Co-reporter:Chen Zhang, Ye Sha, Yue Zhang, Ting Cai, Linling Li, Dongshan Zhou, Xiaoliang Wang, and Gi Xue
The Journal of Physical Chemistry B November 30, 2017 Volume 121(Issue 47) pp:10704-10704
Publication Date(Web):November 7, 2017
DOI:10.1021/acs.jpcb.7b08545
The production and stabilization of amorphous drugs by the nanoconfinement effect has recently become a research hotspot in pharmaceutical sciences. Herein, two guest/host systems, indomethacin (IMC) and griseofulvin (GSF) confined in anodic aluminum oxide (AAO) templates with different pore diameters (25–250 nm) are investigated by differential scanning calorimetry (DSC) and broadband dielectric spectroscopy (BDS). The crystallization of the confined drugs is suppressed, and their glass transition temperatures show an evident pore-size dependency. Moreover, a combination of dielectric and calorimetric results demonstrates that the significant change in the temperature dependence of the structural relaxation time during the cooling process is attributed to the vitrification of the interfacial molecules and the local density heterogeneity under isochoric confinement. Interestingly, compared with the case of IMC/AAO, which can be described by a typical two-layer model, GSF/AAO presents an rare scenario of three glass transition temperatures under fast cooling (40–10 K/min), indicating that there exists a thermodynamic nonequilibrium interlayer between the bulk-like core and interfacial layer. In contrast, the slow cooling process (0.5 K/min) would lead confined GSF into the stable core–shell nanostructure. Using surface modification, the interfacial effect is confirmed to be an important reason for the different phenomena between these two guest/host systems, and intermolecular hydrogen bonding is also suggested to be emphasized considering the long-range effect of interfacial interactions. Our results not only provide insight into the glass transition behavior of geometrically confined supercooled liquids, but also offer a means of adjusting and stabilizing the nanostructure of amorphous drugs under two-dimensional confinement.
Co-reporter:Linling Li, Jingwen Liu, Linlin Qin, Chen Zhang, Ye Sha, Jing Jiang, Xiaoliang Wang, Wei Chen, Gi Xue, Dongshan Zhou
Polymer 2017 Volume 110(Volume 110) pp:
Publication Date(Web):10 February 2017
DOI:10.1016/j.polymer.2016.12.081
•Fractionated crystallizations initiated by heterogeneous and homogeneous nucleation for sPP in large AAO nanopores are observed.•A systematic study of how cooling rate affects the crystallization of sPP confined in nanopores is presented.•Crystallization kinetics of sPP located inside nanopores is investigated by an isothermal step crystallization technique.•Both of the nuclei density and secondary nucleation rate are found to decrease for sPP in nanopores.Crystalline polymers can exhibit anomalous crystallization behaviors as restricted into nanodomains. Herein, syndiotactic polypropylene (sPP) was infiltrated into nanoporous alumina templates with different pore diameters, and their nonisothermal and isothermal crystallization kinetics were investigated. As located inside nanopores, the crystallization of sPP becomes sluggish. The crystallization temperatures reveal a pronounced cooling rate dependence for sPP in large nanopores. At fast cooling rates, the homogeneous nucleation is dominated. While, at slow cooling rates, the splits of crystallization peaks can be ascribed to fractionated crystallizations initiated by heterogeneous and homogeneous nucleation, respectively. For sPP in small nanopores, the homogeneous nucleation always predominates, which induces less cooling rate effect. In addition, based on the Avrami equation and Lauritzen-Hoffman growth theory, isothermal crystallization experiments indicate that the characteristic crystallization times of sPP under confinement are much longer, and both of the nuclei density and secondary nucleation rate are decreased for sPP confined in nanopores.Download high-res image (250KB)Download full-size image
Co-reporter:Guoqing Chang, Aike Li, Xiaoqian Xu, Xiaoliang Wang, and Gi Xue
Industrial & Engineering Chemistry Research 2016 Volume 55(Issue 25) pp:7048-7051
Publication Date(Web):June 16, 2016
DOI:10.1021/acs.iecr.6b00686
Twisted polymer microfiber/nanofiber yarns were manufactured by using a direct twisted electrospinning method. Compared with typical electrospinning setup, a significant difference in this method was that a high-speed motor was used to induce the spinneret tip with relatively short collecting distance at the electrospinning process. Two types of polymer self-bundling yarns were prepared successfully: poly(vinylpyrrolidone) and poly(ether sulfones). The collecting distance was a very important factor to achieve twisted polymer microfiber/nanofiber yarns from ejected fiber bundles by this self-bundling and rotating electrospinning method. In addition, the possible mechanism for the self-bundling formation of twisted microfiber/nanofiber yarn was proposed.
Co-reporter:Ye Sha;Qing Zhu;Yuanxin Wan;Linling Li;Xiaoliang Wang;Dongshan Zhou
Journal of Polymer Science Part A: Polymer Chemistry 2016 Volume 54( Issue 15) pp:2413-2420
Publication Date(Web):
DOI:10.1002/pola.28116
ABSTRACT
A new type of chain transfer agent used in reversible addition fragmentation chain transfer (RAFT) polymerization named 9-anthracenylmethyl (4-cyano-4-(N-carbazylcarbodithioate) pentanoate) (ACCP) was synthesized with a total yield over 75% by the incorporation of both fluorescent donor and acceptor chromophores. Polymerization of heterotelechelic α,ω end-labeled dye-functionalized polystyrene (PS), poly(methyl methacrylate) (PMMA), and poly(n-butyl methacrylate) (PBMA) with adjustable molecular weights and narrow polydispersity could be conducted by a one-pot procedure through RAFT polymerization with this bischromophore chain transfer agent. The polymerizations demonstrated “living” controlled characteristics. By taking advantage of the characteristic fluorescence resonance energy transfer (FRET) response between the polymer chain terminals, the variation of chain dimensions in solution from the dilute region to the semidilute region can be monitored by changes in the ratio of the fluorescence intensities of the carbazolyl group to the anthryl group, which lends itself to potential applications in characterizing chain dimensions in solutions for thermodynamic or dynamic studies. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2413–2420
Co-reporter:Ye Sha, Yunlong Xu, Dongliang Qi, Yuanxin Wan, Linling Li, Hong Li, Xiaoliang Wang, Gi Xue, and Dongshan Zhou
Macromolecules 2016 Volume 49(Issue 21) pp:8274-8281
Publication Date(Web):October 20, 2016
DOI:10.1021/acs.macromol.6b01726
We report on the synthesis of heterotelechelic α,ω-dye-labeled polystyrene and poly(methyl methacrylate) via a combination of site-specific atom transfer radical polymerization (ATRP) and click chemistry. By using the advantages of the living polymerization characteristics and a robust coupling efficiency, the Förster/fluorescence resonance energy transfer (FRET) pairs (i.e., carbazolyl and anthryl) were dictated to be at the near-stoichiometric chain ends. The distribution of the end-to-end distance was well described by the energy transfer response of the fluorescent groups between chain ends, which is in reasonable agreement with Gaussian statistics. The synthetic approach described here provides an opportunity to prepare polymeric materials with customized responsive elements and in-depth insight into the statistical scaling dimension of polymers.
Co-reporter:Yuanxin Wan, Ye Sha, Shaochuan Luo, Weijia Deng, Xiaoliang Wang, Gi Xue, Dongshan Zhou
Journal of Power Sources 2015 Volume 295() pp:41-46
Publication Date(Web):1 November 2015
DOI:10.1016/j.jpowsour.2015.06.125
•Ultrasmall tin dioxide nanoparticles constrained in graphene gel: SnO2@GG.•SnO2@GG composite is prepared by a facile one-pot strategy.•The graphene framework provides large void space and good conductivity.•This composite exhibits an excellent electrochemical performance.Tin dioxide (SnO2) is an attractive material for anodes in energy storage devices, because it has four times the theoretical capacity of the prevalent anode material (graphite). The main obstacle hampers SnO2 from practical application is the pulverization problem caused by drastic volume change (∼300%) during lithium-ion insertion or extraction, which would lead to the loss of electrical conductivity, unstable solid-electrolyte interphase (SEI) formation and consequently severe capacity fading in the cycling. Here, we anchored the SnO2 nanocrystals into three dimensional graphene gel network to tackle this problem. As a result of the three dimensional (3-D) architecture, the huge volume change during cycling was tolerated by the large free space in this 3-D construction, resulting in a high capacity of 1090 mAh g−1 even after 200 cycles. What's more, at a higher current density 5 A g−1, a reversible capacity of about 491 mAh g−1 was achieved with this electrode.
Co-reporter:Yuanxin Wan, Ye Sha, Weijia Deng, Qing Zhu, Zhen Chen, Xiaoliang Wang, Wei Chen, Gi Xue, Dongshan Zhou
Electrochimica Acta 2015 Volume 167() pp:69-74
Publication Date(Web):10 June 2015
DOI:10.1016/j.electacta.2015.03.042
Tin dioxide (SnO2) is one of the most promising anode materials for the next generation Li-ion batteries due to its high capacity. To solve the problems caused by the large volume change (over 300%) and the aggregation of the tin particles formed during cycling, nano SnO2/C composites are proved to be ideal anode materials for high performance Li-ion batteries. However, it is still a challenge to disperse ultrasmall (<6 nm) SnO2 nanoparticles with uniform size in carbon matrix. Here, we report a facile hydrothermal way to get such optimized nano SnO2/C composite, in which well dispersed ultrasmall SnO2 nanocrystals (3∼5 nm) are embedded in a conductive carbon matrix. With this anode, we demonstrate a high stable capacity of 928 mAh g−1 based on the total mass of the composite at a current density of 500 mA g−1. At high current density of 2 A g−1, this composite anode shows a capacity of 853 mAh g−1 in the first charge, in such high current density, we can even get a capacity retention of more than 91% (779 mAh g−1) after 1000 cycles.
Co-reporter:Xuena Zhang, Rong Wang and Gi Xue
Soft Matter 2015 vol. 11(Issue 13) pp:2706-2706
Publication Date(Web):04 Mar 2015
DOI:10.1039/C5SM90046H
Correction for ‘Programming macro-materials from DNA-directed self-assembly’ by Xuena Zhang et al., Soft Matter, 2015, 11, 1862–1870.
Co-reporter:Xuena Zhang, Rong Wang and Gi Xue
Soft Matter 2015 vol. 11(Issue 10) pp:1862-1870
Publication Date(Web):05 Feb 2015
DOI:10.1039/C4SM02649G
DNA is a powerful tool that can be attached to nano- and micro-objects and direct the self-assembly through base pairing. Since the strategy of DNA programmable nanoparticle self-assembly was first introduced in 1996, it has remained challenging to use DNA to make powerful diagnostic tools and to make designed materials with novel properties and highly ordered crystal structures. In this review, we summarize recent experimental and theoretical developments of DNA-programmable self-assembly into three-dimensional (3D) materials. Various types of aggregates and 3D crystal structures obtained from an experimental DNA-driven assembly are introduced. Furthermore, theoretical calculations and simulations for DNA-mediated assembly systems are described and we highlight some typical theoretical models for Monte Carlo and Molecular Dynamics simulations.
Co-reporter:Xiaoqian Xu, Yuanxin Wan, Ye Sha, Weijia Deng, Gi Xue and Dongshan Zhou
RSC Advances 2015 vol. 5(Issue 108) pp:89092-89098
Publication Date(Web):20 Oct 2015
DOI:10.1039/C5RA16460E
A composite of nanoporous iron oxide (Fe2O3) nanoparticles coated with a thin layer of carbon (designated as nanoporous Fe2O3@C) is synthesized using a convenient one-pot solvothermal method. Although the thickness of the carbon framework is only 6 nm on average, which is very small compared to the size of Fe2O3 nanoparticles, the carbon framework significantly enhances the electrochemical performance of nanoporous Fe2O3@C composites when they are used as an anode material for lithium-ion batteries. Thanks partly to the relatively low carbon content of 6.7 wt%, the nanoporous Fe2O3@C anodes exhibit a high reversible capacity of 767 mA h g−1 after 100 cycles at a current density of 500 mA g−1 and 545 mA h g−1 even at a higher current density of 2 A g−1. In comparison to commercial Fe2O3 nanoparticles and bare nanoporous Fe2O3 nanoparticles, the nanoporous Fe2O3@C anodes show superior cycle life. The nanoporous structure offers void space for volume change of Fe2O3 nanoparticles, while the thin carbon framework improves the stability of structures and SEI (solid electrolyte interphase) films during the continuous intercalation/deintercalation processes of Li ions.
Co-reporter:Lili Zhu, Xiaoliang Wang, Qiang Gu, Rongchun Zhang, Tianxiong Ju, Yong Wang, Pingchuan Sun, Gi Xue
Polymer 2015 Volume 77() pp:14-20
Publication Date(Web):23 October 2015
DOI:10.1016/j.polymer.2015.09.013
•The surfactant may be introduced to the surface of gold nanoparticles by synthesis methods.•Solid state NMR was efficient to characterize the residual surfactant.•The surfactant was found to cause decrease in the Tg of polystyrene on gold nanoparticles.The adsorbed species on nanofillers is one of the most important factors that may influence the performance of polymer nanocomposites. Herein, we performed a systematic investigation of the effects of the residual surfactant introduced by a synthetic method on the glass transition temperature (Tg) of polystyrene/gold nanoparticle nanocomposites. The surfactant was found to cause an obvious decrease in the Tg of polystyrene confined on gold. Furthermore, we used dipolar-filtered 1H solid-state nuclear magnetic resonance to characterize the mobility of the molecules confined on gold. It was impossible to completely remove the surfactant once it had been adsorbed on the gold nanoparticles; thus it is important to choose suitable methods of synthesis, and special attention should be paid to the adsorbed species on nanofillers.
Co-reporter:Linling Li, Jiao Chen, Weijia Deng, Chen Zhang, Ye Sha, Zhen Cheng, Gi Xue, and Dongshan Zhou
The Journal of Physical Chemistry B 2015 Volume 119(Issue 15) pp:5047-5054
Publication Date(Web):March 25, 2015
DOI:10.1021/jp511248q
The glass transitions of poly(methyl methacrylate) (PMMA) oligomer confined in alumina nanopores with diameters much larger than the polymer chain dimension were investigated. Compared with the case of 80 nm nanopores, PMMA oligomer confined in 300 nm nanopores shows three glass transition temperatures (from from low to high, denoted as Tg,lo, Tg,inter, and Tg,hi). Such phenomenon can be interpreted by a three-layer model: there exists an interphase between the adsorbed layer and core volume called the interlayer, which has an intermediate Tg. The behavior of multi-Tg parameters is ascribed to the propagation of the interfacial interaction during vitrifaction process. Besides, because of the nonequilibrium effect in the adsorbed layer, the cooling rate plays an important role in the glass transitions: the fast cooling rate generates a single Tg; the intermediate cooling rate induces three Tg values, while the ultraslow cooling rate results in two Tg values. With decreasing the cooling rate, the thickness of interlayer would continually decrease, while those of the adsorbed layer and core volume gradually increase; meanwhile, the Tg,lo gradually increases, Tg,inter almost stays constant, and the Tg,hi value keeps decreasing. In such a process, the dynamic exchanges between the interlayer and adsorbed layer, core volume should be dominant.
Co-reporter:Gi Xue
Science China Materials 2015 Volume 58( Issue 12) pp:911-912
Publication Date(Web):2015 December
DOI:10.1007/s40843-015-0106-6
The problems to efficiently and robustly pack the objects together have been studied for centuries due to their mathematic aesthetics and direct applications to understand the myriad phase structures compacted from spherical metallic atoms to other polyhedral building blocks. For the simplest polyhedron, rigid tetrahedra were shown to form crystalline and quasi-crystalline phases by analytical calculations or computer simulations if only packing or shape entropy dominates the free energy. However, related experimental observations of the structures or their formation mechanisms are remained largely unexplored, possibly mainly due to two reasons: firstly, enthalpy interaction in real system cannot be ruled out as in modeling, and secondly, precise control of the shape and tuning of the enthalpy interaction of the building blocks are so far extremely challenging experimentally. Recently, Prof. Stephen Z. D. Cheng from University of Akron and his collaborators including Dr. Wen-Bin Zhang from Peking University have represented a rigorous work to show how to control the selective assembly of a class of nanosized giant tetrahedra by precisely mediating the interactions between the tetrahedra and the overall molecular geometry.
Co-reporter:Jie Xu, Ying Diao, Dongshan Zhou, Yisha Mao, Gaurav Giri, Wei Chen, Nan Liu, Stefan C. B. Mannsfeld, Gi Xue and Zhenan Bao
Journal of Materials Chemistry A 2014 vol. 2(Issue 16) pp:2985-2991
Publication Date(Web):29 Jan 2014
DOI:10.1039/C3TC32581D
In organic thin film transistors (OTFTs), the molecular structure of the first few monolayers at the semiconductor–dielectric interface is crucial to the device performance. The assumption of homogeneous molecular packing throughout the thickness of the film is not always valid considering interfacial effects. However, it remains challenging to unambiguously determine the molecular packing at both the top surface and the buried bottom interface, due to the lack of a nanoscopic tool. Here we show that a combination of Raman spectroscopy and surface enhanced Raman scattering (SERS) provides a means for effective characterization of the interfacial packing in 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene) films. We observed that the TIPS-pentacene crystal lattices assume a non-equilibrium packing state near the substrate interface, which gradually relaxes towards equilibrium packing near the top interface. Our investigation suggests the existence of non-equilibrium molecular packing for TIPS-pentacene.
Co-reporter:Linling Li, Dongshan Zhou, Dinghai Huang, and Gi Xue
Macromolecules 2014 Volume 47(Issue 1) pp:297-303
Publication Date(Web):December 26, 2013
DOI:10.1021/ma4020017
Recently, confinement of polymers with different geometries has become a research hotspot. Here, we report the dramatic deviation of glass transition behaviors of poly(methyl methacrylate) (PMMA) confined in cylindrical nanopores with diameter significantly larger than chain’s radius of gyration (Rg). Fast cooling a PMMA melt in the nanopores results in a glass with one single glass transition temperature (Tg). But two distinct Tgs are detected after slow cooling the melt. The deviation in Tg could be as large as 45 K. This phenomenon is interpreted by a two-layer model. During vitrification under slow cooling two distinct layers are formed: a strongly constrained interfacial layer showing an increased Tg as compared to that of the bulk polymer and a core with a decreased Tg. By thermal annealing experiments, we find that these two Tgs are inherently correlated. In addition, the deviation of Tg for PMMA confined in nanopores reveals a dependence on molecular weight.
Co-reporter:Linling Li, Xiaoliang Wang, Dongshan Zhou, Chao Teng, Qing Sun, and Gi Xue
Macromolecules 2014 Volume 47(Issue 6) pp:2131-2139
Publication Date(Web):March 10, 2014
DOI:10.1021/ma402200d
We investigated the diffusion behavior of polystyrene/poly(2,6-dimethyl-1,4-phenylene oxide) (PS/PPO) nanoparticles mixture prepared by the nanoprecipitation method. The diffusion experiments of liquid PS into the glassy PPO matrix (l-PS/g-PPO) were conducted by annealing the PS/PPO mixture at temperatures between the glass transition temperatures (Tgs) of the PS and PPO components. By tracing the Tg evolution of the PS-rich domain behind the diffusion front, we obtained the master curve of PS volume fraction during diffusion by time–temperature superposition (TTS) and studied the diffusion mechanism of the l-PS/g-PPO system based on the core–shell model. As there is ongoing debate on the diffusion mechanism for the liquid/glassy polymers interdiffusion, herein we confirm that the diffusion behavior of PS/PPO nanoparticles mixture follows the characteristics of the Fickean mechanism rather than the case II mechanism. Both of the shift factors (aT) and the diffusion coefficients in the initial (Dinitial) obey the Arrhenius equation, which yield almost the same apparent activation energy (Edf) (about 153.6 kJ/mol). As the PS/PPO nanoparticles mixture is a limited liquid supply system, both of the calorimetric and rheological measurements reveal the departure in the time scaling laws, which corresponds to the change of PS chain dynamics from the reptation type to the Rouse type during the diffusion process.
Co-reporter:Ye Sha, Linling Li, Xiaoliang Wang, Yuanxin Wan, Jie Yu, Gi Xue, and Dongshan Zhou
Macromolecules 2014 Volume 47(Issue 24) pp:8722-8728
Publication Date(Web):December 2, 2014
DOI:10.1021/ma5017715
The dynamics of poly(n-butyl methacrylate) confined in porous anodic aluminum oxide (AAO) templates are investigated using differential scanning calorimetry (DSC) and fluorescence nonradiative energy transfer (NRET). Two glass transition temperatures (Tg,low and Tg,high) are obtained at higher infiltration temperatures via capillary force followed by slow cooling. Tg,low resembles the Tg of the bulk phase and represents the transition of the core layer. Tg,high represents the transition of the adsorbed layer in the confined polymer glass. The temperature threshold to form one or two glass transitions is determined by adjusting the infiltration temperatures and the pore diameters. It is shown that the adsorbed layer has increased interchain proximity relative to the bulk. In addition, the glass transition behavior is hypothesized to be mediated by the counterbalance of the size and interfacial effects in the confined space. The easily synthesized core–shell nanofibers with one glassy and one rubbery component without the need for block polymers have promising potential for use in several processing strategies.
Co-reporter:Jie Xu, Lei Ding, Jiao Chen, Siyang Gao, Linling Li, Dongshan Zhou, Xiang Li, and Gi Xue
Macromolecules 2014 Volume 47(Issue 18) pp:6365-6372
Publication Date(Web):September 15, 2014
DOI:10.1021/ma500864k
The perspective by Ediger and Forrest stated that, while we know that the dynamics of polymers in ultrathin films can be significantly altered by substrate interfaces, our understanding of how this depends on the polymer structure and the particular interfaces is rudimentary. Here, we show that fluorescence nonradiative energy transfer (NRET) is an extremely sensitive method for characterizing the interfacial adsorption of polystyrene onto silicon dioxide, even though their interaction is often suggested to be weak. We observed that tensile stress was generated in the supported film by substrate adsorption, which imposes constraints on molecular motion and prevents a reduction of the glass transition temperature (Tg). Furthermore, our investigation suggests that modifying the surface chemistry of the substrate can change the film conformation and dynamics when the film is thinner than 40 nm.
Co-reporter:Liang Yang, Zhaoqun Wang, Yucheng Ji, Jianing Wang, and Gi Xue
Macromolecules 2014 Volume 47(Issue 5) pp:1749-1756
Publication Date(Web):February 28, 2014
DOI:10.1021/ma402364r
The fabrication of graphene-based polymer composite materials is of interest and significance from an academic and an application viewpoint. The widely used method to obtain such composites was liquid-phase blend of graphene nanosheets (GNSs) and polymer solutions followed by casting or heat pressing. Until now, the challenge of dispersing the GNSs uniformly in the polymer matrix to form controllable and regular structure still remains. Here, we developed a unique “particle-constructing” method for fabricating highly ordered 3D graphene-based polymer composite materials, throughout which the GNSs formed intact, uniform and well-defined network structure. The strategy contains two steps: wrapping polymer microspheres with GNSs and mold-compressing them at room temperature, followed by an appropriate heat treatment. The composite materials exhibited outstanding electrical properties involving extremely low percolation threshold and much higher conductivity. The method can be easily extended to fabricate highly ordered GNS aerogels and more GNS-based composite materials. The results represent an important step toward developing GNS-based composite materials with high performance.
Co-reporter:Jiao Chen, Linling Li, Dongshan Zhou, Jie Xu, and Gi Xue
Macromolecules 2014 Volume 47(Issue 10) pp:3497-3501
Publication Date(Web):May 12, 2014
DOI:10.1021/ma500188b
It was reported that glass transition temperature (Tg) measured by differential alternating current (ac) chip calorimetry showed little thickness dependence for polymer films. Here we demonstrate the detection of Tg in thin films by ac-chip calorimeter and show that Tg is decreased as the thickness is reduced for oligomers and star-shaped polymers, as compared with their long linear analogues. The deviation range is a few to more than ten Kelvin. Such a depression in Tg is quite pronounced for ac-chip calorimetric measurement at a high frequency of 10 Hz. We argue that the perturbation in the increased interfacial free volume for spin-cast oligomers and dendrimers is the major reason for increasing segmental dynamics for ultrathin films.
Co-reporter:Yang Liu, Rongchun Zhang, Xiaoliang Wang, Pingchuan Sun, Wei Chen, Jianyi Shen, Gi Xue
Polymer 2014 Volume 55(Issue 12) pp:2831-2840
Publication Date(Web):6 June 2014
DOI:10.1016/j.polymer.2014.04.037
Hydrogenation has been proved to be an efficient way to remove the toxicity of phthalate plasticizer. However, other influences of this hydrogenation are still unknown. Here we chose di-2-ethylhexyl phthalate (DOP) and di(2-ethylhexyl) cyclohexane-1,2-dicarboxylate (DEHHP) to study the influence on interaction with poly(vinyl chloride) (PVC). By combining experiment and calculation, we found the interaction was stronger in PVC/DEHHP than in PVC/DOP. Low-Field 1H NMR results showed that PVC chains could restrict much more DEHHP molecules than DOP. FTIR results showed that the interaction exists in form of hydrogen bonding complex, and it was stronger in PVC/DEHHP than in PVC/DOP system. Combined with FTIR results, theoretical calculation results revealed the three-center hydrogen bonded structure of the complex. Both the proportion and the binding energy of pre-complex in DEHHP are much larger than in DOP. Here, the hydrogenation-induced change of interaction was elucidated systematically and could be generalized to other phthalate plasticizers.
Co-reporter:Chunhong Yu ; Lili Zhu ; Rongchun Zhang ; Xiaoliang Wang ; Chengchen Guo ; Pingchuan Sun
The Journal of Physical Chemistry C 2014 Volume 118(Issue 19) pp:10434-10440
Publication Date(Web):April 21, 2014
DOI:10.1021/jp501020k
In this article, we characterized the polymeric gold(I) thiolates that precipitated from the intermediate solutions during the synthesis process of gold nanoparticles (GNPs) by the Brust–Schiffrin two-phase method and investigated the formation mechanism of the polymeric gold(I) thiolates. The solution 1H NMR confirmed the complete reduction from Au(III) to Au(I) with the addition of the first two equivalents of thiols, while only the third and fourth equivalents of thiols were found to participate in forming gold(I) thiolates. Gold(I) thiolates, [Au(I)SR]n, precipitated from these solutions were further characterized by 1H solid-state NMR spectroscopy under fast magic angle spinning (MAS), Raman spectroscopy, and thermogravimetric analysis. Further quantitative studies revealed that the composition of [Au(I)SR]n could be controlled by changing the order of addition of the third and fourth equivalents of thiols. This work has great significance to better understand the mechanism of gold nanoparticle formation and thus to tailor the properties of the final products.
Co-reporter:Lili Zhu, Qiang Gu, Pingchuan Sun, Wei Chen, Xiaoliang Wang, and Gi Xue
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 20) pp:10352
Publication Date(Web):September 23, 2013
DOI:10.1021/am403449j
Understanding interfacial water behavior is essential to improving our understanding of the surface chemistry and interfacial properties of nanomaterials. Here using 1H solid-state nuclear magnetic resonance (1H SSNMR), we successfully monitored ligand exchange reaction between oleylamine (OLA) and adsorbed water on titanium dioxide nanoparticles (TiO2 NPs). Three different types of interfacial waters with different reactivities were distinguished. The mobility of the adsorbed water molecules was characterized by dipolar filtered 1H SSNMR. Our experimental results demonstrate that the adsorbed water can be categorized into three different layers: (i) rigid water species with restricted mobility closest to the surface of TiO2 NPs, (ii) less mobile water species weakly confined on TiO2 NPs, and (iii) water molecules with high mobility. Water in the third layer could be replaced by OLA, while water in the first and second layers remained intact. The finding that the interfacial water with the highest mobility has the strongest reactivity has guiding significance for tailoring the hydrophilic and hydrophobic properties of TiO2 NPs.Keywords: 1H solid-state NMR; interfacial water; TiO2 nanoparticles;
Co-reporter:Lili Zhu, Chen Zhang, Chengchen Guo, Xiaoliang Wang, Pingchuan Sun, Dongshan Zhou, Wei Chen, and Gi Xue
The Journal of Physical Chemistry C 2013 Volume 117(Issue 21) pp:11399-11404
Publication Date(Web):May 6, 2013
DOI:10.1021/jp402116x
There is an ongoing intensive debate on the mechanism of gold nanoparticles formation regarding the intermediate precursors prior to the addition of reducing agent. A new detailed view of the widely used Brust–Schiffrin two-phase method to prepare gold nanoparticles is presented here. Precursor species of these reactions have been identified and quantified by NMR, UV–visible, Fourier-transform Raman spectroscopy, etc. We demonstrate that tetraalkylammonium gold complexes ([TOA][AuX2]) and soluble gold thiolate ([TOA][AuSRX] and [TOA][Au(SR)2]) were detectable as the precursors by NMR spectroscopy. Their relative contents depend on the concentration of reactants. Higher concentration of the reactants is favorable for the formation of soluble thiolate. Polymeric gold thiolate [Au(I)SR]n could eventually precipitate from the solution under specific conditions. The clear mechanism presented here is of great significance to tailor the size and properties of the final products.
Co-reporter:Jiao Chen, Jie Xu, Xiaoliang Wang, Dongshan Zhou, Pingchuan Sun, and Gi Xue
Macromolecules 2013 Volume 46(Issue 17) pp:
Publication Date(Web):August 22, 2013
DOI:10.1021/ma401257y
When most prior studies on thin polymer films have shown that glass transition temperature (Tg) decreases under nanoconfinement, the differential alternating current chip (ac-chip) calorimetric method shows little dependence of Tg on thickness for supported film. To reveal this contradiction, we have manipulated a controlled interface by spin-coating polystyrene (PS) with immiscible surfactants such as tetraoctylammonium bromide or citric acid. Since the immiscible surfactants did not show plasticizing effect for PS, there was no observable reduction of Tg from the bulk value ether in powdered blends or in thick films. However, the ultrathin film with thickness h ∼ 25 nm, consisting of 95 wt % PS and 5 wt % surfactants, showed a reduction of Tg by 6–7 °C, as compared to thick film with the same composition. We propose that the surfactant molecules assembled on the interface between thin film and substrate due to phase separation. The molecular mobility of molecules at the interface was dramatically increased, which was detected by 1NMR with dipolar filter sequence. It appeared that the deviation range was not so large as that measured by other methods. But considering that we were measuring Tg at a high frequence (10 Hz), this amount of deviation was quite significant for ac-chip calorimetry. As a result, ac-chip calorimetry measured Tg data unambiguously demonstrate that thickness dependence of Tg is a real property of confined thin film.
Co-reporter:Zhu Liu;Zhi-Bin Jiang;Hong Yang;Shu-Ming Bai
Chinese Journal of Polymer Science 2013 Volume 31( Issue 11) pp:1491-1500
Publication Date(Web):2013 November
DOI:10.1007/s10118-013-1346-0
The crowding agent induced phase transition of amphiphilic block copolymers in solution was explicitly considered. The influence of the size and the volume fraction of the crowding agent on the phase separation of amphiphilic diblock copolymers is investigated by using self-consistent field theory (SCFT) method. The concentration of the disorder to order transition of the block copolymer decreases when the size of the crowding agent is larger than that of the solvent. The higher volume fraction of the crowding agent will induce the transition of the block copolymer from disorder to order state at a lower concentration. The relation between the size and the volume fraction of the crowding agent is elucidated. When the size of the crowding agent is larger, its volume fraction of the disorder to order transition of the block copolymer will be lower. The conformation of the crowding agent considered as a polymer chain is also studied and compared.
Co-reporter:Lili Zhu, Xiaoliang Wang, Qiang Gu, Wei Chen, Pingchuan Sun, and Gi Xue
Macromolecules 2013 Volume 46(Issue 6) pp:2292-2297
Publication Date(Web):March 4, 2013
DOI:10.1021/ma302643y
The mobility and glass transition temperature (Tg) for polymers under nanoscale confinement differ substantially from the bulk. Whereas many studies have focused on the one-dimensional confinement, it has great significance to extend studies to higher geometries. Here, we systematically investigate the mobility by dipolar-filter sequence in solid-state NMR and Tg by DSC for thiolated polystyrene (PS-SH) on gold nanoparticles. The increase in Tg and signal suppression in NMR spectra clearly indicate that the surface confinement dominates molecular mobility as well as Tg. The molecular weight of PS-SH and nanoparticles size show significant influence on the immobilization and Tg. Our results can be fitted with a core–two shell model; the inner shell is under strong constraints while the outer shell with less confinement. This work is essential to better understand the confinement effect and also provides a step toward the ultimate desire to tailor the properties of nanomaterials.
Co-reporter:Chao Teng, Yun Gao, Xiaoliang Wang, Wei Jiang, Chen Zhang, Rong Wang, Dongshan Zhou, and Gi Xue
Macromolecules 2012 Volume 45(Issue 16) pp:6648-6651
Publication Date(Web):July 31, 2012
DOI:10.1021/ma300885w
Rheology experiments were performed to monitoring the kinetics of the entanglement recovery process of freeze-dried polystyrene. Complete reentanglement time requires unexpected long time, which does not monotonically reduce with the concentration of precursor solution. The entanglement recovery was treated as the complementary process of stress relaxation in Doi–Edwards model and was found to agree well with the exponential law. We clarified that freeze-drying is an effective way to achieve disentanglement for polymer chains. The correlation between recovery time and the concentration of precursor solution is in good agreement with previous results from molecular dynamics (MD) simulations.
Co-reporter:Yunxing Li, Zhaoqun Wang, Chunjian Wang, Yunfei Pan, Hao Gu, and Gi Xue
Langmuir 2012 Volume 28(Issue 35) pp:12704-12710
Publication Date(Web):August 13, 2012
DOI:10.1021/la302068c
The design and fabrication of functional nanocomposites is an active area of research because composite particles have significantly improved physical and chemical properties over those of their single-component counterparts. Traditionally, chemical pretreatments of the components were used to enhance their physicochemical or chemical interactions. Here, we propose a novel approach to taking advantage of the beauty of thermodynamics. A series of functional materials, including graphene nanosheets, carbon nanotubes, noble metals, magnetic materials, conducting polymers, attapulgite, and etc. were incorporated with polystyrene particles by a thermodynamic driving force. This unique approach is facile and versatile and shows the considerable significance of developments in both scientific methodology and particle engineering.
Co-reporter:Qiang Gu, Xiaoliang Wang, Pingchuan Sun, Dongshan Zhou and Gi Xue
Soft Matter 2011 vol. 7(Issue 2) pp:691-697
Publication Date(Web):26 Oct 2010
DOI:10.1039/C0SM00379D
In this paper, we characterized the interdiffusion of deuterated polystyrene (PS-D) and hydrogenated poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) by 1H dipolar filter solid-state NMR under fast magic angle spinning (MAS). It is observed that the interdiffusion process of PS-D/PPO is composed of two stages, the wetting stage and the diffusion stage. The characteristic time of the transition from the wetting to diffusion stage is independent of the temperature and PS-D molecular weight. On the other hand, the increment of dipolar filtered 1H NMR signal intensity at the wetting stage depends strongly on the temperature. The PS-D chains can be easily mixed with the PPO chains intimately when the temperature is above the glass transition temperature (Tg) of PPO. However, when the temperature is below the Tg of PPO, the PPO chains are frozen and it is more difficult for the PS-D chains to approach the PPO at a molecular level.
Co-reporter:Rong Wang, Zhibin Jiang, Gi Xue
Polymer 2011 Volume 52(Issue 10) pp:2361-2365
Publication Date(Web):4 May 2011
DOI:10.1016/j.polymer.2011.03.010
The self-assembly of amphiphilic AB diblock copolymer in solution with different molecular size was investigated by using the self-consistent field theory (SCFT). By continuously varying the solvent size and the polymer concentration, the phase diagram is constructed. The aggregate concentration of the amphiphilic AB diblock copolymer decreases in solution with larger solvent size. The phase will transit in solution with different solvent size due to the excluded volume interaction effect. This widely existing excluded volume effect is very useful for the separation of polymers and helpful for understanding the crowding effect in bio-molecules.
Co-reporter:Jie Xu, Dawei Li, Jiao Chen, Lei Din, Xiaoliang Wang, Fangfang Tao, and Gi Xue
Macromolecules 2011 Volume 44(Issue 18) pp:7445-7450
Publication Date(Web):August 29, 2011
DOI:10.1021/ma200962c
We used fluorescence nonradiative energy transfer (NRET) to detect the interchain distances r at the overlapping regions of polymer chains. Freeze-dried polystyrene (PS) is found to have an increased r value and thus a reduced chain packing density, which shows an increased segmental mobility under uniaxial compression. We clarify that it is the interchain coupling that restricts the chain motion in a glassy oligomer in which chain entanglement is absent.
Co-reporter:Xiaolin Lu;Zhan Chen;Xinping Wang
Frontiers of Chemistry in China 2010 Volume 5( Issue 4) pp:435-444
Publication Date(Web):2010 December
DOI:10.1007/s11458-010-0220-7
Sum frequency generation (SFG) vibrational spectroscopy has been proved to be a powerful technique which substantially impacts on many research areas in surface and interfacial sciences. This paper reviews the recent progress of applying this nonlinear optical technique in the studies of polymer surfaces and interfaces. The theoretical background of SFG is introduced first. Current applications of SFG in polymer science are then described in more detail to demonstrate the significance of this technique. Finally, a short summary is presented on this relatively new but widely applicable spectroscopic technique.
Co-reporter:Yong Wang;Wei Chen;Dongshan Zhou
Macromolecular Chemistry and Physics 2009 Volume 210( Issue 11) pp:936-941
Publication Date(Web):
DOI:10.1002/macp.200900016
Co-reporter:Chuanwei Zuo;Jianglong Han;Zhihuai Si
Journal of Applied Polymer Science 2009 Volume 114( Issue 6) pp:3889-3895
Publication Date(Web):
DOI:10.1002/app.29752
Abstract
A new epoxy resin containing both binaphthyl and biphenyl moieties in the skeleton (BLBPE) was synthesized and confirmed by electrospray ionization mass spectroscopy, 1H-nuclear magnetic resonance spectroscopy, and infrared spectroscopy. To evaluate the combined influence of two moieties, one epoxy resin containing binaphthyl moiety and another containing biphenyl moiety were also synthesized, and a commercial biphenyl-type epoxy resin (CER3000L) was introduced. Thermal properties of their cured polymers with phenol p-xylene resins were characterized by differential scanning calorimetry, dynamic mechanical, and thermogravimetric analyses. The cured polymer obtained from BLBPE showed remarkably higher glass transition temperature and lower moisture absorption, as well as comprehensively excellent thermal stability. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Co-reporter:Xiaolin Lu, Dawei Li, Cornelius B. Kristalyn, Jianglong Han, Nick Shephard, Susan Rhodes, Gi Xue and Zhan Chen
Macromolecules 2009 Volume 42(Issue 22) pp:9052-9057
Publication Date(Web):October 14, 2009
DOI:10.1021/ma901757w
We developed a methodology to directly probe molecular ordering at the buried polymer/metal interface. Using sum frequency generation (SFG) vibrational spectroscopy, we observed ordering of ester methyl groups at the buried poly(methyl acrylate) (PMA)/silver (Ag) interface. In order to directly probe the PMA/Ag interface, we collected SFG signal from a thin PMA film sandwiched between a fused silica substrate and a silver surface. It was found that the observed SFG signal intensity does not depend on the PMA film thickness. According to the calculated Fresnel coefficients of the fused silica/PMA and PMA/Ag interfaces with PMA films of different thicknesses, it was shown that SFG signals are solely contributed by the PMA/Ag interface. Further studies indicated that the ester methyl groups at the PMA/Ag interface tilt away from the Ag surface.
Co-reporter:Yong Wang;Chunhong Yu;Zhen Li;Dongshan Zhou;Wei Chen
Colloid and Polymer Science 2009 Volume 287( Issue 11) pp:
Publication Date(Web):2009 November
DOI:10.1007/s00396-009-2093-1
Spiral dislocation morphology on the surface of cetyltrimethylammounium bromide (CTAB) crystallites has been discovered for the first time. By addition of ammonium peroxydisulfate into CTAB crystalline suspension, a drastic change in the morphology of result crystallites is observed from spiral to two dimensional (2D) islands. The spiral and 2D-island structures of these crystallites could be use as the templates for the synthesis of spiral and ring-like polypyrrole (PPy) nanowires, respectively, via direct chemical oxidative polymerization of pyrrole due to the oxidation reaction occurring preferentially at the steps of these crystallites. The mechanism of adsorption of pyrrole oligomers on the steps of these crystallites is proposed for the growth of PPy spiral and ring-like nanowires.
Co-reporter:Xiaolin Lu, Jianglong Han, Nick Shephard, Susan Rhodes, Alex D. Martin, Dawei Li, Gi Xue and Zhan Chen
The Journal of Physical Chemistry B 2009 Volume 113(Issue 39) pp:12944-12951
Publication Date(Web):September 9, 2009
DOI:10.1021/jp9058092
Epoxy and phenolic resins are extensively used for modern microelectronics, for example, as packaging materials. Humidity may greatly alter or degrade their function and application, leading to failure of the device. A nonlinear optical laser technique, sum frequency generation (SFG) vibrational spectroscopy, was used to investigate the molecular surface structures of the epoxy and phenolic resins after exposure to humid air. It was found that the adsorbed water molecules at the phenolic resin surface can induce substantial surface restructuring. The surface phenyl groups were reoriented closer to a perpendicular position to the surface after exposure to humid air from a more parallel position in air. Epoxide group surface restructuring was not observed.
Co-reporter:Fangfang Tao;Xiaoliang Wang;Bo Che;Dongshan Zhou;Wei Chen;Dawei Zou;Zuoxiu Tie
Macromolecular Rapid Communications 2008 Volume 29( Issue 2) pp:160-164
Publication Date(Web):
DOI:10.1002/marc.200700578
Co-reporter:Shuangjun Chen;Wei Chen
Macromolecular Bioscience 2008 Volume 8( Issue 6) pp:478-483
Publication Date(Web):
DOI:10.1002/mabi.200700273
Co-reporter:Wei Jiang, Chuanwei Zuo, Jinglei Hu, Qiang Gu, Wei Chen and Gi Xue
Macromolecules 2008 Volume 41(Issue 14) pp:5356-5360
Publication Date(Web):June 27, 2008
DOI:10.1021/ma8005153
Interchain coupling of polymers was investigated by detecting the segmental proximity using 1H solid-state NMR under fast magic angle spinning. The NMR experiment based on the dipole−dipole interaction provided information about intersegment distances on length scales of several angstroms, over which the van der Waals attraction force occurs. The NMR and DSC were combined to get insight into the dependence of the enthalpy relaxation by sub-Tg annealing on the local segmental motion. Parameters of the TNM model were used to quantitatively discuss the glassy-state structural relaxation behavior near the glass transition of the prepared samples. Our experimental results demonstrated that if the intersegment distance was controlled to be larger than 0.5 nm, the enthalpy relaxation time spectrum through the glass transition region became narrower and the stretch exponent β for the TNM model was larger. When the polystyrene (PS) sample was a cast film or powder prepared from a concentrated solution, the chains were detected to be in close proximity, and thus their β value became smaller. It is interesting that the PS sample from a 10 wt % solution in DOP exhibited nearly the same relaxation behavior as the sample prepared from a 0.1 wt % solution in benzene. 1H solid-state NMR detection indicated that these two samples showed a similar level of intersegmental proximities, although they had different entanglement concentrations. On the basis of our experimental results, we argued that the segmental proximity restricted the local segmental motions on short length scales and thus influenced the glassy-state relaxation behavior.
Co-reporter:Fangfang Tao, Jianglong Han, Qiang Gu, Chao Teng, Dawei Zou, Dongshan Zhou and Gi Xue
Macromolecules 2008 Volume 41(Issue 24) pp:9890-9895
Publication Date(Web):November 14, 2008
DOI:10.1021/ma8016986
The association and aggregation of polymers in the semidilute solution regime during cooling from above to below the Θ temperature were investigated by the nonradiative energy transfer (NET) and rheological method. The molecular size of the solvent was found to affect the association and aggregation behaviors of the chains. When the normal small-sized solvent, for example decalin or cyclohexane is used, the polystyrene chains first associate among each other, and form aggregates of chains with strong interchain interpenetration at the end of cooling process. However, when the solvent with larger molecular size (also called middle-sized solvent), for example dioctyl phthalate (DOP) is used, polystyrene chains contract separately and form aggregates of collapsed globules at the end of cooling process. The interpenetration between chains for the polystyrene solid sample freeze-dried from different concentrations was detected by a new strategy using dipolar filter 1H solid-state NMR under fast magic angle spinning. We found that when the small-sized solvent was used, the extent of interpenetration in the polystyrene glasses basically kept constant with the concentration of the original solution and it increased suddenly near the critical overlapping concentration ([η]c ∼ 4). However, in the case of middle-sized solvent, even up to [η]c = 10, the extent of the interpenetration kept in a very low level comparable to that from extremely dilute ([η]c ∼ 0.01) small-sized solvent solution. Such results help us to understand the behaviors of fast crystallization and relaxation dynamics of serials of polymer samples freeze-dried from middle-sized solvent solutions discovered in this laboratory.
Co-reporter:Chaoqing Bian;Yijun Yu
Journal of Applied Polymer Science 2007 Volume 104(Issue 1) pp:
Publication Date(Web):27 DEC 2006
DOI:10.1002/app.25636
Conducting polyaniline (PANI)/titanium dioxide (TiO2) composite nanofibres with an average diameter of 80–100 nm were prepared by one-step in situ polymerization method in the presence of anatase nano-TiO2 particles, and were characterized via Fourier-transform infrared spectra, UV/vis spectra, wide-angle X-ray diffraction, thermogravimetric analysis, and transmission electron microscopy, as well as conductivity and cyclic voltammetry. The formation mechanism of PANI/TiO2 composite nanofibres was also discussed. This composite contained ∼ 65% conducting PANI by mass, with a conductivity of 1.42 S cm−1 at 25°C, and the conductivity of control PANI was 2.4 S cm−1 at 25°C. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Co-reporter:Chaoqing Bian, Gi Xue
Materials Letters 2007 Volume 61(Issue 6) pp:1299-1302
Publication Date(Web):March 2007
DOI:10.1016/j.matlet.2006.07.023
Co-reporter:Shuangjun Chen;Wei Chen;Zhihuai Si;Dongshan Zhou
Macromolecular Rapid Communications 2006 Volume 27(Issue 5) pp:328-332
Publication Date(Web):16 FEB 2006
DOI:10.1002/marc.200500705
Summary: SEBS is used as building blocks to fabricate size controllable polypyrrole (PPy) capsules. Polypyrrole shells grow on the surfaces of the size controllable oxidant sub-microparticles dispersed in the solution cast film of a SEBS copolymer by vapor phase polymerization. After washing in ethanol, PPy sub-microcapsules dispersed in a SEBS matrix are obtained. This technique shows advantages of lower cost and less pollution, as compared with the gold-template method reported in the literature.
Co-reporter:Wei Chen, Gi Xue
Progress in Polymer Science 2005 Volume 30(Issue 7) pp:783-811
Publication Date(Web):July 2005
DOI:10.1016/j.progpolymsci.2005.03.002
The complex formed between heteroaromatic monomers and a Lewis acid solvent such as trifluroborate–ethyl ether (BFEE) markedly lowers the electrochemical polymerization potential. The resulting heteroaromatic conducting polymer (HCP) films show improved mechanical properties and conductivities. The transport of charge is believed to be principally along the conjugated chains, dominating interchain hopping modes. The specific electrical resistance across the HCP film thickness is more than 104 times larger than that along the film plane. Recent developments of polymerization techniques by low potential electrochemical methods are reviewed, along with several electrical devices in which the compact HCP films are used.
Co-reporter:Yijun Yu;Chu Ouyang;Wei Chen;Yun Gao;Zhihuai Si;Zhaoqun Wang
Journal of Polymer Science Part A: Polymer Chemistry 2005 Volume 43(Issue 23) pp:6105-6115
Publication Date(Web):17 OCT 2005
DOI:10.1002/pola.21114
We demonstrate here a feasible approach to the preparation of multiwalled carbon nanotube (MWNT)/polypyrrole (PPy) core–shell nanowires by in situ inverse microemulsion. Transmission electron microscopy and scanning electron microscopy showed that the carbon nanotubes were uniformly coated with a PPy layer with a thickness of several to several tens of nanometers, depending on the MWNT content. Fourier transform infrared spectra suggested that there was strong interaction between the π-bonded surface of the carbon nanotubes and the conjugated structure of the PPy shell layer. The thermal stability and electrical conductivity of the MWNT/PPy composites were examined with thermogravimetric analysis and a conventional four-probe method. In comparison with pure PPy, the decomposition temperature of the MWNT/PPy (1 wt % MWNT) composites increased from 305 to 335 °C, and the electrical conductivity of the MWNT/PPy (1 wt % MWNT) composites increased by 1 order of magnitude. The current–voltage curves of the MWNT/PPy nanocomposites followed Ohm's law, reflecting the metallic character of the MWNT/PPy nanocomposites. The cyclic voltammetry measurements revealed that PPy/MWNT composites showed an enhancement in the specific charge capacity with respect to that of pure PPy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6105–6115, 2005
Co-reporter:Liang Li;Feng Yan
Journal of Applied Polymer Science 2004 Volume 91(Issue 1) pp:303-307
Publication Date(Web):11 NOV 2003
DOI:10.1002/app.13257
Porous conducting polypyrrole (PPy) films have been obtained by electrochemical synthesis–solvent extraction method. The results of scanning electron microscopy (SEM) show that the size and the distribution of pores can be controlled during the electrochemical synthesis. The porous PPy films have sufficiently good mechanical properties, and electrochemical voltammetric studies imply that the porous films also have high electrical conductivity and good electrochemical reversibility. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 303–307, 2004
Co-reporter:Wei Chen, Xingwei Li, Gi Xue, Zhaoqung Wang, Wenqing Zou
Applied Surface Science 2003 Volume 218(1–4) pp:216-222
Publication Date(Web):30 September 2003
DOI:10.1016/S0169-4332(03)00590-7
Abstract
We reported here the preparation of Fe3O4–polypyrrole (PPy) nanocomposites with both magnetic and conducting properties. The magnetic properties of the resulting composites were investigated by vibrating sample magnetometer (VSM). The Fe3O4–PPy nanocomposites had coercive force from 98.4 to 116.3 Oe and saturation magnetization from 0.268 to 9.23 emu/g with the increasing Fe3O4 content. The electrical conductivities ranged from 10−5 to 10−2 S/cm, depending on the Fe3O4 content. The average size of Fe3O4–PPy nanocomposites with core-shell structure was about 50 nm. Structural characterizations by Fourier transform infrared (FTIR) and thermogravimetric analysis (TGA) proved the interaction between Fe3O4 and PPy chains.
Co-reporter:Zhenggang Xiao, Qing Sun, Gi Xue, Zuanru Yuan, Qingping Dai, Youliang Hu
European Polymer Journal 2003 Volume 39(Issue 5) pp:927-931
Publication Date(Web):May 2003
DOI:10.1016/S0014-3057(02)00313-0
Isotactic polypropylene (iPP) with narrow molecular mass distribution was freeze-extracted from n-octane solutions with varying concentrations. The recovered samples were characterized by differential scanning calorimetry. It is found that the sample recovered from the very dilute solution exhibits the higher non-isothermal crystallization temperature, faster isothermal crystallization rate, and smaller Avrami index. And there should exist a critical concentration corresponding with the critical overlap concentration proposed by de Gennes in the polymer solutions. In the solution well below the critical concentration, the iPP chains were isolated from each other, resulting in an acceleration of melt crystallization for the recovered samples. It seems that the chain entanglement is a barrier to the melt crystallization of polymer.
Co-reporter:Zhenggang Xiao, Liang Li, Dongshan Zhou, Gi Xue, Zuanru Yuan, Qingping Dai
Thermochimica Acta 2003 Volume 404(1–2) pp:283-288
Publication Date(Web):4 September 2003
DOI:10.1016/S0040-6031(03)00186-2
The kinetics of isothermal crystallization from the melt of low ethylene content polypropylene random (PPR) copolymer with isotactic propylene sequence recovered from physical gel formed in solvents of varying molecular size was studied by differential scanning calorimetry (DSC). The kinetics analysis for these samples indicates that the PPR recovered from n-hexadecane is easier to crystallize and exhibits higher crystallization rate than the sample recovered from decalin. The influence of melt annealing time on isothermal crystallization was also investigated.
Co-reporter:Feng Yan, Gi Xue and Fen Wan
Journal of Materials Chemistry A 2002 vol. 12(Issue 9) pp:2606-2608
Publication Date(Web):30 Jul 2002
DOI:10.1039/B206896F
A flexible giant magnetoresistance (GMR) film was prepared completely by electrochemical synthesis; the composite film has potential in applications as flexible magnetic recording heads, actuators and sensors etc.
Co-reporter:Fen Wan;Liang Li;Xiaobo Wan
Journal of Applied Polymer Science 2002 Volume 85(Issue 4) pp:814-820
Publication Date(Web):14 MAY 2002
DOI:10.1002/app.10672
Electrochemical copolymerization of pyrrole and indole was performed galvanostatically in a solvent of acetonitrile (AN)/water (vol %: 99/1). The product obtained was characterized by cyclic voltammetry and infrared spectroscopy. The influence of the monomer feed ratio of pyrrole and indole on the synthesis of the copolymer was investigated. The amount of pyrrole units in the copolymer chain increased with increase of the concentration of the pyrrole monomer in the solution. The results showed that the electrochemical activity of the copolymer was improved as the incorporation of pyrrole units increased. Thermogravimetric analysis was carried out to investigate the properties of the copolymer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 814–820, 2002
Co-reporter:Liang Li;Jin-Bo He;Xiao-Bo Wan;Tian-Wei Wang;Dong-Shan Zhou
Journal of Applied Polymer Science 2002 Volume 86(Issue 12) pp:3160-3165
Publication Date(Web):3 OCT 2002
DOI:10.1002/app.11343
The degradation of polyfuran in a wet acetonitrile solution and in an aqueous solution has been investigated with a cyclic voltammetry technique, along with Fourier transform infrared and Fourier transform Raman spectroscopy techniques. Infrared spectroscopy shows that the main defects that exist in polyfuran after cycling in dried acetonitrile are mainly saturated CH structures, whereas those after cycling in an aqueous solution are mainly carbonyl groups in the polymer chain. This may be because polyfuran can undergo degradation through a crosslinking mechanism in a dried acetonitrile solution, whereas in an aqueous solution, it undergoes degradation through a nucleophilic attack mechanism. Raman spectroscopy shows that not all the furan rings are involved in the degradation process, although the electrochemical activity of polyfuran is totally lost in an aqueous solution after only one cycle. The sites that are sensitive to the degradation process may be the electrochemically active sites, that is, the positively charged sites in polyfuran chains. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3160–3165, 2002
Co-reporter:Qing Sun;Qiang Fu;Wei Chen
Macromolecular Rapid Communications 2001 Volume 22(Issue 14) pp:
Publication Date(Web):27 SEP 2001
DOI:10.1002/1521-3927(20011001)22:14<1182::AID-MARC1182>3.0.CO;2-4
Syndiotactic poly(propylene)s (s-PPs) were freeze-dried from toluene solutions of various concentrations. FT-IR spectroscopy and wide-angle X-ray diffraction were used to characterize the s-PPs prepared. The isothermal crystallization behavior was also investigated by means of differential scanning calorimetry. The disentangled particles are of high crystallinity and show rapid crystallization rates. A trans-planar conformation is developed when s-PP was freeze-dried from more dilute solution.
Co-reporter:Feng Yan, Gi Xue, Jin Chen, Yun Lu
Synthetic Metals 2001 Volume 123(Issue 1) pp:17-20
Publication Date(Web):22 August 2001
DOI:10.1016/S0379-6779(00)00572-5
We report here the preparation of an electrically conducting polypyrrole/ferromagnet composite film by means of the technique anodic-oxidation. The doubly-functionalized composite film is flexible and has good mechanical properties. The composite films we synthesized exhibit ferromagnetic properties at room temperature, show low hysteresis coercive force () in the magnetic field and has excellent environmental stability especially in the acid environment.
Co-reporter:Feng Yan;Mingshi Zhou
Journal of Applied Polymer Science 2000 Volume 77(Issue 1) pp:135-140
Publication Date(Web):3 MAY 2000
DOI:10.1002/(SICI)1097-4628(20000705)77:1<135::AID-APP18>3.0.CO;2-B
Nanoscopic conducting polypyrrole powder was prepared in an oil/water microemulsion with FeCl3 as a dopant. Compared with solution and conventional emulsion polymerizations, a microemulsion polymerization system increases the yield of the resultant polypyrrole. The results of FTIR spectra and thermal analysis studies indicate that the microemulsion polymerization system increased the extent of the π-conjugation length along the polymer backbone and ordered the arrangement of the macromolecule chains. These two effects bring about enhanced conductivity as well as higher thermal stability of polypyrrole. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 135–140, 2000
Co-reporter:Xiaobo Wan, Wei Zhang, Shi Jin, Gi Xue, Qi-Dong You, Bo Che
Journal of Electroanalytical Chemistry 1999 Volume 470(Issue 1) pp:23-30
Publication Date(Web):19 July 1999
DOI:10.1016/S0022-0728(99)00205-3
Electrochemical copolymerization of furan and pyrrole was performed potentiostatically in a binary solvent system consisting of boron trifluoride ethyl ether and additional ethyl ether. The influence of applied polymerization potential and the monomer feed ratio of furan and pyrrole on the synthesis of copolymer was investigated. The higher potential favored the incorporation of furan units into the copolymer, while the amount of pyrrole units incorporated into the film increased with the increasing concentration of pyrrole in the solution. The film obtained was characterized by cyclic voltammetry, infrared and Raman spectroscopies.
Co-reporter:Yuqin Li
Macromolecular Rapid Communications 1998 Volume 19(Issue 11) pp:549-552
Publication Date(Web):16 DEC 1998
DOI:10.1002/(SICI)1521-3927(19981101)19:11<549::AID-MARC549>3.0.CO;2-T
The molecular chain conformation of the dried gel of syndiotactic polystyrene (sPS) in octadecyl benzoate solution was investigated. sPS gels form rapidly through solid-liquid phase separation. The obtained sPS chains are in the highly ordered all-trans TT skeletal conformation which is different from a twofold TTGG helical conformation that sPS assumes in normal solvents. The size of the solvent molecule is considered to play an important role in the formation of the conformation of sPS in solution.
Co-reporter:Liang Zhou, Yuqin Li, Gi Xue
Thin Solid Films 1998 Volume 335(1–2) pp:112-116
Publication Date(Web):19 November 1998
DOI:10.1016/S0040-6090(98)00957-2
Co-reporter:Xiang Li, Chen Zhang, Ye Sha, Linling Li, Dongshan Zhou, Zexin Zhang, Gi Xue, Xiaoliang Wang
Polymer (24 February 2017) Volume 111() pp:67-72
Publication Date(Web):24 February 2017
DOI:10.1016/j.polymer.2017.01.029
Co-reporter:Jie Xu, Ying Diao, Dongshan Zhou, Yisha Mao, Gaurav Giri, Wei Chen, Nan Liu, Stefan C. B. Mannsfeld, Gi Xue and Zhenan Bao
Journal of Materials Chemistry A 2014 - vol. 2(Issue 16) pp:NaN2991-2991
Publication Date(Web):2014/01/29
DOI:10.1039/C3TC32581D
In organic thin film transistors (OTFTs), the molecular structure of the first few monolayers at the semiconductor–dielectric interface is crucial to the device performance. The assumption of homogeneous molecular packing throughout the thickness of the film is not always valid considering interfacial effects. However, it remains challenging to unambiguously determine the molecular packing at both the top surface and the buried bottom interface, due to the lack of a nanoscopic tool. Here we show that a combination of Raman spectroscopy and surface enhanced Raman scattering (SERS) provides a means for effective characterization of the interfacial packing in 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene) films. We observed that the TIPS-pentacene crystal lattices assume a non-equilibrium packing state near the substrate interface, which gradually relaxes towards equilibrium packing near the top interface. Our investigation suggests the existence of non-equilibrium molecular packing for TIPS-pentacene.
![Poly[oxy(2,6-dimethyl-1,4-phenylene)]](http://img.cochemist.com/ccimg/25000/24938-67-8.png)
![Poly[oxy(2,6-dimethyl-1,4-phenylene)]](http://img.cochemist.com/ccimg/25000/24938-67-8_b.png)
![Poly[oxy(1-oxo-1,6-hexanediyl)]](http://img.cochemist.com/ccimg/25300/25248-42-4.png)
![Poly[oxy(1-oxo-1,6-hexanediyl)]](http://img.cochemist.com/ccimg/25300/25248-42-4_b.png)
