Structure and Dynamics of Polymer Melts at Solid Surfaces

A. DE VIRGILIIS; J. SARABADANI; A. MILCHEV; TH. VILGIS

Workshop; Theory and Computer Simulation of Polymers: New Developments; 2015

Martin_luther-University Halle-Wittenberg

We investigate the dynamic and static properties of a polymer melt near solid surfaces. The melt, composed of linear chains, is confinedbetween two solid walls with one of the walls being repulsive; whereas the opposite, attractive wall, is characterized by different degreesof roughness, caused by an array of short perpendicular pillars with variable grafting density. We demonstrate the remarkable fact that theconformations of chains in the melt at the interfaces are mostly unaffected by the strength of substrate/polymer attraction. Moreover, theypractically coincide with the conformations of a single end-grafted chain at the critical point of adsorption, in agreement with Silberberg?shypothesis. This agreement is corroborated by the analysis of the size distributions of trains, loops, and tails of melt chains at the walls thatare found to be perfectly described by analytical expressions pertaining to end-grafted single chains at critical adsorption. Eventually, a study of the polymer dynamics at the rough interface reveals that surface roughness leads to dramatic drop of the coefficient for lateral diffusion whenever the separation between obstacles (neighboring pillars) becomes less than ≈ 2Rg where Rg is the unperturbed radius of gyration of chains in the bulk.