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

## TL;DR

This paper uses molecular simulations to explore how different chemicals affect the structure and conductivity of PEDOT:PSS, a conducting polymer.

## Contribution

The study provides atomistic insights into how electrolytes, dopamine, and PEG-400 influence PEDOT:PSS morphology and conductivity.

## Key findings

- Dopamine reduces conductivity by disrupting interdomain connectivity in PEDOT:PSS.
- PEG-400 enhances conductivity by improving interlamellar connectivity without altering PEDOT chain conformation.
- CuCl2 increases conductivity via PEDOT conformational changes, while NaCl shows minimal effects.

## Abstract

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.