The Navy has identified a need for new environmentally friendly polymeric coating materials which possess high mechanical strength, high adhesion to substrates, and resistance to the surface build up of marine organisms. We propose the use of hybrid organic/inorganic epoxy thermosets based on silsesquioxane cubes ([(RO)SiO1.5]8, where R is an epoxy terminated organic group) in combination with amine-terminated polydimethylsiloxane hardeners as fouling release coatings on inlet side heat exchangers. Such hybrids would combine the demonstrated resistance of polydimethylsiloxanes to marine fouling organism with the direct incorporation of robust (SiO1.5)8 clusters into the polymer backbone, resulting in high thermal and chemical stability, low organic content, high mechanical strength, and excellent adhesion to a variety of substrates. Our objective for Phase I is to demonstrate that these advanced coatings can be easily fabricated using epoxy-terminated silsesquioxane resins and amine-terminated poly(dimethylsiloxane) hardeners and that they possess the desired physical properties. To achieve this we will 1) study the curing behavior of silsesquioxane resins with amine-terminated poly(dimethylsiloxane) of various molecular weight, 2) prepare a library of thermoset thin films with varied compositions, 3) measure their contact angle, adhesive strength, and hardness and 4) vary sample properties with the inclusion of commercial resins and hardeners. In Phase II we will further optimize the thermoset formulations, determine their long term stability in water, and fully assess their resistance to marine organisms.
