Abstract
Marine fouling of shipping vessels induces ecological disasters with the transport of invasive species as well as economical costs for shipping due to frictional resistance on the surface vessels. To address this issue, fouling release coatings, without toxic biocide, gradually replaced bioactive antifouling coatings. However, the main candidates, the silicones, offer limited static fouling which can be improved by using amphiphilic additive. To render more attractive the incorporation of additive in the paint formulation, they can additionally be photosensitive allowing to repel the marine organisms under light and mitigate the fouling formation. This study presents silicone coatings using photosensitive azobenzene polyoxazoline (POx) additive able to reversibly switch from trans to cis configuration under UV/Visible (Vis) light. To avoid any additive-matrix incompatibility, that is a current issue specific to commercial hydrophilic additives, amphiphilic POx were designed. Di- and triblock POx containing hydrophobic poly(2-phenyl-2-oxazoline) blocks and hydrophilic poly(2-methyl-2-oxazoline) blocks were covalently incorporated in PDMS matrix by crosslinking via self-condensation. The impact of the macromolecular architecture of additive, UV irradiation and Vis light exposure on the surface and the mechanical properties of resulting coatings was investigated by contact angle, Atomic Force Microscopy (AFM) and nanoindentation. The reversibility of the photo-response was also evaluated. Finally, the macrofouling properties of the coated surface mediated by UV/Vis light were monitored during 120 days by real-time immersion of coatings in Atlantic Ocean and macroscopic fouling evaluation of the immersed surfaces.