Azo Polymers for Reversible Optical Storage. 9. Copolymers Containing Two Types of Azobenzene Side Groups

A series of copolymers with two structural units 1-(4-nitrophenyl)-2-(4-{[2-(methacryloyloxy)ethyl]ethylamino}phenyl)diazene (DR1M), which contains donor−acceptor substituents in the azobenzene group, and 4-[2-(methacryloyloxy)ethyl]azobenzene (MEA), which has no donor−acceptor substituents was prepared. The maximum obtainable photoinduced birefringence and the fraction of birefringence conserved after relaxation increase with increasing DR1M concentration in the copolymer. The rate of inducing birefringence is independent on the copolymer composition. In terms of the relaxation of the photoinduced birefringence, copolymers with higher DR1M content relax faster. The β-parameter of the stretched exponential functions describing the growth and relaxation of the photoinduced birefringence also appears to be independent of copolymer composition. The electronic spectra, as well as the birefringence studies, reveal that there is no significant interaction between DR1M and MEA structural units in the copolymers.