Impact of oxidation-induced ordering on the electrical and mechanical properties of a polythiophene co-processed with bistriflimidic acid

The interplay between the nanostructure of a doped polythiophene with oligoether side chains and its electrical as well as mechanical properties is investigated. The degree of order of the polymer is found to strongly vary when co-processed with bistriflimidic acid (H-TFSI). The neat polythiophene as well as strongly oxidized material are largely disordered while intermediate concentrations of H-TFSI give rise to a high degree of pi-stacking. The structural disorder of strongly oxidized material correlates with a decrease in the kinetic fragility with H-TFSI concentration, suggesting that positive interactions between TFSI anions and the polymer reduce the ability to crystallize. The electrical conductivity as well as the Young's modulus first increase upon the addition of 4-10 mol% of H-TFSI, while the loss of pi-stacking observed for strongly oxidized material more significantly affects the latter. As a result, material comprising 25 mol% H-TFSI displays an electrical conductivity of 58 S cm(-1) but features a relatively low Young's modulus of only 80 MPa. Decoupling of the electrical and mechanical properties of doped conjugated polymers may allow the design of soft conductors that are in high demand for wearable electronics and bioelectronics.

Automated summary

This study investigates the interplay between the nanostructure, electrical properties, and mechanical properties of a doped polythiophene with oligoether side chains. It is found that the degree of order of the polymer significantly varies with the co-processing of bistriflimidic acid (H-TFSI). The addition of intermediate concentrations of H-TFSI leads to a high degree of pi-stacking, while strongly oxidized material shows structural disorder. The electrical conductivity and Young's modulus increase upon the addition of 4-10 mol% of H-TFSI, but the loss of pi-stacking has a more significant effect on the latter.