Introduction of carboxyl group onto polystyrene surface using plasma techniques

We report the methods to introduce a large amount of carboxyl group onto polystyrene (PS) surface using plasma techniques. The method involves the immobilization of vinylmethylether–maleic anhydride copolymer (VEMA) on PS by plasma-induced crosslink reaction of PS, followed by hydrolysis of the maleic anhydride moiety to generate carboxyl group. The resultant vinylmethylether–maleic acid copolymer (VEMAC)-immobilized PS (PS/VEMAC) surface was characterized by water-contact angle measurement, X-ray photoelectron spectroscopy (XPS), and cell adhesion behavior. The surface wettability was significantly improved as compared with that for non-treated PS surface, and remained nearly unchanged at a low level, close to the initially acquired value, for at least 24 h. The microscopic observation of cells in culture showed a good attachment and spreading behavior of cells on the PS/VEMAC surface.