Vapor deposition of quaternary ammonium methacrylate polymers with high antimicrobial activity: Synthetic route, toxicity assessment, and durability analysis

Abstract

In this study, vapor phase deposition of quaternary ammonium polymers on different substrates was reported. Thin films of the poly(diethylaminoethyl methacrylate) (PDEAEMA) homopolymer and the poly(diethyl aminoethyl methacrylate-co-vinylbenzyl chloride) [P(DEAEMA-VBC)] copolymer were deposited by an initiated chemical vapor deposition (iCVD) technique using tert-butyl peroxide as an initiator. The variation of monomer feed ratios allowed control over the film structure. In the film structure, the tertiary amine group of DEAEMA is a key functionality behind the antibacterial activity, as verified after Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy analyses. The PDEAEMA homopolymer could be quaternized in a dry manner using an oxygen plasma treatment. The P(DEAEMA-VBC) copolymer, however, did not need an extra quaternization step because the tertiary amine group of the polymer could be readily quaternized by the chlorine moiety of the VBC unit. Both the homo- and copolymers exhibited high antibacterial activity on three different substrates, namely, glass, a polyethylene terephthalate sheet, and fabric. The antibacterial activity depended on the intensity of the quaternized nitrogen atoms in the as-deposited polymer. The adhesion and durability of the copolymer films were superior to that of the homopolymer film, verified using an adhesive tape peel-off test. The most durable copolymer film exhibited very high log-reduction values (>3) against gram-negative and gram-positive bacteria. Based on e cell viability analysis, the antibacterial films deposited by iCVD in this study were found to be nontoxic.