Why does solvent treatment increase the conductivity of PEDOT : PSS? Insight from molecular dynamics simulations

Area of Science:

• Materials Science
• Polymer Science
• Computational Chemistry

Background:

• Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is a crucial conducting polymer with low intrinsic conductivity.
• Solvent treatment, particularly with dimethyl sulfoxide (DMSO), significantly enhances PEDOT:PSS conductivity, but theoretical explanations remain incomplete.

Purpose of the Study:

• To provide a theoretical understanding of the morphological changes in PEDOT:PSS films upon DMSO solvent treatment using molecular dynamics simulations.
• To elucidate the mechanisms behind the conductivity enhancement in PEDOT:PSS after solvent treatment.

Main Methods:

• Martini coarse-grained molecular dynamics simulations were employed to model the DMSO solvent treatment of PEDOT:PSS films.
• Analysis focused on changes in polymer chain arrangement, inter-chain coupling, and crystallite formation.

Main Results:

• DMSO treatment causes dissolution of some deprotonated polystyrene sulfonate (PSS) chains.
• Post-treatment drying leads to closer proximity of Poly(3,4-ethylenedioxythiophene) (PEDOT) regions, with PEDOT chains interpenetrating PSS regions, enhancing coupling.
• Improved π-π stacking and increased average size of PEDOT crystallites contribute to conductivity enhancement.

Conclusions:

• Coarse-grained molecular dynamics simulations offer a powerful approach to understand the morphology of conducting polymers.
• The study provides a theoretical basis for the observed conductivity enhancement in PEDOT:PSS, paving the way for materials design and improvement.