Crosslinked Anionic Polymer Film for Permselectivity Under Strong Base
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Solution Overview
Problem
Existing ion exchange membranes, particularly cation exchange membranes, face challenges in achieving optimal permselectivity and mechanical strength, especially under strong basic conditions, and often incorporate fluoro groups that are environmentally undesirable.
Innovation Solution
A polymer film comprising anionic groups, a crosslinking agent without fluoro groups, and a non-ionic crosslinking agent, with specific amounts of these components to ensure proper curing and enhance permselectivity, is developed. This film is prepared using a composition that includes a crosslinking agent of certain formulas and a non-ionic crosslinking agent, which are partially but not completely cured to maintain their presence within the polymer structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard ion exchange membranes are used, then permselectivity can be achieved, but mechanical strength deteriorates under strong basic conditions
Solution Approach 1:
The patent uses a composite membrane structure combining a porous support (providing mechanical strength) with an ion-exchange polymer layer (providing permselectivity). The porous support is impregnated with a crosslinking composition containing component (a) and component (b), creating a composite material that integrates both functional requirements.
Solution Approach 2:
The patent optimizes the crosslinking degree by controlling the amounts of components (a) and (b) within specific ranges (0.01-20 mg/g for component (a) and 0.01-20 mg/g for component (b)). This parameter control ensures sufficient crosslinking for mechanical strength while preventing excessive crosslinking that would reduce permselectivity, particularly under strong basic conditions.
2Strength
If crosslinking agents with fluoro groups are used, then mechanical strength can be improved, but environmental harm increases
Solution Approach 1:
The patent explicitly excludes fluoro groups from the crosslinking agents by specifying that component (a) must be free from fluoro groups. This extraction of the harmful element (fluoro groups) from the crosslinking agent structure eliminates environmental harm while maintaining the essential crosslinking function for mechanical strength.
Solution Approach 2:
The patent employs alternative crosslinking agents without fluoro groups that are environmentally friendly. These substitutes may have shorter service lives or lower costs but eliminate the environmental persistence and harm associated with fluorinated compounds, aligning with green chemistry principles.
3Strength
If excessive crosslinking is performed, then mechanical strength is improved, but permselectivity deteriorates
Solution Approach 1:
The patent applies partial crosslinking by limiting the amounts of components (a) and (b) to specific ranges (0.01-20 mg/g each). This partial action provides sufficient crosslinking for mechanical strength while avoiding excessive crosslinking that would overly densify the membrane structure and impair ion transport and permselectivity.
Solution Approach 2:
The patent precisely controls the crosslinking parameters by specifying optimal amount ranges for components (a) and (b). This parameter optimization balances the competing requirements of mechanical strength (requiring crosslinking) and permselectivity (requiring adequate pore structure for ion transport), achieving the best compromise through controlled parameter selection.
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 polymer film exhibits excellent permselectivity and mechanical strength, particularly under strong basic conditions, while avoiding the environmental concerns associated with fluoro groups, thus enabling effective use in applications such as fuel cells and electrodialysis.
Implementation Method 1
a crosslinking agent which is free from fluoro groups and comprises a group of Formula (I)... a non-ionic crosslinking agent... which are partially but not completely cured to form the polymer film
Data Source
AI summary
A polymer film comprising anionic groups and 0.008 to 25 mg/g of each of components (a) and (b): (a) a crosslinking agent which is free from fluoro groups and comprises a group of Formula (I); and (b) a non-ionic crosslinking agent; Formula (I) wherein M+ is a cation and * indicates the attachment points to other elements of the crosslinking agent.