Tuning of the elastic modulus of a soft polythiophene through molecular doping

TitleTuning of the elastic modulus of a soft polythiophene through molecular doping
Publication TypeJournal Article
Year of Publication2021
AuthorsZokaei, Sepideh, Donghyun Kim, Emmy Järsvall, Abigail M. Fenton, Albree R. Weisen, Sandra Hultmark, Phong H. Nguyen, Amanda M. Matheson, Anja Lund, Renee Kroon, Michael L. Chabinyc, Enrique D. Gomez, Igor Zozoulenko, and Christian Müller
JournalMaterials Horizons

Molecular doping of a polythiophene with oligoethylene glycol side chains is found to strongly modulate not only the electrical but also the mechanical properties of the polymer. An oxidation level of up to 18% results in an electrical conductivity of more than 52 S cm−1 and at the same time significantly enhances the elastic modulus from 8 to more than 200 MPa and toughness from 0.5 to 5.1 MJ m−3. These changes arise because molecular doping strongly influences the glass transition temperature Tg and the degree of π-stacking of the polymer, as indicated by both X-ray diffraction and molecular dynamics simulations. Surprisingly, a comparison of doped materials containing mono- or dianions reveals that – for a comparable oxidation level – the presence of multivalent counterions has little effect on the stiffness. Evidently, molecular doping is a powerful tool that can be used for the design of mechanically robust conducting materials, which may find use within the field of flexible and stretchable electronics.