To immobilize zwitterion moiety onto silica gel surface, the grafting of zwitterion-type polymer, poly[3-diethyl(methylmethacryloylethy)ammonium propanesulfonate], polyDAEMA(+)(SO3)(-), onto the surface was investigated. The grafting of the zwitterion-type polymer onto silica gel surface was successfully achieved by the treatment of poly[2(dimethylamino)ethyl methacrylate] (polyDAEMA)-grafted silica gel, which was prepared by the graft polymerization of DAEMA initiated by azo groups introduced onto the surface, with 1,3-propane sultone; the percentage of polyDAEMA(+)(SO3)(-) grafting was determined to be 144.3%. However, the reaction of dimethyl amino groups of grafted polymer with 1,3-propane sultone incompletely proceeded. The grafting of the zwitterion-type polymer (polyDAEMA(+)(SO3)(-)) onto silica gel surface was also successfully achieved by the photopolymerization of DAEMA(+)(SO3)(-) initiated by azo groups introduced onto the surface: the percentage of polyDAEMA(+)(SO3)(-) grafting was determined to be 54.3%. The grafting of the zwitterion-type polymer onto the surface was confirmed by infrared spectra and SEM aspect of the polymer-grafted silica gel. It was found that the zwitterion-type polymer-grafted silica gel was applicable to stationary phase for ion chromatography. (C) 2004 Elsevier B.V. All rights reserved.