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Designing Coatings to Have Low Adhesion Surfaces Through Self-stratification

Lecture

Please join Dean C. Webster of the Department of Coatings and Polymeric Materials, North Dakota State University for a seminar on Tuesday, August 21.

Designing coatings to have important functions is an ever-increasing area of coatings science. Many applications of coatings require systems that have surfaces tailored to deter adhesion to their surfaces. These applications include low dirt pick-up coatings, anti-graffiti coatings, biomedical coatings, anti-icing coatings, and non-fouling and fouling-release marine coatings. Using the concept of self-stratification, it is possible to decouple the surface and bulk properties of coatings so that the bulk and surface properties can be tuned individually to meet the material requirements. The approach of self-stratification has been applied to the design of mechanically robust marine fouling-release coatings. By combining functional poly(dimethyl siloxane) (PDMS) with a polyurethane system, coatings having the bulk properties of polyurethanes (good adhesion, toughness) as well as low surface energy can be designed that have good fouling-release performance for a wide variety of marine organisms. However, there are some marine organisms that are able to adhere well to a low surface energy surface such as PDMS. An amphiphilic variation on the SiPU coating system was investigated that created amphiphilic coating surfaces through combining hydrophobic siloxane and hydrophilic poly(ethylene glycol) (PEG) components into the coating. Laboratory fouling-release studies showed systematic trends in bio-adhesion as a function of coating composition. This same set of coatings was subjected to ice adhesion measurements and a number of the coatings had very low ice adhesion values. Remarkably, the trends in ice adhesion as a function of coating composition paralleled the trends in barnacle adhesion, indicating that the underlying coating design concepts for marine coatings and ice phobic coatings are similar.

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