Scalable inter-diffused zwitterionic polyurethanes for durable antibacterial coatings

Abstract In the past decades, the omnipresent bacterial attachment and biofilm formation on surfaces have facilitated the transmission of infectious diseases on global scale, inflicting significant public health concern and financial burden. Among the most affected surfaces, polyurethane (PU) based coatings used in wide range of human-touching settings were profoundly influenced by bacterial adhesion. To eliminate the undesired bacterial attachment on PU coatings, we designed a novel zwitterionic polyurethane (ZPU) with high content of sulfobetaine zwitterionic moieties for enabling surface hydrophilicity to hydrophobic acrylic polyurethane (APU) via an inter-diffused structured coating. The diffusion between ZPU and the underlying APU base ensures long-lasting surface hydrophilicity by allowing the zwitterionic moieties to be anchored into the interior of the coating films. Moreover, the excess ZPU on the surface during inter-diffusion also enhanced biocompatibility by quenching the toxic isocyanate groups on the surface. Compared with simple blending of ZPU into APU as an additive, the novel route demonstrated improved toughness of 3.14 MPa and superior antibacterial efficacy due to the enriched ZPU on the coating surface. The antibacterial property against bacterial attachment was retained even after the coating surface was mechanically abraded for 1000 cycles. Moreover, the inter-diffused PU coating can be readily applied onto commercialized vinyl tarpaulin on large scale via similar spray coating process. A relatively low batch-to-batch deviation with no delamination was observed, suggesting the inter-diffused PU coating is feasible to be readily scaled from laboratory to practical production.