聚合物/液晶有序复合材料的结构调控与性能

Holography is one of the most significant techniques to fabricate ordered polymer-based composites. In this project, we focus on the polymer/liquid crystal (LC) system. The liquid-like LC microcapsules with the size of nanometer to sub-micrometer, liquid-like vinyl-functionalized nanosilica and alkyl-functionalized nanozirconia are initially synthesized based on the principle of molecular design, in-situ interfacial emulsion copolymerization and surface modification techniques. Then, they are introduced to the holographic polymer/LC system. During the visible-light-driven photopolymerization, the viscosity reduction effect of hyperbranched monomers, liquid-like components and LCs is expected to enhance the phase separation degree of the monomer/LC/inorganic nanoparticle composites. As a result, the complex of LC microcapsules, nanozirconia with high refractive index and LCs is located in the dark region of interference patterns to form the LC-rich phase, which can increase the refractive index modulation between the bright region and the dark one in the ordered polymer/LC gratings. Meanwhile, the vinyl-functionalized polyhedral oligomeric silsesquioxane (POSS) or silica nanoparticles whose refractive indices are similar to that of polymer are located in the bright region of interference patterns to form the polymer-rich phase, which is expected to decrease the volume shrinkage during photopolymerization. There are three main aims of this proposal. First, the synergistic effects of phase separation, volume shrinkage and refractive index modulation on microstructures and grating properties of the holographic polymer/LC/inorganic nanoparticle composites will be fully investigated. Secondly, we will develop novel applications of the storage of full-color three dimensional images and electric-optical responsive gratings based on these new holographic polymer/LC/inorganic nanoparticle composites. Finally, novel findings and conclusions of above research will advance the theory of ordered polymer-based composites, provide theoretical bases and new strategies for preparing high performance and functional ordered polymer-based composites.

激光全息技术是高分子材料有序复合的重要方法，本项目以聚合物/液晶体系为对象，通过分子设计原理、乳液界面原位共聚法和表面修饰技术，合成纳米-亚微米液晶微胶囊类流体、乙烯基纳米二氧化硅类流体和烷基化纳米二氧化锆。利用超支化单体、类流体和液晶在可见光聚合中的降粘作用，调控激光全息光聚合过程中单体/液晶/纳米无机粒子复合体系的相分离，使液晶微胶囊、高折射率的烷基化纳米二氧化锆和液晶复合体定位于相干条纹暗区，形成复合液晶相以增加聚合物/液晶有序复合材料的折射率对比度；将与聚合物折光率相近的乙烯基多面体低聚倍半硅氧烷或乙烯基纳米二氧化硅类流体定位于相干条纹亮区，形成复合聚合物相以克服体积收缩。研究相分离、体积收缩、折射率对比度等协同效应对有序复合材料结构与光栅性能的影响，探索三维全彩色图像存储和电光响应光栅应用，丰富、发展高分子有序复合理论，为制备高性能高分子有序复合材料提供理论基础和新方法。

激光全息技术是一种重要的高分子有序复合方法，而全息高分子/液晶复合材料是通过激光全息光聚合诱导相分离方法制得的结构有序高分子复合材料。如何对光聚合反应动力学和流变学行为实施高效瞬时控制与空间调控是实现相分离结构规整化以及提高全息高分子/液晶复合材料性能的关键科学问题。针对该科学问题，项目组开展了以下研究：(1)提出了“光引发阻聚剂”概念，基于光引发与光阻聚的竞争与协同效应制得了结构规整的全息高分子/液晶复合材料；阐明了光引发阻聚剂的作用机理，进而精确调控了全息高分子/液晶复合材料的相分离结构和复合光栅的电光响应性能。(2)系统研究了液晶与无机纳米粒子的相互作用，并研究了液晶与无机纳米粒子的协同效应对单体/液晶/无机纳米粒子复合体系光聚合反应动力学、流变学行为、相分离程度与结构、体积收缩率和折射率对比度的影响规律，进而制备了衍射效率高、光散射损失小、驱动电压低、响应速度快的全息高分子/液晶/无机纳米粒子复合材料。(3)基于Stokes-Einstein扩散系数和Fick第二扩散定律，建立了全息高分子复合材料加工的数学模型，解决了全息高分子复合材料加工效率与光栅衍射效率难以同时提高的矛盾，为全息高分子复合材料的高效加工奠定了理论基础。(4)创新了实物全息、母版全息、数字全息等多种图像存储技术，实现了尺寸达A4纸张的彩色三维图像存储和协同响应性多重图像的无串扰存储。(5)通过氢键网络控制相分离过程，突破了高黏度体系难以获得规整相分离结构的瓶颈，实现了全息高分子复合材料前驱体的直接印刷，为柔性全息打印奠定了基础。(6)系统研究了小分子液晶在亚微米尺度液晶微胶囊、手性液晶物理凝胶以及光响应型液晶物理凝胶中的受限相行为，制得了兼具高模量和低驱动电压的液晶显示材料。研究成果为制备结构有序的功能高分子复合材料提供了新理论与新方法，丰富和发展了高分子有序复合理论。