Interfacial Polymerization for Microporous Separation Membranes
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Solution Overview
Problem
Current thin film composite membranes for nanofiltration in organic solvents face limitations due to the instability of support membranes in polar solvents and the thickness of the separating layer, which affects permeability and selectivity, and prior art membranes with intrinsic microporosity are restricted to soluble non-network polymers.
Innovation Solution
An interfacial polymerization process forming a thin film composite membrane with a support membrane coated by a network polymer possessing intrinsic microporosity, where at least one of the reactive monomers has concavity, resulting in a covalently cross-linked 3-dimensional polymeric network with interconnected intermolecular voids, and optional capping and curing steps to enhance surface chemistry and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thin film composite membrane is formed by coating a support membrane with a separating layer, then separation performance is improved, but the support membrane stability in polar solvents deteriorates
Solution Approach 1:
The invention uses a composite membrane structure consisting of a support membrane and a separating layer formed by interfacial polymerization. The support membrane provides mechanical strength and stability, while the separating layer provides separation performance. This composite structure resolves the contradiction by combining materials with complementary properties.
Solution Approach 2:
The separating layer is formed with specific local properties through interfacial polymerization, creating a thin film with controlled porosity and chemical composition on the surface of the support membrane. This allows the membrane to have different properties in different regions: the support provides stability while the separating layer provides separation performance.
2Productivity
If the separating layer thickness is reduced to improve permeability, then flux increases, but selectivity deteriorates
Solution Approach 1:
The invention optimizes the thickness and porosity parameters of the separating layer through control of interfacial polymerization conditions. By adjusting reaction time, monomer concentration, and solvent composition, a thin separating layer with optimized pore structure is formed that achieves both high flux and good selectivity.
Solution Approach 2:
The separating layer is formed as a porous structure through interfacial polymerization, creating a network of interconnected voids that allow selective transport. The porous structure enables molecules to pass through based on size and interaction with the pore walls, achieving both high permeability and selectivity simultaneously.
3Ease of manufacture
If soluble non-network polymers are used for intrinsic microporosity, then membrane formation is simplified, but membrane stability deteriorates
Solution Approach 1:
The invention employs interfacial polymerization, a chemical reaction process that occurs at the interface between two immiscible phases. This chemical approach creates strong covalent bonds in the separating layer, providing excellent stability while maintaining ease of manufacture through controlled reaction conditions.
Solution Approach 2:
The invention replaces physical mixing of soluble polymers with a chemical polymerization process at the interface. This substitution of mechanical assembly with chemical bonding creates a more stable structure that is equally easy to manufacture through controlled interfacial reaction.
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 membranes exhibit higher permeabilities and selectivities for gas separation and nanofiltration, particularly in organic solvents, with improved stability and thinner separating layers, allowing for efficient separation of solvents and solutes while maintaining high flux and rejection performance.
Implementation Method 1
the reaction of the first and second reactive monomers results in the in-situ formation of a covalently cross-linked 3-dimensional polymeric network possessing intrinsic microporosity
Implementation Method 2
said intrinsic microporosity being defined as a continuous network of interconnected intermolecular voids, said voids arising from the structure of the first and second monomers
Implementation Method 3
The membrane has use in a variety of applications, including, but not limited to, gas separation, pervaporation, nanofiltration, desalination and water treatment, and particularly the nanofiltration of solutes dissolved in organic solvents
Implementation Method 4
In glassy polymers, gas permeability depends strongly on the amount and distribution of free volume in the polymer (i.e. the space not occupied by polymer molecules) and on chain mobility
Implementation Method 5
Polymers with the highest permeabilities have rigid, twisted macromolecular backbones that give rise to microvoids. When the free volume is very high, these microvoids are interconnected resulting in intrinsic microporosity
Data Source
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AI summary
The present invention relates to a composite membrane for gas separation and/or nanofiltration of a feed stream solution comprising a solvent and dissolved solutes and showing preferential rejection of the solutes. The composite membrane comprises a separating layer with intrinsic microporosity. The separating layer is suitably formed by interfacial polymerisation on a support membrane. Suitably, at least one of the monomers used in the interfacial polymerisation reaction should possess concavity, resulting in a network polymer with interconnected nanopores and a membrane with enhanced permeability. The support membrane may be optionally impregnated with a conditioning agent and may be optionally stable in organic solvents, particularly in polar aprotic solvents. The top layer of the composite membrane is optionally capped with functional groups to change the surface chemistry. The composite membrane may be cured in the oven to enhance rejection. Finally, the composite membrane may be treated with an activating solvent prior to nanofiltration.