摘要
通过酯交换反应,合成了一系列以对乙酰氧基苯甲酸(PHB),4.4,—二乙酰氧基二苯基丙烷(BPA)和对苯二甲酸(TPA)为单体的三元共聚酯。采用热台偏光显微镜(TOT)、示差扫描量热仪(DSC)和广角x射线衍射(WAXD),较详细地研究了液晶共聚酯的结构、性能及其与分子链组成的关系。DSC和TOT结果表明,共聚酯的玻璃化温度较高,介于166—188℃之间,熔化温度一组成关系的相图具有最低共熔点;共聚酯中PHB链节含量在10～50％时均呈现向列型液晶特征,随温度升高.均无各向同性转变,固态共聚酯具有冻结向列液晶结构。WAXD结果指出无规共聚是破坏结晶结构,降低熔点的有效手段。
A series of wholly aromatic thermotropic Liquid crystal copolyesters synthesized by three units copolyrnerization of p—acetoxy—benzoic acid(PHB)、terephthalic acid (TPA)and acetoxybisphenol A (BPA)were studied by using DSC and thermal polarizing microscopy. It was found that the glass temperatures Tg of the copolyesters were high, ranging from 166— 188℃, and the melting points decreased first and then increased as p—acetoxy—berzoic acid unit content increased. The study proved that copolyesters in which PHB mole amount was from 10—50％displayed schlieren or thread like nematic state at melt. Ti was too high to be observed. It was revealed by WAXD that the melt temperature depression of copolyesters via random eopolyeondensation was due to the disruption of crystal structure in essence.
关键词
共聚酯
热致液晶性
转变温度
Copolyesters, thermotropic Liquid crystallinity, transition temperature, crystalline structure, spacing
