Antibacterial, Transparency, and Mechanical Properties of Cationic Radical Initiator Triggered Polystyrene Sheets Obtained by Thermal Blending

Polystyrene (PS) is widely used because of its transparency, mechanical strength, and ease of production. With rising health concerns, antibacterial PS is increasingly sought after, but few polymer-based antibacterial agents have been prepared to date. In this study, polystyrene was synthesized using a cationic radical initiator, 2,2'-azobis-[2-(1,3-dimethyl-4,5-dihydro-1<i>H</i>-imidazol-3-ium-2-yl)] propane triflate (ADIP), and evaluated as an antibacterial additive. The PS polymerized with ADIP (ADIP-PS) was prepared with number-average molecular weights (<i>M_n</i>) from 15,000 to 40,000. Further, blending 5-10% ADIP-PS with an <i>M_n</i> of 23,000 into general-purpose polystyrene (GPPS) provided antibacterial activity against <i>Staphylococcus aureus</i> while maintaining the transparency and strength of GPPS. Surface analysis revealed hydrophilic properties and exposed cationic groups, as confirmed by contact angle measurement and anionic dye titration, respectively. In addition, the antibacterial activity increased with higher cationic group concentrations, particularly at lower molecular weights. This method presents a promising approach to introducing antibacterial properties to PS products.