Mesostructured titanium dioxide films have been synthesized by modifying sol-gel methods in the presence of poly( ethylene oxide)-block-poly(propylene oxide)-blockpoly( ethylene oxide) block copolymer surfactants as a structure-directing agent. The synthesized films were analyzed using X-ray diffraction (XRD), field emission transmission electron microscopy (FE-TEM) and selected area electron diffraction ( SAED). XRD investigation revealed that as-deposited and as-dried films showed a hexagonal arrangement. With increasing heat-treatment temperature, the mesostructure of the films degraded. From TEM and SAED studies, the degradation of the mesostructure can be explained by the grain growth of microcrystalline titanium dioxide. (C) 2003 Kluwer Academic Publishers.