The possibility of refining the functionality of vinyl alcohol-sodium acrylate copolymer, P(VA-AANa), regarding its curative effect on chemo-embolic agents by plasma treatment, was examined, We have carried out argon plasma-irradiation onto the P(VAAANa) microsphere and the surface radicals formed were studied by ESR and compared with those of vinyl alcohol-acrylic acid copolymer, P(VA-AA), as well as its respective component homopolymer, PVA, PAA and its sodium salt (PAANa). It was found that the ESR spectra have shown a vast difference in pattern between P(VA-AANa) and P(VA-AA), demonstrating the strong sodium carboxylate effect on the nature of plasma-induced surface radical formation resulting from the difference in the surface morphology between P(VA-AANa) and P(VA-AA). (C) 2003 Elsevier B.V. All rights reserved.