Ferroelectric nematic phases formed from polar rod-like polymers

以羟基苯甲酸和羟基萘甲酸为单体，合成了不同含量、不同聚合度的芳香族聚酯，并对其热致液晶行为和结构进行了研究。最有趣的是，聚合度大于30-40的聚合物可以形成一种新型的顺磁液晶，这种液晶具有沿着顺磁指向矢的极性有序性。在Cs对称性模型下，采用镜面围绕分子轴旋转无序的方法，很好地模拟了二次谐波产生（SHG）谱随入射SH偏振的变化.这意味着极性双折射液晶是双轴的，其中极性沿着c指向矢以及n指向矢沿着存在。Cs对称性可以通过引入间羟基苯甲酸改变为Cv。这可以用扭结结构的出现来解释，扭结结构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.