Ferroelectric nematic phases formed from polar rod-like polymers

以两组分的不同馏分和不同聚合度制备了羟基苯甲酸和羟基萘酸组成的芳香聚酯，并对其热致液晶行为和结构进行了研究。得到的最有趣的事实是聚合度大于30-40的聚合物可以沿向列取向形成具有极性有序的新型向列液晶。在沿分子轴旋转无序的镜像平面的Cs对称模型下，较好地模拟了二次谐波产生（SHG）曲线作为SH偏振入射的函数。这意味着极性向列液晶是双轴的，其中极性沿c方向存在，也沿n方向存在。引入间羟基苯甲酸可以改变Cs对称性为cv。这可以很好地解释为扭结结构的出现，它可以消除垂直于链轴的极性。

The aromatic polyesters composed of hydroxy benzoic acid and hydroxy naphthoic acid were prepared with different fractions of two components and different degrees of polymerization, and their thermotropic liquid crystalline behavior and structures were examined. The most interesting fact obtained is that the polymers with the degree of polymerization more than 30-40 can form a novel nematic liquid crystals with polar ordering along the nematic director. The second harmoinc generation (SHG) profiles as a function of incident of SH polarizations are well simulated under the model of Cs symmetry with a mirror plane rotationally disordered about the molecular axis. This means that the polar nematic liquid crystal is biaxial in which the polarity exists along the c-director as well as n-director. Cs symmetry can be altered to C v by the introduction of meta-hydroxy benzoic acid. This can be well explained by the occurence of the kink structure which can extinct the polarity perpendicular to the chain axis.