Poly(amide imide)-epoxysilane (coupling agent) composites were reacted with silica, a condensation product of tetraethylorthosilicate (TEOS), by a sol-gel process and were then cast into films. After this procedure, the chemical characteristics and mechanical and thermal properties were measured. Fourier transform infrared showed that silica existed in the poly(amide imide) matrix. When a proper amount of silica was added to the poly(amide imide) matrix, the tensile strength, elongation, and toughness increased greatly. A poly(amide imide)/30 wt% epoxysilane composite with 20 wt% TEOS had the best mechanical properties. Thermogravimetric analysis under nitrogen and oxygen atmospheres indicated that the char contents increased with the amount of silica. The glass-transition temperatures of the poly(amide imide)-silica nanocomposites were observed around 170-180degreesC with differential scanning calorimetry. This approach may be a new method for the low-temperature thermal curing of poly(amide imide). (C) 2004 Wiley Periodicals, Inc.