DOI:10.1016/S1004-9541(12)60383-8
The driven polymer translocation through a nanopore with unbiased initial configuration has been studied by using Langevin dynamics (LD) simulations. It is found that the scaling relationship between translocation time and the polymer chain length is strongly affected by the friction coefficient in LD and the driving force. However, there is no scaling relationship between the translocation time and the friction coefficient. The translocation time is almost inversely proportional to the driving force, which is in agreement with those obtained in biased translocation. The scaling relationship between gyration radius (Rg) of subchain at the trans side with the subchain length (L) is Rg∼L0.33 that is in good agreement with the limiting value for molten globule state, while the curve of Rg of subchain at the cis side has two distinct stages. During translocation, the subchain at the cis side is being stretched gradually, and the structure of the subchain transforms from sphere-like to rod-like. When the effect of stretching reaches the tail end, the subchain is at the most stretched state. Finally the subchain will rapidly restore to coil structure. According to the results of force analysis, the retarding force at the trans side is more crucial during the practical translocation.
Co-reporter:Yu Liu, Fangyuan Guo, Jun Hu, Shuangliang Zhao, Honglai Liu and Ying Hu
Physical Chemistry Chemical Physics 2016 - vol. 18(Issue 34) pp:NaN24005-24005
Publication Date(Web):2016/07/29
DOI:10.1039/C6CP04645B
Entropy is an important thermodynamic property and serves as a bridge connecting equilibrium and non-equilibrium systems, which provides a basic understanding of various practical phenomena. In this study, classical density functional theory was introduced to efficiently predict entropy. The theory was applied to a high-throughput prediction of entropy and excess entropy for H2 adsorption in metal–organic frameworks. It seems that the entropy screening and uptake screening are generally equivalent at high temperature. Based on the entropy screening, the best hydrogen storage materials have been identified. The correlations between entropy and thermodynamic properties, such as uptake, isosteric heat and adsorption degree, were examined and are explained. The results imply that among the tested thermodynamic properties, the correlation between entropy and isosteric heat is the strongest.
Co-reporter:Yu Liu, Yazhuo Shang, Honglai Liu, Ying Hu and Jianwen Jiang
Physical Chemistry Chemical Physics 2012 - vol. 14(Issue 44) pp:NaN15405-15405
Publication Date(Web):2012/09/24
DOI:10.1039/C2CP42138K
A molecular thermodynamic model is developed to examine crowding effect on DNA melting. Each pair of nucleotides in double-stranded DNA and each nucleotide in single-stranded DNA are represented by two types of charged Lennard-Jones segments, respectively. Water molecules are mimicked explicitly as spherical particles, embedded in a dielectric continuum. Crowders with varying concentration, size, interaction strength, and chain length are considered. For DNA with a sequence of A20, the melting temperature is predicted to increase by 1 K in the presence of Ficoll70 and by 7.5 K in the presence of Ficoll70–polyvinyl pyrrolidone360 mixture. The predictions agree well with experimental data. Furthermore, the melting temperature is found to increase with increasing crowder size, but reduce with increasing interaction strength and crowder length. The predicted changes of Gibbs energy, entropy and enthalpy are consistent with experimentally measured values. The study reveals that DNA melting in a crowded environment is influenced by both entropic and enthalpic effects.
Co-reporter:Jianhai Zhou, Xiang Zhu, Jun Hu, Honglai Liu, Ying Hu and Jianwen Jiang
Physical Chemistry Chemical Physics 2014 - vol. 16(Issue 13) pp:NaN6083-6083
Publication Date(Web):2014/02/03
DOI:10.1039/C3CP55498H
A fully atomistic simulation study is reported to provide mechanistic insight into the superior performance experimentally observed for a polymer membrane (Carta et al., Science, 2013, 339, 303–307). The membrane namely PIM-EA-TB is produced by a shape-persistent ladder polymer of intrinsic microporosity (PIM) with rigid bridged bicyclic ethanoanthracene (EA) and Tröger's base (TB). The simulation reveals that PIM-EA-TB possesses a larger surface area, a higher fraction free volume and a narrower distribution of torsional angles compared to PIM-SBI-TB, which consists of less rigid spirobisindane (SBI). The predicted surface areas of PIM-EA-TB and PIM-SBI-TB are 1168 and 746 m2 g−1, close to experimental values of 1120 and 745 m2 g−1, respectively. For five gases (CO2, CH4, O2, N2 and H2), the solubility and diffusion coefficients from simulation match well with experimental data, except for H2. The solubility coefficients decrease in the order of CO2 > CH4 > O2 > N2 > H2, while the diffusion coefficients increase following CH4 < CO2 < N2 < O2 < H2. In terms of the separation for CO2/N2, CO2/CH4 and O2/N2 gas pairs, PIM-EA-TB exhibits higher permselectivities than PIM-SBI-TA, in good agreement with experiment. From a microscopic perspective, this simulation study elucidates that the presence of bridged bicyclic units in PIM-EA-TB enhances the rigidity of polymer chains as well as the capability of gas permeation and separation, and the bottom-up insight could facilitate the rational design of new high-performance membranes.
Co-reporter:Xiejun Xu, Xingqing Xiao, Shouhong Xu and Honglai Liu
Physical Chemistry Chemical Physics 2016 - vol. 18(Issue 36) pp:NaN25473-25473
Publication Date(Web):2016/08/16
DOI:10.1039/C6CP05145F
Recent experiments in our lab (Phys. Chem. Chem. Phys., 2016, 18, 10129–10137) suggested using leucine zipper peptides to enhance the thermosensitivity of liposomes. To understand the mechanisms of temperature-responsive control by the leucine zipper peptide in liposomes, we firstly performed quantum mechanics calculations and implicit-solvent replica exchange molecular dynamics simulations to study the thermo-stability of two leucine zipper peptides, CH3(CH2)4–CO–[VAQLEVK-VAQLESK-VSKLESK-VSSLESK] (termed the capped peptide) and A-[VAQLEVK-VAQLESK-VSKLESK-VSSLESK] (termed the ALA peptide). The analysis of dihedral angle principal components and protein secondary structures was conducted to determine the temperature-dependence conformation transition of the two peptides. Simulation results revealed that our computed transition temperature of the capped peptide is 319.1 K that accords with experimental measurement, 321.1 K. Later, explicit-solvent conventional molecular dynamics simulations were carried out to examine the process of folding and unfolding of the ALA and capped peptides complexed with a lipid bilayer and water in the vicinity of their transition temperatures. A further analysis of conformation and energy of the folded peptides showed that the increase of temperature gives rise to a notable decrease in the number of intra-chain hydrogen bonds and a significant increase in the potential energy of the peptides, thereby reducing the folding stability of the two peptides. As compared to the ALA peptide, a lower transition temperature caused by less intra-chain hydrogen bonds was observed in the capped peptide, which is closer to the temperature of tumor cells. This fact suggests that the capped peptide is more suitable to produce highly sensitive liposomes for the delivery of cancer drugs.
Co-reporter:Tian Jin, Yan Xiong, Xiang Zhu, Ziqi Tian, Duan-Jian Tao, Jun Hu, De-en Jiang, Hualin Wang, Honglai Liu and Sheng Dai
Chemical Communications 2016 - vol. 52(Issue 24) pp:NaN4457-4457
Publication Date(Web):2016/02/03
DOI:10.1039/C6CC00573J
We present a rational design and synthesis of a novel porous pyridine-functionalized polycarbazole for efficient CO2 capture based on the density functional theory calculations. The task-specific polymer, generated through a one-step FeCl3-catalyzed oxidative coupling reaction, exhibits a superior CO2 uptake at 1.0 bar and 273 K (5.57 mmol g−1).
Co-reporter:Sijia Wang, Yinxing Shen, Junqi Zhang, Shouhong Xu and Honglai Liu
Physical Chemistry Chemical Physics 2016 - vol. 18(Issue 15) pp:NaN10137-10137
Publication Date(Web):2016/03/11
DOI:10.1039/C6CP00378H
Thermo-sensitive drug carriers are receiving increasing attention for use with localized hyperthermia at abnormal tissue sites or to easily implement hyperthermia. In this study, a thermo-sensitive lipopeptide was designed, consisting of a carbon chain and a leucine zipper with an amino acid sequence CH3-(CH2)4-CO-NH-VAQLEVK-VAQLESK-VSKLESK-VSSLESK-COOH. They could form dimers by the hydrophobic force at body temperature and separate into single random coils above the melting temperature (Tm). The lipopeptide was mixed with phospholipids to form a hybrid liposome (Lipo-LPe). The Tm of the free lipopeptide and lipopeptide in Lipo-LPe was found to be 48.0 °C and 42.5 °C from circular dichroism data, respectively. Compared with the pure liposome, the phase-transition temperature (Ttr) of Lipo-LPe, which was obtained by differential scanning calorimetry, was increased by about 5 °C, showing an improvement of thermal stability. The drug release rate of Lipo-LPe was slightly decreased at body temperature but greatly increased at mild hyperthermia in vitro. Drug release under intermittent heating was performed, and the reversibility of thermo-sensitive on/off switch was confirmed. Furthermore, Lipo-LPe achieved the maximum amount of cell death under mild hyperthermia. We concluded that Lipo-LPe, as a novel thermo-sensitive drug carrier, provides a promising opportunity for controlling drug release.
Co-reporter:Xiang Zhu, Shannon M. Mahurin, Shu-Hao An, Chi-Linh Do-Thanh, Chengcheng Tian, Yankai Li, Lance W. Gill, Edward W. Hagaman, Zijun Bian, Jian-Hai Zhou, Jun Hu, Honglai Liu and Sheng Dai
Chemical Communications 2014 - vol. 50(Issue 59) pp:NaN7936-7936
Publication Date(Web):2014/05/02
DOI:10.1039/C4CC01588F
A porous triazine and carbazole bifunctionalized task-specific polymer has been synthesized via a facile Friedel–Crafts reaction. The resultant porous framework exhibits excellent CO2 uptake (18.0 wt%, 273 K and 1 bar) and good adsorption selectivity for CO2 over N2.
Co-reporter:Xiang Zhu, Chengcheng Tian, Tian Jin, Jitong Wang, Shannon M. Mahurin, Wenwen Mei, Yan Xiong, Jun Hu, Xinliang Feng, Honglai Liu and Sheng Dai
Chemical Communications 2014 - vol. 50(Issue 95) pp:NaN15058-15058
Publication Date(Web):2014/10/07
DOI:10.1039/C4CC07255C
Thiazolothiazole-linked porous organic polymers have been synthesized from a facile catalyst-free condensation reaction between aldehydes and dithiooxamide under solvothermal conditions. The resultant porous frameworks exhibit a highly selective uptake of CO2 over N2 under ambient conditions.
Co-reporter:Haiying Li, Bo Meng, Song-Hai Chai, Honglai Liu and Sheng Dai
Chemical Science (2010-Present) 2016 - vol. 7(Issue 2) pp:
Publication Date(Web):
DOI:10.1039/C5SC04034E
Co-reporter:Xiang Zhu, Yihua Zhu, Chengcheng Tian, Tian Jin, Xuejing Yang, Xianbo Jin, Chunzhong Li, Hualin Wang, Honglai Liu and Sheng Dai
Journal of Materials Chemistry A 2017 - vol. 5(Issue 9) pp:NaN4512-4512
Publication Date(Web):2017/01/11
DOI:10.1039/C6TA09604B
Developing new techniques for the synthesis of N-doped carbon nanotubes (N-CNTs) with high porosities and abundant N-doped active sites is significant for energy conversion and utilization. We report herein a novel non-CVD methodology that exploits a conjugated-nanoporous-polymer-driven, self-templated route toward a new family of highly N-doped carbon nanotubes. The utilization of a task-specific tubular nanoporous polycarbazole as a template maintains both high porosity and density of N-doped active sites, while simultaneously affording a hollow nanotube-like morphology of the final N-doped carbons. Attributed to these unique functionalities, the resultant N-CNT-based electrocatalyst exhibits a superior oxygen reduction reaction (ORR) activity with a half-wave potential of 0.88 V (vs. the reversible hydrogen electrode), higher long-term stability, and better methanol tolerance than commercial 20% Pt/C in alkaline media. More importantly, the ORR performance in an acidic medium exceeds that of the most previously reported non-precious carbonaceous catalysts. These findings could provide an alternative approach towards highly efficient non-precious N-CNT-based electrocatalysts for the ORR.
Co-reporter:Haiying Li, Bo Meng, Shannon M. Mahurin, Song-Hai Chai, Kimberly M. Nelson, David C. Baker, Honglai Liu and Sheng Dai
Journal of Materials Chemistry A 2015 - vol. 3(Issue 42) pp:NaN20918-20918
Publication Date(Web):2015/08/18
DOI:10.1039/C5TA03213J
Recently, microporous organic polymers, especially those hyper-crosslinked from functionalized aromatic monomers, have been shown to be effective for CO2 capture and storage with considerable capacity and selectivity. Herein, a class of novel microporous hyper-crosslinked polymers (HCPs), based on green and renewable carbohydrates, was synthesized by Friedel–Crafts alkylation for carbon capture and storage by hydrogen bonding and dipole–quadrupole interactions. These carbohydrate polymers, which have BET surface areas around 800 m2 g−1, can absorb a considerable amount of CO2 with the CO2/N2 selectivity up to 42 at 273 K, and 96 under 100 kPa in the mixed gases (0.15 mol CO2 and 0.85 mol N2). Furthermore, we experimentally and computationally studied the structures of carbohydrate backbones and determined several features that govern their CO2 absorption ability, which sheds light on understanding the structure/function relationship for designing better CO2 separation materials.
Co-reporter:Cheng Lian, Alejandro Gallegos, Honglai Liu and Jianzhong Wu
Physical Chemistry Chemical Physics 2017 - vol. 19(Issue 1) pp:NaN457-457
Publication Date(Web):2016/11/17
DOI:10.1039/C6CP07124D
Ionic transport through nanopores is of fundamental importance for the design and development of nanofiltration membranes and novel electrochemical devices including supercapacitors, fuel cells and batteries. Recent experiments have shown an unusual variation of electrical conductance with the pore size and the electrolyte parameters that defies conventional scaling relations. Here ionic transport through voltage-gated nanopores was studied by using the classical density functional theory for ion distributions in combination with the Navier–Stokes equation for the electroosmotic flow. We identified a significant influence of the gating potential on the scaling behavior of the conductance with changes in the pore size and the salt concentration. For ion transport in narrow pores with a high gating voltage, the conductivity shows an oscillatory dependence on the pore size owing to the strong overlap of electric double layers.
Co-reporter:Fei Gao, Yankai Li, Zijun Bian, Jun Hu and Honglai Liu
Journal of Materials Chemistry A 2015 - vol. 3(Issue 15) pp:NaN8097-8097
Publication Date(Web):2015/03/03
DOI:10.1039/C4TA06645F
For the real industrial process of CO2 capture, it is still a great challenge for adsorbents to exhibit excellent CO2 adsorption capacity in the presence of water. By combining a pre-seeding process and a two-step temperature controlling crystallization, a zeolitic imidazolate framework (ZIF-8) shell is introduced on the commercial zeolite adsorbent (5A) core to produce a series of 5A@ZIF-8 composites with an enhanced surface hydrophobicity. Each 5A@ZIF-8 composite exhibits a dynamic hydrophobic hindrance effect for the separation of CO2 from the simulated humid flue gas (15% CO2 and 90% humidity at 298 K). Among these, the CO2 adsorption capacity and the CO2/H2O selectivity of 5A@ZIF-8(I) can be as high as 2.67 mmol g−1 and 6.61, respectively, at the optimized adsorption time of 10 min. More importantly, over 10 adsorption–desorption cycles, there is almost no degradation of the adsorption performance. Therefore, the novel strategy of utilizing the dynamic hydrophobic hindrance effect through a core–shell structure would be a good solution for improving the CO2 separation performance in practical applications.
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