A poly(vinyl alcohol) (PVA)/silica (SiO2) nanocomposite was prepared with a novel self-assembled monolayer technique, and its morphology and thermal properties were studied with different material characterization instruments. The treated SiO2 nanoparticles were dispersed in the PVA matrix homogeneously, and the thermal properties of the nanocomposite were markedly improved in comparison with those of pure PVA. Under the same isothermal heating conditions, the decomposition of the nanocomposite was delayed significantly in comparison with that of PVA. The thermal degradation of the nanocomposite was a two-step reaction, including the degradation of the side chain and main chain. The products of side-chain degradation were mainly carboxylic acid, whereas main-chain degradation primarily produced carbon dioxide and low-molecular-weight conjugated polyene. (c) 2005 Wiley Periodicals, Inc.