Molecular modeling of stretchable electronics

A theoretical prediction of favorable ion exchange between PEDOT:PSS and hard-cation-soft-anion ionic liquids (IL) is confirmed experimentally and computationally by treating PEDOT:PSS with a new IL composed of an extremely hard protic cation MIM+ and an extremely soft anion TCB–. This protic IL significantly improves both conductivity and stretchability of PEDOT:PSS, outperforming its aprotic counterpart, EMIM :TCB, which has been the best IL employed for this purpose so far. This electrical and mechanical enhancement is speculated as a result of the aromatic and protic cation MIM+ which does not only provide efficient ion exchange with PEDOT:PSS but also serves as a molecular glue holding together multiple PEDOT domains by strong ionic as well as hydrogen bonds, because washing MIM+ out of the film degrades the stretchability while keeping the morphology. Our results offer molecular-level insights on the morphological, electrical, and mechanical properties of PEDOT:PSS and a molecular-interaction-based enhancement strategy for intrinsically stretchable conductive polymers.