Polypropylene containing terminal unsaturation was modified with a hydride-terminated polydimethylsiloxane (PDMS) at three different temperatures through a catalytic hydrosilylation reaction in the melt phase. A comprehensive study on the surface characteristics of hydrosilylated polypropylene (SiPP) was conducted by combining macroscopic thermodynamics, microstructure, and chemical composition measurements. Axisymmetric drop shape analysis-profile (ADSA-P) was used to characterize the surface wettability. The morphology, roughness, and heterogeneity of the surfaces were investigated by the lateral-force mode of atomic force microscopy (LFM). X-ray photoelectron spectroscopy (XPS) was used to quantify the surface chemical composition. LFM images showed that all sample surfaces were rough and heterogeneous on a micrometer scale. XPS analysis showed that the surfaces investigated were complicated in composition and that various oxides existed on the surfaces. The surface wettability was well correlated to the surface microstructure and composition. The surfaces investigated were modeled based on the microstructure observed, and a new scheme was developed to calculate surface free energy and adhesion work. For SiPPs, the lower the reaction temperature, the more PDMS incorporation was observed, the smaller the surface free energy and the work of adhesion, the more hydrophobic the surface, and the lower the permeability. (C) 2003 Wiley Periodicals, Inc.