Dual photochromism of copolymers containing two different types of photoisomerizable side groups

Copolyacrylates containing the side groups presented by the two types of ph otosensitive fragments such as cyanoazobenzene and benzylidene-p-menthane-3 -one groups were synthesized. As was shown, upon irradiation of the films o f copolymers with a wavelength of 313 nm, primarily E-Z photoisomerization of benzylidene-p-menthane-3-one chromophores is observed whereas, under irr adiation with a wavelength of 365 nm, a preferential isomerization of azobe nzene groups takes place. Hence, selecting the light wavelength, one may ea sily control the type of the groups participating in photoprocess. Isomeriz ation of benzylidene-p-menthane-3-one groups was found to be thermally irre versible whereas, in the case of cyanoazobenzene groups, annealing leads to the back process of Z-E isomerization. The kinetics of forward and back pr ocesses was studied. The effect of the configuration of benzylidene-p-menth ane-3-one groups (content ratio between E and Z form) of polymer matrix on the kinetics of forward and back processes of isomerization of cyanoazobenz ene groups was demonstrated. (C) 2001 Published by Elsevier Science B.V.