Crosslinked Norbornene AEMs for High Conductivity and Alkaline Stability
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Solution Overview
Problem
Current anion exchange membranes (AEMs) face challenges in achieving high conductivity, long-term alkaline stability, robust mechanical properties, and controlled water uptake, which are essential for efficient operation in electrochemical devices such as fuel cells and electrolyzers.
Innovation Solution
A random copolymer derived from specific monomers, with crosslinked repeat units, is developed to form anion exchange membranes that exhibit high ionic conductivity and chemical stability, featuring ion exchange capacities up to 4 meq/g and stability for over 1000 hours in 1 M sodium hydroxide solution at 80°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If early anion exchange membranes were used, then ion exchange capacity was achieved, but chemical stability at high pH was poor and water uptake was high
Solution Approach 1:
The patent employs a composite polymer structure combining hydrophobic cycloolefinic backbone segments with hydrophilic ionic segments containing quaternary ammonium groups. This composite architecture enables simultaneous achievement of high ion exchange capacity and chemical stability in alkaline environments, resolving the contradiction between quantity of substance and reliability.
Solution Approach 2:
The patent creates local hydrophilic domains within the polymer matrix where ion exchange occurs, while maintaining a hydrophobic bulk structure. This local quality differentiation allows high ion exchange capacity in specific regions without compromising overall chemical stability and reduces excessive water uptake in the bulk material.
2Reliability
If ion exchange capacity is increased, then conductivity improves, but water uptake increases
Solution Approach 1:
The patent concentrates ionic groups in localized hydrophilic domains within the polymer structure, creating efficient ion transport pathways. This local concentration achieves high ionic conductivity without requiring uniform distribution of ionic groups throughout the material, thereby limiting excessive water uptake while maintaining conductivity.
Solution Approach 2:
The patent creates a microstructured morphology with nanoscale porous channels formed by the self-assembly of hydrophobic and hydrophilic segments. These controlled porous structures provide efficient ion transport pathways for high conductivity while the hydrophobic matrix limits overall water uptake.
3Adaptability or versatility
If polymer membrane is used for high pH applications, then non-precious metal catalysts can be used, but chemical stability deteriorates
Solution Approach 1:
The patent designs a composite polymer structure with chemically inert cycloolefinic backbone segments that provide stability in high pH environments, combined with functional ionic segments that enable compatibility with non-precious metal catalysts. This composite approach resolves the contradiction between adaptability and reliability.
Solution Approach 2:
The patent employs cost-effective cycloolefinic monomers and quaternary ammonium functional groups that provide sufficient chemical stability for practical applications without requiring expensive perfluorinated polymer structures, achieving economical high pH membrane solutions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The membranes demonstrate high hydroxide conductivity of up to 200 mS/cm at 80°C and long-term stability, making them suitable for various electrochemical applications, including fuel cells and electrolyzers, while maintaining mechanical robustness and minimizing water uptake.
Implementation Method 1
anion exchange membranes that exhibit high ionic conductivity and chemical stability, featuring ion exchange capacities up to 4 meq/g
Implementation Method 2
using an anion conducting solid polymer electrolyte as the ion conducting medium between the two electrodes and the ion conducting medium within the electrodes acting as the ionic conduit
Data Source
AI summary
Embodiments in accordance with the present invention encompass a variety of polymers derived from polycyclic olefin monomers, such as hydrocarbon functionalized norbornenes. The polymers so formed function as ionomers and are suitable as anion exchange membrane for fabricating a variety of electrochemical devices, among others. More specifically, the ionomeric polymers used herein are derived from a variety of quaternized amino functionalized norbornene monomers and are lightly crosslinked (less than ten mol %). The membranes made therefrom exhibit very high ionic conductivity of up to 198 mS/cm at 80° C. This invention also relates to using an anion conducting solid polymer electrolyte as the ion conducting medium between the two electrodes and the ion conducting medium within the electrodes acting as the ionic conduit between electroactive material and electrolyte. The electrochemical devices made in accordance of this invention are useful as fuel cells, gas separators, and the like.