Controlled-Crosslinking Anion Exchange Polymers for Robust AEMs
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Solution Overview
Problem
Existing anion exchange membranes (AEMs) and membrane electrode assemblies (MEAs) in AEMFCs and AEMELs suffer from low mechanical robustness, leading to premature failure due to pinholes, tearing, and catalyst washout, primarily caused by water erosion and polymer dissolution during operation.
Innovation Solution
Development of crosslinkable anion exchange polymers that can form crosslinked AEMs and MEAs through controlled crosslinking using alkaline solutions without additional crosslinking reagents, enhancing mechanical stability and reducing swelling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional crosslinking methods using crosslinking reagents at high concentrations are used, then mechanical stability is improved, but polymer compatibility is limited and contamination risk increases
Solution Approach 1:
The polymer contains built-in crosslinkable functional groups (vinyl, vinylidene, allyl, or acetylenic groups) that enable self-crosslinking through chemical reactions such as addition polymerization, cycloaddition, or condensation. This eliminates the need for external crosslinking reagents and allows the polymer to crosslink autonomously under appropriate conditions, thereby achieving both mechanical stability and broad polymer compatibility
Solution Approach 2:
The crosslinking process is controlled by adjusting parameters such as temperature, pH, and reaction time to activate the crosslinkable functional groups. By changing these parameters, the crosslinking reaction can be initiated and controlled without requiring high concentrations of external reagents, thus avoiding contamination while achieving the desired mechanical stability
2Strength
If crosslinking reagents are used at high concentrations, then mechanical stability is improved, but contamination and undesired membrane properties occur
Solution Approach 1:
The polymer contains built-in crosslinkable functional groups (vinyl, vinylidene, allyl, or acetylenic groups) that enable self-crosslinking through chemical reactions such as addition polymerization, cycloaddition, or condensation. This eliminates the need for external crosslinking reagents and allows the polymer to crosslink autonomously under appropriate conditions, thereby achieving both mechanical stability and broad polymer compatibility
Solution Approach 2:
The harmful crosslinking reagents are completely removed from the system by using the polymer's own functional groups for crosslinking. The crosslinking is achieved through intrinsic chemical reactions within the polymer structure itself, eliminating the source of contamination entirely
3Stability of the object's composition
If crosslinking is performed to enhance mechanical stability, then swelling is reduced, but polymer selection is restricted
Solution Approach 1:
The crosslinking process is controlled by adjusting parameters such as temperature, pH, and reaction time to activate the crosslinkable functional groups. By changing these parameters, the crosslinking reaction can be initiated and controlled without requiring high concentrations of external reagents, thus avoiding contamination while achieving the desired mechanical stability
Solution Approach 2:
The crosslinkable functional groups (vinyl, vinylidene, allyl, or acetylenic groups) can be incorporated into various polymer backbones, making the crosslinking approach universally applicable to different polymer types including aromatic and aliphatic polyamides, polyesters, and polyacrylonitrile, thereby expanding polymer selection while maintaining swelling control
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 crosslinked AEMs and MEAs exhibit improved mechanical integrity, reduced swelling, and increased conductivity, stability, and solubility, addressing the mechanical robustness issues and enhancing performance under dry-wet cycles.
Implementation Method 1
Crosslinking enhances the mechanical and dimensional stability of anion exchange membranes (AEM) and membrane electrode assemblies (MEA). By forming covalent chemical bonds between polymer chains, crosslinking creates a relatively rigid and strong polymer network.
Implementation Method 2
This network structure helps to prevent excessive water uptake and swelling, especially under conditions of high temperature and humidity
Implementation Method 3
Anion exchange polymers capable of controlled crosslinking... for use in anion exchange membrane electrochemical devices such as anion exchange membrane fuel cells (AEMFCs) and anion exchange membrane electrolyzers (AEMELs)
Data Source
AI summary
Polymers based on poly(aryl alkylene) that are capable of crosslinking in a controlled manner are provided. Crosslinked anion exchange membranes or anion exchange ionomers formed from these polymers not only have superior chemical stability and hydroxide conductivity but also have decreased water uptake and improved mechanical stability.