Generating Large Thermally Stable Marangoni-Driven Topography in Polymer Films by Stabilizing the Surface Energy Gradient

Abstract

Marangoni forces drive a fluid to flow in response to positional differences in surface energy. In thin polymer films, a difference in surface energy between two coincident liquid polymers could offer a useful route to manufacture topographically patterned surfaces via the Marangoni effect. Previously, we have demonstrated a photochemical method using the Marangoni effect for patterning thin polystyrene films. To generalize the approach, a theoretical model that gives the underlying physics of this process was also developed, which further revealed that low viscosities, low diffusivities, and large surface energy gradients favor rapid evolution of large film thickness variations. However, as described by the Stokes−Einstein equation or the Rouse model, low viscosity is generally correlated with high diffusivity in a single-component system. Herein, we report a strategy to decouple film viscosity and diffusivity by co-casting a high molecular weight surface energy gradient creating copolymer (low diffusivi...