Quantized Contact Angles in the Dewetting of a Structured Liquid

Mark Ilton, Pawel Stasiak, Mark W. Matsen, Kari Dalnoki-Veress
2014 Physical Review Letters  
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
more » ... 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.
doi:10.1103/physrevlett.112.068303 pmid:24580714 fatcat:wzgd6fec6jh7bcutr3yq5lidt4