Electrostatic Contribution to the Persistence Length of a Semiflexible Dipolar Chain

TL;DR

This paper analyzes how dipolar electrostatic interactions influence the stiffness of semiflexible polymers, deriving a renormalized persistence length that depends less strongly on screening length than monopolar models, with a logarithmic dependence.

Contribution

It introduces a new theoretical framework for calculating the electrostatic persistence length of dipolar chains using a 1/D-expansion method, highlighting differences from monopolar interactions.

Findings

The electrostatic persistence length depends logarithmically on screening length.

Dipolar interactions decay faster with distance than monopolar interactions.

The model extends understanding of electrostatic effects on polymer rigidity.

Abstract

We investigate the electrostatic contribution to the persistence length of a semiflexible polymer chain whose segments interact via a screened Debye-H\" uckel dipolar interaction potential. We derive the expressions for the renormalized persistence length on the level of a 1/D-expansion method already successfully used in other contexts of polyelectrolye physics. We investigate different limiting forms of the renormalized persistence length of the dipolar chain and show that in general it depends less strongly on the screening length than in the context of a monopolar chain. We show that for a dipolar chain the electrostatic persistence length in the same regime of the parameter phase space as the original Odijk-Skolnick-Fixman (OSF) form for a monopolar chain depends logarithmically on the screening length rather than quadratically. This can be understood solely on the basis of a swifter decay of the dipolar interactions with separation compared to the monopolar electrostatic interactions. We comment also on the general contribution of higher multipoles on the electrostatic renormalization of the bending rigidity.