PEG oligomers were covalently attached to nonequilibrium, low-pressure, RF-plasma-functionalized silicone medical- and industrial-grade silicon rubber surfaces, in the absence and presence of linear and branched polyglycidol spacer-chain molecules. All surface-modification reactions were carried out in a two-step process involving an initial argon-plasma activation of the surface, followed by "in situ" reaction with dichlorosilane in the absence of the discharge, and the attachment of PEG molecules or the graft polymerization of polyglycidol structures, and the attachment of PEG molecules. The surface of substrates was analyzed after each reaction step, using ESCA, ATR-FTIR, and AFM. It was found that PEG molecules directly attached to medical-grade silicone rubber surface as brush-type structures, and generate stronger antifouling characteristics in comparison to similar structures generated on food-grade substrates. The presence of additives on the food-grade silicon rubber surfaces that might be etched and removed during the postplasma washing cycles could contribute to a less efficient attachment of PEG molecules. Surfaces resulting from PEG molecules attached through intermediate, linear, and branched polyglycidol molecules did not reduce bacterial attachment. It is suggested that macromolecular entanglement might be responsible for this behavior. (c) 2006 Wiley Periodicals, Inc.