Interfacial Properties for liquid-crystalline Polymer solutions

在这个研究项目中，我们研究了共存的溶致液晶聚合物溶液的各向同性相和液晶相之间的界面性质。我们最关心的是检查（1）各向同性-各向异性界面附近各向异性相的分子排列，（2）界面张力对链长度的依赖性，以及（3）界面张力对链刚度的依赖性。我们选择了特征良好的刚性和半柔性聚合物，裂褶多糖（一种三螺旋多糖）、聚异氰酸正己酯（PHIC）和聚异氰酸正丁酯（PBIC），其本体溶液性质已得到详细研究。（1）通过带有补偿器的偏光显微镜观察各向同性液晶界面，其补偿器与交叉偏振器方向成45°，观察结果表明刚性聚合物分子自行排列(2)采用座滴法或悬滴法测量了裂褶多糖、PHIC和PHIC/PBIC混合物溶液共存各向同性相和液晶相之间的界面张力。对于裂褶多糖溶液，界面张力几乎与聚合物分子量成反比。另一方面，PHIC溶液的界面张力几乎与聚合物分子量无关。分子量依赖性与棒状聚合物溶液的理论预测一致，而后者的分子量独立性与线圈极限中蠕虫链溶液的理论预测一致。已知PHIC比裂褶多糖更灵活。我们还发现界面张力强烈依赖于分子量分布和化学上不同的聚合物种类的添加。

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.