Quaternary Ammonium AEM Polymers With Low Swelling
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Solution Overview
Problem
The development of durable anion exchange membranes (AEMs) that can withstand highly basic media without degradation and maintain low ionic resistance for efficient electrochemical device performance has been hindered by the lack of polyelectrolytes with high charge densities and controlled swelling ratios.
Innovation Solution
A method for preparing cationic polymers with a plurality of quaternary amino groups, involving a precursor polymer with specific repeat units and a cationic amine compound, to form membranes with high charge densities and reduced swelling ratios, enabling their use in anion exchange membranes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional polyelectrolytes are used in anion exchange membranes, then membrane ionic resistance can be reduced, but membrane durability in highly basic media deteriorates due to degradation
Solution Approach 1:
The patent changes the chemical parameters of the polymer by incorporating fluorinated side chains and quaternary ammonium groups with specific structures (Formulas I-IV). This modifies the membrane's chemical resistance to basic media while maintaining ionic conductivity through controlled charge density and ionomer content.
Solution Approach 2:
The patent creates a composite polymer structure combining fluorinated hydrocarbon backbones with quaternary ammonium functional groups. This composite approach integrates the chemical stability of fluorinated materials with the ionic conductivity of polyelectrolytes, achieving both durability and low resistance.
2Loss of energy
If charge density in anion exchange membranes is increased to improve conductivity, then membrane swelling ratio increases, but excessive swelling degrades membrane performance
Solution Approach 1:
The patent optimizes the charge density parameter by controlling the ratio of repeat units with quaternary ammonium groups (Formulas I-IV) within specific ranges (x, y, z values). This controlled parameter adjustment achieves adequate conductivity while preventing excessive swelling that would occur with higher charge densities.
Solution Approach 2:
The patent introduces fluorinated side chains as local structural modifications that provide steric hindrance and hydrophobic effects. These localized features restrict polymer chain mobility and reduce water uptake, thereby controlling swelling in regions with high charge density while maintaining overall conductivity.
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 resulting cationic polymers enhance conductivity and maintain low swelling ratios, achieving high durability and efficiency in highly basic media, addressing the limitations of existing AEMs.
Implementation Method 1
reacting the pendant *—R3-L groups (which correspond to R2 groups) of the precursor polymer with a cationic amine compound having at least one tertiary amino group and at least one quaternary amino group to form the cationic polymer having the plurality of pendant quaternary amino groups
Implementation Method 2
Anion exchange membranes based on polymerization of long chain alpha olefins... cationic polymers having a plurality of quaternary amino groups... used to make solid, polymeric membranes, including membranes that can be used as polymneric anion exchange membranes
Data Source
AI summary
Described herein are cationic polymers having a plurality of quaternary amino groups, methods of making such polymers, and uses of such polymers as ion exchange membranes in electrochemical devices.