Co-reporter:Ping Liu, Xin Guo, Fuchun Nan, Yongxin Duan, and Jianming Zhang
ACS Applied Materials & Interfaces 2017 Volume 9(Issue 3) pp:
Publication Date(Web):December 27, 2016
DOI:10.1021/acsami.6b12953
Iridescent films formed from the self-assembly of cellulose nanocrystals (CNCs) are brittle and difficult to handle or integrate within an industrial process. Here we present a simple approach to prepare iridescent CNC films with tunable pliability and coloration through the addition of ionic liquids (ILs) of 1-allyl-3-methylimidazolium chloride (AmimCl) as plasticizers. By using the undried CNC film as a filter membrane and ILs solution as a leaching liquid, it was found that the filtration process made ILs uniformly interpenetrate into CNC film due to the strong ionic interaction between CNC and AmimCl. Unexpectedly, the filtration process also gave rise to partial desulfurization of CNC film, which is conducive to the improvement of thermal stability. Benefiting from the improved thermal stability and the dissolving capacity of AmimCl for cellulose at high temperature, the incorporated ILs enable the cholesteric CNC film to be further toughened via a hot-pressing treatment. This study demonstrates that ionic liquids have great potential to modify the mechanical, optical properties as well as the thermal stability of iridescent CNC films.Keywords: cellulose nanocrystal; hot-pressing; ionic liquid; plasticization; structural color;
Co-reporter:Kai Pang;Beibei Ding;Xiaoting Liu;Hao Wu;Yongxin Duan
Green Chemistry (1999-Present) 2017 vol. 19(Issue 15) pp:3665-3670
Publication Date(Web):2017/07/31
DOI:10.1039/C7GC01592E
Novel zwitterionic chitin nanofibers (ChNFs) decorated with both cationic (NH3+) and anionic (COO−) groups on the surface have broad applications in various environments. Herein, we demonstrate a rapid and high-yield (up to 85%) synthesis of a zwitterionic ChNF by the combination of partial deacetylation and oxidation using the TEMPO/NaClO2/NaClO system. Meanwhile, we present the potential application of a bio-based ChNF as an environmentally and doubly pH-responsive Pickering emulsifier to replace conventional pH-responsive Pickering emulsifiers such as inorganic nanoparticles or grafted polymers. This high yield preparation achieved by our method will be in favor of the large-scale applications of ChNFs.
Co-reporter:Ping Liu, Hongsheng Yang, Xiaofang Zhang, Min Jiang, Yongxin Duan, Jianming Zhang
Carbon 2016 Volume 107() pp:46-55
Publication Date(Web):October 2016
DOI:10.1016/j.carbon.2016.05.050
Graphene paper assembled from graphene oxide (GO) sheets has attracted great attention due to the intriguing physical and chemical properties. Here, we discovered that the size stability and mechanical performances of reduced graphene oxide (RGO) papers obtained by chemical reduction of the vacuum filtered GO papers are strongly dependent on the pH value of the starting GO suspensions. Moreover, it is found that RGO paper obtained from GO suspension with pH = 7 demonstrated superior performance of both flexural endurance and electrical conductivity. By investigating the structural differences of the prefabricated GO papers and their swelling behaviors during reduction, as well as the unlike microstructures of the obtained RGO papers, we interpreted the origin of the pH-mediated controllable contraction and mechanical performance of RGO papers. This study suggests a simple strategy for controlling the size stability, mechanical performance and electrical conductivity of RGO paper.
Co-reporter:Min Jiang, Xueping Cao, Dandan Zhu, Yongxin Duan, Jianming Zhang
Electrochimica Acta 2016 Volume 196() pp:699-707
Publication Date(Web):1 April 2016
DOI:10.1016/j.electacta.2016.02.094
A core-shell structure composite, zeolitic imidazolate framework @ cetyltrimethylammonium bromide (ZIF-8@CTAB) was synthesized by CTAB micelle controlling the growth of ZIF-8 in aqueous systems. Direct carbonization of ZIF-8@CTAB at a high temperature produced the nitrogen-doped hierarchically porous carbon (named as PC1000@C). In comparison with the carbonization product of pure ZIF-8 (named as PC1000), PC1000@C possesses the higher specific surface area and two-times larger total pore volume. The results from elemental analysis shows the higher N content in PC1000 sample, while X-ray photoelectron spectroscopy curve-fitting shows the higher quaternary-N content in PC1000@C sample. The hierarchical microporous/mesoporous structure, high surface area and favorable N species in PC1000@C play an active role in catalyzing oxygen reduction reaction (ORR). The specific capacitance of porous carbon was calculated from the galvanostatic-discharge curve. PC1000@C exhibits a large specific capacitance of 225 F g−1 at a current density of 0.5 A g−1 and still retains 92% of initial capacitance after 1000 galvanostatic charge-discharge cycles.
Co-reporter:Fuwei Pi, Jiping Wang, Nattaporn Suttiwijitpukdee, Xing Chen, Jianming Zhang
Vibrational Spectroscopy 2016 Volume 86() pp:35-39
Publication Date(Web):September 2016
DOI:10.1016/j.vibspec.2016.05.009
Thickness-dependent ultrathin films of poly(3-hydroxybutyrate) (PHB) were investigated by using infrared reflection-absorption spectroscopy (IRRAS). It was first found that the autogenetic β-form of PHB could be easily obtained through confining the film thickness under 20 nm at room temperature. Moreover, the interphase of PHB simultaneously exists with the β-form of PHB in the films with a thickness less than 10 nm. With the film thickness increasing from several nanometers to about 30 nm, the PHB molecules gradually carry out an orientation shift at the b-axis of PHB crystallite; simultaneously, for the α-form of PHB a conformational rearrangement probably takes place for the growth of helical crystal unit cells in the ultrathin films. The molecular structures and crystal evolutions at sub–100 nm were explained in detail by analyzing the corresponding IRRAS features.
Co-reporter:Yuan Yuan, Yinping Zhang, Xiang Cui, Jianming Zhang
Polymer 2016 Volume 105() pp:88-95
Publication Date(Web):22 November 2016
DOI:10.1016/j.polymer.2016.10.030
As a metastable phase, poly (3-butylthiophene) (P3BT) form II is generally obtained by solvent vapor treatment in rigorous conditions and it is easily transformed to more commonly observed form I with heating. In the present study, by low temperature aging in carbon disulfide (CS2) solution, a simple and feasible method was proposed to prepare neat P3BT form II. Thus prepared crystal exhibits the distinct bundle morphology composed of single-crystal-like nanofibers. With such sample, the transitional mechanism from form II to form I modification is further investigated by in situ WAXD combined with FTIR spectroscopy. It is found that form II transfers to form I via a quasi-ordered smectic phase rather than a direct solid-to-solid transition. This study could be helpful for controlling the crystal structure and morphology in P3BT thin film, which is closely related to its performance in electronic devices.
Co-reporter:Hao Wu, S. Nagarajan, Lijuan Zhou, Yongxin Duan, Jianming Zhang
Polymer 2016 Volume 103() pp:365-375
Publication Date(Web):26 October 2016
DOI:10.1016/j.polymer.2016.09.070
•New FTIR spectral method is developed to quantify the grafting density of CNC-g-PDLA.•The crystallization of PLLA matrix is distinctly enhanced with CNC-g-PDLA.•Stereocomplex interaction of PLLA and CNC-g-PDLA enhance the storage modulu and heat distortion behaviour of composites.As a popular bioplastic, poly (l-lactic acid) (PLLA) still faces some drawbacks mainly related to its low crystallization rate and heat distortion resistance. Herein, we demonstrate a facile and promising route to solve these problems by compositing PLLA with poly(d-lactide) grafted cellulose nanocrystal (CNC-g-PDLA) which can be synthesized via ring-opening polymerization of d-lactide on the CNC surface. The grafting density of PDLA on the CNC surface has been quantified by newly developed spectral method using FTIR technique. Moreover, the non-isothermal and isothermal crystallization behavior of PLLA/CNC-PDLA composites has been investigated by DSC, POM and WXRD. Our results show that the addition of small amount of CNC-g-PDLA could enhance the crystallization rate of PLLA significantly due to the heterogeneous nucleation effect of CNC and the presence of stereocomplex crystals. In addition, the specific stereocomplex interaction in the interphase of PLLA matrix and modified CNC particles results in great improvement of both storage modulus and the heat distortion resistance of the PLLA/CNC-g-PDLA nanocomposites. This study provides a way to design advanced PLLA-based nanocomposites with fast matrix crystallization ability and excellent heat distortion resistance.
Co-reporter:Yuan Yuan, Jie Shu, Krzysztof Kolman, Adam Kiersnowski, Christoph Bubeck, Jianming ZhangMichael Ryan Hansen
Macromolecules 2016 Volume 49(Issue 24) pp:9493-9506
Publication Date(Web):December 14, 2016
DOI:10.1021/acs.macromol.6b01828
On the basis of different film preparation conditions, we address the phase composition and thiophene main-chain and butyl side-chain organization of three regioregular poly(3-butylthiophene) (P3BT) samples prepared by drop-casting. These samples are readily identified by wide-angle X-ray diffraction (WAXD) with the structural P3BT polymorphs commonly referred to as forms I, I′, and II. Here, we show by means of WAXD, solid-state nuclear magnetic resonance (NMR), and Fourier-transform infrared spectroscopy (FTIR) that the P3BT samples identified with these polymeric forms (I, I′, and II) do not contain a single, unique crystalline phase and an amorphous phase, but additionally consist of one (form II) or two (forms I and I′) distinct crystalline phases. Each of the crystalline phases is associated with specific thiophene main-chain packing arrangements and butyl side-chain organizations. We provide a spectroscopic identification for each of the P3BT crystalline phases, enabling a detailed and consistent picture of molecular order and polymer main-chain and side-chain packing. Thus, our results are expected to be valuable in future studies of poly(3-alkylthiophene) (P3AT) thin films, where in particular FTIR studies will permit quick and easy access to both phase composition and identification of multiple thiophene main-chain packing structures.
Co-reporter:Hongsheng Yang, Tongping Zhang, Min Jiang, Yongxin Duan and Jianming Zhang
Journal of Materials Chemistry A 2015 vol. 3(Issue 38) pp:19268-19272
Publication Date(Web):24 Aug 2015
DOI:10.1039/C5TA06452J
We report an ambient pressure dried graphene aerogel (ADGA) with superelasticity (rapidly recoverable from >90% compression) and multifunctionality that could be obtained with ordinary instruments by recasting a partially reduced graphene oxide hydrogel (PRGH) with an ice-template method. This study would be a key progress for realizing cost-effective and large-scale commercial production of high-performance graphene aerogels.
Co-reporter:Tongping Zhang, Xiaoting Liu, Min Jiang, Yongxin Duan and Jianming Zhang
RSC Advances 2015 vol. 5(Issue 93) pp:76302-76308
Publication Date(Web):28 Aug 2015
DOI:10.1039/C5RA15160K
Regenerated cellulose/ionic liquids (ILs)–reduced graphene oxide (IRGO) nanocomposites have been prepared via a simple and green method based on 1-allyl-3-methylimidazoliun chloride (AmimCl). To one's surprise, it is found that the presence of a small amount of IRGO sheets can largely decelerate the dissolution of cellulose in AmimCl, and thus the thermal and mechanical properties of resultant cellulose/IRGO nanocomposites could be controlled simply by changing the dissolution time. Our results suggest that the residual cellulose fibrils with micrometre size are beneficial to the thermal stabilities of regenerated cellulose/IRGO films when short dissolution time is used. However, for obtaining cellulose/IRGO nanocomposites with improved mechanical properties, full dissolution and mixture of cellulose in IRGO/AmimCl solution with prolonged time are required. Compared with the regenerated pure cellulose film, our cellulose/IRGO nanocomposite prepared with dissolution time of 4 h exhibits about 23 °C increase in decomposition temperature, and 10.7% increase in tensile strength and remarkably 387.5% increase in strain at break, respectively.
Co-reporter:Chunrui Sheng;Zhiwei Hu;Hoch Martin;Yongxin Duan
Journal of Applied Polymer Science 2015 Volume 132( Issue 10) pp:
Publication Date(Web):
DOI:10.1002/app.41612
ABSTRACT
Sulfur can be used as crosslink coagent in unsaturated elastomer. In this work, a fully saturated HNBR with 39 wt % nitrile content was selected to investigate the effect of a small amount of sulfur acting as crosslink coagent on the physical and mechanical properties of peroxide-cured vulcanizates. First, selective cleavage of polysulfide (Sx) and monosulfide(S) bond by combined thiol-piperidine treatment were performed and the existence of poly/monosulfide bond in sulfur-contained HNBR compounds was verified. Then, no-filler HNBR compounds with various content of sulfur were investigated to detect the influence of sulfur on the crosslink density and cure kinetics. The MDR results showed that the crosslink density of HNBR compounds reduced only when the amount of sulfur is 0.25 phr and above. Besides, the curing rate of no-filler HNBR compounds increased with the increasing of the amount of sulfur and reached a maximum at a dosage of 0.25 phr sulfur. Finally, physical and mechanical properties of fully formulated compounds were evaluated and it was found that the addition of small amounts of sulfur in fully saturated HNBR compounds could improve the dynamic properties of peroxide-cured HNBR compounds remarkably but at a cost of slightly higher compression set values and a small loss in heat aging resistance. In a conclusion, small amount of sulfur can impart the peroxide vulcanizates some “sulfide properties” like dynamic property, tensile strength, but at the same time, due to the introduction of sulfur, some “peroxide vulcanizates property” like heat-resistance property, hot air resistance were weakened slightly. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41612.
Co-reporter:Yuan Yuan, Jie Shu, Ping Liu, Yinping Zhang, Yongxin Duan, and Jianming Zhang
The Journal of Physical Chemistry B 2015 Volume 119(Issue 26) pp:8446-8456
Publication Date(Web):June 11, 2015
DOI:10.1021/acs.jpcb.5b02805
There has been intense interest in understanding the self-assembled structure of conductive polymer nanowires due to the potential application in photovoltaics area. In the present study, free-standing poly(3-hexylthiophene) (P3HT) thin films consisting of H-aggregated and recently reported J-aggregated nanowires (NWs) were respectively prepared by the vacuum filtration method. The microstructure differences of both samples were studied in detail by combining the multiple techniques, i.e., synchrotron radiation WAXD, solid-state NMR, and IR spectroscopy. It is found that there is stronger π–π interaction ascribed to the slightly closer interchain stacking in J-aggregates than that in H-aggregates, although both aggregates take the same form I crystal modification. The subtle structural difference in the interchain stacking distance (Δd020 = 0.04 Å) is further manifested in the thermal behavior of both aggregates as indicated by the DSC curves, in which J-aggregates exhibit much higher melting point than that of H-aggregates (ΔT = 14 °C). Meanwhile, in situ synchrotron radiation WAXD study suggests that the low-temperature thermal transitions in both aggregates are associated with the shrinkage of the interchain distance. It is expected that this work will be helpful in understanding the structure–properties relationship of varying P3HT aggregate types.
Co-reporter:Tongping Zhang, Ping Liu, Chunrui Sheng, Yongxin Duan and Jianming Zhang
Chemical Communications 2014 vol. 50(Issue 22) pp:2889-2892
Publication Date(Web):16 Dec 2013
DOI:10.1039/C3CC48652D
A green and facile route for producing reduced graphene oxide based on ionic liquids has been proposed, in which the as-prepared graphene can be redispersed stably in water (up to 0.6 mg mL−1) after being made into a flow-directed solid film.
Co-reporter:Qi Chen, Ping Liu, Chunrui Sheng, Lijuan Zhou, Yongxin Duan and Jianming Zhang
RSC Advances 2014 vol. 4(Issue 74) pp:39301-39304
Publication Date(Web):20 Aug 2014
DOI:10.1039/C4RA05921B
By adjusting the dispersibility of graphene oxide (GO) in cellulose nanocrystal (CNC) aqueous solution, two distinct GO/CNC hybrid films with various internal structure have been obtained via vacuum-assisted self-assembly. After reduction, thus prepared GO/CNC hybrid films respectively demonstrate high conductivity or iridescent properties.
Co-reporter:Hongsheng Yang, Ping Liu, Tongping Zhang, Yongxin Duan and Jianming Zhang
RSC Advances 2014 vol. 4(Issue 53) pp:27687-27690
Publication Date(Web):04 Jun 2014
DOI:10.1039/C4RA02950J
High-nanofiller-content graphene/natural rubber nanocomposites with high electrical conductivity (up to 104 S m−1) and excellent mechanical properties (tensile strength, 48 MPa; modulus, 1.2 GPa) have been obtained via vacuum-assisted self-assembly for the first time.
Co-reporter:Chunrui Sheng;Tongping Zhang;Yuan Yuan;Lijuan Zhou;Yongxin Duan
Polymer International 2014 Volume 63( Issue 7) pp:
Publication Date(Web):
DOI:10.1002/pi.4667
The miscibility and effect of physical aging on the crystallization behavior of poly(l-lactic acid) (PLLA)/poly(3-hydroxybutyrate) (PHB) blends with a small amount of PHB (≤10 wt%) have been investigated using differential scanning calorimetry and Fourier transform infrared spectroscopy. It is found that the miscibility of PLLA/PHB blends with a very small percentage of PHB can be modulated by varying the molecular weight of the PHB. That is, a PLLA/PHB blend with low-molecular-weight PHB is miscible, whereas that with high-molecular-weight PHB is immiscible. It is found that physical aging at temperatures far below the glass transition temperature can promote the cold crystallization kinetics of PLLA in PLLA/PHB blends with high-molecular-weight PHB rather than in those with low-molecular-weight PHB. These findings suggest that the effect of physical aging on the crystallization behavior of the main component in a crystalline/crystalline blend with a small percentage of the second component is strongly dependent on the miscibility of the blend system. Enhanced chain mobility of PLLA in the interface region of PLLA matrix and PHB micro-domains is proposed to explain the physical aging-enhanced crystallization rate in immiscible PLLA/PHB blends with high-molecular-weight PHB. © 2013 Society of Chemical Industry
Co-reporter:Xiaojun Wang, Yinping Zhang, Yuan Yuan, Jianming Zhang
Vibrational Spectroscopy 2014 Volume 71() pp:1-5
Publication Date(Web):March 2014
DOI:10.1016/j.vibspec.2013.12.008
Time-resolved infrared spectroscopy has been used to study the melt crystallization behavior of poly(3-octylthiophenes) (P3OT), which is a typical conductive polymer among the family of poly(3-alkylthiophenes) (P3ATs). It is found that, during the isothermal crystallization process at high temperature, the alkyl side chains of P3OT always keep in disordered state, whereas the ordering packing of conjugated backbone takes place. In order to reveal the structural changes and the crystallization kinetics corresponding to the main-chain ordering process, two spectral regions that associated with π–π stacking and the effective conjugation length of P3OT have been analyzed in detail. The characteristic IR bands of crystalline and amorphous phase are identified in each spectral region. Moreover, a simple spectral method has been proposed to calculate the evolution of crystallinity during the isothermal crystallization process of P3OT. Of particular note, the distinct one-dimensional growth kinetic of P3OT crystal has been revealed by Avrami analysis.
Co-reporter:Xiao-jun Wang;Yuan Yuan;Li-li Han;Xia Dong
Chinese Journal of Polymer Science 2014 Volume 32( Issue 9) pp:1158-1166
Publication Date(Web):2014 September
DOI:10.1007/s10118-014-1493-y
In present study, the effect of the solvent annealing temperature on the crystal modifications and the phase transition behavior of the subsequently dried poly(3-octylthiophene) (P3OT) film has been investigated by the combination of DSC, WAXD and FTIR techniques. When chloroform is employed as the solvent, it is unexpectedly found that form I and form II crystal modifications of P3OT could be respectively obtained by room temperature and low temperature annealing. Comparing to the mostly used solvent reported for preparing form II, i.e. carbon disulfide (CS2) which is toxic and corrosive, chloroform is less toxic and corrosive and more suitable for solution processing of P3OT. Therefore, this finding provides an alternative way to obtain form II. By temperature dependent IR spectroscopy, the structural evolution of P3OT during the form II to form I phase transition process has also been studied in detail.
Co-reporter:Qi Chen, Ping Liu, Fuchun Nan, Lijuan Zhou, and Jianming Zhang
Biomacromolecules 2014 Volume 15(Issue 11) pp:
Publication Date(Web):October 9, 2014
DOI:10.1021/bm501355x
Iridescent films composed of the chiral nematic liquid crystal phase of cellulose nanocrystals (CNC) have attracted significant interest due to their fascinating optical properties. However, the current fabrication method, i.e., solution casting with a subsequent evaporation process, has significant limitations and therefore hinders the application of CNC iridescent films. In the present study, we demonstrate, for the first time, that vacuum-assisted self-assembly (VASA) can be used to fabricate highly oriented, large area, smooth, and structurally homogeneous CNC iridescent films. It was found that a long ultrasonic pretreatment is necessary for obtaining CNC iridescent films via VASA. Furthermore, it was also found that the iridescent color of the CNC films can be tuned by the sonication time, suspension volume, and degree of vacuum. By combining CD spectroscopy, SEM, and WAXD techniques, the internal structure of CNC iridescent films prepared by VASA has been investigated in detail. Moreover, the origin of the ultrasonic pretreatment effect on the self-assembly behavior of CNCs is also discussed.
Co-reporter:Linlin An, Yongxin Duan, Yuan Yuan, Lijuan Zhou, Jianming Zhang
Vibrational Spectroscopy 2013 Volume 68() pp:40-44
Publication Date(Web):September 2013
DOI:10.1016/j.vibspec.2013.05.002
The influence of thermal annealing on the structural ordering and orientation rearrangement of as cast P3HT thin film (<100 nm) has been studied by reflection absorption infrared spectroscopy (RAIR). In order to erase the effect of temperature on the spectral intensity, two thermal procedures have been used to investigate the annealing-induced structural change of P3HT thin film. One is the continuous heating mode, in which the RIAR spectra were in situ collected during the heating process. The other is the stepwise heating mode, that is the isothermal annealing, and the spectra were ex situ collected at room temperature after the thermal treatment. It is found that thermal annealing can enhance the π–π interaction in P3HT crystal domain, whereas the improvement on the degree of crystallinity is not so obviously. Meanwhile, our results suggest that annealing-induced structural rearrangement on π–π stacking is irreversible, whereas the change on hexyl side chain packing is reversible.
Co-reporter:Zhongjie Ren, Dianming Sun, Jianming Zhang and Shouke Yan
Journal of Materials Chemistry A 2012 vol. 22(Issue 36) pp:18839-18846
Publication Date(Web):02 Aug 2012
DOI:10.1039/C2JM34379G
Reduced graphene oxide (rGO) sheets covalently functionalized with n-type tetrachloroperylene diimide (PDI) and oligomeric PDI have been prepared by a two-step approach. Firstly, graphene oxide (GO) was modified by an amidation reaction with 3-aminopropyldimethylethoxylsilane or 3-aminopropyldiethoxylmethylsilane, during which GO was reduced thermally. They then react with the silanol modified PDI by dehydration condensation to obtain PDI and oligomeric PDI modified rGO (rGO–PDI and rGO–(PDI)n). The successful preparation of rGO–PDI and rGO–(PDI)n were confirmed by FTIR, Raman, X-ray photoelectron spectroscopy and XRD. The morphologies of rGO–PDI and rGO–(PDI)n sheets were studied using AFM. It was found that surface morphologies and height of rGO–PDI and rGO–(PDI)n sheets are dependent on the solvents used for casting due to differences in the solubility of PDI. Moreover, the fluorescence emission spectrum of rGO–PDI and rGO–(PDI)n shows strong fluorescence quenching and blue shift, especially in ethanol. Current sensing atomic force microscopy (CSAFM) indicated that the rGO–PDI composite shows quite different electric conductivity and optical properties with grafting efficiency and different solvents used for casting. Significantly, the electronic conductivity of rGO–(PDI)n increased by 2–3 orders of magnitude compared to rGO–PDI.
Co-reporter:Yinping Zhang, Minggang Gu, Tongping Zhang, Yuan Yuan, Lijuan Zhou, Yongxin Duan, Jianming Zhang
Vibrational Spectroscopy 2012 Volume 63() pp:338-341
Publication Date(Web):November 2012
DOI:10.1016/j.vibspec.2012.08.009
With a home-made heating cell, the structural evolutions of PLLA ultrathin film during the heating and cooling process were investigated in real time by grazing angle IR reflection absorption spectroscopy (IRRAS). It is found that the phase transition behaviors, including the crystallization, melting and even the glass transition of PLLA ultrathin film, can be clearly revealed by detailed analysis on the temperature-dependent IR spectra collected with IRRAS technique. The quantitative analysis shows that temperature-dependent intensity changes calculated by vibrational modes associated with the CO and COC groups are suitable to reflect the subtle glass transition of PLLA ultrathin film. The qualitative spectral analysis on the CC backbone vibrational modes suggest that the 10/7 helical chain of PLLA formed during the heating process (i.e. cold crystallization) is preferably flat on the Au substrate, whereas it is perpendicular to substrate during the cooling process (i.e. melt crystallization). Our studies show that temperature dependent IRRAS technique is not only valid to study the glass transition but also the confined crystallization behavior of PLLA ultrathin film deposited on a substrate, which is hard to test by the conventional DSC technique. Besides, it can provide more structural information to understand the various phase transition behaviors of polymer ultrathin films on a molecular level.
Co-reporter:Minggang Gu, Yinping Zhang, Xing Chen, Tongping Zhang, Jian Hu, Jianming Zhang
Vibrational Spectroscopy 2012 Volume 61() pp:214-218
Publication Date(Web):July 2012
DOI:10.1016/j.vibspec.2012.03.002
The bulk and thin film crystallization behaviors of PLLA/CNTs nanocomposites were investigated by in situ transmittance IR and reflection absorption IR spectroscopy, respectively. The results show that CNTs can enhance both the cold and melt crystallization rates of bulk PLLA, which is consistent with the common observation in the literature. However, it is interesting to find that the crystallization rate of PLLA thin film is suppressed by the addition of CNTs. Moreover, it is found that the existence of CNTs could not alter the preferred orientation of PLLA helical chain in the thin film. The different crystallization kinetics of PLLA induced by the addition of CNTs in bulk and thin film were explained by the confined crystallization behavior of polymer thin film.
Co-reporter:Dr. Zhongjie Ren;Dianming Sun; Huihui Li;Qiang Fu; Dongge Ma; Jianming Zhang; Shouke Yan
Chemistry - A European Journal 2012 Volume 18( Issue 13) pp:4115-4123
Publication Date(Web):
DOI:10.1002/chem.201103684
Abstract
A ladder polysilsesquioxanes with side chain of dibenzothiophene groups (BS-LPSQ) was successfully synthesized. The ladder structure of BS-LPSQ was characterized by MALDI-TOF MS, XRD, and 1H NMR spectroscopy. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), atomic force microscopy (AFM), and spectroscopic analyses revealed that the BS-LPSQ has good film-forming ability, high thermal and morphological stability, and good miscibility to the dopant iridium bis(4,6-difluorophenyl)pyridinato-N,C2-picolinate (FIrpic), high triplet energy, and a wide bandgap. In addition, compared with the ringed polysiloxane BS-PSQ phosphorescent host material reported previously, the ladder structure of BS-LPSQ has not only a higher thermal resistance, but also could prevent molecular aggregation and effectively avoid quenching of fluorescence. Thus, the BS-LPSQ may be used as a better host for the blue-light-emitting iridium complex FIrpic. The performance of the electrophosphorescent device, based on the ladder BS-LPSQ as the active layer, is superior to that of ringed BS-PSQ and any other polyhedral oligomeric silsesquioxane (POSS)-based or polymer host materials.
Co-reporter:Jian Hu, Tongping Zhang, Minggang Gu, Xing Chen, Jianming Zhang
Polymer 2012 Volume 53(Issue 22) pp:4922-4926
Publication Date(Web):12 October 2012
DOI:10.1016/j.polymer.2012.09.012
By cold drawing the amorphous PLLA sample at 65 °C (just above the glass transition temperature of PLLA), a set of uniaxially oriented samples with various draw ratios was prepared. The mesomorphic ordering and chain orientation in PLLA mesophase induced by the cold drawing process was examined by the WAXD and polarized FTIR techniques. Of note, it is interesting to find that the characteristic backbone vibration mode of PLLA mesophase around 918 cm−1, which has been firstly identified by Stoclet et al. in previous study [Macromolecules 2010, 7228–7237], actually demonstrates a symmetrical peak shifting with increasing the draw ratio. By considering the WAXD data, the correlation between the peak positions for this characteristic backbone vibration mode (located around 918–921 cm−1) that related to the chain conformation and the distance of interchain packing in PLLA mesophase obtained at various draw ratios was revealed.Graphical abstract
Co-reporter:Ke Liu, Yuan Yuan, Jianming Zhang
Vibrational Spectroscopy 2011 Volume 57(Issue 1) pp:81-86
Publication Date(Web):16 September 2011
DOI:10.1016/j.vibspec.2011.05.004
Isothermal crystallization behavior of water at −30 °C in PVME aqueous solution with the PVME concentration in the range of 40–60 wt% was investigated in detail by time-dependent infrared spectroscopy and two dimensional correlation analysis. The result suggests that when the PVME concentration is between 40 and 60%, the crystallization rate decreases with increasing PVME concentration, and the crystallization of water in low temperature is kinetically controlled. Of particular interest is that the so-called “unfrozen bound water” can be frozen slowly when PVME aqueous solution is annealed at a suitable low temperature. The crystallization mechanism of water in PVME/water system is elucidated by 2D correlation analysis.
Co-reporter:Tongping Zhang, Jian Hu, Yongxin Duan, Fuwei Pi, and Jianming Zhang
The Journal of Physical Chemistry B 2011 Volume 115(Issue 47) pp:13835-13841
Publication Date(Web):October 18, 2011
DOI:10.1021/jp2087863
The structural evolutions and kinetics of melt-quenched poly(l-lactic acid) (PLLA) during the process of isothermal physical aging below the glass transition temperature (Tg) were investigated by time-resolved infrared spectroscopy. The results show that local ordered structure is developed with aging time. Such local ordered structure shows the same characteristic band at 918 cm–1 as that of the mesomorphic structure formed during the unaxially drawn process of PLLA from the glassy state. On the basis of spectroscopic evidence, we therefore proposed that the so-called local ordered structure formed by physical aging can be ascribed to a kind of mesophase of PLLA. Of particular note, a very small amount of mesophase already exists in the initial state of melt-quenched PLLA sample, whereas it is totally undetectable in the melt-quenched poly(d,l-lactide) (PDLLA) sample. By temperature-dependent IR spectroscopy, it is found that the local ordered structure formed during the physical aging process will be “partially molten” rather than “totally molten” in the temperature region corresponding to the physical aging peak of aged PLLA. Such an observation can explain the phenomenon of physical aging enhanced cold crystallization rate.
Co-reporter:Yuan Yuan, Jianming Zhang, and Jiaqian Sun
Macromolecules 2011 Volume 44(Issue 15) pp:6128-6135
Publication Date(Web):July 5, 2011
DOI:10.1021/ma200945j
The effect of solvent evaporation rate on the crystal modification and the thermal stability of solution cast regioregular poly(3-butylthiophene) (P3BT) film was investigated by WAXD, DSC, and FTIR. It is found that, independent of the solvent evaporation rates, the P3BT films prepared from chloroform solution demonstrate essentially the same interlayer distance, which is very close to the reported value of form I′, rather than the conventional form I. However, in the DSC heating curves, it is interesting to find that a single “melting” peak and a double one in the temperature region of 45–100 °C can be observed respectively for P3BT films prepared with fast and extremely slow solvent evaporation rates. The double melting behavior of P3BT in this low-temperature region has never been discussed in the literature. By temperature-dependent infrared spectroscopy, it is shown that these low-temperature “melting” peaks are related to the order-to-disorder phase transition (form I′ to form I) of P3BT. Furthermore, our spectral studies reveal that the “melting” peak around 58 °C in the DSC heating trace is associated with the conformational disordering of butyl side chains, whereas the destruction of backbone planarity and the disordering of π–π stacking can take place at higher temperature (ca. 82 °C) with decreasing the solvent evaporation rate.
Co-reporter:Ningjing Wu, Meichun Ding, Chenwei Li, Yuan Yuan, and Jianming Zhang
The Journal of Physical Chemistry B 2011 Volume 115(Issue 40) pp:11548-11553
Publication Date(Web):September 14, 2011
DOI:10.1021/jp203110u
In situ reflection–absorption infrared (RAIR) spectroscopy was used to investigate the molecular orientation and crystallization dynamics of PLLA thin films crystallized at various temperatures. The results show that the annealing temperature has significant effect on the lamellar orientation of PLLA thin films, which is confirmed by atomic force microscopy (AFM) data. It is found that edge-on lamellar crystals of PLLA thin films are mainly formed by cold crystallization at low temperatures (70–90 °C), whereas the flat-on crystals occur when the crystallization temperature reaches to 100 °C. Of particular note, our in situ RAIR data collected during the whole isothermal crystallization process suggests that the orientation of PLLA chain takes place in the early stage of the crystallization process. Moreover, the analysis on the crystallization dynamics of PLLA thin film indicates that the crystal growth dimensional and nucleation modes are also strongly affected by the crystallization temperature.
Co-reporter:Jianming Zhang, Chenwei Li, Yongxin Duan, Abraham J. Domb, Yukihiro Ozaki
Vibrational Spectroscopy 2010 Volume 53(Issue 2) pp:307-310
Publication Date(Web):20 July 2010
DOI:10.1016/j.vibspec.2010.03.015
A detailed analysis of the IR spectral changes of melt-quenched poly(l-lactic acid) (PLLA) sample is presented. It is found that the glass transition, cold crystallization, disorder-to-order and melting behavior of melt-quenched PLLA can be clearly revealed by choosing suitable characteristic bands and combing the 1st derivative manipulation. Of particular note, it is found that, there are chain segment relaxation for both the irregular conformation and the regular helical conformation in the process of glass transition. During the disorder-to-order phase transition, the content of 10/3 helix as indicated by the helical band at 921 cm−1 increases slightly, which suggests that the structural rearrangement and recrystallization may take place at the same time. These results provide more information to understand the glass transition and disorder-to-order phase transition behavior of PLLA at molecular level.
Co-reporter:Jianming Zhang, Yongxin Duan, Abraham J. Domb and Yukihiro Ozaki
Macromolecules 2010 Volume 43(Issue 9) pp:4240-4246
Publication Date(Web):March 5, 2010
DOI:10.1021/ma100301h
A detailed analysis of the IR spectrum of melt-quenched PLLA−PEG−PLLA sample and its change with temperature is presented. It was found that, in the initial state of the melt-quenched PLLA−PEG−PLLA sample, the PLLA constituent does not exist as a normal amorphous or crystalline phase but as a kind of mesophase, which is confirmed by the WAXD data. The IR data suggest that both chain conformation and chain packing are disordered to some extent in such a mesophase. Therefore, this mesophase is less thermally stable than the ordered α phase and even the disordered α phase (α′) of PLLA. In the heating process, the mesophase of PLLA in the PLLA−PEG−PLLA copolymer starts the partial melt first upon heating in a stepwise way, and subsequently it is reorganized directly into the stable α phase but not through the α′ phase of PLLA. These phase transition behaviors are examined and discussed at the molecular functional group level.
Co-reporter:Yongxin Duan, Jianming Zhang, Haibo Chang, Shouke Yan, Chunming Yang, Isao Takahashi and Yukihiro Ozaki
Macromolecules 2010 Volume 43(Issue 12) pp:5315-5322
Publication Date(Web):May 19, 2010
DOI:10.1021/ma100228r
Melting behavior of epitaxially crystallized polycarprolactone (PCL) on a highly oriented polyethylene (PE) substrate was investigated by synchrotron small-angle X-ray scattering (SAXS) and Fourier transform infrared spectroscopy (FTIR). It is found that two dominant crystal thicknesses are clearly identified in the final melting stage around the melting point. In contrast to the normal melting process of polymers, the original PCL crystal and the melt-reorganized one with various lamellar thicknesses are molten and diminished simultaneously. During the melting process, orientations of the residual crystal and ordered all-trans PCL chain are found to be kept. However, the average chain orientation relaxation in the amorphous region is synchronously decreased with the evolution of melting process. A sliding diffusion mechanism was used to explain the melt behavior of PCL on the highly oriented PE substrate.
Co-reporter:Yuan Yuan ; Jianming Zhang ; Jiaqian Sun ; Jian Hu ; Tongping Zhang ;Yongxin Duan
Macromolecules () pp:
Publication Date(Web):November 3, 2011
DOI:10.1021/ma2017106
Poly(3-hexyllthiophene) (P3HT) with high crystallinity was prepared by controlling the solvent evaporation rate together with the aid of chloroform vapor annealing. According to the infrared spectroscopy combined with the thermal analysis and the X-ray diffraction (XRD) data, a new crystal modification named as form I′ was identified for P3HT sample crystallized under extremely slow evaporation rate at low temperature (13 °C). Such crystal modification has shorter interlayer distance than that of the more common but more disordered form I of P3HT. Moreover, it demonstrates a distinct endothermic peak around 54 °C and a characteristic IR band at 823 cm–1, which have never been reported for P3HT in the literature. The origin of the structural transition around 54 °C is investigated in detail by temperature-dependent infrared spectroscopy combined with the in situ synchrotron WAXD measurement. It is found that, during the heating process of P3HT form I′ crystal, there is the form I′-to-form I phase transition from 30 to 60 °C, which belongs to the solid-to-solid phase transition.
Co-reporter:Zhongjie Ren, Dianming Sun, Jianming Zhang and Shouke Yan
Journal of Materials Chemistry A 2012 - vol. 22(Issue 36) pp:NaN18846-18846
Publication Date(Web):2012/08/02
DOI:10.1039/C2JM34379G
Reduced graphene oxide (rGO) sheets covalently functionalized with n-type tetrachloroperylene diimide (PDI) and oligomeric PDI have been prepared by a two-step approach. Firstly, graphene oxide (GO) was modified by an amidation reaction with 3-aminopropyldimethylethoxylsilane or 3-aminopropyldiethoxylmethylsilane, during which GO was reduced thermally. They then react with the silanol modified PDI by dehydration condensation to obtain PDI and oligomeric PDI modified rGO (rGO–PDI and rGO–(PDI)n). The successful preparation of rGO–PDI and rGO–(PDI)n were confirmed by FTIR, Raman, X-ray photoelectron spectroscopy and XRD. The morphologies of rGO–PDI and rGO–(PDI)n sheets were studied using AFM. It was found that surface morphologies and height of rGO–PDI and rGO–(PDI)n sheets are dependent on the solvents used for casting due to differences in the solubility of PDI. Moreover, the fluorescence emission spectrum of rGO–PDI and rGO–(PDI)n shows strong fluorescence quenching and blue shift, especially in ethanol. Current sensing atomic force microscopy (CSAFM) indicated that the rGO–PDI composite shows quite different electric conductivity and optical properties with grafting efficiency and different solvents used for casting. Significantly, the electronic conductivity of rGO–(PDI)n increased by 2–3 orders of magnitude compared to rGO–PDI.
Co-reporter:Hongsheng Yang, Tongping Zhang, Min Jiang, Yongxin Duan and Jianming Zhang
Journal of Materials Chemistry A 2015 - vol. 3(Issue 38) pp:NaN19272-19272
Publication Date(Web):2015/08/24
DOI:10.1039/C5TA06452J
We report an ambient pressure dried graphene aerogel (ADGA) with superelasticity (rapidly recoverable from >90% compression) and multifunctionality that could be obtained with ordinary instruments by recasting a partially reduced graphene oxide hydrogel (PRGH) with an ice-template method. This study would be a key progress for realizing cost-effective and large-scale commercial production of high-performance graphene aerogels.
Co-reporter:Tongping Zhang, Ping Liu, Chunrui Sheng, Yongxin Duan and Jianming Zhang
Chemical Communications 2014 - vol. 50(Issue 22) pp:NaN2892-2892
Publication Date(Web):2013/12/16
DOI:10.1039/C3CC48652D
A green and facile route for producing reduced graphene oxide based on ionic liquids has been proposed, in which the as-prepared graphene can be redispersed stably in water (up to 0.6 mg mL−1) after being made into a flow-directed solid film.
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