聚合物液晶的奇偶现象及其结晶行为

Even-Odd Effect of Polymer Liquid Crystals and Their Crystalline Behavior

用直接缩聚法从4,4′-(1,4,7-三氧亚庚基)-二苯甲酸和4 4′-(α,ω-二氧亚烷基)-二苯酚合成了一系列芳香族聚酯(亚烷基碳数为2～6,10)。并对其结构进行了表征。采用DSC和偏光显微镜方法研究了聚合物的液晶行为。发现n=2～6的五个聚合物均具有热致型液晶行为。其中除n=4的聚合物具有近晶相和向列相两个中介相以外均呈向列型中介相。随着n的变化,聚合物液晶转交温度均呈现出奇偶现象,且为奇低偶高。液晶相温度范围在4和5之间出现最大值。本文还研究了热史对转变的影响。并用偏光显徽镜和X-衍射方法,发现此聚合物具有良好的结晶性,不易在淬火条件下保持液晶的织态结构。

A new series of aromatic polyesters were prepared by direct polycondensation from 1, 4, 7-trtoxaheptamethylep-4,4'-dibenzoic acid and 4, 4'-dihydroxy-α,ω-diphenoxy-alkanesand were characterized. The liquid crystalline behavior of the polymers was studied by DSC and polarized optical microscopy. The results showed that five polymers in which n ranges from 2 to S are thermotropic liquid crystals, while the polymer with n=10 is not. Liquid crystalline polymers obtained appeared to be smectic and/or nematic textures. Even-odd effect of the transition temperatures was observed with increased spacer length. The temperature range of the stable mesophase of these polymers presented a maximum between 4 and 5. Moreover, the polymers were found to show a good crystalline behavior by polarized optical microscopy and X-ray diffraction.