Self-assembled treelike patterns from an evaporating binary solution

Abstract

Spontaneous formation of treelike patterns which developed during evaporation of the solvent from a phase-separated bilayer resulting from a binary polymer solution spin-coated onto a solid substrate has been studied. The initial bilayer consists of a poly(isobutyl methacrylate) (BMA) layer on top of a nitrocellulose (NC) solution layer. During evaporation, the top BMA layer becomes unstable and transforms into short ridges. Finally, the inhomogeneous evaporation of the solvent from the NC solution layer connects the BMA ridges to treelike patterns. To support our model, we present results of a complementary experiment based on casting of the BMA solution on an inclined glass substrate.