Preparation and evaluation of fouling-release properties of amphiphilic perfluoropolyether-zwitterion cross-linked polymer films

Abstract

The biofouling of marine structures presents a problem for maritime industries, including increasing fuel and operational costs. There has been much work developing and evaluating chemically ‘ambiguous’ amphiphilic coatings based upon hydrophobic fluoropolymer and hydrophilic poly(ethylene glycol) (PEG). Many of these coatings have shown good fouling-release performance against diatoms, which present a fouling challenge to commercially-available state-of-the-art silicone-based fouling-release coatings. However, PEG is prone to oxidation, which limits its practical use in the marine environment, and thus an alternative hydrophilic material would be desirable in the future development of amphiphilic coatings. In this regard, zwitterionic materials are emerging as a promising class of hydrophilic antifouling material, which we hypothesized would be a suitable alternative to PEG within amphiphilic coatings. To test this hypothesis, cross-linked amphiphilic films consisting of commercially available perfluoropolyethers and the zwitterionic monomer sulfobetaine methacrylate were developed and studied. The difficulty in formulating these chemically incompatible species was overcome by careful choice of solvents and a series of prototype cross-linked films were prepared in which increasing quantities of zwitterion were systematically incorporated. The fouling-release performance of these films was tested against the diatom Navicula incerta, a common microfouling organism responsible for the formation of so-called ‘slime’ layers, and antifouling performance with cypris larvae of two barnacle species, Balanus amphitrite, and Balanus improvisus. To expand the scope of the study, the clinically-relevant biofilm-forming pathogen Staphylococcus aureus, which is a major culprit in the infection and failure of millions of indwelling medical devices, was also evaluated. Results indicate that the incorporation of zwitterion into perfluoropolyethers leads to significant improvements in fouling-release performance and these amphiphilic coatings display potential in fouling-release applications.