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

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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.