The third-order optical nonlinearities and time responses of three new polymeric materials, which were prepared by polymerization of benzoguanamine (BGA) and pyromellitic dianhydride (PMDA), m,m'-diaminobenzophenone (m,m'-DABP) and PMDA, BGA, and 2,4-tolylenediisocyanate (TDI) under microwave radiation, were measured by a picosecond forward three-dimensional degenerate four-wave mixing technique. The experimental results showed that nonresonant optical nonlinearity [chi((3))] of the three polymers is larger by microwave than by heating and that third-order optical nonlinearities were not only affected by the length of polymer chain, but also by the polymer chain structure. (C) 2003 Wiley Periodicals, Inc.