Surface graft copolymerization of viologens on polymeric substrates

Preparation of pendent-type viologens on polymeric substrates was carried out by a surface graft copolymerization technique. This method involved a two-step process whereby vinyl benzyl chloride (VBC) was first graft copolymerized on the polymeric substrate followed by the attachment of viologen moieties to the graft-copolymerized benzyl chloride groups. The graft copolymerization was carried out by placing the plasma pretreated polymeric substrate in contact with VBC under UV irradiation. The effects of plasma pretreatment time, UV graft copolymerization time, solvent, and monomer concentration on the VBC graft copolymer concentration on the films were studied. Two different methods for the subsequent formation of viologens were also attempted. The graft-modified films were characterized using atomic force microscopy, X-ray photoelectron spectroscopy, and UV-visible absorption spectroscopy. The response of the viologen-grafted films to photoirradiation and the bleaching of the irradiated films were investigated and found to be dependent on the viologen graft concentration, the counteranion associated with the viologen, and the light intensity.