Synthesis and characterization of side-chain polyimides for second-order nonlinear optics via a post-azo-coupling reaction

A two-step, generally applicable synthetic approach for nonlinear optical ( NLO) side-chain polyimides was developed. This included the preparation of a preimidized, organosoluble polyimide with benzene moiety pendant from mai n chains, followed by the covalent bonding of the NLO chromophores onto the polyimide backbone via a post-ate-coupling reaction. The degree of functio nalization of polyimides was estimated by UV-VIS spectroscopy. The glass tr ansition temperature (T-g) of a polyimide decreased by only 10-20 degrees C after the functionalization, which was much smaller than the decrease in T -g when the chromophores were chemically bonded to the polyimide main chain s through an ether linkage using a post-Mitsunobu condensation. The solubil ity and thermal stability of polyimides were also studied. (C) 2000 John Wi ley & Sons, Inc.