Method for efficiently functionalizing PDMS (polydimethylsiloxane) film as well as product and application thereof

Abstract

The invention provides a method for efficiently functionalizing a PDMS (polydimethylsiloxane) film, which adopts an interfacial polymerization method to synchronously complete the preparation and functionalization processes of the PDMS film, and specifically comprises the following steps: S1, dissolving an amino-terminated PDMS prepolymer and polyether amine in hexane to prepare an oil phase solution; dissolving aldehyde and metal scandium sulfonate in deionized water to prepare a water phase solution; s2, soaking a polyacrylonitrile porous support body in a water phase solution, taking out the soaked support body, removing redundant liquid on the surface by using dust-free paper, putting the support body into an interfacial polymerization device, pouring an oil phase solution for reaction, taking out the support body after the reaction is finished, and putting the support body into a drying oven for drying, so as to obtain the functionalized modified PDMS membrane. Through experimental analysis, the affinity of PDMS to CO2 is improved by an ether bond group introduced into a PDMS matrix, and the CO2 / N2 selectivity is improved by 4 times compared with that before modification.

Description

Technical Field

[0001] The present invention belongs to the technical field of membrane materials, and particularly relates to a method for efficiently functionalizing a PDMS membrane, and products and uses thereof. Background Art

[0002] Membrane separation is gradually regarded as a technology that can replace traditional energy-consuming separation processes. It is worth noting that polymer membranes have been actually applied in industrial production, involving fields such as sewage treatment, seawater desalination, and biofuel production. However, the inherent trade-off between permeability and selectivity of polymer membranes limits their further improvement in separation performance. To overcome this limitation, researchers have been continuously working on developing new polymer materials and structures. Among polymer materials with high permeability, polysiloxane rubber polymers represented by polydimethylsiloxane (PDMS) not only have excellent chemical stability and feasibility, but are also widely used in gas separation, pervaporation, organic solvent nanofiltration, and other membrane separation processes.

[0003] Due to the large bond angle of the silicon-oxygen bond in PDMS, the chain segments have high mobility and free volume. These characteristics endow the material with excellent permeability, but at the same time, the separation accuracy is relatively low. Moreover, the inert groups in the PDMS chain segments are difficult to interact with most gas molecules, which also results in low separation selectivity. To make full use of the advantages of high permeability of PDMS and at the same time improve the separation selectivity, researchers usually use ultraviolet light or plasma irradiation to generate free radicals on the PDMS surface, and further graft chemical functional groups on the material surface. This method has high cost and complex operation, and it is difficult to scale up for application. Therefore, it is necessary to develop a new and efficient PDMS modification method. Summary of the Invention

[0004] Under this background, the present invention proposes a method for efficiently functionalizing a PDMS membrane, and products and uses thereof. The interfacial polymerization system consists of an aqueous phase and an oil phase solution. The aqueous phase solution contains a crosslinking agent and a catalyst. The PDMS prepolymer and a functionalized modified monomer containing an ether bond are dissolved in a hexane solution to form an oil phase solution. The diffusion reaction behavior of the monomer is controlled by the aqueous phase system, that is, the crosslinking agent and the catalyst in the aqueous phase system diffuse into the oil phase solution and quickly crosslink with the PDMS prepolymer and the functionalized modified monomer at the two-phase interface, realizing the preparation and functionalization modification of the PDMS membrane in one step. The nuclear magnetic resonance hydrogen spectrum technology was used to analyze the structure of the polymer obtained by interfacial crosslinking. The results showed that the amine group and the aldehyde group in the two-phase monomers underwent a Schiff base reaction, and the generated imine bond connected the PDMS prepolymer and the functionalized modified monomer, thus forming a three-dimensional crosslinked network. The prepared PDMS composite membrane was applied to the separation of the CO2 / N2 system, and the membrane preparation parameters were optimized to obtain the best separation performance.

[0005] To overcome at least one of the above disadvantages of the prior art, on the one hand, the present invention provides a method for efficiently functionalizing a PDMS membrane, which synchronously completes the preparation and functionalization of the PDMS membrane by interfacial polymerization. Specifically, S1 Prepare an oil-phase solution by dissolving an amine-terminated PDMS prepolymer and a polyetheramine in hexane; prepare an aqueous-phase solution by dissolving an aldehyde and a scandium metal sulfonate in deionized water, where the aldehyde serves as a cross-linking agent and the scandium metal sulfonate serves as a catalyst; S2 First, soak a polyacrylonitrile porous support in the aqueous-phase solution, take out the soaked support, remove the excess liquid on the surface with lint-free paper, place it in an interfacial polymerization device, pour in the oil-phase solution for reaction, take it out after the reaction is completed, and place it in an oven for drying to obtain a functionalized and modified PDMS membrane.

[0006] Relative to the uncertainty of the homogeneous cross-linking system, there are already various strategies that can be used to control the functionalization and modification process, such as applying surfactants and thickeners or controlling the temperature to regulate the monomer diffusion rate and cross-linking network; using the interfacial polymerization method can introduce various molecules with characteristic functional groups into the reaction system, greatly expanding the diversity and applicability of functionalization and modification. It is expected to introduce functional groups into the PDMS matrix to improve its performance in specific separation systems.

[0007] Further, in the step S1, the concentration of the amine-terminated PDMS prepolymer in the oil-phase solution is 0.1 wt%.

[0008] Further, the aldehyde is glyoxal, and the concentration of the glyoxal cross-linking agent in the aqueous-phase solution is 1 wt%.

[0009] Further, in the step S2, the soaking time of the aqueous-phase solution is 3 - 5 min.

[0010] Further, in the step S2, the interfacial polymerization device includes a support foot, a silicone sealing gasket, a liquid storage enclosure, and a clamp. When performing the interfacial polymerization reaction, place the polyacrylonitrile porous support soaked in the aqueous-phase solution between the sealing gasket and the support foot, then assemble the liquid storage enclosure, and use the clamp for sealing and reinforcement.

[0011] Further, in the step S1, the number-average molecular weight Mn of the polyetheramine is 230.

[0012] Further, in the step S1, the number-average molecular weight Mn of the amine-terminated PDMS is 1000.

[0013] The second aspect of the present invention provides a functionalized and modified PDMS membrane obtained by the above method for efficiently functionalizing a PDMS membrane.

[0014] The present invention also provides a use of the functionalized modified PDMS membrane, specifically for application in the separation of the CO 2 / N 2 system.

[0015] The beneficial effects of the present invention are as follows: Different from the prior art, interfacial polymerization (IP) is an efficient functionalization modification strategy based on a heterogeneous reaction system. The present invention constructs a heterogeneous reaction system suitable for the functionalization modification of PDMS based on the principle of interfacial polymerization, which has two advantages. On the one hand, the cross-linking of the PDMS material can be achieved at the interface of the two-phase solution; on the other hand, the polyetheramine introduced into the oil phase as a functionalization modification monomer can be polymerized with the PDMS prepolymer through a Schiff base reaction, thereby realizing the efficient functionalization modification of PDMS. Through experimental analysis, the introduction of ether bond groups into the PDMS matrix improves the affinity of PDMS for CO 2 ; the CO 2 / N 2 selectivity is increased by 4 times compared with that before modification; the best CO 2 / / N 2 separation performance is obtained by regulating the concentration of polyetheramine. The CO 2 permeability reaches 5102 GPU, and the CO 2 / N 2 selectivity reaches 39; in the pressure resistance test and long-term continuous test, the modified PDMS membrane can show the stability of performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be further described below with reference to the drawings and embodiments.

[0017] Figure 1 is a diagram of the interfacial polymerization component device; Figure 2 is a schematic diagram of the functionalization modification of PDMS; Figure 3 is the 1H NMR spectrum of the functionalized modified PDMS; Figure 4 is the reaction mechanism of the functionalization modification of PDMS; Figure 5 is the influence of polyetheramine on the separation performance of the PDMS membrane for the CO2 / N2 system; Figure 6 is the influence of the operating pressure on the performance of the modified PDMS membrane; Figure 7 is the separation performance of the PDMS membrane during long-term continuous operation. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] Before discussing the exemplary embodiments in more detail, it should be noted that some exemplary embodiments are described as processes or methods depicted as flowcharts. Although the flowcharts depict operations as sequential processes, many of the operations can be implemented in parallel, concurrently, or simultaneously. In addition, the order of the operations can be rearranged. The process can be terminated when its operations are completed, but it can also have additional steps not included in the figures. The process can correspond to a method, function, procedure, subroutine, subprogram, and so on.

[0019] It should be understood that although terms such as "first" and "second" may be used herein to describe various units, these units should not be limited by these terms. These terms are only used to distinguish one unit from another. For example, without departing from the scope of the exemplary embodiments, the first unit can be referred to as the second unit, and similarly, the second unit can be referred to as the first unit. The term "and / or" as used herein includes any and all combinations of one or more of the listed associated items.

[0020] The present invention provides a method for efficiently functionalizing a PDMS membrane: the process of preparing and functionalizing the PDMS membrane is synchronously completed by interfacial polymerization. Specifically, S1: Dissolve an amine-terminated PDMS prepolymer and a polyetheramine in hexane to prepare an oil-phase solution; dissolve an aldehyde and a metal scandium sulfonate in deionized water to prepare an aqueous-phase solution. S2: First, soak a polyacrylonitrile porous support in the aqueous-phase solution, take out the soaked support, remove the excess liquid on the surface with lint-free paper, put it into an interfacial polymerization device, pour in the oil-phase solution for reaction, take it out after the reaction is completed, and put it into an oven for drying to obtain a functionalized and modified PDMS membrane.

[0021] The functionalization of PDMS is completed by interfacial polymerization. The interfacial polymerization system consists of an aqueous-phase and an oil-phase solution. Glyoxal in the aqueous-phase solution serves as a crosslinking agent, and a metal scandium sulfonate serves as a catalyst; the PDMS prepolymer and a functionalized and modified monomer polyetheramine containing an ether bond are dissolved in a hexane solution to form an oil-phase solution. Using a self-made interfacial polymerization device, first pour the aqueous-phase solution onto the surface of the polyacrylonitrile support, pour out the solution after soaking for a period of time, and add the oil-phase solution for reaction after the surface is dry. After the reaction is completed, put it into an oven at 60 o C and dry to obtain the final PDMS membrane. Apply the prepared PDMS composite membrane to CO 2 / N 2Separation of the system. To optimize the separation performance, the monomer concentration was investigated in the present invention and the optimal monomer concentration was obtained. Further, the pressure resistance and long-term operation stability of the PDMS composite membrane were comprehensively investigated. The present invention provides a design idea and method for preparing a high-performance PDMS composite membrane and functionalization modification.

[0022] The materials and their sources used in the following examples are as follows: Amino-terminated PDMS (Mn = 1000), glyoxal, polyetheramine (PEA, Mn = 230), n-hexane, deionized water. All purchased chemical reagents can be used directly without further purification. The polyacrylonitrile (PAN) support was provided by Beijing Haicheng Shijie Filtration Equipment Company with a pore size of 25 nm.

[0023] Example 1 As Figure 1 shown, the interfacial polymerization device includes a support foot, a silica gel sealing gasket, a liquid storage enclosure, and a clamp. When performing the interfacial reaction, the polyacrylonitrile porous support soaked in the aqueous solution is placed between the sealing gasket and the support foot, and then the liquid storage enclosure is assembled, and the clamp is used for sealing and reinforcement. Referring to Figure 2 the schematic diagram of the PDMS functionalization modification shown, the specific operation is as follows: S1 Prepare an oil-phase solution by dissolving the amino-terminated PDMS prepolymer and polyetheramine in hexane, where the concentration of amino-terminated PDMS is 0.1 wt%; dissolve the cross-linking agent glyoxal and the catalyst metal scandium sulfonate in deionized water to prepare an aqueous solution, where the concentration of glyoxal is 1 wt% and the concentration of metal scandium sulfonate is 0.5 wt%; S2 First, soak the polyacrylonitrile porous support in the aqueous solution for 3 min, take out the soaked support, remove the excess liquid on the surface with lint-free paper, and put it into the interfacial polymerization device. Specifically, the polyacrylonitrile porous support soaked in the aqueous solution is placed between the sealing gasket and the support foot, and then the liquid storage enclosure is assembled, and the clamp is used for sealing and reinforcement. Pour in the oil-phase solution and react for 3 min. After the reaction is completed, take it out and put it into an oven at 60 o °C and dry for 6 h to obtain the functionalized modified PDMS membrane.

[0024] Since the PDMS prepolymer has strong hydrophobicity and cannot be dissolved in aqueous solutions; while glyoxal can be partially dissolved in non-polar solvents such as hexane, the diffusion behavior of the monomers is mainly composed of the diffusion of glyoxal from the aqueous phase to the oil phase and the diffusion of polyetheramine from the oil phase to the aqueous phase. Moreover, the metal salt catalyst can also be bound to glyoxal by hydration and co-diffused into the oil phase to promote the reaction. Metal scandium sulfonate as a catalyst can significantly increase the reaction rate of the Schiff base reaction, ensuring that the polymerization reaction and the functionalization modification process can proceed rapidly at the interface.

[0025] The functionalized PDMS membrane prepared by the method provided by the present invention is tested and analyzed below.

[0026] Gas separation experiment The separation performance of the PDMS membrane and the functionalized PDMS membrane for the CO 2 / N 2 (15 vol% / 85 vol%) mixed gas is tested. A gas permeation instrument is used for the test, the transmembrane pressure difference is 0.1 MPa, and each component permeates depending on its own partial pressure during the permeation process. When investigating the influence of the inlet pressure on the membrane performance, the inlet pressure is increased from 0.1 MPa to 1.2 MPa. Finally, the composition of the permeate is analyzed by a gas chromatograph (Agilent, 7820A, USA).

[0027] After the system reaches a stable state, the gas permeation coefficient can be calculated by the following formula: (1) In the formula P is the gas permeability (1 GPU = 10 −6 cm 3 (STP) cm −2 s −1 cmHg), Δp is the transmembrane pressure difference (cmHg), A represents the effective membrane area (cm 2 ), T is the test temperature ( o °C), V m is the fixed volume on the downstream side (cm 3 ), dp / dt is the change rate of the pressure on the permeate side with time.

[0028] The separation factor of the binary mixed gas is calculated by the following formula: (2) In the formula, x , y —Volume fractions of each component on the feed side and the permeate side ( y A is the CO concentration on the permeate side 2 , y B is the N concentration on the permeate side 2 , x A is the CO concentration on the feed side 2 , x B is the N concentration on the feed side 2 ).

[0029] 2.2 Characterization of polymer structure using H NMR spectroscopy The oil phase and water phase solutions prepared above were directly mixed, and after reacting for 30 min, the polymer synthesized at the interface of the two phases was taken out and dried. Deuterated chloroform was used as a solvent to prepare the samples required for NMR characterization, and the characterization results were analyzed using MestReNova software.

[0030] Molecular structure of PDMS after functionalization modification like Figure 3 As shown, the molecular structure of the modified PDMS was analyzed using H-NMR spectroscopy. The results showed that both the PDMS-terminated amine groups and the polyetheramine-terminated amine groups reacted with the aldehyde groups in glyoxal to form imine bonds. It also proved that the ether bonds were successfully introduced into the PDMS matrix. The molar content of ether bonds was calculated to be 23% by classifying and integrating the hydrogen atoms in the PEA molecule. Based on the conclusions of H-NMR spectroscopy, the reaction mechanism between PDMS prepolymer, polyetheramine and glyoxal can be obtained, as shown in Figure 2. Figure 4 shown.

[0031] Optimization of polyetheramine concentration To obtain the best CO 2 / N 2 Separation performance requires optimization of the concentration of polyetheramine in the aqueous phase. Figure 5 As shown in Figure 2, with the increase of polyetheramine concentration, the modified PDMS membrane has a 2 The permeability of CO will gradually decrease, while 2 / N 2 The selectivity of CO increases and then decreases. When the concentration of polyetheramine reaches 0.5 wt%, the selectivity reaches a maximum of 43.5. 2 The permeability is 5461 GPU. When the concentration of polyetheramine exceeds 0.5 wt%, both the selectivity and the permeability will decrease significantly, so the optimal polyetheramine concentration is 0.5 wt%. The reason for the above phenomenon is that the polyetheramine molecule contains both ether bonds and methyl groups, so polyetheramine has a certain solubility in water and hexane, which causes the polyetheramine to diffuse from the oil phase to the water phase. Excessive concentration will enhance the concentration gradient of polyetheramine between the oil phase and the water phase, and promote the diffusion of polyetheramine molecules from the oil phase into the water phase. After excessive polyetheramine diffuses into the water phase, it reacts and polymerizes with glyoxal, thereby blocking the pores of the support and causing pore permeation, reducing the permeability of the gas. At the same time, the blockage of the support pores will also hinder the diffusion of acetaldehyde molecules into the oil phase, resulting in a decrease in the degree of cross-linking of the PDMS prepolymer and defects, so CO 2 / N 2 The selectivity will gradually decrease.

[0032] Operational stability testing and evaluation We comprehensively investigated the performance stability of the modified PDMS membrane by increasing the intake pressure and prolonging the operation time. As Figure 6 shown, with the increase of the intake pressure, the unmodified PDMS membrane showed excellent stability in both CO 2 permeability and selectivity. However, the CO 2 permeability of the modified PDMS membrane decreased slightly with the increase of pressure, from 4870 GPU to 4023 GPU. On the one hand, this is because high-pressure CO 2 caused plasticization of the polymer structure. On the other hand, it is because the rigid chain segments in the modified PDMS polymer network increased, enhancing the inhibitory effect of plasticization on performance. In addition, as Figure 7 shown, under 200 h of continuous operation, the CO 2 permeability and CO 2 / N 2 selectivity of the modified PDMS membrane could remain stable, with an average CO 2 permeability of 5102 GPU and an average CO 2 / N 2 selectivity of 39.

[0033] The above are only embodiments of the present invention. Specific structures and common knowledge such as characteristics well known in the art are not described in detail here. Those of ordinary skill in the art know all the common general technical knowledge in the technical field to which the invention pertains before the application date or the priority date, can know all the prior art in this field, and have the ability to apply conventional experimental means before this date. Those of ordinary skill in the art can, under the inspiration given in this application, combine their own abilities to improve and implement this solution. Some typical well-known structures or well-known methods should not become obstacles for those of ordinary skill in the art to implement this application. It should be noted that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can still be made, and these should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicality of the patent. The protection scope required by this application should be based on the content of its claims, and the specific implementation manners described in the specification can be used to interpret the content of the claims.

Claims

1. A method for efficiently functionalizing a PDMS membrane, characterized in that: The interfacial polymerization method is used to simultaneously complete the process of PDMS membrane preparation and functionalization, specifically, S1: dissolving an amine-terminated PDMS prepolymer and a polyetheramine in hexane to prepare an oil phase solution; dissolving an aldehyde and a metal scandium sulfonate in deionized water to prepare an aqueous phase solution; S2 first soaks the polyacrylonitrile porous support in an aqueous solution, takes out the soaked support, removes excess liquid on the surface with dust-free paper, puts it into an interfacial polymerization device, pours in an oil phase solution for reaction, takes it out after the reaction is completed, puts it in an oven for drying, and obtains a functionalized modified PDMS membrane.

2. The method for efficiently functionalizing a PDMS membrane according to claim 1, wherein: In the step S1, the concentration of the amine-terminated PDMS prepolymer in the oil phase solution is 0.1 wt%.

3. The method for efficiently functionalizing a PDMS membrane according to claim 1, wherein: In the step S1, the aldehyde is glyoxal, and the concentration of the glyoxal crosslinking agent in the aqueous solution is 1 wt%.

4. The method for preparing a method for efficiently functionalizing a PDMS membrane according to claim 1, characterized in that: In step S2, the immersion time of the aqueous solution is 3 to 5 minutes.

5. The method for preparing a method for efficiently functionalizing a PDMS membrane according to claim 1, characterized in that: In step S2, the interfacial polymerization device includes a support foot, a silicone sealing gasket, a liquid storage enclosure and a clamp. When the interfacial polymerization reaction is carried out, the polyacrylonitrile porous support body soaked in an aqueous solution is placed between the sealing gasket and the support foot, and then the liquid storage enclosure is assembled and sealed and reinforced with a clamp.

6. The method for preparing a method for efficiently functionalizing a PDMS membrane according to claim 1, characterized in that: In the step S1, the number average molecular weight Mn of the polyetheramine is 230.

7. The method for preparing a method for efficiently functionalizing a PDMS membrane according to claim 1, characterized in that: In the step S1, the number average molecular weight Mn of the amino-terminated PDMS is 1000.

8. A functionalized modified PDMS membrane, characterized in that: Prepared by the method according to any one of claims 1 to 7.

9. Use of the functionalized modified PDMS membrane according to claim 8, characterized in that: Applied to the separation of CO2 / N2 system.

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