Polymer microspheres with permanent antibacterial surface from surface-initiated atom transfer radical polymerization of 4-vinylpyridine and quaternization

Crosslinked poly(4-vinylbenzyl chloride) (PVBC) microspheres of about 550 mu m in diameter were first synthesized by suspension copolymerization of 4-vinylbenzyl chloride (VBC) in the presence of a crosslinking agent, ethylene glycol dimethacrylate (EGDMA). Subsequent surface-initiated atom transfer radical polymerization (ATRP) of 4-vinylpyridine (4VP), using the VBC units of PVBC on the microsphere surface as the macroinitiators, produced well-defined (nearly monodisperse) and covalently tethered poly(4-vinylpyridine) (P4VP) brushes. Quaternization of the tertiary amine groups of the P4VP brushes with hexyl bromide gave rise to a high concentration of quaternary ammonium salt (QAS) on the microsphere surfaces. The chemical composition of the microsphere surfaces at various stages of surface modification was characterized by X-ray photoelectron spectroscopy (XPS). The bactericidal effect of the QAS-functionalized microspheres on Escherichia coli (E. coli) was demonstrated. No significant loss in the surface bactericidal activity of the microsphere was observed during repeated applications.