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Directional Deformations in Photosensitive Azopolymers

Introduction

Azobenzene polymers have been extensively explored in the last decade as photo-deformable smart materials. They have a number of technical applications as data storage media, aligning layers in display and semiconductor technology, light-controllable artificial muscles, etc. We develop a theory of light-induced deformation of azobenzene polymers both for glassy polymers and for crosslinked azobenzene elastomers. The reorientation of azo-chromophores perpendicular to the polarization of light is found to be a self-sufficient explanation for the photo-mechanics of azo-polymers. The theory demonstrates that the light-induced stress caused by azo-reorientation is enough to deform glassy polymers irreversibly and the sign of deformation (expansion/contraction) depends on the chemical structure of the molecules. The results of the theory are in agreement with molecular dynamic simulations performed by us to study light-induced deformation of azobenzene polymers with different chemical architecture. Presently we study the effects of orientation interactions between chromophores on the light-induced deformation and the kinetics of this deformation.

Highlights:

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    Local direction of opto-mechanical stress in azobenzene containing polymers during surface relief grating formation
    Macromolecular Materials and Engineering, accepted
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    Molecules 26 (2021) 7674
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    Orientation approach to directional photodeformations in glassy side-chain azopolymers
    J. Phys. Chem. B 123 (2019) 3337–3347
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    Langmuir 35 (2018) 311–321
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    Kinetics of ordering and deformation in photosensitive azobenzene lc networks
    Polymers 10 (2018) 531
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    Photoisomerization kinetics and mechanical stress in azobenzene-containing materials
    Journal of Physical Chemistry Letters 8 (2017) 1094-1098