Temperature-Controlled Slip of Polymer Melts on Ideal Substrates

TL;DR

This study investigates how temperature affects slip behavior of PDMS polymer melts on ideal, non-attractive surfaces, revealing a viscosity-dependent slip length influenced by surface interactions and activation energies.

Contribution

It introduces a molecular model explaining the temperature-dependent slip behavior based on activation energies of viscosity and interfacial friction.

Findings

Slip length is proportional to viscosity on both surfaces.

Surface type significantly influences slip temperature dependence.

Slip behavior correlates with activation energies of viscosity and friction.

Abstract

The temperature dependence of the hydrodynamic boundary condition between a PDMS melt and two different non-attractive surfaces made of either an OTS (octadecyltrichlorosilane) self-assembled monolayer (SAM) or a grafted layer of short PDMS chains has been characterized. A slip length proportional to the fluid viscosity is observed on both surfaces. The slip temperature dependence is deeply influenced by the surfaces. The viscous stress exerted by the polymer liquid on the surface is observed to follow exactly the same temperature dependences as the friction stress of a cross-linked elastomer sliding on the same surfaces. Far above the glass transition temperature, these observations are rationalized in the framework of a molecular model based on activation energies: increase or decrease of the slip length with increasing temperatures can be observed depending on how the activation energy of the bulk viscosity compares to that of the interfacial Navier's friction coefficient.