Distribution of dopant ions around poly(3,4-ethylenedioxythiophene) chains: a theoretical study

Abstract

The effect of counterions and multiple polymer chains on the properties and structure of poly(3,4-ethylenedioxythiophene) (PEDOT) doped with ClO has been examined using density functional theory (DFT) calculations with periodic boundary conditions (PBCs). Calculations on a one-dimensional periodic model with four explicit polymer repeat units and two ClO molecules indicate that the latter are separated as much as possible, with the salt structure and band gap obtained from such ClO distribution being in excellent agreement with those determined experimentally. On the other hand, DFT calculations on periodic models that include two chains indicate that neighboring PEDOT chains are shifted along the molecular axis by a half of the repeat unit length, with dopant ions intercalated between the polymer molecules acting as cement. In order to support these structural features, classical molecular dynamics (MD) simulations have been performed on a multiphasic system consisting of 69 explicit PEDOT chains anchored onto a steel surface, explicit ClO anions embedded in the polymer matrix, and an acetonitrile phase layer onto the polymer matrix. Analyses of the radial distribution functions indicate that the all-anti conformation, the relative disposition of adjacent PEDOT chains and the distribution of ClO dopant ions are fully consistent with periodic DFT predictions. The agreement between two such different methodologies allows reinforcing the microscopic understanding of the PEDOT film structure.

Study on the control of porosity in films of polythiophene derivatives

“…Nevertheless, the obtained inter-chain S•••S distances are significantly lower than those previously reported from 1D-PBC DFT calculations on PEDOT doped with ClO 4 ions (d = 5.89 Å). [30] Thus, the present study indicates that compaction effect is larger than reported in previous works. PEDOT models, while Fig.…”

“…Initial coordinates were obtained from a previous crystallographic study using 1D-PBC approach. [30] The other four systems were used to model PEDOT surfaces, which were build starting from the previous optimized bulk system but adding a vacuum region of 45 Å along lattice vector b. In this case, two of the models simulated the raw surface while the other two simulated the porous nanomembrane.…”

“…[28,29] Moreover, the cohesion between polymer chains was found to increase when dopant ions are intercalated among them. [30] Within the context of structure-electronic properties relationships, theoretical calculations on ICPs are usually conducted using either oligomers with a growing number of repetitive units or applying periodic boundary conditions (PBC) along the direction of growth of the polymer chain (1D-PBC), [31][32][33][34] while more complex solid state calculations with 2D-or 3D-PBC approaches have been scarcely reported. [35,36] The main goal of this work is to evaluate the influence of the doping level on the pore size of ICP films combining advanced theoretical approaches based on 3D-PBC models and experimental measures.…”

Spectroscopic Characterization of Pedot:pss Conducting Polymer by Resonance Raman and Serrs Spectroscopies

“…In the borders C α C β double bond characters are greater and have higher order indexes, indicating that the π conjugation is less present. 16,30 This parameter indicates that the EDOT 16 is a suitable model to represent the PEDOT polymeric chains. EDOT 16 oligomer model was used for calculation of vibrational modes of PEDOT polymer, but the absence of resonance effects precludes the use of its theoretical Raman spectra for analysing relative intensities of the experimental bands.…”

Morphology and ion diffusion in PEDOT:Tos. A coarse grained molecular dynamics simulation

“…In earlier theoretical work doped PEDOT with tosylate or other counterions was analyzed using density functional theory (DFT) assuming perfect infinite crystalline order. [28][29][30] Recent All Atomistic (AA) Molecular Dynamics (MD) calculations for PEDOT doped with different molecular counterions (including Tos) reveal a complex morphology where small crystallites consisting of several p-p stacking PEDOT chains are embedded in a polymer matrix including PEDOT chains, Tos counterions and water molecules. 16,31 Because of computational limitations, AA MD simulations do not always allow one to reach a lengthscale needed to study the morphology of a realistic material.…”