Development and Characterization of Novel Hydrolysable Marine Coatings

Abstract

High operational and maintenance costs are significant problems associated with the fouling of marine vessels. Traditionally, fouling of such vessels was mitigated via paints, applied below the water line, that released organometallic compounds that were toxic to fouling species. Increased regulation of these paints has stimulated much research in the development of environmentally benign alternatives and replacements. Low surface energy materials, such as silicone elastomers and fluoropolymers have shown great promise due to their ability to resist both initial microbial colonization, as well as their “fouling release” characteristics. However, the implementation of these materials in the form of marine coatings is problematic, and the development of a suitable antifouling coating remains elusive. In order to maximize the efficiency of marine coatings, the development of materials with multiple antifouling mechanisms is required. This thesis describes a series of polymeric materials that exhibit a combination of three different approaches to fouling: low surface energy, antimicrobial activity, and hydrolysability. Novel polymer coatings with low surface energy domains, tethered broad spectrum antimicrobials, and non-toxic hydrolysable linkages have been synthesized. Low surface energy materials have shown great promise in reducing adhesion and colonization of microbes at surfaces and remain a suitable first line of defense. Additionally, low surface energy domains may provide the ability for materials to release accumulated fouling via hydrodynamic/sheer forces as a ship moves through the water. Despite reduced adhesion and fouling release properties that are well known for low surface energy materials, microbes are still able to colonize at the surface, which typically led to the formation of biofilms. To minimize the formation of biofilms from adhered microbes, quaternary ammonium salts (QAS) were incorporated into the urethane backbone to provide an effective active antimicrobial defense mechanism. Finally, incorporating a non-toxic hydrolysable linkages provide the material with a renewable character allowing a gradual sloughing of the coatings to continuously provide fresh active antimicrobial interfaces. The gradual sloughing of the coatings provides a second mechanism of fouling release due to the constant renewal of the surface which is capable of removing any fouled portions of the coating. Synthesis, structure-property relationships, and antifouling behavior of these materials are detailed.