title: Lateral phase separation in polymer-blend thin films: surface bifurcation.
abstract: We use simulations of a binary polymer blend confined between selectively attracting walls to identify and explain the mechanism of lateral phase separation via a transient wetting layer. We first show that equilibrium phases in the film are described by one-dimensional phase equilibria in the vertical (depth) dimension, and demonstrate that effective boundary conditions imposed by the film walls pin the film profile at the walls. We then show that, prior to lateral phase separation, distortion of the interface in a transient wetting layer is coupled to lateral phase separation at the walls. Using Hamiltonian phase portraits, we explain a "surface bifurcation mechanism" whereby the volume fraction at the walls evolves and controls the dynamics of the phase separation. We suggest how solvent evaporation may assist our mechanism.
authors.affiliation: Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, United Kingdom.
authors.forename: Sam
authors.initials: S
authors.lastname: Coveney
authors.affiliation: Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, United Kingdom.
authors.forename: Nigel
authors.initials: N
authors.lastname: Clarke
mesh_terms: D003198:Computer Simulation; D004058:Diffusion; D044367:Phase Transition; D011108:Polymers / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry; D017155:Wettability
chemical_list: D011108:Polymers; D012997:Solvents