Ferroelectric nematic phases formed from polar rod-like polymers

用不同比例的羟基苯甲酸和不同的聚合度合成了羟基苯甲酸和羟基萘甲酸组成的芳香族聚酯，并研究了它们的热致液晶行为和结构。最有趣的事实是，聚合度在30-40以上的聚合物可以形成一种新型的向列相液晶，沿向列相导向器具有极性有序性。在Cs对称的镜面绕分子轴旋转无序的模型下，较好地模拟了二次哈莫因产生(SHG)随SH极化入射的变化规律。这意味着，极性向列相液晶是双轴的，其中极性既存在于c指向矢上，也存在于n指向矢上。通过引入间羟基苯甲酸，CS的对称性可以改变为Cv。这可以用扭结结构的出现来很好地解释，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.