Yinghan Wang

Sichuan University, Hua-yang, Sichuan, China

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Publications (45)121.58 Total impact

  • Yuliang Zhang · Leishan Shao · Dongyu Dong · Yinghan Wang
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    ABSTRACT: The 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 chemical modified films have been carefully investigated by ATR-IR, gel permeation chromatography (GPC), tensile tests, dynamic mechanical analysis (DMA) and thermogravimetric analyzer (TGA). As the PSF content 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 solvent is also improved significantly. The enhanced water and organic solvent resistances of waterborne polyurethanes (WPUs) are primarily attributed the addition of PSF containing sulfur group. However, the tensile strength and thermal performance are weakened to some extent. This study produces new composite derived from polysulfide, and its high water and solvent resistance performance could contribute to the surface material areas.
    No preview · Article · Feb 2016 · RSC Advances
  • Xinyuan Che · Shiming Gong · Heng Zhang · Bin Liu · Yinghan Wang
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    ABSTRACT: 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 layers surfaces were investigated by atomic force microscopy, surface free energy measurement, X-ray photo-electron spectroscope and polarized attenuated total reflection flourier transformed infrared spectroscopy. It was found that the PI-N9 lost the vertical alignment capability after high-strength rubbing, while the PI-N12 could still induce liquid crystals (LCs) to align vertically under the same condition. The mechanism of the macroscopic molecular orientation of the PIs 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, the 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.
    No preview · Article · Dec 2015 · Physical Chemistry Chemical Physics
  • Yao Gu · Zhen Sun · Shiming Gong · Heng Zhang · Qing Gong · Lulu Liu · Yinghan Wang
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    ABSTRACT: 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 %.
    No preview · Article · Oct 2015 · Journal of Materials Science
  • Qing Gong · Xinguo Zheng · Shiming Gong · Heng Zhang · Lulu Liu · Yinghan Wang
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    ABSTRACT: A novel functional diamine N12, containing triphenylamine moiety, biphenyl, tert-butyl substituents and long alkyl chain, N,N-bis(4-aminophenyl)-p-(3,5-di-tert-butyl-4-dodecyloxy phenyl) aniline (N12), was synthesised and characterised. A series of polyimides (PIs) were prepared based on 2,2ʹ-bis(trifluoromethyl)benzidine, 4,4ʹ-oxydiphthalicanhydride and different contents of N12 via a conventional two-step procedure that included a ring-opening polyaddition to gain polyamic acids, followed by chemical cyclodehydration. The chemical structures of the intermediates, diamines and PIs were characterised by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. All of the PIs were amorphous and exhibited good solubility in both polar aprotic solvents and some low boiling point solvents. PIs containing different content of N12 could induce highly uniform vertical alignment of liquid crystals (LCs). More importantly, PIs derived from N12 showed a good rubbing resistance. Besides, all PI films showed high transmittance in the wavelength range 400–700 nm and good thermal stabilities. Such PIs could be suitable candidates for alignment layers used in the manufacture of high-performance vertical alignment mode LC displays.
    No preview · Article · Sep 2015 · Liquid Crystals
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    ABSTRACT: In this study, we demonstrated that doping polymer matrix with a small amount of reduced graphene oxide (rGO) component (0.05–0.2%) had significant influence on the polymerisation kinetics and electro-optical performances of polymer-dispersed liquid crystal films (PDLCs) fabricated with macro reversible addition-fragmentation chain transfer agents. The effects of rGO content were studied in terms of morphology, compound viscosity, polymer conductivity, polymerisation kinetics and driving voltage of PDLCs. The results exhibited that higher rGO content increased the compound viscosity and the entire process proceeded slowly. Furthermore, the addition of rGO increased the polymer conductivity and local electric field, and reduced the saturation voltage as well as the threshold voltage from 27.3 to 19.5 V and 13.2 to 6.41 V, respectively.
    No preview · Article · Jun 2015 · Liquid Crystals
  • Qing Gong · Shiming Gong · Heng Zhang · Lulu Liu · Yinghan Wang
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    ABSTRACT: A novel functional diamine containing triphenylamine moiety and biphenyl, 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) had been 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 liquid crystal (LC) cell fabricated with the PIs were measured, and rubbing resistance of PIs containing different side chain structure was investigated. PI1 with rigid biphenyl side chain could induce LC parallel alignment after rubbing process. Although PI3 containing flexible alkyl side chain could induce LC vertical alignment before rubbing process, it only induced LC parallel alignment after rubbing process. However, PI2 containing both rigid biphenyl side chain and flexible alkyl side chain could induce LC vertical alignment before and after rubbing process. A new method for improving rubbing resistance of PIs and a generation mechanism of rubbing resistance had been proposed. In addition, all PI films showed high thermal stability and high transmittance in the wavelength range of 400-700 nm.
    No preview · Article · Jun 2015 · RSC Advances
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    ABSTRACT: 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 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 pretilt angle of the PIs were investigated. Furthermore, the results were compared with the PIs′ derived from 4-dodecyloxy-biphenyl-3′,5′-diaminobenzoate (DBPDA). The PIs derived from DBDTA exhibited better transparency and thermal stability than the PIs′ from DBPDA. When the content of functional diamines was only 10%, the PI1 derived from DBDTA displayed better solubility than the PI1′ from DBPDA. In addition, all PIs could induce uniform vertical alignment of liquid crystals (LCs) before and after the rubbing process, but PI1′ only induced parallel alignment of LCs after rubbing process. It is suggested that PI1 film can resist larger rubbing strength than PI1′.
    No preview · Article · Mar 2015 · RSC Advances
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    ABSTRACT: In this study, macro-(RAFT) reversible additional fragmental chain transfer agent prepared by reversible additional fragmental chain transfer polymerisation has been incorporated into polymer dispersed liquid crystals (PDLCs). The effects of concentration, molecular weight and glass transition temperature of macro-RAFT agent were studied in terms of morphology, polymerisation kinetics, molecular weight of polymer matrix and electro-optical properties of the films. It was found that the key factor influencing morphology was the mobility of macro-RAFT agent chain rather than polymerisation rate and molecular weight of polymer matrix. Furthermore, the decrease in the mobility of macro-RAFT agent chain caused less liquid crystal nematic fraction, smaller liquid crystal domain size and greater driving voltage.
    No preview · Article · Dec 2014 · Liquid Crystals
  • Jingjing Li · Leishan Shao · Xiaohai Zhou · Yinghan Wang
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    ABSTRACT: 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.
    No preview · Article · Sep 2014 · RSC Advances
  • Shiming Gong · Ming Liu · Zhen Sun · Senlin Xia · Yinghan Wang
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    ABSTRACT: A new triphenylamine-based functional diamine monomer named N, N-bis (4-aminophenyl)-4-(nonyloxy-biphenyl)-4′-aminophenyl ether (N9) was successfully synthesised from cesium fluoride-mediated N,N-diarylation of 4-(nonyloxy-biphenyl)-4′-aminophenyl ether with p-fluoronitrobenzene and subsequent reduction of the resultant dinitro compound. A series of polyimides (PIs) with triphenylamine (TPA) moieties were prepared from the newly synthesised diamine monomer, 3,3′-dimethyl-4,4′-methylene-dianiline and 4,4′-oxydiphthalic anhydride through a conventional two-step procedure that included a ring-opening polyaddition to give polyamic acids, followed by chemical cyclodehydration. The PIs were completely amorphous and exhibited good solubility in organic solvents. PI films attained from a casting method showed high transmittance above 90% in the wave length range of 400–700 nm and could align liquid crystals vertically before and after rubbing treatment. The PIs derived from N9 exhibited much higher thermal stability compared with the corresponding PIs from 4-dodecyloxy-biphenyl-3′,5′-diaminobenzoate (D12). The results demonstrated that the introduction of TPA units into the polymer backbone could largely enhance the thermal stability of PIs while sustaining its solubility.
    No preview · Article · Sep 2014 · Liquid Crystals
  • Shiming Gong · Ming Liu · Senlin Xia · Yinghan Wang
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    ABSTRACT: 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.
    No preview · Article · Sep 2014 · Journal of Polymer Research
  • Tian Lan · Yu Zhang · Haiping Wang · Liping Yang · Wenjie Yang · Yinghan Wang
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    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 (RAFT) and atom transfer radical polymerization (ATRP), was employed to prepare PDLCs with graft copolymer matrix in our previous work. Compared with linear copolymer matrix PDLCs prepared using linear macroinitiator, it was found that although low-memory-effect PDLC was obtained, the driving voltage and transmittance of the PDLC were sacrificed to some extent unfortunately. Thus, it is necessary to improve the electro-optical properties of PDLCs on the basis of the original research performed by us. In this article, a kind of linear macroinitiator with high refractive index (RI) and another graft macroinitiator with flexible branched chains were employed to prepare PDLCs. The results showed that by using mixed macroinitiators, the EO properties of PDLCs could be improved, and a possible mechanism was proposed.
    No preview · Article · Sep 2014 · Polymer International
  • Tian Lan · Wenjie Yang · Juan Peng · Mingke Li · Yinghan Wang
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    ABSTRACT: In this article, a kind of graft macroinitiator, synthesized by RAFT polymerization and ATRP, 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 PDLCs was investigated. The results showed that graft macroinitiators could make a big difference in the EO properties of PDLCs. The memory effect was reduced remarkably, but driving voltage increased and transmittance decreased, and the possible mechanism was presented.
    No preview · Article · Sep 2014 · Polymer International
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    ABSTRACT: The reduction extent of graphene oxide (GO) was tailored by adjusting the solvothermal reduction time. The effects of 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 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 to balance and optimize interfacial interactions and mechanical strength of rGO.
    No preview · Article · Jun 2014
  • Tian Lan · Wenjie Yang · Hao Huang · Yinghan Wang
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    ABSTRACT: 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.
    No preview · Article · Mar 2014 · RSC Advances
  • Jingjing Li · Leishan Shao · Lihua Yuan · Yinghan Wang
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    ABSTRACT: 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.
    No preview · Article · Feb 2014 · Materials and Design
  • Tian Lan · Wenjie Yang · Juan Peng · Mingke Li · Yinghan Wang
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    ABSTRACT: 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., 2014. © 2014 Society of Plastics Engineers
    No preview · Article · Feb 2014 · Polymer Engineering and Science
  • Bin Liu · Yinghan Wang
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    ABSTRACT: 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.
    No preview · Article · Jan 2014 · Progress in Organic Coatings
  • Wenjie Yang · Tian Lan · Senlin Xia · Lipeng Ma · Yinghan Wang
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    ABSTRACT: Glass transition temperature (T-g), an important parameter of polymer, was reported to have great influence on the electro-optical properties of polymer dispersed liquid crystals (PDLCs). In this study, macroinitiators with different T-g were synthesised by reversible addition fragmentation chain transfer polymerisation, and used to prepare PDLCs with different T-g block chains. The effect of different T-g of the block chains on response times was investigated. It was found that rise time decreased and decay time increased with the decrease of the block chain's T-g. We proposed a possible mechanism by which T-g of the block chains influence response times.
    No preview · Article · Oct 2013 · Liquid Crystals
  • Senlin Xia · Longfei Yi · Zhen Sun · Yinghan Wang
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    ABSTRACT: 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 (T 5) 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.
    No preview · Article · Aug 2013 · Journal of Polymer Research