Photochromic Behavior of Spiropyran in Polyurethane Thin Films

Abstract

The aim of this work is to characterize the photochromic properties of a commercial grade of polyurethane (PU) that contains small quantities of spiropyran (SP) [1-hexyle-3,3-dimethyl-6'-nitrospiro (indoline-2',2'-benzopyran)]. PU photochromic films were illuminated with ultraviolet irradiation (365 nm) at room temperature and the absorbance spectra are recorded after scanning from 400 to 800 nm (visible zone). The effects of film thickness, irradiation time, and SP concentration on the polymer photochromic response have been studied. Furthermore, the photochromic behavior of polymer films under stretching and the kinetics of thermal decoloration of these films will be discussed.