On the Mechanism of Pinning in Phase-Separating Polymer Blends

TL;DR

This study uses numerical simulations of the Cahn-Hilliard equation to investigate the kinetics of spinodal decomposition in polymer blends, finding no evidence of pinning phenomena with the current free energy model.

Contribution

It demonstrates that the Flory-Huggins-De Gennes free energy functional alone does not account for pinning in phase-separating polymer blends.

Findings

No pinning observed in simulations without thermal noise

Late-stage coarsening occurs without pinning

Current free energy functional may be insufficient to model pinning

Abstract

We re-explore the kinetics of spinodal decomposition in off-critical polymer blends through numerical simulations of the Cahn-Hilliard equation with the Flory-Huggins-De Gennes free energy functional. Even in the absence of thermal noise, the solution of the discretized equation of motion shows coarsening in the late stages of spinodal decomposition without evidence of pinning, regardless of the relative concentration of the blend components. This suggests this free energy functional is not sufficient to describe the physics responsible for pinning in real blends.