Ordering of anisotropic polarizable polymer chains on the full many-body level

TL;DR

This paper investigates how dielectric anisotropy in polymers influences their equilibrium ordering, revealing that n-body van der Waals interactions can induce phase transitions and that the full n-body analysis favors the axial nematic phase.

Contribution

It introduces a full n-body formalism for van der Waals forces in anisotropic polymers, showing how these interactions determine the stable nematic phase and the transition mechanism.

Findings

Dielectric anisotropy induces an isotropic-nematic transition.

Two-body interactions resemble self-aligning nematic interactions.

Full n-body interactions favor the axial nematic phase.

Abstract

We study the effect of dielectric anisotropy of polymers on their equilibrium ordering within mean-field theory but with a formalism that takes into account the full n-body nature of van der Waals forces. Dielectric anisotropy within polymers is to be expected as the electronic properties of the polymer will typically be different along the polymer than across its cross section. It is therefore physically intuitive that larger charge fluctuations can be induced along the chain than perpendicular to it. We show that this dielectric anisotropy leads to n-body interactions which can induce an isotropic--nematic transition. The two body and three body components of the full van der Waals interaction are extracted and it is shown how the two body term behaves like the phenomenological self-aligning-pairwise nematic interaction. At the three body interaction level we see that the nematic phase that is energetically favorable is discotic, however on the full n-body interaction level we find that the normal axial nematic phase is always the stable ordered phase. The n-body nature of our approach also shows that the key parameter driving the nematic-isotropic transition is the bare persistence length of the polymer chain.