Department of Physics, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran.
Laboratory of Organic Electronics, ITN, Linköping University, 60174 Norrköping, Sweden.
Phys Chem Chem Phys. 2022 Sep 21;24(36):22073-22082. doi: 10.1039/d2cp02655d.
Poly(3,4-ethylenedioxythiophene) : polystyrene sulfonate (PEDOT : PSS) is one of the most important conducting polymers. In its pristine form its electrical conductivity is low, but it can be enhanced by several orders of magnitude by solvent treatment, dimethyl sulfoxide (DMSO). There are various (and often conflicting) explanations of this effect suggested in the experimental literature, but its theoretical understanding based on simulation and modelling accounting for the complex realistic morphology of PEDOT : PSS is missing. Here, we report Martini coarse-grained molecular dynamics simulation for the DMSO solvent treatment of the PEDOT : PSS film. We show that during solvent treatment a part of the deprotonated PSS chains are dissolved in the electrolyte. After the solvent treatment and subsequent drying, the PEDOT-rich regions become closer to each other, with a part of the PEDOT chains penetrating into the PSS-rich regions. This leads to an efficient coupling between PEDOT-rich regions, leading to the enhancement of the conductivity. Another factor leading to the conductivity improvement is the π-π stacking enhancement resulting in more π-π stacks in the film and in the increased average size of PEDOT crystallites. Our results demonstrate that course-grained molecular dynamics simulations of a realistic system represent a powerful tool enabling theoretical understanding of important morphological features of conducting polymers, which, in turn, represents a prerequisite for materials design and improvement.
聚（3,4-亚乙基二氧噻吩）-聚苯乙烯磺酸盐（PEDOT：PSS）是最重要的导电聚合物之一。在其原始形式下，其电导率较低，但通过溶剂处理（二甲基亚砜（DMSO））可以提高几个数量级。实验文献中提出了各种（通常相互矛盾的）解释这种效应的方法，但基于模拟和建模的理论理解，考虑到 PEDOT：PSS 的复杂实际形态，这种方法仍然缺失。在这里，我们报告了用于 PEDOT：PSS 薄膜的 DMSO 溶剂处理的马蒂尼粗粒度分子动力学模拟。我们表明，在溶剂处理过程中，部分去质子化的 PSS 链溶解在电解质中。溶剂处理和随后的干燥后，富 PEDOT 区域彼此靠近，一部分 PEDOT 链渗透到富 PSS 区域。这导致富 PEDOT 区域之间的有效耦合，从而提高了电导率。另一个导致电导率提高的因素是π-π 堆积增强，导致薄膜中更多的π-π 堆积和 PEDOT 微晶平均尺寸的增加。我们的结果表明，对实际系统的粗粒度分子动力学模拟代表了一种强大的工具，可以实现对导电聚合物重要形态特征的理论理解，这反过来又是材料设计和改进的前提。
