Synthesis and photoinduced birefringence of polymethacrylates with azo-substituted pyrazoline in the side chain

Two azo-containing polymers with pyrazoline group (polymers II and III) have been synthesized and their reversible optical storage properties tested in comparison with electron donor and acceptor substituted azobenzene-containing polymer I. The growth and relaxation process of birefringence signals were fit with biexponential functions. It was found that polymer II, in which azo chromophores are connected with the main chain through pyrazoline groups, has fast storage rate and good storage stability. The storage efficiency indicated that the introduction of pyrazoline groups in the polymers II and III has a positive effect. The birefringence per mole of azo chromophore showed that polymers II and III have four times the value of polymer I. The relative stability of the photoinduced birefringence decreased with the increase of temperature.