Materials with Altered Surface Wettability for Practical Applications

Abstract

By altering how liquids wet different surfaces (i.e., surface wettability) through careful chemical and physical surface manipulation, researchers have prepared materials with altered surface wettabilities that have since been used in several exciting applications. These include, but are not limited to, resisting the adhesion of biological entities (i.e., anti-biofouling), repelling liquid and solid contaminants (i.e., self-cleaning), preventing the formation of ice (i.e., anti-icing), prevent corrosion (i.e., anti-corrosion), and preventing surfaces from fogging (i.e., anti-fogging). While the potential of these materials is truly astounding, widespread commercial adoption has been slow due to several serious disadvantages present in these systems. Herein, this thesis outlines the development of new materials that counter these disadvantages and further enhance our collective understanding of surface wettability. This was accomplished through the creation of chemically and spatially patterned (super)hydrophilic/hydrophobic surfaces, which not only demonstrated that the Cassie equation cannot accurately predict wettability on composite surfaces, but also illustrated that barriers to droplet movement could be minimized by matching the contact angle hysteresis (CAH) between (super)hydrophilic and hydrophobic domains. Further, ice-shedding materials possessing both good mechanical properties and low ice adhesion values, which have long been mutually exclusive, were developed by adding a crosslinking density and compositional gradient into a durable polyurethane matrix. Not only did the resulting material have mechanical properties akin to those of other commercial plastics, but it easily shed ice when infused with an appropriate lubricant. Finally, the self-cleaning properties and surface reconstruction kinetics of a self-cleaning polymer coating was modified by altering the architecture of incorporated liquid-like polymer chains. It was found that samples possessing the longer linear chains had the best self-cleaning properties while shorter chains with multiple branches had poor self-cleaning properties and rapidly underwent surface reconstruction. This performance difference was attributed to the shorter length of the branched chains, which resulted in poor surface coverage and hence poor dewetting performance and easily reconfigured surfaces.