Small-angle X-ray scattering and spectroscopic (infrared and ultraviolet-visible) techniques were used to investigate the interactions between titanium dioxide (TiO2) and the semiconductor polymer poly[N-(4-sulfophenyl)aniline] (PSA) in a poly[N-(4-sulfophenyl)aniline]/TiO2 composite (TPSA). The radius of gyration of the cross section, the radius and length of the rodlike particle, the persistence length, the surface fractal dimension, and the PSA layer thickness on TiO2 in aqueous solutions and in powder form were calculated. The results indicated that the aggregation of TiO2 particles on drying was reduced by the formation of the composite with the semiconductor poly-mer. Only the particle length of the TPSA particle (which had a rodlike shape) increased on drying, probably because of increasing void sizes and the formation of aggregation. The persistence length of the TPSA particles decreased with respect to its individual components. The PSA layer thickness on TiO2 was about 3.6 nm and decreased (to 2.6 nm) on dehydration because of the expulsions of water molecules from the TiO2/PSA composite. (C) 2003 Wiley Periodicals, Inc.