Polyamideimide (PAI)-epoxysilane (coupling agent) composites were reacted with oligomeric poly-climethylsiloxane (PDMS), a condensation product of difunctional silane, by using the sol-gel process, and were then dried into films. After this procedure, the surface, mechanical, and thermal properties were measured. The study showed that PDMS existed in the PAI matrix by the use of FTIR. With respect to mechanical properties, the maximum elongation and toughness were increased in the PAI with silane groups, although the maximum tensile strength was slightly decreased. In this experiment, PAI-30 wt % epoxysilane composite had the best mechanical properties. The intensive dispersion of the silane groups on the surface of PAI was confirmed through XPS measurement. As a function of the siloxane contents, the TGA curve shows less thermal stability in terms of their initial weight loss. However, in an oxygen atmosphere at about 700degreesC, the series of PAI-siloxane composites indicated a significant increase in char concentration. In the end, PAI with a relevant amount of silane groups was improved in both toughness and surface properties. This experiment showed that PDMS added to PAI had better properties than those of classical materials. (C) 2003 Wiley Periodicals, Inc.