Entanglement reduction induced by geometrical confinement in polymer thin films

TL;DR

This study uses simulations to show that geometrical confinement in polymer thin films reduces entanglements by compressing chain conformations, with effects varying by position within the film, and tests a theory predicting this behavior.

Contribution

It provides new simulation evidence on how confinement alters polymer entanglements and tests a recent theoretical prediction.

Findings

Confinement compresses chain conformations uniaxially.

Reduced chain volume decreases inter-chain contacts and entanglements.

The effect varies depending on the chain's position within the film.

Abstract

We report simulation results on melts of entangled linear polymers confined in a free-standing thin film. We study how the geometric constraints imposed by the confinement alter the entanglement state of the system compared to the equivalent bulk system using various observables. We find that the confinement compresses the chain conformation uniaxially, decreasing the volume pervaded by the chain, which in turn reduces the number of the accessible inter-chain contact that could lead to entanglements. This local and non-uniform effect depends on the position of the chain within the film. We also test a recently presented theory that predicts how the number of entanglements decreases with geometrical confinement.