Quaternary ammonium surfmers: synthesis, characterization and antibacterial performance

Abstract

Quaternary ammonium surfmers not only possess antibacterial activity, but also provide new active monomers for the synthesis of polymer cationic surfactants. In this study, four quaternary ammonium surfmers (nQAS) were synthesized through the quaternization of dimethylaminoethyl acrylate and brominated alkanes with different carbon chain lengths (n). Their structures were confirmed by ¹H nuclear magnetic resonance spectroscopy and high-resolution mass spectrometry. Their surface activities, including surface tension curves, were measured, and the micellar microenvironment of the QASs in pure water and solutions containing electrolytes was studied. With Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) as representatives of Gram-positive and Gram-negative bacteria, respectively, the minimal inhibition concentration (MIC) and minimum bactericidal concentration (MBC) were investigated by the classical plate counting method. The 18QAS surfmer showed a very low MIC and MBC of 0.937 and 3.75 μmol L⁻¹, respectively, against S. aureus, with a killing efficiency of 4.23 log CFU, and 16QAS showed a superior killing efficiency of 2.61 log CFU against E. coli at a concentration of 32.25 μmol L⁻¹. These quaternary ammonium surfmers could provide functional monomers for long-term antibacterial surface coating and other biological applications.