Advances in Liquid Crystals

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Authors: Chun Xiu Zhang, Jia Ling Pu, Zhi Qun He, Ming Zhang, Hao Wu, Ya Nan Li
Abstract: A novel triphenylene-based hyper-branched macromolecule was synthesized from the functional compound-2, 6, 10-trihydroxy-3, 7, 11–tris (pentyloxy) triphenylene serving as core, using α,ω-dibromodecane as spacer and 1-bromopentane as terminal group for end capping by using a very simple synthesis method, one-pot reaction. The structure of the hyperbranched macromolecule was determined by FTIR and 1HNMR. The molecule weight and the molecular weight distribution were measured by GPC. Mesophase and their structural orders were determined using a polarized optical microscope and a differential scanning calorimeter.
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Authors: Xin De Tang, Long Cheng Gao, Nian Feng Han
Abstract: The effect of flexible spacer length on the liquid crystalline property of ABA-type triblock copolymers containing azobenzene groups was investigated. For the study, the monomers, n-[4-(4-ethoxyphenylazo)phenoxy]alkyl methacrylates with varying methylene groups (n = 0, 2, 6) were used to synthesize a series of azobenzene-containing amphiphilic triblock copolymers PAnC-PEG-PAnC by atom transfer radical polymerization (ATRP). Differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and one-dimensional X-ray diffraction (1D WAXD) have shown that the glass transition temperatures of these copolymers decreased as n increases. PA0C-PEG-PA0C has no mesophase, while both PA2C-PEG-PA2C and PA6C-PEG-PA6C have a nematic mesophase. These differences derive of the length of spacer groups between the polymer main chain and side chain.
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Authors: Jun Gang Gao, Cai Yun Zhang, Li Huo, Yuan Yuan Zhang
Abstract: A liquid crystalline epoxy resin of p-biphenylene di-4-(2,3-epoxypropyloxy)benzoate (p-BDEPB) was synthesized from allyl bromide, 4-hydroxy ethyl benzoate and 4,4-dihydroxybiphenyl. Its structure and liquid crystalline behavior were characterized by DSC, 1H-NMR, FTIR, POM and XRD. The results are shown that this compound is smectic liquid crystalline.The melting point of p-BDEPB is 210 oC and clearing point is over 300 oC, the epoxy value is 0.312 mol/100g. The average curing Ea of p-BDEPB/3-methyl-tetrahydrophthalic anhydride (MeTHPA) system is 97.2kJ/mol. The gel point of cured-system Tgel is 89.0 oC, curing temperature Tcu is 132.5 oC and finishing temperature Tf is 146.5 oC. The curing reaction can be described by the autocatalytic Šesták-Berggren (S-B) equation, the two reaction orders m and n is 0.23 and 0.74, respectively.
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Authors: Wen Guang Wang, Xu Ying Liu, Ling Liu, Jia Ling Pu
Abstract: Asymmetric substituted coronenes as building blocks for preparation of materials used as functional molecular devices in the fields of self-organization, organic light-emitting diode, photovoltaic solar cell and field effect transistor are easily converted to potential interesting coronene’s derivatives. A novel kind of derivative of dibenzocoronene with perylene tetracarboxdiimide as discotic liquid crystal with two kinds of soft and long chains was designed and synthesized. Its structure was confirmed by 1HNMR and IR. Its UV-vis was measured. Its properties as discotic liquid crystal are investigated in progress.
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Authors: Yuan Ming Huang, Qing Lan Ma, Bao Gai Zhai
Abstract: A bent-core compound with three benzene-ring cores 1,3-phenylene-bis [4-(nonylcarboyloxyl)benzyl ideneamine] was synthesized. Its mesomorphic properties were characterized with differential scanning calorimetry and polarized optical microscopy, respectively. This kind of bent-core compound exhibited mesophases in the temperature range of 155-185oC for the first cooling but cyclic heating and cooling could lower the phase transition temperatures for this bent-core liquid crystal. Our results demonstrated that bent-core molecules with three benzene-ring cores can also form mesophases as those five benzene-ring containing bent-core molecules do.
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Authors: Zhong Xiao Li, Wei Wei, Wu Kun Fan, Jia Ling Pu
Abstract: A new kind of triphenylene derivative sym-(OC3H6OCOC2H4COOH)6 with triphenylene at the core and carboxyl groups at the peripheral chains was synthesized and characterized by FT-IR and 1H-NMR. Thermal gravimetry analysis (TGA) and differential scanning calorimetry (DSC) showed that these compounds have a good thermal stability, which is dependent on the flexibility and interaction of the peripheral chains. Red shifts in electronic absorption spectra of the compounds were found in solution with increasing concentration.
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Authors: Yu Shun Jin, Fei Xiao, Wen Li Guo, Shu Xin Li
Abstract: The microsphere copolymer [poly(St-co-HEMA)] of monodispersed styrene and 2-hydroxyethyl methacrylate(HEMA) was synthesized by suspension polymerization. New type of hydrophobic microsphere was synthesized by surface grafting polylactic acid using the hydroxyl-terminated of poly (St-co-HEMA) as initiator. The microspheres’ structures and properties were characterized by FT-IR, SEM and thermogravimetric analysis. The results have demonstrated that the copolymer [poly(St-co-HEMA)] is a random copolymer. The volume of the polylactide which was grafted with the microspheres can be controlled by changing the amount of microspheres and hydroxyl in microspheres.
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Authors: Yuan Ming Huang, Ye Tang Guo, Qing Lan Ma, Wei Wei Liu
Abstract: A cholesteric liquid crystal cholesteryl nonanoate was synthesized and then characterized by means of differential scanning calorimetry and polarized optical microscopy. As temperature decreased from its clearing point, cholesteric phase was formed for cholesteryl nonanoate and accompanied by continuous evolution of colors in the focal conic textures. Furthermore, beautiful spherulite crystals were observed to grow out of the cholesteric phase as the crystallization continued. The evolution of the colors in recorded textures was contributed to temperature-dependent selective reflection of the liquid crystal.
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Authors: Chen Xi Zhang, Shao Rong Lu, Jian Feng Ban
Abstract: Hyperbranched liquid crystalline polymer (HLCP) were prepared by pentaerythritol with 1,2,4-benzenetricarboxylic anhydride(BTCA) and p-hydroxy benzoic acid. The thermotropic properties, the melting point (Tm) and the isotropization temperature (Ti) of the synthesized HLCP were characterized by differential scanning calorimetry (DSC), fourier transform infrared spectroscopy (FTIR) and polarizing optical microscopy (POM). It showed that the new reactive thermotropic liquid polymer containing polyester mesogenic units exhibited thermotropic liquid crystalline properties between 140°C and 230°C.
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Authors: Hong Chi Zhao, Juan Li Guo, Ai Juan Sun, Ling Ling Gao
Abstract: Polystyrene (PS) was synthesized by emulsion polymerization. The linear chloroacetylated PS was prepared high effectively by Friedel-Crafts acetylation of PS using chloroacetyl chloride and anhydrous aluminium chloride as chloroacetylation reagent and catalysts, respectively. The structure of chloroacetyl group is similar to that of chloromethyl group. In this method, carcinogenic compound (chloromethyl ether etc.) was avoided and the reactions of secondary cross link and multi-substitute could be eliminated. The resultant polymers were characterized by Fourier transform infrared spectrometery (FTIR) and thermogravimetric analysis. The effects of reaction conditions on chloroacetylation were studied, and the optimum reaction conditions were obtained. Chloroacetyl group was introduced into benzene ring of PS because of the appearance of the absorption peaks at 1695cm-1 (due to C=O bonds) and 644cm-1 (due to C-Cl bonds) in the FTIR spectrum. The thermal stability of the chloroacetylated PS was decreased with increasing chloroacetyl group. Moreover, there were two decomposing stages. The glass transition temperature of chloroacetylated PS increased with substitution value increasing. The effects of the reaction conditions such as reaction temperature, the solvent amount and the concentration of chloroacetyl chloride and anhydrous aluminium chloride on the chloroacetylation of PS were obvious. The certain loading can be controlled when it is lower than the maximum loading of chloroacetylated PS. The reaction condition is gentle and the operation is safe, simple and economical so that Friedel-Crafts acetylation of PS is an ideal reaction method.
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