Significant Enhancement of the Electrical Conductivity of Conjugated Polymers by Post-Processing Side Chain Removal

James F Ponder Jr; Shawn A Gregory; Amalie Atassi; Akanksha K Menon; Augustus W Lang; Lisa R Savagian; John R Reynolds; Shannon K Yee

doi:10.1021/jacs.1c11558

Significant Enhancement of the Electrical Conductivity of Conjugated Polymers by Post-Processing Side Chain Removal

J Am Chem Soc. 2022 Jan 26;144(3):1351-1360. doi: 10.1021/jacs.1c11558. Epub 2022 Jan 10.

Authors

James F Ponder Jr¹, Shawn A Gregory², Amalie Atassi², Akanksha K Menon¹, Augustus W Lang², Lisa R Savagian², John R Reynolds^{2

3}, Shannon K Yee¹

Affiliations

¹ George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States.
² School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States.
³ School of Chemistry and Biochemistry, Center for Organic Photonics and Electronics, Georgia Tech Polymer Network, Georgia Institute of Technology, Atlanta, Georgia 30332, United States.

PMID: 35007084
DOI: 10.1021/jacs.1c11558

Abstract

The processability and electronic properties of conjugated polymers (CPs) have become increasingly important due to the potential of these materials in redox and solid-state devices for a broad range of applications. To solubilize CPs, side chains are needed, but such side chains reduce the relative fraction of electroactive material in the film, potentially obstructing π-π intermolecular interactions, localizing charge carriers, and compromising desirable optoelectronic properties. To reduce the deleterious effects of side chains, we demonstrate that post-processing side chain removal, exemplified here via ester hydrolysis, significantly increases the electrical conductivity of chemically doped CP films. Beginning with a model system consisting of an ester functionalized ProDOT copolymerized with a dimethylProDOT, we used a variety of methods to assess the changes in polymer film volume and morphology upon hydrolysis and resulting active material densification. Via a combination of electrochemistry, X-ray photoelectron spectroscopy, and charge transport models, we demonstrate that this increase in electrical conductivity is not due to an increase in degree of doping but an increase in charge carrier density and reduction in carrier localization that occurs due to side chain removal. With this improved understanding of side chain hydrolysis, we then apply this method to high-performance ProDOT-alt-EDOT_x copolymers. After hydrolysis, these ProDOT-alt-EDOT_x copolymers yield exceptional electrical conductivities (∼700 S/cm), outperforming all previously reported oligoether-/glycol-based CP systems. Ultimately, this methodology advances the ability to solution process highly electrically conductive CP films.