Spatial distribution of entanglements in thin free-standing films

TL;DR

This study uses simulations to analyze how entanglements in thin free-standing polymer films vary spatially, revealing that entanglement properties depend on the ratio of chain and entanglement lengths to film thickness, with challenges in understanding heterogeneities.

Contribution

It introduces a detailed comparison of spatially resolved entanglement measures with theoretical models in thin polymer films, highlighting scale-dependent effects and unresolved heterogeneity issues.

Findings

Film-averaged entanglement properties match predictions.

Spatial heterogeneities are complex when entanglement and chain lengths are small.

Challenges remain in characterizing local entanglement variations.

Abstract

We simulate entangled linear polymers in free-standing thin film geometries where the confining dimension is on the same scale or smaller than the bulk chain dimensions. We compare both film-averaged and layer-resolved, spatially inhomogeneous measures of the polymer structure and entanglement network with theoretical models. We find that these properties are controlled by the ratio of both chain- and entanglement-strand length scales to the film thickness. While the film-averaged entanglement properties can be accurately predicted, we identify outstanding challenges in understanding the spatially resolved character of the heterogeneities in the entanglement network, particularly when the scale of both the entanglement strand and the chain end-to-end vector is comparable to or smaller than the film thickness.