Impact of an Irreversibly Adsorbed Layer on Local Viscosity of Nanoconfined Polymer Melts

Tadanori Koga, N. Jiang, P. Gin, M. K. Endoh, S. Narayanan, L. B. Lurio, and S. K. Sinha

Phys. Rev. Lett. 107, 225901 – Published 21 November 2011

Abstract

We report the origin of the effect of nanoscale confinement on the local viscosity of entangled polystyrene (PS) films at temperatures far above the glass transition temperature. By using marker x-ray photon correlation spectroscopy with gold nanoparticles embedded in the PS films prepared on solid substrates, we have determined the local viscosity as a function of the distance from the polymer-substrate interface. The results show the impact of a very thin adsorbed layer ( $\sim 7 nm$ in thickness) even without specific interactions of the polymer with the substrate, overcoming the effect of a surface mobile layer at the air-polymer interface and thereby resulting in a significant increase in the local viscosity as approaching the substrate interface.

Received 20 June 2011

DOI:https://doi.org/10.1103/PhysRevLett.107.225901

Authors & Affiliations

Tadanori Koga^1,2,*, N. Jiang², P. Gin², M. K. Endoh², S. Narayanan³, L. B. Lurio⁴, and S. K. Sinha⁵

¹Chemical and Molecular Engineering Program, Stony Brook University, Stony Brook, New York 11794-2275, USA
²Department of Materials Science & Engineering, Stony Brook University, Stony Brook, New York 11794-2275, USA
³Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois, 60439, USA
⁴Department of Physics, Northern Illinois University, DeKalb, Illinois, 60115, USA
⁵Department of Physics, University of California San Diego, La Jolla, California, 92093, USA