SYNTHESIS AND CHARACTERIZATION OF PHOTOCHROMIC HOMOPOLYMER COPOLYMER/

Photochromic spiropyran homopolymer/copolymers have been prepared by r adical polymerization of lamino-1,3,3-trimethylindolino-6'-nitro-8'-me thoxy spiropyran using different vinyl monomers such as methyl methacr ylate, methyl acrylate, and styrene. The polymerization was carried ou t at 80 degrees C in dimethylformamide using alpha,alpha'-azobisisobut yronitrile as initiator. The polymers have been characterized by visco metry, gel permeation chromatography, thermogravimetric analysis, and infrared spectroscopy. The kinetics of photochromic behavior have been investigated by preparing a film of one copolymer blended with poly(m ethyl methacrylate). This film, on exposure to sunlight or suitable wa velength, showed a very strong photochromic effect. The decoloration r eaction kinetics follow a first-order relationship. The duration for r eturn of the color depends upon the intensity of incident light, ambie nt temperature, moisture content, and thermal treatment of the film. ( C) 1997 John Wiley & Sons, Inc.