Interfacial Properties for liquid-crystalline Polymer solutions

在本研究项目中，我们研究了溶向液晶聚合物溶液中共存的各向同性和液晶相之间的界面性质。我们最关心的是研究(1)各向异性相中各向异性界面附近的分子排列，(2)界面张力与链长的关系，(3)界面张力与链刚度的关系。我们选择了表征良好的刚性和半柔性聚合物，裂叶多糖（一种三螺旋多糖），聚（正己基异氰酸酯）（PHIC）和聚（正丁基异氰酸酯）（PBIC），并对其体溶液性质进行了详细研究。(1)利用偏光显微镜对各向同性液晶界面进行了观察，发现刚性聚合物分子与界面平行排列。(2)采用固滴法和垂滴法测定了裂茶树、菲和菲/PBIC混合溶液的各向同性和液晶相之间的界面张力。对于裂叶植物溶液，界面张力几乎与聚合物分子量成反比。另一方面，环状结构溶液的界面张力几乎与聚合物的分子量无关，前者的分子量依赖性与理论对棒状聚合物溶液的预测一致，后者的分子量独立性与理论对螺旋状链状溶液的预测一致。众所周知，菲氏体比裂叶植物更灵活。我们还发现，界面张力在很大程度上取决于分子量分布和化学性质不同的聚合物种类的加入。

In this research project, we have dealt with properties of interface between coexisting isotropic and liquid-crystal phases of lyotropic liquid-crystalline polymer solutions.Our utmost concern was to examine (1) the molecular alignment in the anisotropic phase near the isotropic-anisotropic interface, (2) the dependence of the interfacial tension on chain length, and (3) the dependence of the interfacial tension on chain stiffness.We have chosen well characterized rigid and semiflexible polymers, schizophyllan (a triple-helical polysaccharide), poly(n-hexyl isocyanate) (PHIC), and poly(n-butyl isocyanate) (PBIC), whose bulk solution properties have been studied in detail.(1) The isotropic-liquid-crystal interface was observed by a polarizing microscope with a compensator oriented at 45ﾟ to the directions of the crossed polarizers, and the observations revealed that rigid polymer molecules align themselves parallel to the interface.(2) The interfacial tension between coexisting isotropic and liquid-crystal phases of solutions of schizophyllan, PHIC, and PHIC/PBIC mixtures was measured by the sessile or pendant drop method.For schizophyllan solutions, the interfacial tension is almost inversely proportional to the polymer molecular weight.On the other hand, the interfacial tension for PHIC solutions is almost independent of the polymer molecular weight The former molecular weight dependence agrees with the prediction of theories for rodlike polymer solutions, and the latter molecular weight independence is consistent with the prediction of a theory for wormlike-chain solutions in the coil limit.It is known that PHIC is more flexible than schizophyllan.We also found that the interfacial tension strongly depends on the molecular weight distribution and addition of chemically different polymer species.