Intermolecular adhesion in conjugated polymers: The role of the band gap and solitonic excitations

TL;DR

This paper investigates how electronic tunneling and solitonic excitations influence intermolecular adhesion in conjugated polymers, revealing that binding mechanisms significantly affect the chains' structural properties and persistence length.

Contribution

It introduces a combined analytic and numerical approach to model inter-chain electronic states and their impact on polymer chain pairing and flexibility.

Findings

Inter-chain electronic tunneling induces localized binding sites.

Binding mechanisms can alter the persistence length of polymer pairs.

The model predicts a wide range of structural behaviors based on electronic interactions.

Abstract

Conjugated polymers are soft, one-dimensional conductors that admit complex interactions between their polymeric, conformational degrees of freedom and their electronic ones. The presence of extended electronic states along their backbone allows for inter-chain electronic tunneling at points where these polymers make near passes. Using a combination of analytic modeling and Hartree-Fock numerical calculations, we study the localized electronic states that form due to such close encounters between semiconducting conjugated polymers and explore how these states lead to chain--chain binding. We also study the interaction of these inter-chain binding sites with solitonic excitations on the chains. From these results and a modified Poland-Scheraga model, we determine the equilibrium structures of paired-chains formed by intermolecular electronic tunneling. We calculate the energetic ground state of such pairs and show the effective thermal persistence length of the paired chains can vary over an order of magnitude due to the intermolecular binding mechanism.