Plasma pretreatment has been used to generate reactive radicals and oxygenated groups on polymer surfaces for graft polymerization. The polymer substrates studied were composed of a polypropylene-polyethylene (PP-PE) copolymer, which was predominantly PP, and also contained blended ethylene-propylene rubber (EPR) as either about 15 or about 60 mol %. A pure PP substrate was also studied for comparison. The grafted polymer was polystyrene (PS). Raman microspectroscopic 2-dimensional mapping was used to elucidate the role of crystallinity and EPR in the plasma treatment and graft polymerization process. It was found that the plasma pretreatment favored the EPR component of the substrate and the graft yield was related to the EPR content. Crystallinity seemed to have a much less significant effect on the grafting reaction. (C) 2003 Wiley Periodicals, Inc.