Protic Ionic Liquids for Intrinsically Stretchable Conductive Polymers.

Area of Science:

• Materials Science
• Polymer Chemistry
• Electrochemistry

Background:

• Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is a widely used conductive polymer.
• Enhancing PEDOT:PSS conductivity and mechanical properties, particularly stretchability, is crucial for advanced applications.
• Ionic liquids (ILs) have shown promise in modifying PEDOT:PSS properties via ion exchange.

Purpose of the Study:

• To investigate the effect of a novel protic ionic liquid (p-MIM:TCB) on PEDOT:PSS properties.
• To explore the mechanism of ion exchange and molecular interactions between p-MIM:TCB and PEDOT:PSS.
• To develop an enhancement strategy for intrinsically stretchable conductive polymers.

Main Methods:

• Treatment of PEDOT:PSS with a protic ionic liquid (p-MIM:TCB) composed of 3-methylimidazolium (p-MIM+) and tetracyanoborate (TCB-).
• Comparison of p-MIM:TCB with an aprotic IL (EMIM:TCB) for PEDOT:PSS modification.
• Characterization of PEDOT:PSS thin films for electrical conductivity, morphology, and mechanical stretchability (tensile strain).

Main Results:

• p-MIM:TCB achieved comparable ion-exchange-mediated PEDOT:PSS separation, nanofibril formation, and electrical conductivity (~2500 S/cm) to the best aprotic ILs.
• p-MIM:TCB significantly improved PEDOT:PSS stretchability, outperforming EMIM:TCB.
• The enhanced stretchability is attributed to the p-MIM+ cation acting as a molecular adhesive via ionic intercalation and hydrogen bonding.

Conclusions:

• The protic IL p-MIM:TCB is an effective agent for simultaneously enhancing the electrical conductivity and stretchability of PEDOT:PSS.
• The molecular interactions involving the protic cation p-MIM+ are key to the improved mechanical properties.
• This study provides molecular-level insights and a novel strategy for designing intrinsically stretchable conductive polymers.