Dynamics of polymers in coarse-grained nematic solvents

TL;DR

This study uses numerical simulations to explore how nematic liquid crystal environments influence polymer conformation and anisotropic diffusion, revealing the formation of hairpins and their impact on polymer dynamics.

Contribution

It introduces a hybrid simulation method to analyze the effects of nematic order on polymer shape and movement, highlighting the role of coupling strength in conformational features.

Findings

Polymer elongation is driven by coupling to nematic fields.

Hairpins form due to the competition between anisotropic forces and entropy.

Hairpin diffusion slows exponentially with increased coupling.

Abstract

Polymers are a primary building block in many biomaterials, often interacting with anisotropic backgrounds. While previous studies have considered polymer dynamics within nematic solvents, rarely are the the effects of anisotropic viscosity and polymer elongation differentiated. Here, we study polymers embedded in nematic liquid crystals with isotropic viscosity via numerical simulations, to explicitly investigate the effect of nematicity on macromolecular conformation and how conformation alone can produce anisotropic dynamics. We employ a hybrid technique that captures nematic orientation, thermal fluctuations and hydrodynamic interactions. The coupling of the polymer backbone to the nematic field elongates the polymer, producing anisotropic diffusion even in nematic solvents with isotropic viscosity. For intermediate coupling, the competition between background anisotropy and macrmolecular entropy leads to hairpins - sudden kinks along the backbone of the polymer. Experiments of DNA embedded in a solution of rod-like fd viruses qualitatively support the role of hairpins in establishing characteristic conformational features that govern polymer dynamics. Hairpin diffusion along the backbone exponentially slows as coupling increases. Better understanding two-way coupling between polymers and their surroundings could allow the creation of more biomimetic composite materials.