Main-chain polymers with nonlinear optical chromophores as a slipped shoulder-to-shoulder arrangement

Abstract

New second-order nonlinear optical main-chain polymers have been synthesized in very high yields by a two-stage Knoevenagel polycondensation from 3,6-diformyl-9-heptylcarbazole and bis(cyanoacetate)s. In these main-chain polymers, two kinds of nonlinear optical (NLO) chromophores, carbazole with two acceptor groups and 4′-nitrophenyl-azoaniline, were introduced in a slipped shoulder-to-shoulder arrangament. All polymers were determined to be amorphous and to have glass transition temperatures in the range of 134-158°C by a differential scanning calorimeter. THe chloroform soluble main-chain polymers show very high weight and number average molecular weights measured by a gel permeation chromatography. Thin films of the polymers could be obtained by a spin coating method. The orientation of dipoles could be achieved by applying an electric field. These poled films show good reasonable and stable second-order nonlinear optical responses.