Marine biofouling is the accumulation of organisms onto surfaces immersed in sea water. Fouling of ships causes an increase in hydrodynamic drag which leads to performance issues such as increased fuel consumption and a reduced top operating speed. Fouling-release (FR) coatings are one way that paints have been used in combating biofouling by allowing for the easy removal of settled organisms. Traditional FR coatings are silicone elastomers which are soft, easily damaged, and require a tie coat for adhesion to marine primers. Siloxanepolyurethane FR coatings have shown promise as FR coatings, providing enhanced durability and toughness, better adhesion to marine primers, and comparable FR performance to commercial coatings. Preliminary studies were conducted to explore the use of PDMS macromers in the preparation of siloxane-polyurethane FR coatings. Attachment and removal of fouling organisms on the siloxane-polyurethane coatings based on PDMS macromers was comparable to commercial FR coatings. Extended water aging was also carried out to determine effects of extended water immersion on the fouling-release performance of the coatings. At up to four weeks of aging, the FR performance of the coatings was not affected. Static immersion marine field testing was performed to determine the fouling-release performance of siloxane-polyurethane coatings prepared with PDMS macromers. The performance was found to be comparable to commercial FR coatings for up to one year, including water jet removal of slimes, barnacle push-off removal, and soft sponging. The coatings showed good fouling-release performance until extremely heavy fouling was allowed to settle. Underwater hull cleaning was conducted for one siloxane-polyurethane composition identified as a top performer from static field testing. The coating was easily cleaned of fouling with rotating brushes for six months. The cleaning capability of the coating was reduced when large barnacles and other extremely heavy fouling was present. A commercial FR coating became heavily damaged with brush cleaning while the siloxane-polyurethane coating remained mostly undamaged. With more frequent cleaning, it is suspected that siloxanepolyurethane coatings would show cleaning capability for longer periods of time. Pigmentation of siloxane-polyurethane coatings based on difunctional PDMS and PDMS macromers was explored to investigate the effect on FR performance. Pigmentation with titanium dioxide caused a slight decrease in FR performance in some cases, but this was easily overcome by the addition of slightly more PDMS in the coating binder, thus illustrating the feasibility of siloxane-polyurethane coatings as effective, pigmented FR coatings. Finally, the exploration of unique PDMS polymer architectures has been explored for the development of additional, novel, fouling-release coatings. The incorporation of end-functional PDMS homopolymer molecular brushes and branched PDMS macromers into siloxane-polyurethane fouling-release coatings shows promise for the development of unique coatings where improved FR performance may be obtained. / Office of Naval Research (U.S.)