Amphiphilic Surface-Active Methacrylic Urethane Additives for the Design of Photopolymerized Coatings with Great Potential for Marine Fouling-Release Applications

Amphiphilic photopolymerized network films are prepared, based on a hexyl acrylate (HA) hydrophobic matrix containing varied amounts of urethane dimethacrylates bearing a hydrophilic poly(ethylene glycol) segment and terminated with hydrophobic, low surface energy groups, i.e., a short perfluorohexyl chain (for EF) or a fluorine-free heptamethyltrisiloxane group (for ES). These films are extensively characterized in bulk and at the surface by thermal, mechanical, solvent and water uptake, contact angle, and X-ray photoelectron spectroscopy measurements. On one hand, surface characterizations reveal that the amphiphilic chains of the additives enrich the topmost layer of the films, thus generating a water-responsive surface. The reconstruction process is found to be faster for the perfluorinated additive EF and slower for the fluorine-free ES ones. On the other hand, HA provides a hydrophobic matrix with low elastic modulus, dimensional stability, and adhesion to the substrates even after the absorption of water after prolonged immersion. A field immersion trial carried out in a touristic harbor in Leghorn points out that the films, although being ineffective in preventing organism settlement, are easily cleaned by a water jet after three months of immersion, showing a final residual coverage of panels as low as 15%.Acrylic formulations with a hydrophobic, low elastic modulus matrix, are photopolymerized in air with an easily scalable procedure. They contain varied amounts of amphiphilic urethane dimethacrylates bearing a hydrophilic poly(ethylene glycol) segment and terminated with hydrophobic, low surface energy groups, i.e., a short perfluorohexyl chain or a fluorine-free heptamethyltrisiloxane group. Water immersion triggers a reconstruction of their interfaces that results in a hydrophilization of the surface, whose kinetic and extent are dependent on the chemistry of the additive. Finally, fluorine-free formulations demonstrate a higher potential as fouling release coatings, notwithstanding the lack of a silicone matrix.image