Cellulose acetate (CA) composites using two types of silane coupling agents (methyltrimethoxysilane and phenyltriethoxysilane) were prepared through two methodologies: direct reaction between CA and the specific monomer and reaction of CA with oligomers, which were produced by prehydrolysis of the same monomers. The thermal behavior and morphology of the materials were studied. The composites showed thermal stability similar to pure CA, increase of residue content at 790 degrees C and reduction in the glass transition temperature. Complementary microscopy techniques were applied to investigate the distribution of polysilsesquioxane in the CA matrix. Silicon mapping images showed the presence of domains with higher polysilsesquioxane concentration than the matrix and also the presence of silicon-rich nanodomains dispersed throughout the matrix. Based on mapping characterization, a schematic representation of the CA/polysilsesquioxane composite morphology was proposed. The organosilane type and architecture influenced the thermal behavior and the morphology of these materials. The results suggest that the silane coupling agents could be used to produce CA films with a range of properties. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 2027-2035, 2012