Induction of the vector polyphotochromism in side-chain azopolymers

Abstract

The phenomenon of vector photochromism was observed in some high-efficient polarization-sensitive materials depending on the radiant exposure of the inducing linearly polarized actinic light. When radiant exposure exceed certain value specific to each material, a sharp change in the transmission spectrum of the probing linearly polarized nonactinic beam is observed after analyzer. While probing with unpolarized light the transmission spectrum is practically unchanged and does not depend on the magnitude of the radiant exposure. The mechanism of this phenomenon is discussed. The effect is an interference nature and depends on the path difference between the ordinary and extraordinary rays in material with photo-induced anisotropy. It is shown that the kinetics of this effect depends on the photosensitive layer thickness and the concentration of the chromophore.The beams with a wavelength away from the absorption band of the material were used as a probing. It is shown that in this case birefringence has made the main contribution in photoanisotropy. The experiments were carried out for polarization-sensitive materials with varying degrees of components integration, in particular, two synthesized side-chain azopolymers obtained by immobilization of polar azo dyes on polymethylmethacrylate backbone. It is shown that the maximum value of the birefringence Δn = 0.162 achieved in azopolymers with covalently bonded components. In this case a third order of interference of the probing beam is observed.