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Effectively negating the deleterious impact of marine biofouling on the world's maritime fleet in an environmentally conscientious manner presents a difficult challenge due to a variety of factors including the complexity and diversity of fouling species and the differing surface adhesion strategies. Understanding how surface properties relate to biofouling can inform and guide the development of new antibiofouling coatings to address this challenge. Herein, we report on the development of a living photopolymerization strategy used to tailor the surface properties of silicone rubber using controlled anisotropic poly(acrylamide) patterns and the resulting antibiofouling efficacy of these surfaces against zoospores of the model marine fouling organism, Ulva linza . Chemical patterns were fabricated using reversible addition-fragmentation chain-transfer (RAFT) living polymerization in conjunction with photolithography. Pattern geometries were inspired by the physical (i.e., nonchemical) Sharklet engineered microtopography system that has been shown to be effective against the same model organism. Sharklet chemical patterns and analogous parallel channels were fabricated in sizes ranging from 2 to 10 μm in the lateral dimension with tailorable feature heights ranging from tens to hundreds of nanometers. Nonpatterned, chemically grafted poly(acrylamide) silicone surfaces inhibited algal spore attachment density by 59% compared to the silicone control; however, attachment density on chemical nanotopographies was not statistically different from the control. While these results indicate that the chemical nanotopographies chosen do not represent an effective antibiofouling coating, it was found that the Sharklet pattern geometry, when sized below the 5 μm critical attachment size of the spores, significantly reduced the algal spore density compared to the equally sized channel geometry. These results indicate that specific chemical geometry of the proper sizing can impact the behavior of the algal spores and could be used to further study the mechanistic behavior of biofouling organisms.

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.