Role of Doping Agent Degree of Sulfonation and Casting Solvent on the Electrical Conductivity and Morphology of PEDOT:SPAES Thin Films

Abstract

Poly(3,4-ethylenedioxythiophene) (PEDOT) plays a key role in the field of electrically conducting materials, despite its poor solubility and processability. Various molecules and polymers carrying sulfonic groups can be used to enhance PEDOT’s electrical conductivity. Among all, sulfonated polyarylether sulfone (SPAES), prepared via homogenous synthesis with controlled degree of sulfonation (DS), is a very promising PEDOT doping agent. In this work, PEDOT was synthesized via high-concentration solvent-based emulsion polymerization using 1% w/w of SPAES with different DS as dopant. It was found that the PEDOT:SPAESs obtained have improved solubility in the chosen reaction solvents, i.e., N, N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, and N-methyl-2-pyrrolidone and, for the first time, the role of doping agent, DS and polymerization solvents were investigated analyzing the electrical properties of SPAESs and PEDOT:SPAES samples and studying the different morphology of PEDOT-based thin films. High DS of SPAES, i.e., 2.4 meq R-SO3−g−1 of polymer, proved crucial in enhancing PEDOT’s electrical conductivity. Furthermore, the DMSO capability to favor PEDOT and SPAES chains rearrangement and interaction results in the formation of a polymer film with more homogenous morphology and higher conductivity than the ones prepared from DMAc, DMF, and NMP.

Synthesis and Characterization of a Conductive Polymer Blend Based on PEDOT:PSS and Its Electromagnetic Applications

“…According to the results, as the amount of solvent increases, the size of the PEDOT:PSS polymer agglomeration decreases and the overall distribution becomes uniform. Consequently, the conductive PEDOT particles are uniformly distributed and the connection between the chains of the neighboring PEDOT polymers is enhanced so that the electrical conductivity increases [9,16,22]. These morphological analysis results are in good agreement with the chemical analysis results, which showed that the PEDOT polymer structure changes to a linear or expanded coil shape.…”

“…Additionally, the weak mechanical properties can also be improved by mixing or hybridizing the conducting polymer with general-purpose binders [6]. In addition, the electrochemical properties of the conducting polymer can be controlled or improved through synthesis with various organic solvents [8,9,16].…”

“…A representative conductivity enhancement additive is the amide N-Methylpyrrolidone (NMP), dimethylformamide (DMF), and the dimethylsulfoxide (DMSO). According to various studies, DMSO is widely used and can effectively increase the electrical conductivity of PEDOT:PSS polymer film [9,16,18]. In addition, to improve the workability and surface quality of the conductive thin film fabricated by the screen-printing process, a small amount of rheology modifier was added to adjust the viscosity of the conductive paste to fit the screen-printing process.…”