Porous membranes were prepared by immersion in pure water or in water-NaOH baths of poly(vinylidene fluoride) solutions in different types of solvent (N,N-dimethylfonnamide or 1-methyl-2-pyrrolidone or triethylphosphate). Membranes were characterized through ultrafiltration tests, scanning electron microscope observations and vibrational spectroscopy (FT-Raman and FT-IR) measurements. The presence of NaOH in the immersion bath caused not only chemical dehydrofluorination of the polymer but also affected the membrane formation thus leading to membranes with different structures, permeability and retention properties. Membrane prepared by coagulation in NaOH rich bath were treated with NaOCl and H2O2 to attack the double bonds and to obtain membrane with improved hydrophilicity. (c) 2005 Elsevier B.V. All rights reserved.