Enhancing the antibacterial activity and yields of cationic polystyrene particles via copolymerization with hydrophilic acrylate monomers

Abstract

Cationic polymer particles exhibit weak antibacterial activity, and the material properties that influence this activity remain unclear. In this study, we enhanced the antibacterial activity of cationic polystyrene particles by introducing acrylate comonomers through soap-free emulsion polymerization using a cationic radical initiator. Compared with polystyrene emulsions, incorporating acrylate monomers with a lower log P than that of styrene afforded higher yields of cationic polymer particle emulsions. The antibacterial activities of these emulsions against Staphylococcus epidermidis were measured. The highest antibacterial activity was obtained for the acrylate monomer, with a log P of ~1.3. Among the emulsions obtained from acrylate monomers with comparable log P values, those with a lower glass transition temperature (Tg) exhibited higher antibacterial activity. Poly(styrene-co-methylmethacrylate-co-(vinylbenzyl)trimethylammonium chloride), which has a high Tg, demonstrated antibacterial activity against Escherichia coli and Staphylococcus aureus and suppressed the replication of nonenveloped Feline calicivirus. Skin irritation and microbial mutagenicity tests using cultured human skin models were negative. These polymer particles have potential applications as coating agents, base materials in the biomedical field, and hygiene products. We increased the antibacterial activity and yield of styrene-based cationic particles by copolymerizing them with acrylate monomers with optimal log P values via soap-free emulsion polymerization. The cationic poly(styrene-co-methyl methacrylate) particles exhibited greater antibacterial activity than did the cationic polystyrene particles. These particles also demonstrated antiviral activity and did not mutate bacterial DNA or irritate human skin.