Mechanically Adaptive Mixed Ionic-Electronic Conductors Based on a Polar Polythiophene Reinforced with Cellulose Nanofibrils

Mariza Mone; Youngseok Kim; Sozan Darabi; Sepideh Zokaei; Lovisa Karlsson; Mariavittoria Craighero; Simone Fabiano; Renee Kroon; Christian Müller

doi:10.1021/acsami.3c03962

Mechanically Adaptive Mixed Ionic-Electronic Conductors Based on a Polar Polythiophene Reinforced with Cellulose Nanofibrils

ACS Appl Mater Interfaces. 2023 Jun 14;15(23):28300-28309. doi: 10.1021/acsami.3c03962. Epub 2023 Jun 1.

Authors

Mariza Mone^{1

2}, Youngseok Kim¹, Sozan Darabi^{1

2}, Sepideh Zokaei¹, Lovisa Karlsson¹, Mariavittoria Craighero¹, Simone Fabiano^{3

4}, Renee Kroon^{3

4}, Christian Müller^{1

2}

Affiliations

¹ Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 412 96 Göteborg, Sweden.
² Wallenberg Wood Science Center, Chalmers University of Technology, 412 96 Göteborg, Sweden.
³ Laboratory of Organic Electronics, Department of Science and Technology, Linköping University, 602 21 Norrköping, Sweden.
⁴ Wallenberg Wood Science Center, Linköping University, 602 21 Norrköping, Sweden.

Abstract

Conjugated polymers with oligoether side chains are promising mixed ionic-electronic conductors, but they tend to feature a low glass transition temperature and hence a low elastic modulus, which prevents their use if mechanical robust materials are required. Carboxymethylated cellulose nanofibrils (CNF) are found to be a suitable reinforcing agent for a soft polythiophene with tetraethylene glycol side chains. Dry nanocomposites feature a Young's modulus of more than 400 MPa, which reversibly decreases to 10 MPa or less upon passive swelling through water uptake. The presence of CNF results in a slight decrease in electronic mobility but enhances the ionic mobility and volumetric capacitance, with the latter increasing from 164 to 197 F cm^-3 upon the addition of 20 vol % CNF. Overall, organic electrochemical transistors (OECTs) feature a higher switching speed and a transconductance that is independent of the CNF content up to at least 20 vol % CNF. Hence, CNF-reinforced conjugated polymers with oligoether side chains facilitate the design of mechanically adaptive mixed ionic-electronic conductors for wearable electronics and bioelectronics.

Keywords: cellulose nanofibrils (CNF); chemical doping; conjugated polymer; organic electrochemical transistor (OECT); organic mixed ionic-electronic conductors.