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

Automated summary

Amphiphilic photopolymerized network films with water-responsive surfaces have been prepared using hydrophobic matrices and additives with hydrophilic and hydrophobic groups. The surface reconstruction process is dependent on the chemistry of the additive. The hydrophobic matrix provides elasticity, dimensional stability, and adhesion even after water absorption.