Quaternary ammonium monomers for UV crosslinked antibacterial surfaces

UV reactive quaternary ammonium monomers, that is, methacryloyloxyethyldimethylalkyl ammonium bromides with an alkyl chain in the C2–C16 range (QAMs), have been synthesized in a simple way through the quaternization of tertiary amines with alkyl bromides and used as comonomers in the UV photopolymerization of diacrylic resins. The insertion of QAM structural units into the polymer network has been pointed out by means of FTIR and DSC analysis and the biocide property of the polymer has been verified through contact with suspensions of Escherichia coli and Staphylococcus aureus bacteria strains. The observed bioactivity has been ascribed to both free QAM molecules in solution and to QAM structural units bonded to the polymer surface, the highest activity being shown by the QAMs with the longest alkyl chain. XPS analysis of the polymer surfaces and contact angle measurements have pointed out an enrichment of QAM structural units on the surface layer and have suggested biocidal activity that depends not only on the charge density of the surface but also on its hydrophobic characteristics.