Flow boundary conditions for chain-end adsorbing polymer blends

TL;DR

This paper investigates how the boundary conditions of polymer melt flow are affected by the structure of the adsorbed layer, showing a transition from slip to no-slip conditions influenced by surface additives.

Contribution

It reveals the sensitivity of hydrodynamic boundary conditions to the epitaxial layer structure in adsorbing polymer melts, highlighting the role of chain ends and additives.

Findings

Surface layer becomes thinner and solidifies with more adsorbed additives

Transition from slip to no-slip boundary condition occurs as additive concentration increases

Slip length varies non-monotonically with surface concentration of adsorbed ends

Abstract

Using the phenol-terminated polycarbonate blend as an example, we demonstrate that the hydrodynamic boundary conditions for a flow of an adsorbing polymer melt are extremely sensitive to the structure of the epitaxial layer. Under shear, the adsorbed parts (chain ends) of the polymer melt move along the equipotential lines of the surface potential whereas the adsorbed additives serve as the surface defects. In response to the increase of the number of the adsorbed additives the surface layer becomes thinner and solidifies. This results in a gradual transition from the slip to the no-slip boundary condition for the melt flow, with a non-monotonic dependence of the slip length on the surface concentration of the adsorbed ends.