Poly(amide acid) gels were first synthesized by the reaction of a poly(amide acid) with diisocyanates as crosslinking agents. Poly(amide acid) was synthesized from 3,3＇,4,4＇-benzophenonetetracarboxylic dianhydride (BTDA) and bis(4-amino-3-ethylphenyl)methane (DEDPM). From the change in the IR spectra, the key process of crosslinking was determined to be the decarboxylation from the reaction product of the carboxyl group and isocyanate group. The gels markedly change their volume with the composition change of NMP-water mixed solvent. Thermal properties of the poly(amide acid) gels are also studied. (C) 2000 Elsevier Science B.V. All rights reserved.