Preparation and photochromic properties of oligomeric poly(dimethylsiloxane) with the spiropyran or spirooxazine moiety in the side chain

Spirobenzopyran 1, with the 3‐(diethoxymethylsilyl)‐propyl group at the N atom, was synthesized. The condensation reaction of the spiropyran 1 and diethoxydimethylsilane gave oligomeric poly(dimethylsiloxane) with the spiropyran moiety in the side chain. The oligomer was photochromic; its colour changed from colorless to purple‐red on uv irradiation and the color faded on visible irradiation or on standing in the dark. The half‐decay time of the thermal decoloration was about twice that of monomeric spiropyran dissolved in the dimethylsiloxane oligomer. Photochromic poly(dimethylsiloxane) with the spirooxazine moiety in the side chain was also prepared.