Predicted field-induced hexatic structure in an ionomer membrane

TL;DR

This study uses molecular dynamics simulations to reveal how a strong electric field induces a stable, hexatic-structured morphology in an ionomer membrane, with potential implications for material design.

Contribution

It demonstrates the formation and persistence of a field-induced hexatic structure in an ionomer, a novel morphological insight not previously documented.

Findings

Electric field induces aligned rod-like and hexatic structures.

Hexatic array persists after field removal with lower free energy.

Formation of helical sulfonate structures observed.

Abstract

Coarse-grained molecular-dynamics simulations were used to study the morphological changes induced in a Nafion$^{\tiny \textregistered}$-like ionomer by the imposition of a strong electric field. We observe the formation of novel structures aligned along the direction of the applied field. The polar head groups of the ionomer side chains aggregate into clusters, which then form rod-like formations which assemble into a hexatic array aligned with the direction of the field. Occasionally these lines of sulfonates and protons form a helical structure. Upon removal of the electric field, the hexatic array of rod-like structures persists, and has a lower calculated free energy than the original isotropic morphology.