Block Copolymer Membrane Crazing for Scalable Nanopore Filtration
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Solution Overview
Problem
Current ultrafiltration membranes made from block copolymers (BCP) face high manufacturing costs and laborious processes, limiting their industrial application, while existing pore formation techniques are slow and difficult to control, making them unsuitable for scalable production.
Innovation Solution
A new method involving mechanical stretching of an ultrathin block copolymer film supported on a porous polyethersulfone substrate under tensile strain, which cavitates minor block domains to create predictable nanopores without the need for block removal or reconstruction steps, resulting in high-performance, scalable BCP membranes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If block copolymer membranes are used for ultrafiltration, then filtration performance is improved, but manufacturing cost increases
Solution Approach 1:
The membrane is segmented into two functional layers: a thin block copolymer selective layer (50-500 nm) that provides high filtration performance, and a thick macroporous support layer that provides mechanical strength and allows scalable manufacturing. This segmentation allows each layer to be optimized independently for its specific function.
Solution Approach 2:
The invention replaces expensive bulk block copolymer membranes with a composite structure where only a thin layer of expensive BCP is needed for the selective function, while the bulk of the membrane is made from inexpensive macroporous support material. This dramatically reduces the quantity of costly BCP required.
2Quantity of substance
If traditional pore formation techniques are used, then porosity is achieved, but manufacturing complexity increases
Solution Approach 1:
The block copolymer is self-assembled into a phase-separated morphology on the macroporous support before any pore formation step. The minor block domains are pre-positioned to become the pore locations, eliminating the need for complex post-assembly pore creation steps.
Solution Approach 2:
The block copolymer's inherent microphase separation automatically creates a template structure where minor block domains are naturally positioned to form pores. This self-organization eliminates the need for external pore-forming agents or complex reconstruction steps.
3Quantity of substance
If block removal steps are implemented, then pore formation is achieved, but manufacturing time increases
Solution Approach 1:
Instead of removing blocks to form pores, the invention extracts only the necessary function: the minor block domains serve as pore templates during stretching, and their original positions define the pore locations without requiring complete removal or reconstruction steps.
Solution Approach 2:
The pore-forming capability is built into the block copolymer structure during self-assembly, before stretching. The minor block domains are pre-positioned to become pores, eliminating the need for subsequent block removal steps that would add time and complexity.
4Productivity
If membrane thickness is reduced, then permeability is improved, but mechanical strength decreases
Solution Approach 1:
The membrane is divided into a thin selective layer (50-500 nm) for high permeability and a thick support layer (microns to mm) for mechanical strength. This segmentation allows each layer to be optimized for its primary function without compromise.
Solution Approach 2:
The thin block copolymer selective layer acts as a flexible, highly permeable film that relies on the rigid macroporous support for mechanical strength. The support layer provides the structural framework that allows the thin selective layer to function without compromising integrity.
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 method enables the production of thin, permeable membranes with near-complete rejection of 40 nm gold nanoparticles, offering a cost-effective and efficient manufacturing process.
Implementation Method 1
Phase separated block copolymer (BCP) thin films supported on a porous polyethersulfone (PES) support craze under tensile strain, leaving behind pores of predictable size based on initial domain size and extent of strain
Implementation Method 2
Application of tensile strain caused the minor block domains to cavitate and elongate thereby creating a nanoporous structure
Implementation Method 3
Phase separated block copolymer (BCP) thin films supported on a porous polyethersulfone (PES) support
Data Source
AI summary
A porous composite ultrafiltration membrane including a block copolymer layer having (a) one or more soft block polymer(s) having an elongation at break of greater than about 50%, as measured by ASTM D638 and an elastic modulus of between 10 MPa to 3 GPa as measured by the ASTM D638 tensile test; and (b) one or more hard block polymer(s) having an elongation at break of less than about 65%, as measured by ASTM D638, and an elastic modulus of higher than 1 GPa as measured by the ASTM D638 tensile test, and a macroporous support layer having a pore size larger than a pore size of the block copolymer layer. Also described is a method for making the porous composite membrane.