Surface functionalization of glass and polymeric substrates via graft copolymerization of viologen in an aqueous medium

Abstract

Surface functionalization of low-density polyethylene (LDPE), silanized glass, and free-standing polyaniline (PANI) films via UV-induced graft copolymerization with 1,1′-bis(4-vinyl-benzyl)-4,4′- bipyridinium dichloride (VBV) was carried out. The vinyl group containing viologen was synthesized by the double Anderson reaction using 4,4′-bipyridine and vinyl benzyl chloride and characterized by elemental analysis, FTIR spectrum, and X-ray photoelectron spectroscopy. The graft copolymerization of VBV was carried out by placing the plasma-pretreated substrate in contact with an aqueous solution of VBV under UV irradiation. The effects of the plasma-pretreatment time of the substrate, UV-induced graft copolymerization time, and monomer concentration on the VBV-graft copolymer concentration were investigated. The responses of the VBV-graft-copolymerized LDPE films and silanized glass slides to photoirradiation were monitored. In both cases, intensely blue viologen radical cations were formed after 10 min of UV irradiation in a vacuum and bleaching occurred when the substrate was exposed to air upon termination of the irradiation. VBV-graft-copolymerized PANI films with good conductivity can be prepared, and these films may have possible applications as active templates in biosensors where the viologen groups may serve as electron transfer mediators from the electrode surface to the active site of biomaterials. This method of surface functionalization of viologen moieties offers a number of advantages over a previously developed technique.