Block Copolymer Membrane Crazing for Controlled Pore Formation
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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, and existing pore formation techniques are slow and difficult to control, making them unsuitable for commercialization.
Innovation Solution
A new method involving mechanical stretching of an ultrathin block copolymer film supported on a porous polyethersulfone (PES) substrate under tensile strain to form high-aspect ratio pores, eliminating the need for block removal steps and enabling scalable production of thin, permeable membranes with precise pore sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If block copolymer membranes are used to achieve improved ultrafiltration performance, then selectivity and permeability are enhanced, but manufacturing cost and material cost increase significantly
Solution Approach 1:
The membrane is divided into two functional segments: a thin block copolymer selective layer (providing ultrafiltration performance) and a thick porous support layer (providing mechanical strength and reducing overall cost). This segmentation allows each layer to be optimized independently for its specific function.
Solution Approach 2:
The invention uses a composite structure combining block copolymer material with a porous support material. The block copolymer provides the selective filtration function while the support provides structural integrity, creating a composite membrane that balances performance and cost-effectiveness.
2Manufacturing precision
If traditional pore formation strategies (minor block removal or reconstruction) are used, then pores are created in the block copolymer, but the process is slow and difficult to control
Solution Approach 1:
The invention replaces complex chemical pore formation processes (block removal or reconstruction) with a simple mechanical stretching process. By applying tensile strain to the block copolymer layer, pores are formed rapidly and controllably through physical deformation rather than slow chemical reactions.
Solution Approach 2:
The pore formation is achieved by changing the mechanical parameter (applying tensile strain) rather than using chemical parameters. The strain magnitude and direction can be precisely controlled to determine pore size, shape, and distribution, enabling rapid and controllable pore formation.
3Manufacturing precision
If phase inversion is used for pore formation, then pores are created in the membrane, but large amounts of costly block copolymer are required
Solution Approach 1:
The block copolymer is first deposited as a thin continuous layer on the porous support, establishing the selective layer structure before pore formation. This preliminary deposition uses minimal block copolymer, and subsequent stretching creates pores in this pre-formed layer without requiring additional material.
Solution Approach 2:
Instead of using block copolymer to create pores through phase inversion (which consumes large amounts of material), the invention takes out the pore formation step from the material deposition step. The thin block copolymer layer is deposited first, then pores are extracted or created through mechanical stretching of this existing layer.
4Productivity
If the selective layer thickness is reduced to improve permeability, then permeability increases, but the layer becomes more fragile and difficult to manufacture
Solution Approach 1:
The invention uses an ultrathin block copolymer film (selective layer) that is flexible and conformal, deposited on a rigid porous support. The thin film provides high permeability while the support provides the mechanical strength and stability, allowing the selective layer to be extremely thin without compromising overall membrane integrity.
Solution Approach 2:
The porous support layer serves multiple functions: it provides mechanical strength to the thin selective layer, acts as a substrate for selective layer deposition, and contributes to overall membrane stability. This multi-functionality allows the selective layer to be made ultrathin for high permeability without sacrificing strength.
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 allows for the rapid creation of cost-effective, scalable BCP membranes with near-complete rejection of 40 nm gold nanoparticles and high permeability, overcoming the limitations of traditional manufacturing processes.
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
mechanical stretching of an ultrathin block copolymer film supported on a porous polyethersulfone (PES) support
Implementation Method 3
Phase separated block copolymer (BCP) thin films
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.