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–3upon 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.