Coating Architects: Manipulating Multiscale Structures To Optimize Interfacial Properties for Coating Applications

Polymeric coatings are ideal materials for the surface modification of many solid substrates. The interfacial properties of these coatings, i.e., surface energy and tribological features, impact a surface's resulting wettability, repellency, friction, wear, and other performance metrics. To design polymer coatings for various applications, numerous studies have been dedicated to elucidating key structure–property relationships. This review highlights recent efforts to develop such relationships for the various length-scales across which different phenomena arise. For example, the surface energies of polymer coatings have been correlated to molecular aggregation (0.5–10 nm) and nanoscale phase separation (1 nm–1 μm), along with microscale phase separation (1–100 μm) and surface chemistry patterning (10–500 μm). In a similar vein, the low friction, ultra-low wear performance of polymer composites is highlighted, along with links to microscale phase separation, with emphasis on several studies that have connected micrometer features to improved tribological characteristics, such as reduced friction and wear. The limitations of current structure–property studies with respect to surface coatings also are discussed, and potential methods to overcome these limitations are presented. Finally, an outlook for future structured polymer coatings is provided, along with proposed opportunities for the next generation of polymer-based surfaces.