Bioinspired coating of TiO2 nanoparticles with antimicrobial polymers by Cu(0)-LRP: grafting to vs. grafting from

Abstract

In this study, titanium dioxide (TiO₂) nanoparticles coated with non-leachable biocides were prepared by chemically attaching tertiary-amine-containing polymers to the surface of TiO₂. Copper(0)-mediated living radical polymerization (Cu(0)-LRP) was utilized to fabricate the effective antibacterial surfaces via both “grafting to” and “grafting from” strategies. The Cu(0)-LRP of 2-(dimethylamino)ethyl methacrylate (DMAEMA) and 2-(diethylamino)ethyl methacrylate (DEAEMA) was first performed directly from an unprotected dopamine-functionalized initiator using either a commercial copper wire or in situ generated copper powders from the disproportionation of CuBr/Me₆TREN as the activators. The synthesized dopamine-terminal polymers were grafted on the surface of TiO₂via strong catechol bonding to yield an environmental-responsive surface. Subsequently, the tertiary amine polymers were directly grafted from the TiO₂ nanoparticles via surface initiated Cu(0)-LRP in DMSO or aqueous solutions, which showed a higher grafting density. The obtained TiO₂@polymer hybrid nanocomposites showed good dispersion stability in water and efficient recovery could be achieved due to the self-flocculation effect. The degradation of rhodamine B under the irradiation of simulated sunlight proved the maintenance of photocatalytic ability after the surface modification of TiO₂. The antibacterial activity of the tertiary amine polymer-coated nanocomposites before and after quaternization was tested against Escherichia coli (E. coli), during which the unmodified tertiary amine polymer surprisingly inhibited the growth of E. coli and the quaternized polymer showed almost 100% killing efficiency.