Large scale mobility calculations in PEDOT (Poly(3,4-ethylenedioxythiophene)): Backmapping the coarse-grained MARTINI morphology

Abstract

Designing new high performances materials based on conducting polymers necessitates the development of multiscale models to investigate the charge transport in large realistic systems. In this work, we utilize Coarse-Grained (CG) Molecular Dynamics (MD) simulations to generate morphologies of Poly(3,4-ethylenedioxythiophene) (PEDOT) doped with Tosylate (TOS) ions, and we develop a backmapping protocol to retrieve the atomistic details of the molecules afterwards. We demonstrate that the proposed protocol corrects for the nanostructure distortions induced by Coarse-Graining the system, namely a wrong density and an over-estimated π-π stacking distance. Quantum chemical calculations are performed on the systems obtained after backmapping in order to calculate hopping rates for charge transport, and charge mobilities as a function of the PEDOT chain length and hydration level are then calculated by solving a master equation for transport. The results are identical to the calculations performed on PEDOT morphologies obtained by direct All-Atomistic (AA) MD simulations: the mobility increases with the chain length and decreases with the hydration level, this last effect being more pronounced for short chains. This definitely shows that the workflow CG MD → backmapping → mobility calculations is in position to calculate charge mobility in PEDOT based materials, paving the way for theoretical investigations of transport in more complex materials such as PEDOT doped with Polystyrene Sulfonate (PSS).