Synthesis and characterization of photochromic homopolymer/copolymer

Photochromic spiropyran homopolymer/copolymers have been prepared by radical polymerization of 5-acrylamino-1,3,3-trimethylindolino-6'-nitro-8'-methoxy spiropyran using different vinyl monomers such as methyl methacrylate, methyl acrylate, and styrene. The polymerization was carried out at 80 degrees C in dimethylformamide using alpha,alpha'-azobisisobutyronitrile as initiator. The polymers have been characterized by viscometry, 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(methyl methacrylate). This film, on exposure to sunlight or suitable wavelength, showed a very strong photochromic effect. The decoloration reaction kinetics follow a first-order relationship. The duration for return of the color depends upon the intensity of incident light, ambient temperature, moisture content, and thermal treatment of the film. (C) 1997 John Wiley & Sons, Inc.