基于氰芪基手性荧光光开关的双模式液晶光子材料的光调控研究

This project aims to investigate phototunable behaviors of reflection-fluorescence dual-mode liquid crystal (LC) photonic materials based on cyanostilbene-based chiral fluorescence photoswitches. Firstly, we synthesize a new kind of chiral fluorescence photoswitches featuring photosensitive cyanostilbene moiety. The photochemistry properties of the chiral photoswitches caused by reversible Z/E photoisomerization upon ultraviolet light irradiation are studied in detail. Then the photoswitching behaviors of cholesteric liquid crystal optical (Ch-LCs) induced by chiral photoswitches as chiral dopant are further investigated, such as the changes of helical pitch and the corresponding reflection band/color. Meanwhile, other important performances are also be addressed, including aggregation-induced enhanced emission, fluorescence changes induced by Z/E photoisomerization and fluorescence enhancement caused by the coupling of reflectance and fluorescence bands. Based on the above experimental results, simultaneous reversible phototuning of the reflection and fluorescence colors in the dual-mode Ch-LCs could be obtained. Second, the LC photonic microcapsules are prepared by employing a microfluidic emulsion method, and the effects of processing conditions and material types on the morphology of the microcapsules are studied. We also investigate the influences of the capsules size and shell thickness of the capsules on the molecular orientation of LCs, and the relationship between the orientation of LC molecules and reflection/fluorescence in confined capsules are explored. Finally, the polymer photonic arrays are fabricated by using transfer printing or screen printing. The investigation on the photoswitching of reflection and fluorescence of the photonic arrays are carried out. The project may open up a new way for the fabrication of novel chiral photoswitches and responsive LC materials.

本申请项目拟开展基于氰芪基手性荧光光开关的反射-荧光双模式液晶光子材料的光调控研究。首先，合成一类光响应氰芪基构筑的手性荧光光开关，研究紫外光诱导的光开关的可逆光异构化及光化学性质的变化。然后由其诱导制备胆甾相液晶（Ch-LCs），研究Ch-LCs的螺旋周期及相应的反射波段的光调控趋势；与此同时，研究光开关在液晶介质中的聚集诱导荧光增强效应，光致异构化导致的荧光变化及反射和荧光波段的偶合导致的荧光增强等。最终得到可UV光同时调控反射和荧光的Ch-LCs。进一步采用微流体乳化法制备光响应的液晶光子微胶囊，研究工艺条件及材料等因素对胶囊形貌的影响。研究胶囊的大小和壁厚等因素对液晶分子取向的影响。探索受限空间内液晶分子取向与反射及荧光之间的关联关系。最后，采用转移印刷或丝印法制备聚合物光子阵列，研究其反射-荧光双模式的光调控行为。本项目的开展为手性光开关及响应性液晶材料的制备开辟一条新的途径。

本课题涉及氰芪基手性荧光光开关的制备及其构建的双模式液晶光子材料的光调控性能研究。本研究从氰芪基手性荧光光开关的分子设计与制备出发，进一步搭建了几类反射/荧光性能可光调控的胆甾相液晶（CLCs）光子材料。主要研究成果如下：. 1）单氰芪基手性荧光光开关及其构筑的液晶光子材料.首先设计并制备了两种单氰芪基手性荧光光开关，并将其构筑的CLCs成功应用于快速、实时监测紫外光的器件。将手性光开关中α-氰基二苯乙烯结构中的苯环用噻吩环替换，得到的光开关分子Z/E异构化过程由不可逆调控变为部分可逆调控，相应的CLCs的反射和荧光可以动态调节。进一步增加噻吩环的个数以获得共轭结构更大的手性光开关，得到的手性光开关的可逆调控性能进一步改善，在和相反旋向手性添加剂构筑的CLCs中实现了圆偏振发光手性的可逆翻转。. 2）双氰芪基手性荧光光开关及其构筑的液晶光子材料.基于双氰芪基手性荧光光开关构筑了具有较大反射和荧光迁移的反射-荧光双模式图案。进一步优化分子结构，获得了理想的Z/E异构化过程可逆调控的手性荧光光开关。由其掺杂制备的CLCs可用于构筑光写入/光擦除的反射-荧光双模式透明显示器件，构筑的器件具有在自然光状态下和黑暗状态下清晰读取信息的特征。同时，由于对光的快速响应特征，此类器件还可用于光写入/光擦除的非接触操控式手写板的搭建。. 3）双氰基二芳基乙烯手性荧光光开关及其构筑的液晶光子材料.制备了一类双氰基取代二芳基乙烯骨架的手性荧光光开关，这类光开关可以在双向可见光下发生Z/E异构化反应。基于这类光开关构建了双向可见光调控的反射/荧光双模式CLCs器件；进一步利用荧光能量共振效应，制备了双色荧光可逆光调控的液晶光子器件。并且，通过调控980 nm 激光的功率，可以实现单一光源下对这类光开关构筑的液晶体系的动态调控。.总之，本项目的开展为氰芪基手性荧光光开关的制备及由其构建的双模式液晶光子材料在新型显示、传感器及其它智能材料领域的应用提供了新的方法和思路。.