Yinghan Wang

Sichuan University, Hua-yang, Sichuan, China

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Publications (30)59.53 Total impact

  • [Show abstract] [Hide abstract]
    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). · 3.71 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; · 2.13 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; · 2.13 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.
    J. Mater. Chem. A. 06/2014;
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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; · 1.24 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. · 2.30 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; · 3.71 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. · 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 01/2013; 40(6). · 1.96 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). · 1.64 Impact Factor
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    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.
  • Ailin Qin, Zhen Sun, Yuliang Zhang, Yinghan Wang
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    ABSTRACT: Polymer dispersed liquid crystal (PDLC) films were obtained by successive controlled living radical polymerizations: starting polystyrene (M1) was obtained by reversible addition-fragmentation polymerization (RAFT), M1 was converted to P-chloromethylated polystyrene (M2) which was grafted with polystyrene branches by atom transfer radical polymerization (ATRP) to yield RAFT-initiating graft polymer containing trithiocarbonate moieties in the backbone (M3, RAFT-active grafted polystyrene), and then PDLC films were prepared by photo-induced RAFT copolymerization of methyl acrylate with M3 in the presence of a nematic liquid crystal. The electro-optical properties of the films were investigated for the purpose to apply them to optical devices. Experimental results showed that preferable properties could be acquired by controlling the amount of M3 and the liquid crystal E7 in the polymer matrix of PDLC films. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers
    Polymer Composites 02/2012; 33(2). · 1.48 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 01/2012; 39(12). · 1.96 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 01/2012; 23(9). · 1.64 Impact Factor
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    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
    Polymer International 04/2011; 60(7):971 - 975. · 2.13 Impact Factor
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    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
    Journal of Polymer Science Part A Polymer Chemistry 12/2010; 48(23). · 3.54 Impact Factor
  • Ailin QIN, Yinghan WANG
    Acta Polymerica Sinica 07/2010; 010(7):870-875. · 0.68 Impact Factor
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    ABSTRACT: The alignment of nematic liquid crystals by rubbed polyimide surfaces has been well-studied and developed. A novel polyimide film which induced a homeotropic alignment of the nematic liquid crystal without rubbing or with weak rubbing strength was presented. However, there was a transition from homeotropic to planar alignment of the nematic liquid crystal after strong rubbing. In order to study the transition, the polyimide surface was investigated by atomic force microscopy, surface free energy measurement and angle-resolved analysis X-ray photo-electron spectroscopy before and after rubbing with a velvet fabric. It was found that both the change of surface polarity and surface morphology were not the reasons for the transition. The droop of the side chain on the polyimide surface after the rubbing treatment was detected by angle-resolved analysis X-ray photo-electron spectroscopy. Owing to the special structure of the novel polyimide, the X-ray photo-electron spectroscopy was successfully used for the first time to analyse the conformational change of the side chain of a polymer. In conclusion, the transition of nematic liquid crystal alignment from homeotropic to planar after rubbing was influenced by the side chain conformation of the polyimide.
    Liquid Crystals 03/2010; 37(3):271-278. · 1.96 Impact Factor
  • Xin Du, Bin Yan, Yinghan Wang
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    ABSTRACT: In this article, macroinitiators with different glass transition temperature (Tg) were synthesized by reversible additional-fragmental chain transfer polymerization, and used to prepare polymer-dispersed liquid crystals (PDLCs) with methyl acrylate. The memory effect of these PDLCs was investigated. The results showed that remarkable memory effect exhibit only in PDLCs with high and low Tg block chain. The possible mechanism responsible for the behavior is sketched. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 729–732, 2010
    Journal of Polymer Science Part B Polymer Physics 02/2010; 48(6):729 - 732. · 2.22 Impact Factor
  • Zhen Sun, Ailin Qin, Zihua Chen, Yinghan Wang
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    ABSTRACT: Through the polycondensation of a four-functional amine with pyromellitic dianhydride, a hyperbranched polyimide (HPI) was synthesised in this study. The HPI was used for liquid crystal alignment layers. Wide angle X-ray diffraction measurement showed that the HPI film was amorphous. The morphology of the surface layer of film was determined by atomic force microscopy. It is novel that a larger pretilt angle, above 8°, has been achieved with the rubbed HPI alignment layers. This result was different from that in a previous report, in which only a 2.8° pretilt angle was induced by a HPI alignment film.
    Liquid Crystals 01/2010; 37(3):345-348. · 1.96 Impact Factor

Publication Stats

8 Citations
59.53 Total Impact Points

Institutions

  • 2007–2014
    • Sichuan University
      • State Key Laboratory of Polymer Material Engineering
      Hua-yang, Sichuan, China
    • Philadelphia ZOO
      Philadelphia, Pennsylvania, United States