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Siloxane-polyurethane hybrid coatings were assessed for biofouling control caused by freshwater mussels. Invasive species such as zebra ( Dreissena polymorpha ) and quagga ( Dreissena bugensis ) mussels have rapidly spread through the waterways in the United States causing major concerns in reservoir infrastructure and freshwater lakes. Current coating solutions such as biocidal anti-fouling coatings are not suitable given the released biocides which may accumulate in reservoirs. Biocide free fouling release coatings based on silicone elastomers do not have adequate mechanical durability. The siloxane-polyurethane (SiPU) coatings were evaluated using model organism laboratory assays and real-life performance was evaluated in the freshwater field environment. Two coating compositions displayed excellent performance in field trials for up to 2+ years. The surface analysis experiments of the coatings indicate that the morphology of the coatings is affected by the formulations' solvent choice. These coatings show great promise in mitigating biofouling predominated by freshwater mussels.

The effect of incorporation of silicone oils into a siloxane-polyurethane fouling-release coatings system was explored. Incorporation of phenylmethyl silicone oil has been shown to improve the fouling-release performance of silicone-based fouling-release coatings through increased interfacial slippage. The extent of improvement is highly dependent upon the type and composition of silicone oil used. The siloxane-polyurethane (SiPU) coating system is a tough fouling-release solution, which combines the mechanical durability of polyurethane while maintaining comparable fouling-release performance with regard to commercial standards. To further improve the fouling-release performance of the siloxane-PU coating system, the use of phenylmethyl silicones oils was studied. Coatings formulations were prepared incorporating phenylmethyl silicone oils having a range of compositions and viscosities. Contact angle and surface energy measurements were conducted to evaluate the surface wettability of the coatings. X-ray photoelectron spectroscopy (XPS) depth profiling experiments demonstrated self-stratification of silicone oil along with siloxane to the coating-air interface. Several coating formulations displayed improved or comparable fouling-release performance to commercial standards during laboratory biological assay tests for microalgae (Navicula incerta), macroalgae (Ulva linza), adult barnacles (Balanus amphitrite syn. Amphibalanus amphitrite), and mussels (Geukensia demissa). Selected silicone-oil-modified siloxane-PU coatings also demonstrated comparable fouling-release performance in field immersion trials. In general, modifying the siloxane-PU fouling-release coatings with a small amount (1-5 wt % basis) of phenylmethyl silicone oil resulted in improved performance in several laboratory biological assays and in long-term field immersion assessments.