Protic Ionic Liquids for Intrinsically Stretchable Conductive Polymers

Minji Kim, Seung Yeob Lee, Jihyun Kim, Changwon Choi, Yves Lansac, Hyungju Ahn, Sohee Park, Yun Hee Jang, Seoung Ho Lee, Byoung Hoon Lee

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Inspired by the classic hard−soft acid−base theory and intrigued by a theoretical prediction of spontaneous ion exchange between poly(3,4ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and hard-cation−soft-anion ionic liquid (IL), we treat PEDOT:PSS with a new IL composed of a protic (i.e., extremely hard) cation (3-methylimidazolium, p-MIM+) and an extremely soft anion (tetracyanoborate, TCB). In fact, this protic IL (p-MIM:TCB) accomplishes the same levels of ion-exchange-mediated PEDOT−PSS separation, PEDOT-rich nanofibril formation, and electrical conductivity enhancement (∼2500 S/cm) as its aprotic counterpart (EMIM:TCB with 1-ethyl-3-methylimidazolium), the best IL used for this purpose so far. Furthermore, p-MIM:TCB significantly outperforms EMIM:TCB in terms of improving the stretchability (i.e., the highest tensile strain) of the PEDOT:PSS thin film. This enhancement is a result of the aromatic and protic cation p-MIM+, which acts as a molecular adhesive holding the exchanged ion pairs (PEDOT+:TCB-p-MIM+:PSS) via ionic intercalation (at the surface of TCBdecorated PEDOT+ clusters) and hydrogen bonding (to PSS), in which washing p-MIM+ out of the film degrades the stretchability while keeping the morphology. Our results offer molecular-level insight into the morphological, electrical, and mechanical properties of PEDOT:PSS and a molecular-interaction-based enhancement strategy that can be used for intrinsically stretchable conductive polymers.

Original languageEnglish
Pages (from-to)3202-3213
Number of pages12
JournalACS Applied Materials and Interfaces
Issue number2
StatePublished - 2023

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  • conductive polymer
  • ion exchange
  • ionic liquid
  • stretchable electrode


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