Synergistic antibacterial effect and mechanism between Cu2O nanoparticles and quaternary ammonium salt in moisture-curable acrylic coatings

Combining with various antibacterial mechanisms is the preferred strategy to fabricate coatings with effective antibacterial performance. Herein, Cu 2 O nanoparticles and dimethyloctadecyl [3-(trimethoxysilyl) propyl] ammonium chloride, a kind of quaternary ammonium salt (QAS), were simultaneously incorporated into a moisture-curable acrylic resin in order to achieve both contact-killing and release-killing abilities for antibacterial coatings. The surface morphology, surface composition and basic properties of the coatings were thoroughly characterized. The antibacterial performance of the coatings was determined by in-vitro bacteriostatic test. Under the constant total mass fraction of antibacterial agents, both Cu 2 O and QAS content possessed the highest value on the coating surface at Cu 2 O/QAS mass ratio of 1:1, and correspondingly, the coatings reached sterilizing rate above 99 % against both E. coli and S. loihica , indicating the existence of synergistic effect between Cu 2 O and QAS. The synergistic antibacterial mechanism of the coatings involved two aspects. Firstly, the combination of contact-killing and release-killing biocides resulted in high bactericidal and antibiofilm activity against different bacteria. Further, the grafting of QAS molecules on the surface of Cu 2 O particles brought about the spontaneous migration of nanoparticles to the coating surface. The interaction between Cu 2 O and QAS also inhibited the phase separation of QAS and prolonged the release of Cu 2+ at the same time. The coatings, therefore, exhibited stable antibacterial performance at varied service conditions.