ABSTRACT

We present the effect of polymer network on the ferroelectric phase for a polymer stabilised ferroelectric liquid crystal (PSFLC) system. The ferroelectric liquid crystal (FLC) exhibits a very short helical pitch, large tilt angle and relatively high spontaneous polarisation. Electro-optic and dielectric investigations are performed on films with various polymer concentrations. Measurements in the chiral smectic C* (SmC*) phase of the tilt angle and spontaneous polarisation as a function of electric field strength and polymer concentrations were performed. For low electric fields, a deformed helix ferroelectric (DHF) process was observed for pure FLC as well as for the PSFLC films, showing a linear response of the helical structure to electric field. The influence of the polymer network on the FLC properties is also investigated by linear dielectric measurements. Particularly the Goldstone relaxation mechanism. The results reveal a gradual decrease of the dielectric strength with an increase in the network density. However, the relaxation frequency of this mechanism seems to be insensitive to the polymer network density. These behaviours were interpreted by the increase of both the effective elasticity and the rotational viscosity of the SmC* when stabilised by the polymer network.

摘要

我们展示了聚合物网络对聚合物稳定铁电液晶 (PSFLC) 系统铁电相的影响。铁电液晶 (FLC) 表现出非常短的螺距、大的倾角和相对较高的自发极化。对具有各种聚合物浓度的薄膜进行电光和介电研究。进行了作为电场强度和聚合物浓度函数的倾斜角和自发极化的手性近晶 C* (SmC*) 相的测量。对于低电场，观察到纯 FLC 和 PSFLC 薄膜的变形螺旋铁电 (DHF) 过程，显示螺旋结构对电场的线性响应。还通过线性介电测量研究了聚合物网络对 FLC 性能的影响。特别是戈德斯通松弛机制。结果表明，随着网络密度的增加，介电强度逐渐降低。然而，这种机制的弛豫频率似乎对聚合物网络密度不敏感。这些行为被解释为当由聚合物网络稳定时 SmC* 的有效弹性和旋转粘度的增加。