Yinghan Wang

Sichuan University, Hua-yang, Sichuan, China

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Publications (36)83.26 Total impact

  • [Show abstract] [Hide abstract]
    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′.
    RSC Advances 03/2015; 5(32). DOI:10.1039/C4RA16997B · 3.71 Impact Factor
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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.
    Liquid Crystals 12/2014; 41(5):652-661. DOI:10.1080/02678292.2013.873493 · 2.35 Impact Factor
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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.
    RSC Advances 09/2014; 4(82). DOI:10.1039/C4RA07295B · 3.71 Impact Factor
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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.
    Liquid Crystals 09/2014; 41(12):1-12. DOI:10.1080/02678292.2014.951698 · 2.35 Impact Factor
  • Shiming Gong, Ming Liu, Senlin Xia, Yinghan Wang
    Journal of Polymer Research 09/2014; 21(9). DOI:10.1007/s10965-014-0542-0 · 1.90 Impact Factor
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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.
    Polymer International 09/2014; 64(3). DOI:10.1002/pi.4803 · 2.25 Impact Factor
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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.
    Polymer International 09/2014; 63(9). DOI:10.1002/pi.4693 · 2.25 Impact Factor
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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.
    06/2014; DOI:10.1039/C4TA02833C
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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
    Polymer Engineering and Science 02/2014; DOI:10.1002/pen.23857 · 1.44 Impact Factor
  • 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.
    Progress in Organic Coatings 01/2014; 77(1):219–224. DOI:10.1016/j.porgcoat.2013.09.007 · 2.30 Impact Factor
  • 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.
    RSC Advances 01/2014; 4(29):14997. DOI:10.1039/c4ra01225a · 3.71 Impact Factor
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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.
    Liquid Crystals 10/2013; 41(2):202-206. DOI:10.1080/02678292.2013.846427 · 2.35 Impact Factor
  • 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.
    Journal of Polymer Research 08/2013; 20(8). DOI:10.1007/s10965-013-0219-0 · 1.90 Impact Factor
  • Senlin Xia, Zhen Sun, Longfei Yi, Yinghan Wang
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    ABSTRACT: Novel functional diamine, 6-hexyloxy-naphthalen-3’,5’-diaminobenzoate (N6) containing rigid naphthalene unit, was molecularly designed and synthesized successfully. 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 by 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 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 side chains was smaller than that of PI-C6, but much higher T5 was attained. The results demonstrated that the introduction of naphthalene unit into the side chain could effectively improve the thermal stability of PI without sacrificing its solubility. Moreover, the outstanding thermal stability of PIs was explained by the imidization reaction mechanism preliminarily.
    RSC Advances 06/2013; 3(34):-. DOI:10.1039/C3RA42098A · 3.71 Impact Factor
  • Zhen Sun, Ming Liu, Longfei Yi, Yinghan Wang
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    ABSTRACT: 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.
    RSC Advances 04/2013; 3(20):7271-7276. DOI:10.1039/C3RA00147D · 3.71 Impact Factor
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    ABSTRACT: A novel diamine with a side-chain containing naphthalimide ring and non-polar alkyl end group, N-octyl-4-(3,5-dinitrobenzoyl)-amido-1,8-naphthalimide (N8), was synthesised and its chemical structure was confirmed by FTIR (fourier transform infrared) spectroscopy and nuclear magnetic resonance spectroscopy (1H-NMR). Then, a new family of polyimides (PIs) containing naphthalimide unit in the side-chains has been successfully synthesised by reaction of 4,4′-oxydiphthalic anhydride (ODPA) and 3,3′-dimethyl-4,4′-methylenediamine (DMMDA) with the novel functional diamine N8. The obtained polymers showed excellent solubility in a broad range of solvents, including tetrahydrofuran. Thermal properties of polymers were good enough to permit the use of these PIs on liquid-crystal displays (LCDs) applications. Alignment films obtained by casting offered outstanding rubbing-resistant ability, meanwhile kept the pretilt angle high above 89°. The PI seems to be prospective materials for alignment layers in LCDs.
    Liquid Crystals 04/2013; 40(6). DOI:10.1080/02678292.2013.783138 · 2.35 Impact Factor
  • Zhen Sun, Yinghan Wang
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    ABSTRACT: 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.
    Polymers for Advanced Technologies 01/2013; 24(1). DOI:10.1002/pat.3043 · 1.96 Impact Factor
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    ABSTRACT: In this study, a graft polymer matrix prepared by living radical polymerisation had been incorporated into polymer dispersed liquid crystals (PDLCs). The electro-optical properties of the PDLCs were investigated. The results showed that the length and density of graft chain had a great influence on the memory effect of the PDLCs. Low-driving-voltage and weak-memory-effect PDLCs could easily be obtained with a graft polymer matrix.
    Liquid Crystals 12/2012; 39(12). DOI:10.1080/02678292.2012.720288 · 2.35 Impact Factor
  • Zhigang Yang, Ding Li, Cuihong Pan, Yinghan Wang
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    ABSTRACT: 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 (V 90) of PDLC with high glass transition temperature (T g) matrix was as low as 5 V, whereas the V 90 of PDLC with low T g 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 (T ON) 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.
    Polymers for Advanced Technologies 09/2012; 23(9). DOI:10.1002/pat.2046 · 1.96 Impact Factor
  • Source
    Shoulian Wang, Jie He, Yu Zeng, Bin Yan, Yinghan Wang
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    ABSTRACT: The polymer stabilized liquid crystal (PSLC) film is a relatively novel electro-optical material, which is generally obtained by dissolving a small amount of a bifunctional photoreactive monomer in a low molecular mass liquid crystal. In this paper, the PSLC films were prepared with photoreactive biphenyl methacrylate monomers by photopolymerization induced phase separation. The effects of liquid crystal concentration, curing time, monomer structures and alignment layer on the electro-optical properties of PSLC films were investigated. The results show that the transmittance in the OFF state (T OFF) increased with the liquid crystal concentration, but the driving voltage decreased. T OFF was also influenced by the curing time. Furthermore, when polyimide was used as alignment layer, the films prepared from the bifunctional monomer shows a higher T OFF, while those from the single functional monomer exhibited a deformed electro-optical curve due to the unsteady polymer networks.
    Frontiers of Chemical Engineering in China 05/2012; 2(3):265-268. DOI:10.1007/s11705-008-0054-8

Publication Stats

85 Citations
83.26 Total Impact Points

Institutions

  • 2007–2014
    • Sichuan University
      • State Key Laboratory of Polymer Material Engineering
      Hua-yang, Sichuan, China
  • 2012
    • Sichuan University of Science and Engineering
      Hua-yang, Sichuan, China