title: Quantized contact angles in the dewetting of a structured liquid.
abstract: We investigate the dewetting of a disordered melt of diblock copolymer from an ordered residual wetting layer. In contrast to simple liquids where the wetting layer has a fixed thickness and the droplets exhibit a single unique contact angle with the substrate, we find that structured liquids of diblock copolymer exhibit a discrete series of wetting layer thicknesses each producing a different contact angle. These quantized contact angles arise because the substrate and air surfaces each induce a gradient of lamellar order in the wetting layer. The interaction between the two surface profiles creates an effective interface potential that oscillates with film thickness, thus, producing a sequence of local minimums. The wetting layer thicknesses and corresponding contact angles are a direct measure of the positions and depths of these minimums. Self-consistent field theory is shown to provide qualitative agreement with the experiment.
authors.affiliation: Department of Physics and Astronomy and the Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario L8S 4M1, Canada.
authors.forename: Mark
authors.initials: M
authors.lastname: Ilton
authors.affiliation: School of Mathematical and Physical Sciences, University of Reading, Whiteknights, Reading RG6 6AX, United Kingdom.
authors.forename: Pawel
authors.initials: P
authors.lastname: Stasiak
authors.affiliation: School of Mathematical and Physical Sciences, University of Reading, Whiteknights, Reading RG6 6AX, United Kingdom and Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Mark W
authors.initials: MW
authors.lastname: Matsen
authors.affiliation: Department of Physics and Astronomy and the Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario L8S 4M1, Canada and Laboratoire de Physico-Chimie Théorique, UMR CNRS Gulliver 7083, ESPCI, Paris, France.
authors.forename: Kari
authors.initials: K
authors.lastname: Dalnoki-Veress