Novel Ionic Conducting Composite Membrane Based on Polymerizable Ionic Liquids

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Developing efficient polymer electrolyte membranes is crucial for advancing fuel cell technology.
• Medium-temperature fuel cells require membranes with high proton conductivity and thermal stability.
• Supported ionic liquid membranes (SILMs) offer potential advantages over traditional membranes.

Purpose of the Study:

• To design and characterize novel supported ionic liquid membranes (SILMs) for medium-temperature fuel cell applications.
• To investigate the effect of protic ionic liquid structure on membrane properties.
• To optimize the polymerization of ionic liquids within a polyimide support.

Main Methods:

• Impregnation of porous polyimide (Matrimid®) with synthesized protic ionic liquids containing polymerizable groups (vinyl, allyl, methacrylate).
• Optimization of ionic liquid polymerization using varying (photo)initiators, quantities, and reaction times.
• Analysis of mechanical properties (Young's modulus, elongation at break), thermal stability (decomposition temperature), and proton conductivity over a wide temperature range (30–150 °C).

Main Results:

• The synthesized SILMs demonstrated excellent flexibility (Young's modulus: 1371 MPa, elongation at break: 271%) and high thermal stability (decomposition temperature > 300 °C).
• Proton conductivity was good across a broad temperature range (30–150 °C).
• A three-component membrane (Matrimid®/vinylimidazolium/polyvinylimidazolium trifluoromethane sulfonate) achieved high proton conductivity (~5 × 10⁻² mS/cm at 100 °C and ~0.1 mS/cm at 150 °C).

Conclusions:

• The developed SILMs are mechanically robust, thermally stable, and exhibit significant proton conductivity.
• These properties make the membranes highly attractive for medium-temperature fuel cell applications.
• The study highlights the potential of tailored protic ionic liquids in polyimide-supported membranes for energy technologies.