Sulfonated Block Copolymer Membranes for Water Transport
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Solution Overview
Problem
Prior sulfonated block copolymers suffer from excessive water-induced swelling and mechanical weakness, limiting their applications due to the sulfonation of outer blocks, which leads to hydration-induced plasticization and softening of hard domains, resulting in insufficient strength and stability in aqueous environments.
Innovation Solution
The development of sulfonated block copolymers with resistant end blocks and susceptible interior blocks, where sulfonation is selectively directed to the interior blocks using para-substituted styrenic monomers, maintaining hydrophobicity and integrity in hydrated conditions, allowing for the formation of solid membranes with high water transport properties and wet strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If sulfonation is applied to outer blocks to increase water transport properties, then water transport capability is improved, but mechanical strength and dimensional stability deteriorate due to hydration-induced plasticization
Solution Approach 1:
The block copolymer is segmented into distinct functional regions: outer blocks (A) that remain unsulfonated to maintain mechanical strength and dimensional stability, and interior blocks (B) that are sulfonated to provide water transport capability. This spatial segmentation allows each region to fulfill its specific function without compromising the other.
Solution Approach 2:
Sulfonation is applied locally only to the interior blocks rather than uniformly across the entire polymer structure. This localized modification ensures that water transport properties are enhanced in the interior regions while the outer blocks retain their hydrophobic character and structural integrity.
2Productivity
If sulfonation is applied to increase water transport properties, then water permeability is improved, but dimensional stability deteriorates due to excessive swelling
Solution Approach 1:
The polymer structure is segmented into hydrophobic outer blocks that resist swelling and maintain dimensional stability, and hydrophilic sulfonated interior blocks that facilitate water transport. This segmentation creates a balanced structure where swelling is controlled and dimensional stability is preserved.
Solution Approach 2:
The block copolymer functions as a composite material with distinct hydrophobic and hydrophilic phases. The unsulfonated outer blocks form a hydrophobic matrix that provides structural stability, while the sulfonated interior blocks create hydrophilic channels for water transport, achieving a balance between dimensional stability and water permeability.
3Strength
If sulfonation is applied to interior blocks to maintain mechanical strength, then wet strength is improved, but water transport properties may be limited
Solution Approach 1:
Sulfonation is locally applied to interior blocks to create hydrophilic regions that facilitate water transport while maintaining overall structural integrity. The unsulfonated outer blocks preserve mechanical strength, and the sulfonated interior blocks provide water transport pathways, achieving both wet strength and water transport capability.
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
These sulfonated block copolymers achieve a balance of water transport, wet strength, and dimensional stability, enabling their use in various applications where prior art polymers were deficient, as they remain solid and insoluble in water while maintaining tensile strength exceeding 100 psi, even when equilibrated with excess water.
Implementation Method 1
maintaining hydrophobicity and integrity in hydrated conditions
Implementation Method 2
high water transport properties
Data Source
AI summary
A pre-cursor block copolymer for sulfonation which, prior to hydrogenation, has the general configuration A-B-A, A-B-A-B-A, (A-B-A)nX, (A-B)nX, A-D-B-D-A, A-B-D-B-A, (A-D-B)nX, (A-B-D)nX or mixtures thereof, wherein A, B and D blocks do not contain any significant levels of olefinic unsaturation. Each A and D block is a polymer block resistant to sulfonation, and each B block is a polymer block susceptible to sulfonation. Each A block is a segment of one or more polymerized para-substituted styrene monomers, each B block contains segments of one or more vinyl aromatic monomers selected from polymerized (i) unsubstituted styrene monomers, (ii) ortho-substituted styrene monomers, (iii) meta-substituted styrene monomers, (iv) alpha-methylstyrene, (v) 1,1-diphenylethylene, (vi) 1,2-diphenylethylene and (vii) mixtures thereof, and each D block contains polymers having a glass transition temperature less than 20° C. and a number average molecular weight of between 1,000 and 50,000.