(606h) Building an Atomistic Model for Highly-Doped PEDOT Oligomers

Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) is a widely studied conductive polymer complex due to its high conductivity, processability, and transparency. Many reported molecular dynamics investigations have probed the microstructure of PEDOT:PSS films using the default GAFF parameterization, which, however, remains unvalidated for this system. To facilitate reliable molecular modeling of PEDOT:PSS, we develop an all-atom force field for both undoped and highly-doped PEDOT oligomers within the GAFF framework. Molecular geometries, vibrational energies, torsional profiles, conformational energetics calculated with density functional theory are included as training data. Our results suggest that the GAFF parameterization of highly-doped PEDOT overestimates both the barrier to inter-monomer torsion along the molecular backbone and the overall conformational flexibility of PEDOT oligomers. Comparison of final parameter sets underscores the impact of electron-phonon coupling on conjugated polymer flexibility. Results on the statistical properties of PEDOT:PSS complexes in aqueous solutions generated with our forcefield will also be reported.