Second order nonlinear optical performances of polymers containing imidazole and benzimidazole chromophores

Summary: Condensation polymers based on two different NLO-active chromophores, namely 2-[4-[(4-N,N-dihydroxyethylamino)phenylazo]phenyl]-5(6)-nitrobenzimidazole (BZI) and 2-[4-(4-N,N-dihydroxyethylamino)phenylazo]- 4,5-dicyanoimidazole (IMI), have been synthesized and their basic properties measured. The second order NLO properties of poled polymers were investigated by SHG procedures at different temperatures (35, 65 and 85 °C) and exposure times. Resonance free d33 coefficients (lambda = 1368 nm) took values in the range 1.8–4.0 pm/V, but the time stability of their SHG signal was fairly acceptable, particularly for the high Tg (e.g. 188 °C) polymer for which a relaxation time (at 25 °C) of 2.8 years has been determined.