The acrylic resin Nature Cryl™ MC (GC America Inc., Alsip, IL, USA) was obtained commercially. According to the manufacturer’s instructions, the acrylic resin powder and liquid were mixed at a ratio of 1:0.5. Samples were prepared following ISO 24026–2:2020 [32 ] (Plastics — Poly (methyl methacrylate) (PMMA) moulding and extrusion materials — Part 2: Preparation of test specimens and determination of properties) standards. The antibacterial monomer DMAHDM, with an alkyl chain length of 16, was synthesized using a modified Menschutkin reaction method [32 , 33 (link)]. The advantage of this method is that the reaction product is produced quantitatively and does not require further purification [27 (link)]. Briefly, 10 mmol of 2-(dimethylamino) docecane (DMAEMA, Sigma-Aldrich, St. Louis, MO, USA), 10 mmol of 1-bromohexadecane (BHD, TCI America, Portland, OR, USA), and 3 g of ethanol were added to a 20 mL scintillation vial. The vial was capped and stirred at 70 °C for 24 h. When the reaction was complete, the ethanol solvent was evaporated, yielding DMAHDM as a clear, colorless, and viscous liquid [33 (link), 34 (link)]. DMAHDM was mixed with the acrylic resin liquid at DMAHDM/(MMA power + MMA liquid + DMAHDM) mass fractions of 1.5%. Higher DMAHDM mass fractions were not used because previous experiments showed a significant decrease in mechanical strength [30 (link)].
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