Anion Exchange Membranes With Crosslinked Polymer Pores
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Solution Overview
Problem
Ion exchange membranes for water desalination and other applications face challenges in achieving low electrical resistance, high permselectivity, chemical stability, mechanical strength, and durability, particularly in thinner membranes which are more susceptible to dimensional changes and defect formation during production.
Innovation Solution
The development of anion exchange membranes using functional monomers with tertiary amine groups, such as vinylimidazole, polymerized with crosslinking agents and quaternizing agents within the pores of a microporous substrate, creating a cross-linked polymer with low resistance and high permeability, and using specific solvents and initiators for polymerization, such as dipropylene glycol and free radical initiators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If thinner membranes are used to reduce electrical resistance and improve productivity, then membrane resistance decreases and productivity increases, but dimensional stability deteriorates and manufacturing precision worsens
Solution Approach 1:
The patent uses a composite structure consisting of a porous substrate (such as polyolefin or polyester) combined with a gel layer containing ion-exchange functional groups. This composite design allows the thin membrane to maintain mechanical strength and dimensional stability from the substrate while achieving low electrical resistance through the conductive gel layer with high ion-exchange capacity.
Solution Approach 2:
The patent employs a porous substrate with controlled pore structure to provide mechanical support to the thin membrane. The porosity is optimized to allow ion transport while maintaining structural integrity, enabling the membrane to be thin yet stable during operation and manufacturing.
2Productivity
If thinner membranes are used to reduce electrical resistance and improve productivity, then membrane resistance decreases and productivity increases, but manufacturing precision deteriorates due to defect formation
Solution Approach 1:
The patent applies foramina-forming agents during the polymerization process to create a controlled porous structure before the membrane is put into service. This preliminary action during manufacturing ensures uniform pore distribution and prevents defects that would otherwise form in thinner membranes, maintaining manufacturing precision while enabling thin-film productivity.
Solution Approach 2:
The patent changes physical and chemical parameters during manufacturing, including polymerization temperature, solvent selection (such as dipropylene glycol), and crosslinking agents, to optimize the gel layer formation. These parameter adjustments ensure defect-free production of thin membranes with consistent properties.
3Adaptability or versatility
If broader pH operational ranges are achieved through chemical modifications, then adaptability improves, but chemical stability may deteriorate
Solution Approach 1:
The patent introduces functional groups with different pKa values at different locations within the membrane structure. By incorporating both strong base (quaternary ammonium) and weak base (tertiary amine) functional groups, the membrane achieves different chemical properties in different regions, enabling broad pH operational range while maintaining overall chemical stability through the robust polymer backbone.
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
This approach results in membranes with low electrical resistance, high permselectivity, and chemical resistance, allowing for broader operational pH ranges, and achieving properties comparable to thicker membranes, while being more cost-effective and having improved dimensional stability and service life.
Implementation Method 1
polymerized with crosslinking agents and quaternizing agents within the pores of a microporous substrate, creating a cross-linked polymer
Implementation Method 2
Anion exchange membranes transport anions under an electrical or chemical potential. Anion exchange membranes will have fixed positive charges and mobile negatively charged anions.
Implementation Method 3
Under a DC voltage, ions move to the electrode of opposite charge
Implementation Method 4
creating a cross-linked polymer with low resistance and high permeability
Data Source
Figure 1
AI summary
The disclosure describes anion exchange membranes and processes for their manufacture. The anion exchange membrane has a microporous membrane support having a porous first side, a porous second side, and a continuous porous structure comprising pores having a size of 0.05 microns to 10 microns extending from the porous first side to the porous second side; and a crosslinked ion transferring polymer filling the continuous porous structure, the polymer being formed in the continuous porous structure, wherein the anion exchange membrane has an ion permselectivity of greater than 90%.