Ate-dye-structure dependence of photoinduced anisotropy observed in PMMA films

Polarized light-induced anisotropy of 4-dimethylamino-4/-nitroazobenzene (D MANA; NO2-C6H4-N=N-C6H4-N(CH3)(2)) in PMMA is investigated by polarized spe ctroscopy and compared with the anisotropy of Disperse Orange 3 (DO3; NO2-C 6H4-N=N-C6H4-NH2) studied previously. The orientation factors evaluated fro m spectroscopic results show that the trans isomers of DMANA isomerize to c is forms by motion of the p-NO2-C6H4 group easily compared with motion of t he p-N(CH3)(2)-C6H4 group. This result is different from the result of DO3 in PMMA where the trans forms tend to isomerize to cis forms by motion of t he amino group side than that of nitro group side. We consider that this di fference is due to the volume effect of the substituent at the para positio n of a phenyl group. This study clearly indicates that the motion of push-p ull ate-dyes in the isomerization processes strongly depends on the relativ e volume of the p-substituent. (C) 2000 Elsevier Science S.A. All rights re served.