Antibacterial activity of polymeric substrate with surface grafted viologen moieties.

An asymmetric viologen, N-hexyl-N'-(4-vinylbenzyl)-4,4'-bipyridinium bromide chloride (HVV), was synthesized and graft copolymerized with commercial PET films. The surface graft concentration of HVV on the PET film is easily controlled by varying the monomer concentration used in the UV-induced graft copolymerization process. The HVV surface functionalized PET film functions as a smart window whose transmittance is reduced upon exposure to light. Concomitantly, the film possesses antibacterial activity, as shown by its bactericidal effect on Escherichia coli (E. coli). The antibacterial activity depends on the concentration of pyridinium groups on the surface and a surface concentration of 25 nmol/cm2 on PET has been shown to be highly effective in killing the bacteria.