Self-alignment and photomechanical properties of alternative multi-layered films containing azobenzene polymer liquid crystal and polyvinyl alcohol layers

• We fabricated multi-bilayered films consisting of PVA and azobenzene polymer.
• We found photo-mechanical (PM) behavior of the multi-bilayered films.
• The annealed films bent to the opposite side of UV source by irradiation.
• By following visible light irradiation, the films reverted to initial position.
• The orientation control of the azobenzene groups affects PM behaviors.

We demonstrated fabrication of photo-mechanical materials alternatively-including azobenzene-side-chained acrylate polymer, PMAz6Ac, and polyvinyl alcohol, PVA, without cross-linking. The multi-bilayered (PMAz6Ac/PVA)n films were obtained by alternative spin-coating methods of PVA and PMAz6Ac solutions on glass substrates. After thermal treatment, the azobenzene groups as mesogen were self-organized and were induced out-of-plane orientation. After UV irradiation (λ=375 nm), the self-standing films obtained by peeling off was bent to an opposite side of the light source, and the bended film reverted toward the initial position by following visible light irradiation (λ>420 nm). Their optical properties of the PMAz6Ac layers indicated that change of molecular orientation, out-of-plane orientation and disordered random, of azobenzene groups in the PMAz6Ac layers closely related with the photo-mechanical behaviors.