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A new series of chiral shish-kebab type liquid crystal block copolymers that form the smecticC(Sc~*) phase was synthesized by solution polycondensation. The copolymers were characterized by GPC.DSC. TG, POM. X-ray diffraction and polarimeter. The copolymers 7 entered into liquid crystal phase whenthey were heated to their melting temperatures (T_m) and the copolymers 8 were in liquid crystal phase at roomtemperature with low viscosities. The smectic sanded texture or focal-conic texture were observed on POM.All the chiral block copolymers showed high optical activity. No racemization has happened. Temperature-variable X-ray diffraction study together with POM and polarimetric analysis realized that they are chiralsmectic C(Sc~*) phase. Thus we offer in this report the first example of shish-kebab type liquid crystal blockcopolymers that form a chiral smectic C(Sc~*) phase. The variation of melting and isotropization temperatureswith molecular structure was also discussed. 相似文献
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以4.4′-二羟基氧化偶氮苯和1,10-癸二醇作为含羟基单体,按不同的重量配比,合成了一系列含氧化偶氮苯液晶基元的共聚液晶高分子,改变液晶基元的含量,共聚物相变温度可以调节。 相似文献
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Abstract The novel shish-kebab-type liquid crystalline poly(p-phenylene)s were synthesized through Suzuki coupling reaction from 2,5-bis[(4-n-alkoxyl)benzoyloxy]1,4-dibromobenzene (monomer 1) and 1,4-benzenediboronic acid bistrimethylene cyclic ester (monomer 2). Their structure and properties were characterized by GPC, DSC, X-ray diffraction and polarizing optical microscope (POM). It was found that the polymers turned to liquid crystalline phase above their melting point. The melting point (Tm) of the polymers decreases when the length of the alkoxy tails of the mesogenic units increases. The mesophase was identified by X-ray diffraction method. The polymers could dissolve in common organic solvents and show strong blue fluorescence. The maximum absorption bands of polymers prepared from annealed films have large red-shift due to the spontaneous orientation of the liquid crystalline side chains. The same phenomena were also observed in the fluorescence spectra. 相似文献
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A new series of liquid crystal polyesters with T-shaped two-dimensional mesogenic units weresynthesized by melt polycondensation of the diacetates of 2-(4'-alkoxy -phenyl)-hydroquinones with 4,4'-alkylenedioxydibenzoic acid. The polymers were characterized by using polarized microscopy, DSC and X-ray diffraction. It was realized that all the polymers have nematic thermotropic liquid crystallinecharacteristics. The melting temperature (T_m) and isotropization temperature (T_i) of the polymers changeregularly with varying lengths of the alkoxy side group and the length of the alkylene group in the main chainin company with an even-odd effect. The mesophase temperature range also varies regularly with the polymerstructure. It is shown that the mesophase range has been widened. 相似文献
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本文采用Cu2+斜方对称电子顺磁共振(EPR)参量的高阶微扰公式计算了晶体Cu1-xHxZr2(PO4)3中Cu2+的EPR参量(g因子和超精细结构常数A因子).计算结果表明,晶体Cu1-xHxZr2(PO4)3中[CuO6]10-基团的Cu-O键长分别为R||≈0.241 nm,R⊥≈0.215 nm,平面键角τ≈80.1°;由于对称性降低,中心金属离子基态2A1g(θ)和2A1g(ε)有一定程度混合,混合系数α≈0.995.所得EPR谱图的理论计算值与实验数据符合得很好. 相似文献
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SYNTHESIS OF LIQUID CRYSTALLINE COPOLYESTERS WITH T-SHAPED TWO-DIMENSIONAL MESOGENIC UNIT AND CROWN ETHER CYCLE 总被引:1,自引:0,他引:1
A novel series of liquid crystalline copolyesters with T-shaped two-dimensional mesogenic unit and crown ether cycle of cis-4,4′-bis(4-hydroxyphenylazo)dibenzo-18-crown-6 was prepared via solution condensation polymerization from 4,4′-(α,ω-hexanedioyloxy)dibenzoyl dichloride(M_1),2-(4′-ethoxyphenyl)hydroquinone(M_2)and cis-4,4′-bis(4- hydroxyphenylazo)dibenzo-18-crown-6(M_3).The molecular weights of copolyesters are not high,and the intrinsic viscosity [η]of copolyesters ranges from 0.29-0.43.The monomer... 相似文献