Co-reporter:Yu Guan, Wang Li, Yuliang Zhang, Zhiqing Shi, Jiang Tan, Fei Wang, Yinghan Wang
Composites Science and Technology 2017 Volume 144(Volume 144) pp:
Publication Date(Web):26 May 2017
DOI:10.1016/j.compscitech.2017.03.010
•Aramid nanofibers with ultrahigh mechanical properties were prepared through the deprotonation process of STARAMID F-3.•Strong hydrogen bonding interactions were formed between poly (vinyl alcohol) and aramid nanofibers.•Simultaneously superior strength and high toughness of PVA/ANFs nanocomposites were achieved.It remains challengeable for fabricating polymer nanocomposites with combined high strength and toughness. Inspired by spider silk with multiscale hierarchical architectures, we used aramid nanofibers F-3 (ANFs-3) to reinforce poly (vinyl alcohol) (PVA) via hydrogen bonding assembly. The PVA/ANFs nanocomposite films were prepared by a simple solution casting method. Our results showed that the simultaneously significant enhancement in both strength and toughness of the nanocomposites were achieved, due to the multiple hydrogen bonding interactions between PVA and ANFs-3. When the loading amount of ANFs-3 was 5 wt%, the PVA nanocomposite films demonstrated the best combination of tensile strength and toughness, which were 79.2% and 148.8% higher than that of pure PVA, respectively. Moreover, the thermal stability of PVA/ANFs-3 nanocomposites was greatly enhanced. This work offers a novel and facile approach for producing high performance materials which can be potentially used in specific fields in the future.Simultaneously significant enhancement in both strength and toughness of the PVA/ANFs nanocomposites films were achieved via multiple hydrogen bonding interactions.Download high-res image (286KB)Download full-size image
Co-reporter:Yuliang Zhang, Leishan Shao, Bin Liu, Fei Wang, Yinghan Wang
Progress in Organic Coatings 2017 Volume 112(Volume 112) pp:
Publication Date(Web):1 November 2017
DOI:10.1016/j.porgcoat.2017.07.010
•Liquid polysulfide, with low cost and excellent chemistry resistance, is introduced in WPU.•The effect of molecular weight of liquid polysulfide on the properties of WSPU is firstly studied.•Water and organic solvent resistance of WSPU are effectively improved by liquid polysulfide with appropriate molecular weight.In the present work, polyester waterborne polysulfide-based polyurethane (WSPU) films were successfully synthesized from liquid polysulfide(PSF), poly(butylene adipate) (PBA) and isophorone diisocyanate (IPDI). The effect of PSF molecular weight on the chemical structures, mechanical and thermal properties of the resultant films were investigated by Fourier transform infrared (FTIR) spectroscopy, tensile test and Thermogravimetric analyzer (TGA). As the molecular weight of PSF increased, microphase separation was enhanced to some extent, resulting into an enhanced mechanical behavior and thermal stability. Meanwhile, with the increase in molecular weight of PSF, water resistance investigated by means of water uptake and mechanical behavior analysis was enhanced in general. Chemical resistance to organic solvents was also improved. When the molecular weight of PSF was about 5000, the water uptake and solvent swelling decreased to 2.83% and 95.1% respectively. The excellent performance may suggest a broader application in the surface material areas for WSPU films.Download high-res image (78KB)Download full-size image
Co-reporter:Feifei Deng, Yu Guan, Zhiqing Shi, Fei Wang, Xinyuan Che, Yawei Liu, Yinghan Wang
Composites Science and Technology 2017 Volume 150(Volume 150) pp:
Publication Date(Web):29 September 2017
DOI:10.1016/j.compscitech.2017.07.009
In order to improve the dispersion of nanoparticles (NPs) and enhance the interfacial interactions between NPs and Poly (vinyl alcohol) (PVA) matrix, the surface of titanium dioxide (TiO2) was modified by green and biocompatible dopamine (DA). PVA composites containing TiO2 or modified TiO2 (DA-TiO2) were fabricated through simple one-step method. The as-prepared composites were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), tensile experiments and thermogravimetric analysis (TGA). The TEM images demonstrated that DA-TiO2 NPs were dispersed well in the PVA matrix, which may originate from the hydrogen bonding and covalent bond formed between PVA and DA-TiO2 NPs. The tensile experiments exhibited significant improvement for the mechanical properties of PVA composites with proper amount of DA-TiO2 NPs. Especially, the PVA composites with 1 wt% DA-TiO2 NPs displayed the desired consequences in terms of tensile strength and toughness, compared to the pure PVA, which were increased by 47.9% and 145.2%, respectively. The TGA curves showed that DA-TiO2 NPs enhanced the thermal stability of PVA. Additionally, PVA/DA-TiO2 composite showed relatively good optical transparency and water resistance.
Co-reporter:Xinyuan Che, Shiming Gong, Heng Zhang, Bin Liu and Yinghan Wang
Physical Chemistry Chemical Physics 2016 vol. 18(Issue 5) pp:3884-3892
Publication Date(Web):21 Dec 2015
DOI:10.1039/C5CP06488K
Polyimides (PI-N9 and PI-N12) were synthesized from two kinds of functional diamines, whose junction modes between backbones and side chains were different. Side chains of PI-N9 were linked to the backbones with an ether bond spacer; and side chains of PI-N12 were directly linked to the backbones without any spacer. The PI alignment layer surfaces were investigated by atomic force microscopy, surface free energy measurements, X-ray photo-electron spectroscopy and polarized attenuated total reflection Fourier transformed infrared spectroscopy. It was found that PI-N9 lost the vertical alignment capability after high-strength rubbing, while PI-N12 could still induce liquid crystals (LCs) to align vertically under the same condition. The mechanism of the macroscopic molecular orientation of the PI surface is proposed. During the high-strength rubbing process, the side chain could rotate around the flexible ether bond which existed between the side chain and the main chain of PI-N9 and then fell over. Therefore, PI-N9 could not induce the vertical alignment of LCs anymore. But PI-N12 could keep LCs aligning vertically all the time, which proved that the stability of LC alignment induced by PI-N12 was better.
Co-reporter:Yuliang Zhang, Leishan Shao, Dongyu Dong and Yinghan Wang
RSC Advances 2016 vol. 6(Issue 21) pp:17163-17171
Publication Date(Web):02 Feb 2016
DOI:10.1039/C5RA24574E
Environmentally friendly, waterborne polysulfide-based polyurethane (WSPU) films have been successfully synthesized from liquid polysulfide (PSF), polytetramethylene ether glycol (PTMG), isophorone diisocyanate (IPDI) and dimethylolpropionic acid (DMPA). The chemical structures, mechanical and thermal properties of the chemically modified films have been carefully investigated using ATR-IR, gel permeation chromatography (GPC), tensile tests, dynamic mechanical analysis (DMA) and a thermogravimetric analyzer (TGA). As the PSF content increases from 0 to 20%, after an immersion in deionized water for 96 h, the water absorption decreases from 6.2% to 3.4% and the tensile strength retention increases from 74.3% to 91.7%. The chemical resistance to organic solvents is also improved significantly. The enhanced water and organic solvent resistances of waterborne polyurethanes (WPUs) are primarily attributed to the addition of a PSF containing sulfur group. However, the tensile strength and thermal performance are weakened to some extent. This study produces a new composite derived from polysulfide, and its high water and solvent resistance performance could contribute to surface material research.
Co-reporter:Xinyuan Che, Shiming Gong, Leishan Shao, Tian Lan, Fei Wang and Yinghan Wang
RSC Advances 2016 vol. 6(Issue 60) pp:55479-55489
Publication Date(Web):26 May 2016
DOI:10.1039/C6RA09009E
Two series of polyimides (PIs) which contained identical side chains but different backbones were synthesized from the same functional diamine: RPI-X% and SPI-X% (X = 20, 30, 40, X stands for the molar content of functional diamine). Rigid polyimides (RPIs) are PIs whose backbones are composed of wholly rigid aromatic units and soft polyimides (SPIs) are PIs whose backbones are composed of flexible ether units and aromatic units. The surface morphology, chemical composition and molecular orientation of the polyimide (PI) alignment layer surfaces were investigated by atomic force microscopy, X-ray photo-electron spectroscopy and polarized attenuated total reflection Fourier transformed infrared spectroscopy, respectively. The results showed that both RPI and SPI could induce LC to align vertically without a rubbing process when the molar content of the functional diamine reached 30%. However, the rubbed RPI-30% whose side chains were oriented vertically induced vertical alignment of the liquid crystal (LC), while the rubbed SPI-30% whose side chains were oriented parallel induced parallel alignment of the LC. The cause of this distinction was attributed to the different main chain structures: the wholly rigid aromatic units in RPI's main chains could restrict the movements of molecular chains so the side chains can maintain vertical orientation all the time; flexible ether bands in SPI main chains could endow molecular chains with mobility so the side chains fall over easily after rubbing.
Co-reporter:Yu Guan, Leishan Shao, Dongyu Dong, Fei Wang, Yuliang Zhang and Yinghan Wang
RSC Advances 2016 vol. 6(Issue 74) pp:69966-69972
Publication Date(Web):04 Jul 2016
DOI:10.1039/C6RA08904F
Polymer composites exhibit very high strength but this is usually found to be at the expense of toughness, which greatly limits their application in many fields. Inspired by the hierarchical architectures in spider silk, we attempted to combine simultaneous high strength and toughness via a hydrogen bonding network. PVA composites with tannic acid (TA) molecules were fabricated by a green and easy-to-scale-up water casting method. The results showed that the hydrogen bonding crosslinking between PVA and TA has strong effect on the Tg, crystallinity, thermal stability and mechanical properties of PVA. In addition, the PVA composite films with 3 wt% TA exhibited, simultaneously, the best tensile strength and toughness, improving by 46% and 27% compared to the pure PVA, respectively.
Co-reporter:Qing Gong, Shiming Gong, Heng Zhang, Lulu Liu and Yinghan Wang
RSC Advances 2015 vol. 5(Issue 70) pp:57245-57253
Publication Date(Web):23 Jun 2015
DOI:10.1039/C5RA08521G
A novel functional diamine containing a triphenylamine moiety and a biphenyl group, N,N-bis(4-aminophenyl)-4-(biphenyl)-4′-aminophenyl ether (N0), was successfully synthesized and characterized. A series of polyimides (PIs) and poly(amic acid)s (PAAs) were synthesized from cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA), 2,2′-bis(trifluoromethyl)-[1,1′-biphenyl]-4,4′-diamine (TFDB), 4-dodecyloxy-phenyl-4′,4′′-diaminotriphenylamine (C12) and the newly synthesised diamine monomer (N0) through a conventional two-step procedure that included a ring-opening polyaddition to give polyamic acids, followed by thermal cyclodehydration. Pretilt angles of a liquid crystal (LC) cell fabricated with the PIs were measured, and the rubbing resistance of PIs containing different sidechain structures was investigated. PI1 with a rigid biphenyl side chain could induce LC parallel alignment after the rubbing process. Although PI3 containing a flexible alkyl side chain could induce LC vertical alignment before the rubbing process, it only induced LC parallel alignment after the rubbing process. However, PI2 containing both rigid biphenyl side chains and flexible alkyl side chains could induce LC vertical alignment before and after the rubbing process. A new method for improving the rubbing resistance of PIs and a generation mechanism of rubbing resistance have been proposed. In addition, all PI films showed high thermal stability and high transmittance in the wavelength range of 400–700 nm.
Co-reporter:Ming Liu, Xinguo Zheng, Shiming Gong, Lulu Liu, Zhen Sun, Leishan Shao and Yinghan Wang
RSC Advances 2015 vol. 5(Issue 32) pp:25348-25356
Publication Date(Web):02 Mar 2015
DOI:10.1039/C4RA16997B
A novel functional diamine containing triphenylamine moiety and biphenyl as well as a long alkyl chain, 4-dodecyloxy-biphenyl-4′,4′′-diaminotriphenylamine (DBDTA), was synthesized and characterized. A series of polyimides (PIs) were copolymerized from DBDTA, 3,3′-dimethyl-4,4′-methylenedianiline (DMMDA) and 4,4′-oxydiphthalic anhydride (ODPA) via a one-step method. The chemical structures of the diamine and PIs were characterized by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance spectroscopy (1H NMR). Properties such as the solubility, rubbing resistance, thermal stability and pre-tilt angle of the PIs were investigated. Furthermore, the results were compared with the PIs-BZA derived from 4-dodecyloxy-biphenyl-3′,5′-diaminobenzoate (DBPDA). The PIs-TPA derived from DBDTA exhibited better transparency and thermal stability than the PIs-BZA from DBPDA. When the content of functional diamines was only 10%, the PI1-TPA derived from DBDTA displayed better solubility than the PI1-BZA from DBPDA. In addition, all PIs could induce uniform vertical alignment of the liquid crystals (LCs) before and after the rubbing process, but PI1-BZA only induced parallel alignment of the LCs after rubbing process. It is suggested that the PI1-TPA film is more resistant to the rubbing process than PI1-BZA.
Co-reporter:Tian Lan;Yu Zhang;Haiping Wang;Liping Yang;Wenjie Yang
Polymer International 2015 Volume 64( Issue 3) pp:405-412
Publication Date(Web):
DOI:10.1002/pi.4803
Abstract
Aiming to decrease the memory effect of polymer-dispersed liquid crystals (PDLCs), a type of graft macroinitiator, synthesized by reversible addition–fragmentation chain transfer and atom transfer radical polymerization, was employed to prepare PDLCs with graft copolymer matrix in our previous work. Compared with linear copolymer matrix PDLCs prepared using a linear macroinitiator, it was found that, although low-memory-effect PDLCs were obtained, the driving voltage and transmittance of the PDLCs were unfortunately sacrificed to some extent. Thus, it is necessary to improve the electro-optical properties of PDLCs on the basis of the original research performed by us. In the work reported in this article, a kind of linear macroinitiator with high refractive index and another graft macroinitiator with flexible branched chains were employed to prepare PDLCs. The results showed that by using mixed macroinitiators, the electro-optical properties of PDLCs could be improved, and a possible mechanism is proposed.
Co-reporter:Yao Gu;Zhen Sun;Shiming Gong;Heng Zhang;Qing Gong
Journal of Materials Science 2015 Volume 50( Issue 20) pp:6552-6558
Publication Date(Web):2015 October
DOI:10.1007/s10853-015-9186-7
A new triphenylpyridine-containing aromatic diamine monomer named 4-phenyl-2,6-bis(4-aminophenyl) pyridine was successfully synthesized. A series of polyimides (PIs) with triphenylpyridine moieties were prepared from the newly synthesized diamine monomer via a one-step polymerization with oxydiphthalicanhydride. All the PIs were amorphous and showed excellent solubility in many polar aprotic solvents at room temperature and most of them could afford flexible, transparent, and tough films with good mechanical properties. All the PIs had useful levels of thermal stability associated with high glass-transition temperatures (299–341 °C), 10 % weight-loss temperatures in excess of 537 °C, and char yields at 800 °C in nitrogen higher than 54.9 %.
Co-reporter:Tian Lan;Wenjie Yang;Juan Peng;Mingke Li
Polymer Engineering & Science 2015 Volume 55( Issue 1) pp:8-13
Publication Date(Web):
DOI:10.1002/pen.23857
The article aimed to decrease the memory effect of polymer dispersed liquid crystals (PDLCs) films, reversible additional-fragmental chain transfer (RAFT) polymerization was used to synthesize RAFT-polystyrene (RAFT-PS), which was a kind of RAFT macroinitiators and used to prepare PDLCs via photo polymerization induced phase separation (PIPS). Different RAFT agents were used to synthesize RAFT-PS. The effect of photoinitiator concentration on the memory effect of these PDLCs was investigated, and the effect of structures of RAFT macroinitiators on the memory effect of the PDLCs was also discussed. The results showed that PDLC films with higher photoinitiator concentration and polymer matrix which had two rigid chains in two ends showed lower memory effect, which could be reduced from 10.9% to 2.5% in this experiment. POLYM. ENG. SCI., 55:8–13, 2015. © 2014 Society of Plastics Engineers
Co-reporter:Leishan Shao, Jingjing Li, Yuliang Zhang, Shiming Gong, Heng Zhang and Yinghan Wang
Journal of Materials Chemistry A 2014 vol. 2(Issue 34) pp:14173-14180
Publication Date(Web):27 Jun 2014
DOI:10.1039/C4TA02833C
The reduction extent of graphene oxide (GO) was tailored by adjusting the solvothermal reduction time. The effects of the reduction extent of GO on the structure and properties of graphene/poly(vinyl alcohol) (PVA) composites were investigated. Results show that the mechanical properties of polymer composites are sensitive to the reduction extent of GO, and reduced graphene oxide (rGO) with an optimum reduction extent (C/O ratio = 3.94) could more efficiently improve the mechanical properties of PVA than low/high reduction extent rGO. Low reduction extent rGO could enhance the interfacial interactions through the formation of hydrogen bonds with PVA chains, but its mechanical strength is smaller. High reduction extent rGO has stronger mechanical strength while the deep deoxidation of GO significantly weakens interfacial interactions between rGO nanosheets and PVA chains. Achieving optimum reinforcing effects requires balancing and optimizing interfacial interactions and mechanical strength of rGO.
Co-reporter:Jingjing Li, Leishan Shao, Xiaohai Zhou and Yinghan Wang
RSC Advances 2014 vol. 4(Issue 82) pp:43612-43618
Publication Date(Web):04 Sep 2014
DOI:10.1039/C4RA07295B
High strength composite fibers were prepared from poly(vinyl alcohol) (PVA) (degree of polymerization: 6100) reinforced by reduced graphene oxide (rGO). The macroscopically homogeneous PVA/rGO dispersion was obtained through solvothermal reduction of graphene oxide (GO) in PVA/dimethyl sulfoxide (DMSO)/H2O solution, and then extruded into composite fibers by gel spinning followed by hot drawing. It was found that the mechanical properties of PVA fibers were greatly improved by incorporating rGO. At 0.1 wt% rGO loading, tensile strength increased from 1.8 GPa for the pure PVA fiber to 2.2 GPa for the PVA/rGO composite fiber. The results of mechanical properties and FTIR spectra for PVA/rGO composite fibers suggest the relatively strong interfacial interactions between rGO nanosheets and PVA that improve the load transfer from the polymer matrix to the reinforcing phase. Meanwhile, the thermal stability of the composite fibers was also enhanced by rGO addition.
Co-reporter:Tian Lan, Wenjie Yang, Hao Huang and Yinghan Wang
RSC Advances 2014 vol. 4(Issue 29) pp:14997-15002
Publication Date(Web):14 Mar 2014
DOI:10.1039/C4RA01225A
Response time, an important property of polymer dispersed liquid crystals (PDLCs), was reported to be affected by the structures of the polymer matrix. In this study, reversible addition fragmentation chain transfer (RAFT) polymerization and atom transfer radical polymerization (ATRP) were used to synthesize a well-defined copolymer matrix. A kind of graft macroinitiator with both controlled main chain and branched chains was employed to prepare PDLCs with a graft copolymer matrix; meanwhile a linear macroinitiator was also synthesized to prepare PDLCs with a linear copolymer matrix. The effect of different matrix structures on response times was investigated. It was found that the introduction of branched chains made a big difference to response times, and a possible mechanism was proposed.
Co-reporter:Bin Liu, Yinghan Wang
Progress in Organic Coatings 2014 Volume 77(Issue 1) pp:219-224
Publication Date(Web):January 2014
DOI:10.1016/j.porgcoat.2013.09.007
•The influencing factors of the polysulfide rubber emulsion are investigated.•The anti-corrosive property and mechanical behaviour of the epoxy coatings are investigated.•The relationship between anti-corrosive property and microstructure of the epoxy coatings are discussed.•Polysulfide rubber modified epoxy coating has better anti-corrosive property than that of the unmodified epoxy coating.In this study, a polysulfide rubber emulsion was synthesized through the pre-emulsification of polysulfide rubber by mixed-emulsifiers and polyvinyl alcohol as a weight stabilizer and the emulsification by adding deionized water dropwise at a speed of 1 ml/min, stirring at a speed of 1500 rpm and adjusting pH to 8 by ammonia. The epoxy coating was modified by the polysulfide rubber emulsion. The anticorrosive coating was prepared by using waterborne amine dispersion as a curing agent and polysulfide rubber as a modifier. It had a good chemical resistance and excellent overall mechanical performance. The coatings were characterized by Tafel polarization curves and Scanning electron microscope.
Co-reporter:Tian Lan;Wenjie Yang;Juan Peng;Mingke Li
Polymer International 2014 Volume 63( Issue 9) pp:1691-1698
Publication Date(Web):
DOI:10.1002/pi.4693
A type of graft macroinitiator, synthesized by reversible addition–fragmentation chain transfer (RAFT) and atom transfer radical polymerization, was employed to prepare polymer-dispersed liquid crystals (PDLCs) with graft copolymer matrix; meanwhile, a linear macroinitiator was also synthesized via RAFT polymerization. The effect of linear and graft macroinitiators on the electro-optical (EO) properties of the PDLCs was investigated. The results showed that the graft macroinitiator could make a large difference to the EO properties of the PDLCs. The memory effect was reduced remarkably, but the driving voltage increased and transmittance decreased. A possible mechanism is presented. © 2014 Society of Chemical Industry
Co-reporter:Jia-hao Xia;Ying Jiang;Shi-ming Gong;Zhen Sun
Chinese Journal of Polymer Science 2014 Volume 32( Issue 12) pp:1610-1619
Publication Date(Web):2014 December
DOI:10.1007/s10118-014-1550-6
Polyimides (PI) with different side chains in structure were synthesized by copolycondensation of pyromelliticmdianhydride (PMDA) with 3,5-diamino-(4′-methane acid hexyl ester) phenyl-benzamide (C6-PDA), (4-butoxybiphenol)-3′, 5′-diaminobenzoate (C4-BBDA) and 3, 5-diamino-benzoic acid decyl ester (C10-DA) named PI-PDA, PI-C4, PI-DA, respectively. The lengths of side chains of PI-PDA and PI-DA are as similar as that of PI-C4. Through the pretilt angle tests it is demonstrated that neither the structure of side chains nor the rubbing process could make an obvious difference on vertical alignment property when the lengths of the side chains are similar, standing at around 1.6 nm. The measurement of surface energy of PI surfaces further proved this result. The result of the X-ray photo-electron spectroscope measurement indicated that the side chains of PIs stretched out from the polymer bulk phase and accumulated on the surface.
Co-reporter:Shiming Gong;Ming Liu;Senlin Xia
Journal of Polymer Research 2014 Volume 21( Issue 9) pp:
Publication Date(Web):2014 September
DOI:10.1007/s10965-014-0542-0
A novel functional diamine containing triphenylamine and biphenyl moieties as well as a long alkyl chain, N,N-bis (4-aminophenyl)-4-(dodecyloxy-biphenyl)-4′-aminophenyl ether (B12), was successfully synthesized. A series of novel polyimides (PIs) with triphenylamine units in the polymer backbone were prepared from B12, 3,3′-dimethyl-4,4′-methylene-dianiline (DMMDA), and 4,4′-oxydiphthalic anhydride (ODPA) via a conventional two-step procedure that included a ring-opening polyaddition to give polyamic acids (PAAs) followed by chemical cyclodehydration. The chemical structures of the intermediates, diamine, and PIs were characterized by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance spectroscopy (1H NMR). All PIs were amorphous and readily soluble in many organic solvents, including tetrahydrofuran. PI films attained from a casting method showed high transmittance (above 90 %) in the wavelength range 400–700 nm and induced highly uniform vertical alignment of liquid crystals (LCs). PIs-B12 derived from B12, DMMDA, and ODPA exhibited much higher thermal stabilities than with the corresponding PIs-D12 from 4-dodecyloxy-biphenyl-3′,5′-diaminobenzoate (D12). The results demonstrated that the introduction of triphenylamine units into the polymer backbone improves the thermal stability of the PIs without deteriorating their solubility.
Co-reporter:Jingjing Li, Leishan Shao, Lihua Yuan, Yinghan Wang
Materials & Design 2014 54() pp: 520-525
Publication Date(Web):February 2014
DOI:10.1016/j.matdes.2013.08.090
•A new strategy was proposed to make PVA/rGO composites by solvothermal reduction.•The solvent acted not only as a reducing agent but also as a good stabilizer.•The homogeneous dispersion of rGO sheets in the PVA matrix was achieved.•The crystallinity of PVA/rGO nanocomposites was investigated.•Mechanical properties and thermal stability were greatly improved by adding rGO.Poly(vinyl alcohol) (PVA)/reduced graphite oxide (rGO) nanocomposites were synthesized by solvothermal reduction of graphite oxide (GO) in the presence of PVA. The solvent, the mixed dimethyl sulfoxide (DMSO)-dimethylformamide (DMF), could act not only as a reducing agent but also as a good stabilizer, which achieved effectively reduction of GO in the PVA matrix and avoided the agglomeration of rGO during reduction. A 53.0% increase in tensile strength and 52.6% improvement of Young’s modulus were achieved by addition of 3 wt% of rGO. Furthermore, a significant improvement of thermal stability was observed for the PVA/rGO nanocomposites.
Co-reporter:Zhen Sun, Ming Liu, Longfei Yi and Yinghan Wang
RSC Advances 2013 vol. 3(Issue 20) pp:7271-7276
Publication Date(Web):27 Mar 2013
DOI:10.1039/C3RA00147D
A new diamine with a tert-buty-substituted triphenylpyridine unit was synthesized and used in the preparation of polyimides via a one-step polymerization. The polyimides are completely amorphous and exhibit good solubility in organic solvents. As a result of the presence of bulky substituents and rigid triphenylpyridine units, the final polyimide products have high glass transition temperatures (up to 365 °C) and good thermal stability with 10% weight loss temperatures in the range 538–563 °C. Triphenylpyridine units and tert-butyl groups might play a key role in improving the solubility of the polyimides while maintaining high glass transition temperatures and good thermal stability. The polyimide films had good mechanical properties.
Co-reporter:Senlin Xia, Zhen Sun, Longfei Yi and Yinghan Wang
RSC Advances 2013 vol. 3(Issue 34) pp:14661-14670
Publication Date(Web):06 Jun 2013
DOI:10.1039/C3RA42098A
Novel functional diamine, 6-hexyloxy-naphthalen-3′,5′-diaminobenzoate (N6) containing a rigid naphthalene unit, was molecularly designed and successfully synthesized. PIs (polyimides) were obtained by copolymerization of N6, 3,3′-dimethyl-4,4′-methylenediamine (DMMDA) and 4,4′-oxydiphthalic anhydride (ODPA). The structures of the intermediates, diamines and PIs were confirmed by FT-IR and 1H NMR spectra. All PIs obtained could be dissolved in polar aprotic solvents and low-boiling-point solvents. PI (polyimide) films attained using a casting method showed favorably high transmittance above 95% in the wave length range of 400–700 nm and could align LCs vertically before and after rubbing treatment. PI–N6 derived from N6, DMMDA and ODPA exhibited a much higher temperature at a 5% weight loss (T5) compared with the corresponding PI–C6 from 4-hexyloxy-biphenyl-3′,5′-diaminobenzoate (C6). For PI–N6, the weight ratio of the side chains was smaller than that of PI–C6, but a much higher T5 was attained. The results demonstrated that the introduction of a naphthalene unit into the side chain could effectively improve the thermal stability of PI without sacrificing its solubility. Moreover, the outstanding thermal stability of the PIs was explained in a preliminary manner by the imidization reaction mechanism.
Co-reporter:Zhen Sun
Polymers for Advanced Technologies 2013 Volume 24( Issue 1) pp:126-129
Publication Date(Web):
DOI:10.1002/pat.3043
Several hyperbranched polyimides (HBPIs) were applied in liquid crystal (LC) alignment layers and exhibited outstanding performance for LC alignment. The maximum pretilt angle was above 8°, and the minimum pretilt angle was 4.2°. The results of atomic force microscope measurement disclosed that a lot of grooves were aligned parallel to the rubbing direction and found that the grooves were not main factor for LC alignment. The LC alignment and pretilt angles are unambiguously associated with the intrinsic HBPI chemical structures. The results of thermal gravimetric analysis and ultraviolet–visible spectra showed that the HBPIs had good thermal stability and excellent transmittance. T5 and T10 were higher than 360°C and 400°C, respectively. Copyright © 2012 John Wiley & Sons, Ltd.
Co-reporter:Senlin Xia;Longfei Yi;Zhen Sun
Journal of Polymer Research 2013 Volume 20( Issue 8) pp:
Publication Date(Web):2013 August
DOI:10.1007/s10965-013-0219-0
Two functional diamines, octyl-4-(3,5-diaminobenzamido)benzoate (O8, containing phenyl rings) and 3,5-diamino-N-(2-octyl-1,3-dioxoisoindolin-5-yl)benzamide (D8, containing a phthalimide ring), were designed and successfully synthesized. Two kinds of PIs were obtained by copolymerizing 3,3′-dimethyl-4,4′-methylenediamine (DMMDA), 4,4′-oxydiphthalic anhydride (ODPA), and D8 or O8. All of the PIs possessed excellent solubility. The PI films exhibited high transmittance, and were able to align liquid crystals (LCs) vertically. In contrast to the PIs generated from O8 (PI-O8), PIs created from D8 (PI-D8) were able to align LCs vertically even after rubbing, and also exhibited better thermal stability. The temperature at which 5 % of the weight of PI-D8 was lost (T5) was higher than that for PI-O8. The results showed that the introduction of imide groups to the side chain improved the thermal stability and rubbing resistance of PIs without sacrificing their solubility and transmittance.
Co-reporter:Zhigang Yang;Ding Li;Cuihong Pan
Polymers for Advanced Technologies 2012 Volume 23( Issue 9) pp:1321-1327
Publication Date(Web):
DOI:10.1002/pat.2046
Two hyperbranched prepolymers were synthesized via the reversible addition-fragmentation chain transfer copolymerization of butyl acrylate or butyl methacrylate with divinyl benzene, respectively. These prepolymers were used in the photopolymerization-induced phase separation process of preparing polymer dispersed liquid crystal (PDLC) films with no risk of gelation. The morphologies of PDLC samples were investigated. Of particular interest was that the driving voltage (V90) of PDLC with high glass transition temperature (Tg) matrix was as low as 5 V, whereas the V90 of PDLC with low Tg matrix was still high. An explanation for this phenomenon is the hypothesis that different interaction modes function at the interface of liquid crystal and polymer. Meanwhile, the hysteresis of the two systems was minor, which correlated with the hyperbranched structure of polymer. The on-state transmittance (TON) of PDLC films enhanced because of the well matching between the refractive index of polymer and that of liquid crystal. Copyright © 2011 John Wiley & Sons, Ltd.
Co-reporter:Xin Du;Bin Yan;Minke Li;Shu Chen;Jiali Yao
Polymer International 2011 Volume 60( Issue 7) pp:971-975
Publication Date(Web):
DOI:10.1002/pi.3077
Abstract
Macro reversible addition–fragmentation chain transfer (RAFT) agents, i.e. RAFT polystyrene (RAFT-PS) and RAFT poly(n-butyl acrylate) (RAFT-PBA), were mixed. Polymer-dispersed liquid crystals (PDLCs) were prepared using the mixture together with methyl acrylate and liquid crystal E7. The electro-optical properties of the PDLCs obtained were investigated. The results showed that the advantages of the electro-optical properties of RAFT-PS- and RAFT-PBA-dependent PDLCs could be combined in RAFT agent mixture-dependent PDLCs. Copyright © 2011 Society of Chemical Industry
Co-reporter:Yu-Qing Fang, Jian Wang, Qin Zhang, Yu Zeng, Ying-Han Wang
European Polymer Journal 2010 Volume 46(Issue 5) pp:1163-1167
Publication Date(Web):May 2010
DOI:10.1016/j.eurpolymj.2009.12.021
A series of polyimides (PIs) were copolymerized from 4-dodecyloxy-biphenyl-3′,5′-diaminobenzoate (DBPDA), 3,3′-dimethyl-4,4′-methylene-dianiline (DMMDA) and 4,4′-oxydi(phthalic anhydride) (ODPA) via one-step method. The PIs possessed excellent solubility in polar aprotic solvents and easily formed thin flexible films by solution casting. The glass-transition temperatures (Tgs) of the PIs were in the range of 219–242 °C and thermal decomposition temperatures in nitrogen occurred above 350 °C. The resultant PI films exhibited high transparency at wavelengths greater than 400 nm and induced excellent uniform vertical alignment of liquid crystal (LC). Even after the rubbing process, the pretilt angles of LC were still above 89°. The PI seems to be a prospective material for alignment layers in flexible displays.
Co-reporter:Xin Du;Bin Yan;Jiali Yao;Shu Chen;Minke Li
Journal of Polymer Science Part A: Polymer Chemistry 2010 Volume 48( Issue 23) pp:5557-5561
Publication Date(Web):
DOI:10.1002/pola.24367
Abstract
In this article, copolymer macroinitiators prepared with styrene and iso-octyl acrylate by reversible additional-fragmental chain transfer polymerization were used to prepare polymer-dispersed liquid crystals (PDLCs) with methyl acrylate. The electro-optical properties of the PDLCs were investigated. The results showed that the glass transition temperature (Tg) of the macroinitiator has a great influence on the memory effect of the resulting PDLCs. Low driving voltage and low memory effect PDLCs could easily be obtained with copolymer macroinitiators. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010
Co-reporter:Leishan Shao, Jingjing Li, Yuliang Zhang, Shiming Gong, Heng Zhang and Yinghan Wang
Journal of Materials Chemistry A 2014 - vol. 2(Issue 34) pp:NaN14180-14180
Publication Date(Web):2014/06/27
DOI:10.1039/C4TA02833C
The reduction extent of graphene oxide (GO) was tailored by adjusting the solvothermal reduction time. The effects of the reduction extent of GO on the structure and properties of graphene/poly(vinyl alcohol) (PVA) composites were investigated. Results show that the mechanical properties of polymer composites are sensitive to the reduction extent of GO, and reduced graphene oxide (rGO) with an optimum reduction extent (C/O ratio = 3.94) could more efficiently improve the mechanical properties of PVA than low/high reduction extent rGO. Low reduction extent rGO could enhance the interfacial interactions through the formation of hydrogen bonds with PVA chains, but its mechanical strength is smaller. High reduction extent rGO has stronger mechanical strength while the deep deoxidation of GO significantly weakens interfacial interactions between rGO nanosheets and PVA chains. Achieving optimum reinforcing effects requires balancing and optimizing interfacial interactions and mechanical strength of rGO.
Co-reporter:Xinyuan Che, Shiming Gong, Heng Zhang, Bin Liu and Yinghan Wang
Physical Chemistry Chemical Physics 2016 - vol. 18(Issue 5) pp:NaN3892-3892
Publication Date(Web):2015/12/21
DOI:10.1039/C5CP06488K
Polyimides (PI-N9 and PI-N12) were synthesized from two kinds of functional diamines, whose junction modes between backbones and side chains were different. Side chains of PI-N9 were linked to the backbones with an ether bond spacer; and side chains of PI-N12 were directly linked to the backbones without any spacer. The PI alignment layer surfaces were investigated by atomic force microscopy, surface free energy measurements, X-ray photo-electron spectroscopy and polarized attenuated total reflection Fourier transformed infrared spectroscopy. It was found that PI-N9 lost the vertical alignment capability after high-strength rubbing, while PI-N12 could still induce liquid crystals (LCs) to align vertically under the same condition. The mechanism of the macroscopic molecular orientation of the PI surface is proposed. During the high-strength rubbing process, the side chain could rotate around the flexible ether bond which existed between the side chain and the main chain of PI-N9 and then fell over. Therefore, PI-N9 could not induce the vertical alignment of LCs anymore. But PI-N12 could keep LCs aligning vertically all the time, which proved that the stability of LC alignment induced by PI-N12 was better.
![1,4-Benzenediamine, N1-(4-aminophenyl)-N1-[4-[[4'-(nonyloxy)[1,1'-biphenyl]-4-yl]oxy]phenyl]-](/data/chemimg/3783900/1863035-08-8.png)
![1,4-Benzenediamine, N1-(4-aminophenyl)-N1-[4-[[4'-(nonyloxy)[1,1'-biphenyl]-4-yl]oxy]phenyl]-](/data/chemimg/3783900/1863035-08-8_b.png)
![Benzoic acid, 3,5-diamino-, 4'-(dodecyloxy)[1,1'-biphenyl]-4-yl ester](/data/chemimg/3783900/947236-30-8.png)
![Benzoic acid, 3,5-diamino-, 4'-(dodecyloxy)[1,1'-biphenyl]-4-yl ester](/data/chemimg/3783900/947236-30-8_b.png)
![1,4-Benzenediamine, N1-(4-aminophenyl)-N1-[4'-(dodecyloxy)[1,1'-biphenyl]-4-yl]-](/data/chemimg/3783900/1863035-09-9.png)
![1,4-Benzenediamine, N1-(4-aminophenyl)-N1-[4'-(dodecyloxy)[1,1'-biphenyl]-4-yl]-](/data/chemimg/3783900/1863035-09-9_b.png)
![Benzenamine, 4,4'-[4-[4-(octyloxy)phenyl]-2,6-pyridinediyl]bis-](/data/chemimg/3783900/1360882-45-6.png)
![Benzenamine, 4,4'-[4-[4-(octyloxy)phenyl]-2,6-pyridinediyl]bis-](/data/chemimg/3783900/1360882-45-6_b.png)
![Benzenamine, 4,4'-[4-[4-(dodecyloxy)phenyl]-2,6-pyridinediyl]bis-](/data/chemimg/3783900/1654785-04-2.png)
![Benzenamine, 4,4'-[4-[4-(dodecyloxy)phenyl]-2,6-pyridinediyl]bis-](/data/chemimg/3783900/1654785-04-2_b.png)
![Benzenamine, 3,3'-[4-[4-(dodecyloxy)phenyl]-2,6-pyridinediyl]bis-](/data/chemimg/3783900/1654785-07-5.png)
![Benzenamine, 3,3'-[4-[4-(dodecyloxy)phenyl]-2,6-pyridinediyl]bis-](/data/chemimg/3783900/1654785-07-5_b.png)
![Benzenamine, 4,4'-[4-[3-(octadecyloxy)phenyl]-2,6-pyridinediyl]bis-](/data/chemimg/3783900/1654785-11-1.png)
![Benzenamine, 4,4'-[4-[3-(octadecyloxy)phenyl]-2,6-pyridinediyl]bis-](/data/chemimg/3783900/1654785-11-1_b.png)
![Benzenamine, 4,4'-[4-[4-(hexyloxy)phenyl]-2,6-pyridinediyl]bis-](/data/chemimg/3783900/1654785-14-4.png)
![Benzenamine, 4,4'-[4-[4-(hexyloxy)phenyl]-2,6-pyridinediyl]bis-](/data/chemimg/3783900/1654785-14-4_b.png)
![PYRIDINE, 2-BROMO-5-[(HEXADECYLOXY)METHYL]-](http://img.cochemist.com/ccimg/877500/877455-81-7.png)
![PYRIDINE, 2-BROMO-5-[(HEXADECYLOXY)METHYL]-](http://img.cochemist.com/ccimg/877500/877455-81-7_b.png)
![Propanoic acid, 2,2'-[carbonothioylbis(thio)]bis[2-methyl-](/data/chemimg/104200/355120-40-0.png)
![Propanoic acid, 2,2'-[carbonothioylbis(thio)]bis[2-methyl-](/data/chemimg/104200/355120-40-0_b.png)
