基于硫醇-烯烃点击反应的全息光聚合物/液晶复合材料

Holographic photopolymer/liquid-crystal composites are structurally ordered polymer-based composites that are capable of reversibly responding to external stimuli. The step-growth polymerization involving thiol-ene click reactions, has attractive characteristics including but not limited to low volume shrinkage, high gel point monomer conversion and unique oxygen tolerance, thus is envisioned to be the primary approach that substitutes the traditional radical chain-growth polymerization to reconstruct high performance holographic polymer-based composites. Yet, in lack of effective routes to control the holographic photopolymerization process spatially and temporally, it remains a challenge to fabricate holographic photopolymer/liquid-crystal composites with complete phase separation, uniform interface and desired electro-optic performance through thiol-ene click reactions. We are going to initiate this project by synthesizing a thiol monomer named tetra(2-mercaptoethyl)silane, which has been demonstrated to offer high modulus polymer through thiol-ene click reactions with multifunctional ene monomers. Subsequently, we will mix several different thiol and ene monomers with liquid crystals, and then formulate holographic photopolymer/liquid-crystal composites through photo-triggered thiol-ene click reactions and sequential polymerization induced phase separation. The effect of monomer structure on the gel point monomer conversion and composites’ moduli will be systematically investigated, aiming at providing a tailoring route to enhance the performance of holographic polymer-based composites. Following, a newly disclosed photoinitibitor will be utilized to implement spatiotemporal control over the thiol-ene photopolymerization kinetics, gelation behavior, phase separation and electro-optic performance of holographic photopolymer/liquid-crystal composites, and the dependency of the photoinitibitor’s control capability on the gel point monomer conversion and composites’ moduli during the step-growth polymerization will be illustrated, seeking to afford new theories and novel approaches to formulate high performance holographic polymer-based composites. Finally, we will implement 3D image storage under oxygen atmosphere, for a purpose of advancing the applications of structurally ordered polymer-based composites that are fabricated through step-growth polymerization.

全息光聚合物/液晶复合材料是在外场刺激下具有可逆响应行为的高分子有序复合材料。基于硫醇-烯烃点击反应的逐步聚合，具有体积收缩率低、凝胶点单体转化率高、无氧气阻聚的优点，可望取代传统的自由基链式聚合成为构建高性能全息复合材料的主流方法。然而，由于缺乏有效调控的手段，硫醇-烯烃点击反应还难以制备相分离完全、界面结构规整和电光性能优异的全息光聚合物/液晶复合材料。本项目首先合成高模量聚合物单体，再通过单体复配和硫醇-烯烃点击反应构建全息光聚合物/液晶复合材料。研究单体结构对凝胶点单体转化率和复合体系模量的影响规律，为提高复合材料性能提供调控途径。研究光引发/阻聚剂对光聚合动力学、凝胶化行为、相分离行为和电光性能的影响规律，以及上述影响对凝胶点单体转化率和复合体系模量的依赖关系，为制备高性能高分子有序复合材料提供新理论和新方法。在空气环境中存储3D图像，拓展逐步聚合反应在高分子有序复合材料的应用。

全息光聚合物/液晶复合材料是由富聚合物相与富液晶相周期性排列而成的、对外场具有可逆响应行为的结构有序高分子复合材料。由于具有独特的光衍射和电光响应能力，该材料已广泛应用于电光响应型光子晶体、彩色3D图像存储、分布反馈式激光器、传感器、3D显示等领域。项目基于硫醇-烯烃点击反应和光引发阻聚剂的调控，制备了相分离完全、界面结构规整和电光性能优异的全息光聚合物/液晶复合材料。研究发现，当硫醇-烯烃官能团数比为1:1时，全息光聚合物/液晶复合材料的相分离结构最为规整，衍射效率最高（94%）。同时，KCD/NPG光引发阻聚剂对基于硫醇-烯烃点击反应的全息光聚合物/液晶复合材料具有显著的调控能力。当KCD含量低于0.3 wt%时，难以形成结构规整的全息光聚合物/液晶复合材料；随着KCD含量增加，全息复合材料的相分离结构渐趋规整，衍射效率显著增加；当KCD含量高于0.6 wt%时，全息光聚合物/液晶复合材料的衍射效率高于90%。基于硫醇-烯烃点击反应和光引发阻聚剂的调控，在空气氛中存储了裸眼可见的柔性彩色全息图像，为卷对卷柔性全息印刷奠定了理论基础。.此外，基于硫醇-烯烃点击反应，通过原位光聚合物诱导相分离制备了光聚合物/光响应半导体小分子复合材料。该复合材料具有连续的光聚合物层及半导体层、但两层之间具有山丘状的不规整界面。这种特殊的相分离结构在保证界面高效激子分离的同时，促进了空穴载流子的高效传输。基于这一发现，制备了高效薄膜晶体管型柔性紫外光传感器，为拓展高分子复合材料在新型柔性半导体光响应器件中的应用提供了新思路。