Photo-active liquid crystal nanodispersions

这项研究的目标是制备一种新型的聚合物网络液晶，它将具有高度的光敏性。在这些液晶混合体中，光敏纳米颗粒被聚合物链固定在适当的位置，将通过光生电场可逆地和可控地切换液晶导向器。聚合物网络液晶是下一代液晶显示器、微型显示器和基于液晶的空间光调制器的候选者。一般来说，聚合物网络液晶由双折射液晶和高达10%的原位生成的交联聚合物组成。这种特殊类型的液晶之所以被寻找，是因为添加聚合物将大大增强整齐液晶的电光响应性能。提出了利用共价键合表面活性剂来研究纳米粒子，这将在聚合物液晶研究中呈现出前所未有的特点。这些带有表面接枝交联剂的纳米颗粒可以用作纳米颗粒光引发剂，以便将聚合物接枝到不断增长的聚合物网络中并将其固定在其中。因此，纳米粒子将被引入到聚合物网络液晶的高分子链中，以进一步推动这些高灵敏度和响应性光学材料的响应性能。光敏测试设备是拟议项目的重点。铁电陶瓷，如掺铁的铌酸锂，表现出反常的光伏效应：在适当波长的可见光照射下，沿其晶体c轴产生空间电荷分离，在其表面产生高(几个10千伏)的内部电场和消失的电场。因此，由这种材料组成的纳米颗粒可以通过一种独特的机制耦合到液晶导向器上。这种光活性纳米颗粒的使用在推动聚合物网络液晶的响应性能和降低其光开关阈值方面显示出巨大的前景：液晶具有介电各向异性，这使得它们成为感测光生电场并将其转换为光学响应的理想工具。因此，这项研究在降低液晶的光光响应阈值和探索由表现出反常光伏效应的材料组成的纳米粒子的响应特性方面具有很大的前景。

The goal of the proposed research is to fabricate a novel type of polymer network liquid crystal, which will be highly light-sensitive. In these liquid crystal hybrids, light-sensitive nanoparticles, which are hold in place by polymer-chains, will reversibly and controllably photo-switch the liquid crystal director via photo-generated electric fields. Polymer network liquid crystals are candidates for the next generation of liquid crystal displays, microdisplays and liquid crystal-based spatial light modulators. In general, polymer network liquid crystals consist of a birefringent liquid crystal and up to 10% of in-situ generated, crosslinked polymer. This special type of liquid crystal is sought for because added polymer will greatly enhance the electro-optic response properties of neat liquid crystals. It is proposed to investigate nanoparticles with covalently bound photoactive surface agents, which will present an unprecedented feature in polymer liquid crystal research. These nanoparticles with surface grafted crosslinkers can be used as nanoparticulate photoinitiators in order to graft polymer to and fix them inside a growing polymer-network. Accordingly, nanoparticles will be incorporated in the polymer chains of polymer network liquid crystals to further push the response properties of these highly sensitive and responsive optical materials. Photo-active test devices are in the focus of the proposed project. Ferroelectric ceramics like iron-doped lithium niobate show the anomalous photovoltaic effect: If exposed with visible light of appropriate wavelength, a space charge separation is induced along their crystallographic c-axis, which generates high (several 10 kV) internal electric fields and evanescent electric fields at their surfaces. Accordingly, nanoparticles that consist of such materials can couple to the liquid crystal director via a unique mechanism. Use of such photo-active nanoparticles shows great prospects to push the response properties of polymer network LCs and lower their threshold of opto-optic switching: Liquid crystals posses dielectric anisotropy, which makes them an ideal tool to sense photo-generated electric fields and convert them into optic responses. The proposed research therefore has great prospects to lower the threshold of opto-optic responses in liquid crystals and explore the response properties of nanoparticles, which consist of materials that show the anomalous photovoltaic effect.