Preparation of diarylethene copolymers and their photoinduced refractive index change

Diarylethene copolymers were synthesized from 1-(6 ^′-vinyl-2 ^′-methylbenzo[ b]thiophene-3 ^′-yl)-2-(2 ^′′-methylbenzo [ b]thiophene-3 ^′′-yl)hexafluorocyclopentene (VMBTF6) and 1-[6 ^′-(4 ^′′′-vinylbenzoyl)-2 ^′-methylbenzo[ b]thiophene-3 ^′-yl]-2-(2 ^′′-methylbenzo[ b]thiophene-3 ^′′ -yl)hexafluorocyclopentene (VBMBTF6) via living free radical techniques using stable TEMPO derivatives. The diarylethene content was controlled by the feed ratio of diarylethene derivatives and styrene. Transparent photochromic polymer films were prepared from the diarylethene copolymers with narrow molecular weight dispersion (PD∼1.3) by spin coating method. Photoinduced refractive index changes (Δ n _TE) of the polymer films, with 25 mol% of diaryethene content, accompanied by the photochromic change were determined as 0.0009 and 0.0030 for poly(styrene- ran -VMBTF6) and poly(styrene- ran-VBMBTF6), respectively.