Theory of photo-mechanical properties of azobenzene polymers: light-induced deformation dynamics

偶氮聚合物作为一种能够将光能转化为机械应力的光致变形智能材料，在过去的十年中得到了广泛的研究。目前，有一个很大的需求，定量预测这些材料的动态响应的基础上，他们的微观结构。该项目的目的是为两类广泛使用的偶氮聚合物：玻璃态聚合物和高弹性网络（弹性体）发展光致变形动力学理论。光致变形的动力学上的不同效果的影响将被考虑：（i）光致异构化动力学，导致在光学各向异性和光致机械应力，（ii）嵌入到聚合物基体中的偶氮发色团的集体运动，和（iii）分子间的相互作用，如短尺度的相互作用在玻璃状聚合物和长尺度的取向相互作用在液晶偶氮聚合物。光致变形的时间依赖性将作为光强度、偶氮分子的聚合度、交联度、偶氮分子内发色团的取向分布、分子间相互作用的强度、偶氮发色团的物理特性（例如它们的尺寸和吸收系数）、在该项目中建立的结构-性能关系对于有针对性地开发用于各种纳米和微米级应用的光控高速器件的偶氮聚合物具有重要意义。

Azobenzene polymers (azo-polymers) have been extensively explored in the last decade as photo-deformable smart materials which are able to transform light energy into mechanical stress. Presently, there is a great need for quantitative prediction of the dynamic response of these materials based on their microscopic structure. The aim of this project is to develop a theory of the light-induced deformation dynamics for two widely used classes of azo-polymers: glassy polymers and highly elastic networks (elastomers). The influence of different effects on the dynamics of light-induced deformation will be taken into account: (i) photoisomerisation kinetics which results in the optical anisotropy and light-induced mechanical stress, (ii) collective motions of azo-chromophores embedded into a polymer matrix, and (iii) intermolecular interactions such as short-scale interactions in glassy polymers and long-scale orientational interactions in liquid crystalline azo-polymers. The time dependences of the light-induced deformation will be calculated as a function of the light intensity, the degree of polymerization of the azo-molecules, the degree of cross-linking, orientation distribution of chromophores inside azo-molecules, strengths of intermolecular interactions, physical characteristics of azo-chromophores such as their dimensions and absorption coefficient, etc. Structure-property relationships established during the project are of great importance for targeted development of azo-polymers to be used in light-controllable high-speed devices for various nano- and microscale applications.