Mesoporous vanadium pentoxide (V2O5) films have been synthesized by hydrolysis of vanadium tri-isopropoxide (VO(OC3H7)(3)) in the presence of polyethylene glycol (PEG) as a structure-directing agent. The structure, the stoichiometry and the morphology of the films have been studied as a function of the thermal annealing by X-ray diffraction (XRD), micro-Raman spectroscopy, optical microscopy, scanning electron microscopy and atomic force microscopy. XRD patterns and Raman spectra show the presence of two previously unreported crystalline phases. The PEG:V2O5 molar ratio affects the temperature of phase formation, the amount and even the order in which the phases appear. The morphological characterization underlines the role of the surfactant to promote porous networks, formed by micrometric clusters of controlled shapes and patterns embedded in a homogeneous host matrix. (c) 2006 Elsevier B.V. All rights reserved.