Two series of modified polysulfones containing siloxane-aliphatic pendant moieties were analysed by optical microscopy, transmission electron microscopy, electron diffraction, contact angles measurements and X-ray photoelectron spectroscopy (XPS or ESCA), in order to establish the microstructure and surface properties. All samples exhibited biphasic bulk morphology due to a crystallization tendency induced by the pendant moiety, and silicon enriched surface irrespective of the substitution degree. The values of the surface tension calculated from contact angle measurements were in agreement with the hypothesis of surface enrichment. (C) 2004 Elsevier Ltd. All rights reserved.