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 main chains, followed by the covalent bonding of the NLO chromophores onto the polyimide backbone via a post-ate-coupling reaction. The degree of functionalization of polyimides was estimated by UV-VIS spectroscopy. The glass transition 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 chains through an ether linkage using a post-Mitsunobu condensation. The solubility and thermal stability of polyimides were also studied. (C) 2000 John Wiley & Sons, Inc.