PDMS-b-PEO Composite Membrane for CO2/N2 Separation
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Solution Overview
Problem
The hydrophobicity of PDMS intermediate layers leads to low interfacial adhesion of ultra-thin PE-b-PA composite membranes, and the SiOx layer formed during plasma treatment inhibits gas permeation rates in carbon dioxide/nitrogen separation.
Innovation Solution
Incorporating an amphoteric copolymer polydimethylsiloxane block polyethylene oxide (PDMS-b-PEO) into the PDMS intermediate layer, which is treated with air plasma to enhance hydrophilicity, improving interfacial compatibility with the PE-b-PA selective layer, and optimizing preparation conditions such as plasma treatment duration and copolymer amount.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If air plasma treatment is used to enhance hydrophilicity of PDMS intermediate layer, then interfacial adhesion with PE-b-PA selective layer is improved, but SiOx layer formation inhibits gas permeation rate
Solution Approach 1:
The patent optimizes plasma treatment parameters (power, time, gas flow) to achieve the right balance between hydrophilicity enhancement and SiOx layer formation. By controlling treatment duration and power intensity, sufficient adhesion is achieved while minimizing the formation of dense SiOx layers that would block gas transport
Solution Approach 2:
The patent applies plasma treatment to only the surface region of the PDMS intermediate layer rather than penetrating deeply. This partial action modifies the surface chemistry for better adhesion without creating extensive SiOx layers throughout the bulk that would inhibit gas permeation
2Productivity
If ultra-fine thickness of selective layer is used to improve gas permeation rate, then CO2 permeation rate increases, but interfacial defects due to poor adhesion decrease selectivity
Solution Approach 1:
The patent performs plasma treatment on the PDMS intermediate layer before depositing the PE-b-PA selective layer. This preliminary action creates a hydrophilic surface that ensures strong interfacial adhesion, preventing defects and delamination in the subsequent ultra-thin selective layer, thereby maintaining both high permeation rate and selectivity
3Strength
If hydrophilic modification of PDMS surface is performed to improve interfacial binding force, then adhesion of Pebax selective layer is enhanced, but treatment process complexity and equipment investment increase
Solution Approach 1:
The patent employs air plasma treatment, which uses ambient air as the plasma gas source, eliminating the need for expensive specialized gas supplies and complex plasma generation equipment. This low-cost, simple approach achieves effective hydrophilic modification without significant equipment investment
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 approach results in an ultra-thin PE-b-PA/PDMS composite membrane with enhanced carbon dioxide permeation rates and selectivity, achieving a CO2 permeation rate of 2142 GPU and CO2/N2 selectivity of 36, while simplifying the plasma pretreatment process and maintaining membrane integrity.
Implementation Method 1
The current strategies have been largely based on the application of high-energy irradiation (such as plasma and ultraviolet (UV)) to break strong Si—C and Si—O—Si bonds and produce a large number of hydroxyl groups.
Implementation Method 2
A separation process of a polymer membrane follows a solution-diffusion mechanism. An affinity of a membrane material for carbon dioxide and a free volume of mass transport dominate the carbon dioxide/nitrogen dioxide separation performance.
Implementation Method 3
PDMS with a soft backbone chain and a high free volume fraction shows obvious advantages in a permeation rate.
Data Source
AI summary
The present disclosure relates to a polyether block polyamide/polydimethylsiloxane (PDMS) composite membrane for gas separation, and a preparation method and use thereof, and belongs to the technical field of membrane separation. In the present disclosure, an amphoteric copolymer PDMS-polyethylene oxide (PEO) (PDMS-b-PEO) is introduced into an intermediate layer to adjust the interfacial binding performance, thereby promoting preparation of an ultra-thin polyether block polyamide composite membrane. Studies have shown that the surface enrichment of PEO segments not only inhibits a dense SiOx layer formed due to a plasma treatment of a PDMS intermediate layer, but also provides additional hydrophilic sites and interfacial compatibility for the subsequent selective layer. The use of PDMS-b-PEO in an intermediate layer allows the successful preparation of a selective layer with a thickness of about 50 nm.