On/off switching of structural color by using multi-bilayered films containing copolymers having azobenzene and biphenyl side groups

Abstract

In this paper, the change in structural color of multi-bilayered films fabricated by stacking copolymers, PMAz–PMBP (m : n), consisting of azobenzene and biphenyl side chain groups, and polyvinyl alcohol (PVA) alternately, was investigated. The multi-bilayered films consisting of polyacrylates having an azobenzene side chain group and PVA were found to reflect a light of specific wavelength, and to show reversible change in the reflection intensity by thermal annealing and irradiation with non-polarized ultra violet (UV) light. However, a long irradiation time was required for the change in reflection intensity of the multi-bilayered films. Therefore, we synthesized PMAz–PMBP (m : n), consisting of azobenzene and biphenyl side chain group having no absorbance over 300 nm, and the PMAz–PMBP (m : n)/PVA multi-bilayered films were fabricated. All the multi-bilayered films showed reversible change in the reflection intensity by thermal annealing and irradiation with non-polarized UV light. The re-coloration speed of PMAz–PMBP (75 : 25)/PVA 20-multibilayered film was faster than others fabricated in this study. It is related to penetration depth of light into the films. The effect of the introduction of the biphenyl side groups in the copolymers on the response behavior of the change in the structural color will be discussed.