Generation of second harmonics and photoinduced birefringence in comb-like polymers with nonlinear optical (nlo) chromophores in side chains

The effect of second harmonic generation (SHG) and photoinduced birefringence on the chemical structure of comb-like (co)polymers with photochromic chromophores, which exhibit nonlinear optical (NLO) activity, was analyzed. The copolymers were obtained by free-radical polymerization of the corresponding monomers in solution of N,N-dimethylacetamide (DMAA) with an initiator at 60°C. The change in the azodye structure by introduction of a thiazole ring with two heteroatoms in the cojugation chain, results in complete birefringence suppression. The results show that for polymers with considerable birefringence, the SHG signal is unstable.