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

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 similar to 1.3. Among the emulsions obtained from acrylate monomers with comparable log P values, those with a lower glass transition temperature (T-g) exhibited higher antibacterial activity. Poly(styrene-co-methylmethacrylate-co-(vinylbenzyl)trimethylammonium chloride), which has a high T-g, 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.