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

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 T-g and the degree of pi-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.

Automated summary

Molecular doping of polythiophene with oligoethylene glycol side chains significantly enhances both the electrical and mechanical properties of the polymer. This doping method influences the glass transition temperature and pi-stacking of the polymer, with multivalent counterions showing little effect on stiffness at comparable oxidation levels. These findings suggest that molecular doping is a powerful tool for designing mechanically robust conducting materials for flexible and stretchable electronics.