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

Copolyacrylates containing the side groups presented by the two types of photosensitive fragments such as cyanoazobenzene and benzylidene-p-menthane-3-one groups were synthesized. As was shown, upon irradiation of the films of copolymers with a wavelength of 313 nm, primarily E‐Z photoisomerization of benzylidene-p-menthane-3-one chromophores is observed whereas, under irradiation with a wavelength of 365 nm, a preferential isomerization of azobenzene groups takes place. Hence, selecting the light wavelength, one may easily control the type of the groups participating in photoprocess. Isomerization of benzylidene- p-menthane-3-one groups was found to be thermally irreversible whereas, in the case of cyanoazobenzene groups, annealing leads to the back process of Z‐E isomerization. The kinetics of forward and back processes was studied. The effect of the configuration of benzylidene- p-menthane-3-one groups (content ratio between E and Z form) of polymer matrix on the kinetics of forward and back processes of isomerization of cyanoazobenzene groups was demonstrated. © 2001 Published by Elsevier Science B.V.