类液晶物质光学各向同性相的高分子构筑机理、分子设计、调控特性及应用研究

Optically isotropic liquid crystal has exhibited the great advantages in display and photonic fields due to its unique optical characteristics and fast response properties. However, the narrow temperature range, the limitation of materials choice, the complicated preparation and the low electric-induced birefringence of such material hinder its further applications, which is an urgent problem need to be resolved firstly. In our recent studies, we found that an optically isotropic phase of the crystalline mesogen can be constructed by the corresponding polymer template. Besides, the electric-field-driving can be realized as well. The crystalline mesogen has such physical characteristics, it hasn't the liquid crystalline phase, while has the high birefringence generally. There are also many kinds of crystalline mesogen at present, without any limitations of the materials choice. The polymer-construction maintains the stable molecular alignment of the mesogens, thereby widening the temperature range of the isotropic phase; in addition, the material preparation process will be simplified. But the primary problem is the misunderstanding on the inner mechanisms of polymer-construction to the crystalline mesogen, and so blocks the deeper subsequent studies on molecular design, alignment analysis, optimization of material performances and the applications of such material. Considering those, in this project, we plan to start from the mechanisms of polymer-construction, and carry out the molecular design on the basis of mechanisms study, and then obtain the materials with good performances of external field tuning, finally apply the obtained materials on photonic devices.

光学各向同性液晶材料由于其独特的光学性质和高速响应特点在显示和光子器件领域展现出无可比拟的优势。然而其温度区间狭窄，材料体系种类有限、选择面窄，制备复杂，场致双折射低，成为应用化进程中的巨大阻碍，亟待解决。近期我们在研究中发现，使用具有光学各向同性微结构的高分子模板可以成功实现对类液晶物质光学各向同性排列的构筑，并能通过电场驱动。类液晶物质本身不含有液晶相，但通常具有较高的双折射，且种类多、选择面广；高分子构筑则保证了分子排列的稳定性、拓宽温度区间、简化制备工艺；由此可以解决上述所有问题。然而对高分子构筑机理的不理解，导致后续的分子设计、排列结构解析、材料性能优化、应用器件研究无法深入。因而本项目计划从构筑机理入手，在此基础上进行分子设计，从而获得具有优越调控性能的材料体系，最终应用于光子器件。

类液晶材料具有传统液晶材料所类似的分子结构或单元，表现出液晶材料所不具备的物理、化学性质。本项目采用类液晶材料构筑光学各向同性材料体系，通过分子模拟手段，采用分子动力学方法进行类液晶构筑光学各向同性材料体系的分子设计、自组装动力学与构筑机理研究，在保存传统液晶分子的自组装、光学、电学各向异性的基本性质的同时，赋予材料体系独特的表界面特性、分子相互作用以及外场操控性质，并进一步研究该体系在衍射光学与微腔光激射方面的应用。获得了如下四方面研究结果：1. 从传统的高分子稳定光学各向同性体系的思路出发，设计基于可聚合氟取代、弯曲形、氢键给体、受体三种类液晶光学各向同性材料体系，在降低体系驱动电压的同时也减弱了电光迟滞；2. 设计了类液晶光敏取向诱导材料和光敏类液晶基团的聚倍半硅氧烷笼式结构分子，分别通过对表面取向以及自组装结构的光刺激，实现对类液晶光学各向同性材料体系的光响应；3. 提出一种基于新型的二聚体类液晶及光敏手性材料的光、电响应光学螺旋各向同性材料体系，不但实现了其反射光谱在宽谱域范围的电场调制，还可通过光刺激切换该材料体系的螺旋方向；4.开发了电场、光场可控衍射器件和光激射器件，为类液晶光学各向同性材料在外场可控、低能耗、微型光学器件与光子集成技术上的应用提供了可选择的高光学效率材料体系。该项目的研究拓宽了对传统液晶材料的基本认识，为特种功能化液晶材料与器件的开发与应用提供了先期技术支持与探索资料。