Xiangjie Zhao, Cangli Liu, Jiazhu Duan, Jiancheng Zeng, Dayong Zhang, Yongquan Luo
Opt Express. 2014 Jun 16;22(12):14757-68. doi: 10.1364/OE.22.014757.
Polymer network liquid crystal (PNLC) was one of the most potential liquid crystal for submillisecond response phase modulation, which was possible to be applied in submillisecond response phase only spatial light modulator. But until now the light scattering when liquid crystal director was reoriented by external electric field limited its phase modulation application. Dynamic response of phase change when high voltage was applied was also not elucidated. The mechanism that determines the light scattering was studied by analyzing the polymer network morphology by SEM method. Samples were prepared by varying the polymerization temperature, UV curing intensity and polymerization time. The morphology effect on the dynamic response of phase change was studied, in which high voltage was usually applied and electro-striction effect was often induced. The experimental results indicate that the polymer network morphology was mainly characterized by cross linked single fibrils, cross linked fibril bundles or even both. Although the formation of fibril bundle usually induced large light scattering, such a polymer network could endure higher voltage. In contrast, although the formation of cross linked single fibrils induced small light scattering, such a polymer network cannot endure higher voltage. There is a tradeoff between the light scattering and high voltage endurance. The electro-optical properties such as threshold voltage and response time were taken to verify our conclusion. For future application, the monomer molecular structure, the liquid crystal solvent and the polymerization conditions should be optimized to generate optimal polymer network morphology.
聚合物网络液晶（PNLC）是用于亚毫秒级响应相位调制最具潜力的液晶之一，有望应用于仅具有亚毫秒级响应相位的空间光调制器。但迄今为止，液晶指向矢在外加电场作用下重新取向时的光散射限制了其相位调制应用。施加高压时相变的动态响应也尚未阐明。通过扫描电子显微镜（SEM）方法分析聚合物网络形态，研究了决定光散射的机制。通过改变聚合温度、紫外光固化强度和聚合时间制备样品。研究了形态对相变动态响应的影响，其中通常施加高压并经常诱导电致伸缩效应。实验结果表明，聚合物网络形态主要特征为交联单纤维、交联纤维束或两者皆有。虽然纤维束的形成通常会引起较大的光散射，但这种聚合物网络能够承受更高的电压。相比之下，虽然交联单纤维的形成引起的光散射较小，但这种聚合物网络不能承受更高的电压。在光散射和高电压耐受性之间存在权衡。采用阈值电压和响应时间等电光特性来验证我们的结论。对于未来的应用，应优化单体分子结构、液晶溶剂和聚合条件，以产生最佳的聚合物网络形态。
