Sulfonated Polymer Membrane Solubility via Aprotic Solvent Mediation
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Solution Overview
Problem
Existing methods fail to effectively incorporate low molecular phosphonic acids into sulfonated polymer membranes due to poor solubility in organic solvents, limiting their ion exchange capacity and proton conductivity.
Innovation Solution
A process involving the use of acid-base interactions between sulfonic acid groups in sulfonated polymers and aminophosphonic acids in specific solvents like DMSO, allowing for the dissolution and immobilization of aminophosphonic acids within the polymer matrix, enhancing their solubility and ion exchange capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If low molecular phosphonic acids are used in sulfonated polymer membranes, then ion exchange capacity and proton conductivity are improved, but solubility in organic solvents deteriorates
Solution Approach 1:
The patent uses aprotic solvents (NMP, DMSO, DMF, DMAc) as intermediaries to enable the dissolution of both sulfonated polymers and low molecular phosphonic acids. These solvents act as mediators that facilitate acid-base interactions between the sulfonic acid groups and aminophosphonic acids, allowing the phosphonic acids to dissolve in the polymer solution despite their poor solubility in conventional organic solvents.
Solution Approach 2:
The patent changes the solvent parameter from conventional protic or non-polar solvents to specific aprotic solvents with high polarity and basicity. This parameter change enables the solvation of aminophosphonic acids through their interaction with the sulfonic acid groups, transforming the solubility characteristics of the system.
2Reliability
If phosphonic acids are added to sulfonated polymer membranes, then proton conductivity is improved, but manufacturing complexity increases due to solubility issues
Solution Approach 1:
The aprotic solvents serve as intermediaries that simplify the manufacturing process by enabling direct dissolution of phosphonic acids in polymer solutions. This eliminates the need for complex post-treatment methods or multiple processing steps, making the manufacturing process more straightforward despite the improved functionality.
3Quantity of substance
If aqueous solutions of phosphonic acids are used for post-treatment, then some dissolution occurs, but penetration into membrane is marginal and temperature/concentration increases do not help
Solution Approach 1:
The patent changes the solvent parameter from aqueous to aprotic organic solvents. This parameter change fundamentally alters the solubility and penetration characteristics, allowing phosphonic acids to effectively dissolve in and penetrate the membrane matrix, overcoming the limitations of aqueous post-treatment methods.
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 significantly increases the ion exchange capacity and proton conductivity of the membranes, making them suitable for applications like direct methanol fuel cells with reduced methanol crossover and improved mechanical properties.
Implementation Method 1
the dissolution probably occurs because of an acid-base-interaction between the basic nitrogen and the sulfonic acid group
Implementation Method 2
The preferred solvent is DMSO. It was found out surprisingly that the calculated equivalent amounts of the aminophosphonic acids do not dissolve in a solution of sulfonated polyetherketone in NMP
Data Source
AI summary
A method is disclosed for production of solutions of aminophosphonic acids and polymeric sulfonic acids in aprotic solvents. Membranes for membrane methodologies are produced from said solutions. Said membranes can also be doped with phosphoric acid.