Methyl methacrylate( MMA) was copolymerized with vinyl triethoxy silane (VTES) using Co-60 gamma-radiation at varying mol fractions of VTES from 0.02 to 0.11. The homopolymers of MMA and VTES were also synthesized by the same method. Homopolymer blends having different VTES mol fractions varying from 0.03 to 0.15 were prepared. The mol fractions of VTES units in the synthesized copolymers were determined by elemental analysis of Si using inductive coupling plasma spectroscopy (ICP). The thin copolymer and homopolymer blend films were prepared by casting from tetrahydrofurane (THF) on a mercury surface. Contact angles of paraffin, water, ethylene glycol, dimethyl formamide, and glycerol drops were measured on these copolymer and homopolymer blend films. Contact angle data were evaluated for the determination of surface free energy components of the copolymer and homopolymer blend films by using Van Oss-Good methodology. It was observed that the Lifshitz-Van der Waals component (gamma(s)(LW)) and the electron donor component (gamma(s)(-)) of the surface free energy of copolymer and homopolymer blend films were changed to a considerable extent with the change in the VTES mol fraction of both copolymers and homopolymer blends. (C) 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1551-1556, 1998.