Splay--density coupling in semiflexible main-chain nematic polymers with hairpins

TL;DR

This paper develops a macroscopic model for splay-density coupling in semiflexible nematic polymers with hairpins, incorporating chain backfolds as sources and validating the model through Monte Carlo simulations.

Contribution

It introduces a unified description of chain ends and backfolds as sources in the splay-density coupling, supported by simulation data.

Findings

Backfolding weakens splay-density coupling.

Monte Carlo simulations confirm the macroscopic model.

Deviations from ideal gas behavior are discussed.

Abstract

We establish a macroscopic description of the splay--density coupling in semiflexible main-chain nematic polymers with hairpins, using a vectorial continuity constraint for the "recovered" polar order of the chain tangents and introducing chain backfolds (hairpins) as its new type of sources besides chain ends. We treat both types of sources on a unified basis as a mixture of two ideal gases with fixed composition. Performing detailed Monte Carlo simulations of nematic monodomain melts of "soft" worm-like chains with variable length and flexibility, we show via their structure factors that the chain backfolding weakens the splay--density coupling, and demonstrate how this weakening can be consistently quantified on the macroscopic level. We also probe and discuss the deviations from the noninteracting gas idealization of the chain ends and backfolds.