Crosslinked Block Copolymer Membranes for Solvent-Stable Filtration
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Solution Overview
Problem
Existing filter membranes made from block copolymers like poly(isoprene-b-styrene-b-4-vinyl pyridine) are not suitable for use with photolithography solvents as their pore structures collapse upon drying and may dissolve in such solvents, lacking sufficient solvent resistance and integrity.
Innovation Solution
Cross-linking block copolymers to increase molecular weight and improve solvent resistance, thereby enhancing the stability of the membrane's pore structure, allowing it to maintain integrity in the presence of photolithography solvents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If block copolymer membranes are made from poly(isoprene-b-styrene-b-4-vinyl pyridine), then fine control over pore dimensions and pore size distribution is achieved, but the pore structures collapse upon drying and the polymers dissolve in photolithography solvents
Solution Approach 1:
The patent combines block copolymers with crosslinking agents to create a composite material system. The crosslinking agent forms covalent bonds between polymer chains, creating a network structure that maintains the self-assembled pore architecture while preventing polymer dissolution in photolithography solvents. This composite approach allows simultaneous achievement of fine pore size control and solvent resistance.
Solution Approach 2:
The patent modifies the chemical parameters of the block copolymer system by introducing crosslinking functionality. Through controlled crosslinking reactions, the polymer network's molecular weight and structural stability are enhanced, transforming the material from a soluble, structure-collapsing system to an insoluble, structure-stable membrane that resists photolithography solvents while maintaining precise pore dimensions.
2Ease of manufacture
If block copolymer membranes are dried to remove solvent, then the membrane structure is consolidated, but the pore structures collapse
Solution Approach 1:
The patent applies crosslinking treatment before the drying step to pre-stabilize the pore structure. By establishing covalent crosslinks between polymer chains in advance, the membrane framework is reinforced to withstand the stresses of solvent removal during drying, preventing pore collapse while allowing complete consolidation of the membrane structure.
Solution Approach 2:
The crosslinked network acts as a structural cushion that prevents pore collapse during drying. The pre-formed crosslinks provide mechanical support to the self-assembled pore architecture, absorbing and distributing the stresses that would otherwise cause structural collapse during solvent removal, thereby preserving pore integrity throughout the drying process.
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 cross-linked block copolymer membranes exhibit improved solvent resistance and drying stability, maintaining less than 20% change in bubble point after exposure to photolithography solvents for 24 hours, and require minimal or no humectants for preservation.
Implementation Method 1
Cross-linking block copolymers to increase molecular weight and improve solvent resistance
Implementation Method 2
designing macromolecules which microphase separate into periodic, ordered structures
Data Source
AI summary
The disclosure provides certain block copolymer membranes which are useful as components of filters for liquid purification and/or filtration. The block copolymers of the disclosure are subjected to cross-linking reactions to raise the overall molecular weight and are thus believed to impart improved solvent resistance properties to the membranes, thereby rendering such membranes suitable for use with solvents such as photolithography solvents. Additionally, this cross-linking treatment is believed to improve the integrity of the pore structure of the membrane during a drying step.