title: Modulus, confinement, and temperature effects on surface capillary wave dynamics in bilayer polymer films near the glass transition.
abstract: We report relaxation times (τ) for surface capillary waves on 27-127 nm polystyrene (PS) top layers in bilayer films using x-ray photon correlation spectroscopy. At ∼10 °C above the PS glass transition temperature (T(g)), τ tracks with underlayer modulus, being significantly smaller on softer substrates at low in-plane scattering wave vector. Relative to capillary wave theory, we also report stiffening behavior upon nanoconfinement of the PS layers. At PS T(g)+40 °C, both effects become negligible. We demonstrate how neighboring polymer domains impact dynamics over substantial length scales.
authors.affiliation: Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois 60208, USA.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Evans
authors.forename: Suresh
authors.initials: S
authors.lastname: Narayanan
authors.forename: Zhang
authors.initials: Z
authors.lastname: Jiang
authors.forename: John M
authors.initials: JM
authors.lastname: Torkelson