Synthesis of novel urethane-dimethacrylate monomer containing two quaternary ammonium groups for applications in dentistry

The aim of this study was to obtain a new urethane-dimethacrylate monomer. This monomer has a potential antibacterial activity due to the presence of two quaternary ammonium groups, which are able to interact with negatively charged bacterial cell walls. Thanks to the presence of two methacrylate groups, this monomer is able to copolymerize with other dimethacrylate monomers, including those currently used in dentistry. We successfully synthesized new urethane-dimethacrylate monomer via the three steps synthesis route. The designed procedure comprises the transesterification of methyl methacrylate with tertiary N-methyldiethanolamine, Menschutkin reaction of the tertiary amine with a methacrylate moiety (obtained in the previous step) with 1-bromohexadecane and preparation of urethane dimethacrylate resin by reacting the hydroxyl group of the quaternary amine (from the previous step) with the isocyanate groups of 2,4,4-trimethylhexamethylene diisocyanate. The chemical structure of the intermediate products obtained in the first two stages of the synthesis as well as the chemical structure of the final product were confirmed by nuclear magnetic resonance spectroscopy (¹H NMR and ¹³C NMR) and by infrared spectroscopy (FT IR). ¹H NMR, ¹³C NMR and FT IR analysis confirmed that the monomer chemical structure consists of two methacrylate groups, two quaternary ammonium groups, two urethane bonds and two alkyl side chains directly attached to the quaternary nitrogen atoms.