Block Copolyimide Membranes for Gas Separation
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Solution Overview
Problem
Current polyimide membranes for gas separation face a trade-off between permeability and selectivity, with increased permeability often resulting in decreased selectivity, and existing methods to enhance permeability, such as using random copolymers, blends, or additives, fail to achieve commercial viability due to phase separation and reduced selectivity issues.
Innovation Solution
Development of block copolyimides with specific compositions and structures that allow for microphase separation, forming domains smaller than the membrane layer thickness, enhancing permeability while maintaining selectivity, and using inexpensive monomers for cost-effective production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyimide membranes are used for gas separation, then high selectivity is achieved, but permeability remains moderate
Solution Approach 1:
The patent applies composite materials by combining two distinct polyimide blocks (Block A and Block B) with different properties into a single block copolymer system. Block A provides selectivity through its rigid aromatic structure, while Block B enhances permeability through its flexible aliphatic segments. This composite approach allows the membrane to simultaneously achieve high selectivity and high permeability, resolving the traditional trade-off between these two parameters.
Solution Approach 2:
The patent segments the polyimide structure into distinct functional blocks: Block A (selectivity-providing segments with rigid aromatic rings) and Block B (permeability-enhancing segments with flexible aliphatic chains). This segmentation allows each block to perform its specific function independently while working together in the copolymer structure, enabling the membrane to achieve both high selectivity and high permeability simultaneously.
2Productivity
If random copolymers are prepared to increase permeability, then permeability improves, but selectivity decreases continuously
Solution Approach 1:
The patent uses segmentation by creating well-defined block copolymers with distinct Block A and Block B segments, rather than random copolymers. The block structure ensures that selectivity-providing rigid segments and permeability-enhancing flexible segments remain separated into distinct domains, preventing the loss of selectivity that occurs in random copolymers where segments are randomly distributed and cannot maintain proper phase separation.
Solution Approach 2:
The patent applies local quality by assigning specific functional characteristics to specific blocks: Block A is designed with rigid aromatic structures localized to provide selectivity, while Block B is designed with flexible aliphatic structures localized to provide permeability. This localized functional assignment within the block copolymer structure allows each region to optimize its specific function without compromising the other.
3Productivity
If polymer blends are prepared with high permeability polymers, then permeability increases, but phase separation occurs with droplet sizes above 1 μm
Solution Approach 1:
The patent segments the polymer structure at the molecular level by creating block copolymers with distinct Block A and Block B sequences, rather than physically blending separate polymers. This molecular-level segmentation ensures intimate mixing and uniform distribution at the nanoscale, preventing the macroscopic phase separation and large droplet formation (above 1 μm) that occur in conventional polymer blends.
Solution Approach 2:
The patent creates a composite material system at the molecular level by synthesizing block copolymers that combine rigid selectivity-providing blocks and flexible permeability-enhancing blocks. This molecular composite approach ensures homogeneous mixing and controlled microphase separation into domains smaller than 100 nm, avoiding the large-scale phase separation and emulsion formation that plague conventional polymer blend systems.
4Productivity
If additives such as zeolites or MOFs are incorporated, then intrinsic permeability increases, but particle size exceeds membrane layer thickness
Solution Approach 1:
The patent segments the permeability-enhancing function into molecular-scale flexible aliphatic blocks (Block B) within the copolymer structure, rather than incorporating large particulate additives. This segmentation allows the permeability enhancement to occur at the molecular level with domain sizes well below 100 nm, avoiding the particle size problem with conventional additives like zeolites or MOFs that typically exceed membrane layer thickness.
Solution Approach 2:
The patent substitutes the mechanical approach of incorporating particulate additives (zeolites, MOFs) with a molecular-level chemical approach by synthesizing block copolymers with flexible segments. This substitution replaces the need for large particulate matter with molecular-scale structural modifications that achieve the same permeability enhancement effect without the size-related problems of conventional additives.
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 block copolyimides achieve high permeability and selectivity, outperforming prior art membranes by up to 81.5 times in permeability and maintaining comparable selectivity, thus offering improved permselectivity and economic advantages.
Implementation Method 1
highly selective integrally asymmetrical gas separation membranes
Implementation Method 2
permeability and selectivity are conflicting objectives
Data Source
AI summary
The present invention relates to novel block copolyimides for preparing highly selective integrally asymmetrical gas separation membranes of improved permeance, processes for preparing these block copolyimides, membranes prepared from the block copolyimides, and also the use of the block copolyimides and of the membranes prepared therefrom.