Dynamically Textured Polymer Surfaces

PROJECT ABSTRACT This project describes how energetic gases, plasma species, or UV can modify the surfaces of polymers to result in wrinkles, folds, and buckling at the nanoscale. These mechanically induced nanostructures result from strain relief of pre-strained polymers where the surface modification involves a chemical treatment that pervades less than 5 nm into the polymer film. The large changes in nanoscale morphology and hence surface area will have implications for macroscale phenomena, such as superhydrophobicity, controlling liquid-gas phase transitions, and stabilizing vapor phases to reduce drag. Experimental studies will examine different conditions for surface modifications (e.g. reactive gases, plasma conditions, UV, pre-strain, choice of polymer) and will examine time and length scales of wrinkling. Theory and modeling will be used to characterize the surface modifications and to model mechanical deformations when strain is released; the goal is to reduce the wrinkling and buckling times to microseconds through judicious selection of the polymer materials and careful control of surface modification, the amount of pre-strain, and the different mechanisms of strain release (chemical, thermal, physical). A second series of studies are aimed at further modifications to the pre-strained surface and to the buckling process that can be introduced by impacting the surface with nanoparticles, by release of reactive species, and by patterning strain relief points into the polymer surface. In short: we propose to use a reverse approach to understand how functionalizing nanostructures can enable substantial changes in mechanical/chemical properties. That is, we aim to produce nanostructures from bulk polymers by the chemical treatment of their surfaces, and whose resulting functional nanoscale signatures can be visualized by macroscale effects.