Carboxyl-Alkyl Functionalized Conjugated Polyelectrolytes for High Performance Organic Electrochemical Transistors

Zeyuan Sun; Brian Khau; Hao Dong; Christopher J Takacs; Shuhan Yuan; Mengting Sun; Bar Mosevitzky Lis; Dang Nguyen; Elsa Reichmanis

doi:10.1021/acs.chemmater.3c02103

Carboxyl-Alkyl Functionalized Conjugated Polyelectrolytes for High Performance Organic Electrochemical Transistors

Chem Mater. 2023 Nov 2;35(21):9299-9312. doi: 10.1021/acs.chemmater.3c02103. eCollection 2023 Nov 14.

Authors

Zeyuan Sun¹, Brian Khau², Hao Dong¹, Christopher J Takacs³, Shuhan Yuan⁴, Mengting Sun¹, Bar Mosevitzky Lis¹, Dang Nguyen¹, Elsa Reichmanis¹

Affiliations

¹ Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, Pennsylvania 18015, United States.
² School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States.
³ Stanford Synchrotron Radiation Lightsource SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States.
⁴ Department of Applied Health Science, School of Public Health, Indiana University, Bloomington, Indiana 47405, United States.

Abstract

Contemporary design principles for organic mixed ionic electronic conductors (OMIECs) are mostly based on the ethylene glycol moiety, which may not be representative of the OMIEC class as a whole. Furthermore, glycolated polymers can be difficult to synthesize and process effectively. As an emerging alternative, we present a series of polythiophenes functionalized with a hybrid carboxyl-alkyl side chain. By variation of the alkyl spacer length, a comprehensive evaluation of both the impact of carboxylic acid functionalization and alkyl spacer length was conducted. COOH-functionalization endows the polymer with preferential intrinsic low-swelling behavior and water processability to yield solvent-resistant conjugated polyelectrolytes while retaining substantial electroactivity in aqueous environments. Advanced in situ techniques, including time-resolved spectroelectrochemistry and Raman spectroscopy, are used to interrogate the materials' microstructure, ionic-electronic coupling, and operational stability in devices. To compare these materials' performance to state-of-the-art technology for the design of OMIECs, we benchmarked the materials and demonstrated significant application potential in both planar and interdigitated organic electrochemical transistors (OECTs). The polythiophene bearing carboxyl-butyl side chains exhibits greater electrochemical performance and faster doping kinetics within the polymer series, with a record-high OECT performance among conjugated polyelectrolytes ([μC*]_pOECT = 107 ± 4 F cm^-1 V^-1 s^-1). The results provide an enhanced understanding of structure-property relationships for conjugated polyelectrolytes operating in aqueous media and expand the materials options for future OMIEC development. Further, this work demonstrates the potential for conjugated polymers bearing alkyl-COOH side chains as a path toward robust OMIEC designs that may facilitate further facile (bio)chemical functionalization for a range of (bio)sensing applications.