基于超分子组装的光敏形变材料

Photomobile polymer is a novel fascinating material that directly converts light energy into mechanical work. The working principle is that the photoisomerization of chromophore upon irradiation causes the alignment change of the mesogenic groups in the liquid-crystal polymers, so that results in the deformation of the whole material. The elasticity and the alignment of the mesogenic group are two key factors that influence the photomobile properties. Polymers after crosslinking usualy has a low degree of alignment of the mesogenic groups. Supramolcular assembly tends to form a molecular level ordered structure, but the assembly entity usualy lack of elasticity due to absence of intermolecular crosslinking. For a compromise, if we can conduct "supramolecular crosslinking" in the assembly entity, and render it elasticity, then probably will develop a new way to fabricate supramolecular materials with photomobile properties. For this purpose, this project attempt to design molecules bearing photoisomerization chromophore, and prepare micro- / nano-structures by self-assembly; at the same time, introducing strong supramolecular interactions to crosslink the monomers in the assembled entity, so that prepare supramolecule based photomobile materials. In addition, combining Layer-by-Layer technique and soft lithography method, we attempt to assemble the azo-benzene derivatives and small molecule that generate strong supramolecular interactions between the layers, thus the thin films with elasticity and photomobility are fabricated.

光敏形变材料是一类将光能直接转化为机械能的新型材料。其机理是在液晶高分子中引入光致异构发色团，通过光照使发色团发生异构，经类似多米诺效应使介晶基团发生重排，从而引起整个材料的形变。影响这类材料性质的两个关键因素是材料的弹性和介晶基团的有序性。高分子交联后弹性好，但介晶基团的有序性会大大降低。超分子组装很容易制备分子级有序结构，但组装体弹性很差。若能发挥超分子组装的优势，在组装体内引入"超分子交联"，制备超分子弹性体，便为发展以超分子组装为基础的光敏形变材料开辟一条新的思路。本项目一方面将功能基团引入构筑基元并形成有序结构,同时在超分子组装体内引入超分子交联，使之具有一定的弹性性质，从而发展具有光敏形变性质的超分子微纳米结构；另一方面利用层-层组装技术将高分子与功能小分子交替共组装，并在层间引入可形成强超分子作用的基团，织构层间的交联网络，制备具有弹性光敏形变性质的超薄膜。

本项目旨在发展光敏形变材料，通过超分子相互作用在组装体中引入光致异构发色团，利用光照使发色团发生异构，从而引发整个材料的形变。在聚合物组装方面，制备了具有规整偶氮苯基团的聚合物，其在THF中组装形成分布较宽的胶体球。这些纳米球状结构在分散体系中和干态下均显示出较好的光敏形变特性。在小分子组装方面，设计合成了含偶氮苯或α—氰基二苯乙烯基团的小分子，利用这些基团的光致异构特性，发展了自组装体的形貌可通过光照来调控超分子软物质材料。另外，在此项目的支持下，我们还开展了分子设计调控的自组装纳米结构，阴、阳离子响应的荧光强度可调的超分子组装体，以及基于聚集诱导发光的具有高荧光量子效率、良好生物相容性且无细胞毒性的纳米荧光材料。