Stacking of oligo and polythiophenes cations in solution: surface tension and dielectric saturation

TL;DR

This study investigates the stacking behavior of cationic oligo- and polythiophenes in solution using a unified electrostatic and cavitation model, revealing saturation effects and analyzing interactions in dimers and trimers.

Contribution

It introduces a first-principles continuum solvent model to analyze stacking and stabilization effects of charged thiophenes, including higher-order aggregates.

Findings

Dielectric screening saturation occurs at low dielectric constants.

Surface tension significantly influences stacking stability.

Interactions in trimers extend understanding of higher-order nanoaggregates.

Abstract

The stacking of positively charged (or doped) terthiophene oligomers and quaterthiophene polymers in solution is investigated applying a recently developed unified electrostatic and cavitation model for first-principles calculations in a continuum solvent. The thermodynamic and structural patterns of the dimerization are explored in different solvents, and the distinctive roles of polarity and surface tension are characterized and analyzed. Interestingly, we discover a saturation in the stabilization effect of the dielectric screening that takes place at rather small values of $\epsilon_0$. Moreover, we address the interactions in trimers of terthiophene cations, with the aim of generalizing the results obtained for the dimers to the case of higher-order stacks and nanoaggregates.