Morphological Changes in PEDOT:PSS under Electrolytes, Dopamine, and PEG-400 Exposure: A Molecular Simulation...

Poly-(3,4-ethylenedioxythiophene):poly-(styrene sulfonate) (PEDOT:PSS) is a widely used conducting polymer, whose conductivity can be enhanced by incorporation of specific chemical components, whereas diffusion of water into the material can reduce its conductivity. These changes are typically linked to morphological changes in lamella crystallite size, π-π stacking, chain orientation, and interlamella connectivity. However, an atomistic-level understanding of how specific chemical components influence these properties remains limited, particularly in relation to experimentally observed conductivity trends. In this study, molecular dynamics (MD) simulations are employed to investigate the effects of electrolytes, dopamine, and poly-(ethylene glycol) 400 (PEG-400) on PEDOT:PSS morphology and relate the findings to experimental observations. All chemical components were found to screen electrostatic interactions between PEDOT and PSS, potentially affecting the conductivity. Dopamine tends to reduce conductivity by intercalating between PEDOT and PSS, disrupting interdomain connectivity. In contrast, PEG-400 enhances conductivity by improving interlamellar connectivity without altering PEDOT chain conformation, challenging conventional explanations and suggesting an alternative mechanism. CuCl₂ enhances conductivity via PEDOT conformational changes associated with partial PSS loss, whereas NaCl shows minimal morphological changes, in agreement with established explanations. Overall, MD simulations confirm the established trends, provide alternative insights, and challenge commonly accepted explanations, demonstrating their utility in validating, refining, and reinterpreting molecular mechanisms in complex polymer systems.