Surface Reconstruction of Fluoropolymers in Liquid Media.

Surface reconstruction is the rearrangement of atoms or molecules at an interface in response to a stimulus, driven by lowering the overall free energy of the system. Perfluoroalkyl acrylate polymers with short side chains undergo reconstruction at room temperature when exposed to water. Here, we use contact angle aging to examine the liquid- and temperature- dependency of surface reconstruction of plasma polymerized perfluoroalkyl acrylates. We use a first order kinetic model to examine the dynamics of reconstructive processes. Our results show that, above the bulk melting point of the polymers, the contact angles of both polar and nonpolar (hydrocarbon) liquids show a time dependency well fit by the model. We conclude that surface reconstruction can be driven by the preferential segregation of hydrocarbon and fluorocarbon moieties as well as by polar interactions. This has implications in terms of using fluorocarbons to design oleophobic surfaces (and vice versa) and in terms of designing fluorocarbon and/or hydrocarbon surfaces with switchable wettability.

A polymer coating which is sticky yet repulsive to water and slippery yet attractive for oils.

A one-step process has been developed to produce a polymer coating which is hydrophobic and oleophilic, but which oil slides off and water adheres to at all tilt angles - including when vertically inclined or inverted. The polymer is transparent, and the plasma coating process is independent of substrate composition and geometry.