Effect of photo irradiation on the refractive indices of spirobenzopyran film

The effect of photo irradiation on the refractive index of spirobenzopyran (SP) polymer was investigated. Spirobenzopyran polymers were prepared by a radical polymerization using 6-(p-methacryloyloxy-hexyloxyphenyl)carbonylsp irobenzopyran, styrene, and butylmethacrylate. Films with spirobenzopyran p olymers showed color change from pale yellow to deep blue upon irradiation of a monochromatic light of 340 nm. The colored films were bleached either spontaneously or by light of 580 nm. The refractive index changes of the sp irobenzopyran polymers were 5 x 10(-4) and 9 x 10(-4) for 20 wt% and 35 wt% of the spirobenzopyran content, respectively.