Isorefractive Liquid-Assisted Cross-Linking of Polymeric Membranes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for cross-linking polymeric membranes, such as thermal and chemical cross-linking, result in loss of isoporous structure and poor thermal and chemical stability, while irradiation-based cross-linking is limited to the surface, leading to inadequate stability.
Innovation Solution
A method involving immersion in an isorefractive non-solvent liquid followed by UV irradiation to cross-link polymeric membranes, ensuring complete thickness penetration and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermal cross-linking is used, then cross-linking stability is improved, but the isoporous structure is lost
Solution Approach 1:
The patent introduces an intermediary substance (liquid medium with specific refractive index) that enables UV radiation to penetrate through the membrane thickness effectively. This mediator allows cross-linking to occur throughout the bulk without requiring high temperatures that would collapse the isoporous structure, thus resolving the contradiction between achieving stable cross-linking and preserving the membrane's porous morphology.
2Reliability
If chemical cross-linking is used, then cross-linking stability is improved, but the isoporous structure is lost
Solution Approach 1:
The patent replaces chemical cross-linking methods with a physical cross-linking method using UV irradiation. This substitution eliminates the need for chemical reagents that would dissolve or collapse the isoporous structure, while still achieving stable cross-linking through photochemical reactions initiated by UV light penetration in the liquid medium.
3Shape
If UV irradiation cross-linking is used, then isoporous structure is preserved, but cross-linking is limited to surface only
Solution Approach 1:
The patent uses a liquid medium with matched refractive index as an intermediary to enhance UV radiation penetration depth into the membrane. By eliminating refraction and reflection losses at interfaces, the UV light can penetrate through the entire membrane thickness, enabling uniform cross-linking throughout the bulk while preserving the isoporous structure.
Solution Approach 2:
The patent changes the optical parameters of the cross-linking environment by selecting a liquid medium with a refractive index matched to the membrane material. This parameter change optimizes light transmission and penetration depth, allowing UV irradiation to effectively cross-link the entire membrane thickness rather than just the surface layer.
4Ease of manufacture
If conventional UV irradiation is used, then cross-linking is achieved, but thermal and chemical stability is insufficient
Solution Approach 1:
The patent introduces a liquid medium as an intermediary that enables complete and uniform cross-linking throughout the membrane bulk. This results in significantly improved thermal and chemical stability compared to conventional surface-only cross-linking, while maintaining the simplicity of the UV irradiation process.
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 produces membranes with retained cross-sectional structure under harsh conditions, including high temperatures and chemical treatments, enhancing thermal and chemical stability.
Implementation Method 1
immersing the cross-linkable membrane into a non-solvent liquid
Implementation Method 2
subjecting the cross-linkable polymeric membrane to radiation to cause cross-linking of the polymeric membrane
Data Source
Figure 1A~2
Figure 3A~6C
Figure 7A~7C
AI summary
The present invention relates to a method for cross-linking of polymeric membranes and to a membrane material made with said method. The method is also suitable for cross-linking of other polymeric materials such as thin films and porous films. Cross-linking of the membranes is essential for increasing the stability thereof, and cross-linking is generally achieved thermally, by chemical reaction, or by irradiation, such as UV irradiation. Thermal cross-linking, however, requires temperatures of more than 100°C, leading to a loss of the membranes' isoporous structure. Chemical cross-linking requires the use of organic solvents, wherein the membranes are at least partially soluble, also leading to a loss of the membranes' isoporous structure. Cross-linking by irradiation causes a cross-linking only at the first few nanometers of the membrane surface but not through the complete cross-section of the membrane, leading to poor thermal and chemical stability. The present invention provides membranes that combine good selectivity and permeability, and also possess excellent thermal and chemical stability. In an embodiment the present invention relates to a method for cross-linking of polymeric membranes comprising the steps of providing a cross-linkable polymeric material, immersing the cross-linkable membrane into a non-solvent liquid, and subjecting the cross-linkable polymeric membrane immersed into the non-solvent liquid to radiation to cause cross-linking of the polymeric material, wherein the non-solvent liquid is isorefractive with the cross-linkable polymeric material. The cross-linking method presently proposed is not only limited to block copolymer membranes; it can be used as method for cross-linking by irradiation any cross-linkable polymeric material. Therefore, the cross-linking method can be easily transferred to film materials, foams and coatings, and to any kind of porous, isoporous and dense membrane system, all with expectation of achieving cross-linking over the entire thickness (cross-section).