Antibacterial polystyrene with intrinsic antibacterial properties by incorporating hyperthermostable quaternary ammonium monomers

Polystyrene (PS) is widely used in products such as food packaging materials and medical devices, but it lacks inherent antibacterial properties. Organic antibacterial monomers exhibit better compatibility with the PS matrix and higher biosafety compared to inorganic antibacterial agents. However, PS, as a thermoplastic resin, typically requires thermal processing, whereas organic antibacterial monomers generally demonstrate poor thermal stability at elevated temperatures. Herein, a novel heat-resistant antibacterial monomer [16C] was synthesized, which possesses a rigid benzene ring structure and an imidazole ring structure, contributing to an excellent thermal decomposition temperature ( T d,5% >300°C). At the thermal processing temperature (220°C) of PS, the mass loss of [16C] was merely 1.61% after 10 min, and even after extending the duration to 30 min, the mass loss did not exceed 5%, demonstrating its superior thermal stability. The hyperthermostable antibacterial monomer was covalently bonded to PS resin through a simple free radical polymerization process, resulting in the fabrication of PS resin with inherent antibacterial properties (PS16Cs). Antibacterial testing of the thermally processed PS16Cs confirmed that the antibacterial activity remained highly effective even after exposure to high temperatures. Comprehensive testing indicated that the mechanical and thermal properties of the synthesized antibacterial PS resin met the commercial standards for PS. Notably, PS16Cs maintained durable and stable antibacterial activity even after prolonged immersion (in deionized water or phosphate-buffered saline) and repeated washing. Furthermore, it exhibited excellent biocompatibility after exposure to complex environments (varying pH, temperature, and detergent conditions), making it a viable material for applications in food packaging, electronic housings, and medical devices. This study developed a highly thermally stable antibacterial monomer, providing a novel approach for the organic antibacterial modification of polystyrene resin.