Solvent-Resistant Polyimide Nanofiltration Membrane via Coordination Cross-Linking

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Solution Overview

Problem

Current cross-linking methods for polyimide nanofiltration membranes reduce membrane flux and affect separation efficiency, necessitating a method that improves swelling resistance and physical stability without compromising flux.

Innovation Solution

A solvent-resistant polymeric nanofiltration membrane is prepared through a method involving cyclization imidization of diamine and dianhydride monomers, followed by phase inversion and coordination cross-linking with metal ions in a polar organic solvent, maintaining high flux and stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If cross-linking methods are used to improve swelling resistance and physical stability of polyimide nanofiltration membranes, then solvent resistance and mechanical strength are improved, but membrane flux and separation efficiency are reduced

Engineering Contradiction:

Improvesolvent resistanceVSAvoidmembrane flux

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent changes the cross-linking parameters by using coordination cross-linking with metal ions instead of conventional chemical cross-linking agents. This parameter change allows the formation of a three-dimensional network structure that improves solvent resistance while maintaining membrane flux and separation efficiency, as the coordination bonds provide sufficient cross-linking density without excessive densification of the membrane structure.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite structure by incorporating metal ions into the polyimide membrane matrix to form a coordination cross-linked network. This composite approach combines the advantages of polyimide (good mechanical properties and flux) with metal ion cross-linking (improved solvent resistance and stability), achieving both reliability improvement and flux maintenance.

Inventive Principle:

Principle #40Composite materials

2Stability of the object's composition

If cross-linking methods are used to improve physical and chemical stability of polyimide nanofiltration membranes, then swelling resistance is improved, but membrane flux is significantly reduced

Engineering Contradiction:

Improvephysical and chemical stabilityVSAvoidmembrane flux

Core Design Contradiction:

Stability of the object's compositionVSProductivity

Solution Approach 1:

The patent replaces conventional chemical cross-linking mechanisms with coordination chemistry mechanisms. Metal ions coordinate with functional groups in the polyimide matrix to form a three-dimensional network, providing physical and chemical stability without the excessive structural densification caused by traditional cross-linking agents, thus maintaining membrane flux.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the cross-linking mechanism parameter from covalent bonding to coordination bonding. This parameter change results in a more flexible cross-linked structure that provides stability while maintaining pore structure and flux, as coordination bonds allow for greater structural flexibility compared to rigid covalent cross-links.

Inventive Principle:

Principle #35Parameter changes

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 resulting membrane exhibits enhanced solvent resistance, mechanical strength, and compaction resistance, maintaining high flux and separation efficiency in polar organic solvents.

Implementation Method 1

subjecting a diamine monomer and a dianhydride monomer to cyclization imidization under the action of a catalyst in a first polar organic solvent at 160 to 230° C., to form a polyimide

Methodology Applied

Scientific EffectCyclization imidization: Chemical Bonding

Implementation Method 2

dissolving the polyimide in a second polar organic solvent, to form a membrane-forming solution

Methodology Applied

Scientific EffectSolvation: Solvation

Implementation Method 3

treating the intermediate membrane with an organic solution of a metal salt, so that the metal ion is coordinated and cross-linked with the carboxyl group in the polyimide

Methodology Applied

Scientific EffectCoordination cross-linking: Chemical Bonding

Data Source

PatentUS12263444B2Solvent-resistant polymeric nanofiltration membrane, preparation method and use thereof

Publication Date: 2025.04.01 SUZHOU UNIV

AI summary

The invention a solvent-resistant polymeric nanofiltration membrane and preparation method thereof. The method includes subjecting a diamine monomer and a dianhydride monomer to cyclization imidization in a first polar organic solvent at 160 to 230° C., to form a polyimide, wherein the diamine monomer includes a diamine monomer with a carboxyl group and a diamine monomer without a carboxyl group; dissolving the polyimide in a second polar organic solvent, to form a membrane-forming solution; performing phase inversion to obtain an intermediate membrane; treating the intermediate membrane with an organic solution of a metal salt, so that the metal ion is coordinated and cross-linked with the carboxyl group in the polyimide, to obtain a solvent-resistant polymeric nanofiltration membrane, wherein the metal salt is a divalent and/or a multi-valent metal salt. The invention also discloses use of the solvent-resistant polymeric nanofiltration membrane in the separation and/or purification of a compound.