pH Regulates Ion Dynamics in Carboxylated Mixed Conductors
Zeyuan Sun1, Mengting Sun1, Rajiv Giridharagopal2
1Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, Pennsylvania 18015, United States.
Chemistry of Materials : a Publication of the American Chemical Society
|March 2, 2026
Summary
This study reveals how pH controls ion movement and material properties in carboxylated polythiophenes. Precise pH tuning offers a new way to design advanced soft electronics and pH-responsive materials.
Area of Science:
- Materials Science
- Electrochemistry
- Polymer Science
Background:
- Coupled ionic and electronic transport is crucial for many applications, including energy conversion and soft electronics.
- The influence of chemical environments, like pH, on this coupling at the molecular level is not well understood.
Purpose of the Study:
- To investigate how the protonation state of carboxylated polythiophenes affects ion dynamics, doping, and mechanical properties.
- To establish molecular acidity as a strategy for controlling ionic preference and material stability.
Main Methods:
- Utilized a suite of multimodal operando techniques.
- Employed simulations to support experimental findings.
- Mapped material behavior across a range of pH values.
Main Results:
- The protonation state of carboxylated polythiophenes precisely controls ion dynamics, doping efficiency, solvent uptake, and mechanical response.
- pH dictates the balance of cation/anion uptake during electrochemical doping.
- A quasi-nonswelling regime (pH ≈ 3-3.5) was identified, showing minimal volume change with significant stiffening.
Conclusions:
- Molecular acidity provides a general strategy to program ionic preference and mechanical stability in materials.
- Findings offer design principles for pH-responsive mixed conductors and soft electronic materials.
- Developed materials effectively couple ionic, electronic, and mechanical functionalities.
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