CN107051215B - Amphiphilic polymer brush carbon nanotube/PVDF nanofiltration membrane and preparation method thereof - Google Patents

Amphiphilic polymer brush carbon nanotube/PVDF nanofiltration membrane and preparation method thereof Download PDF

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CN107051215B
CN107051215B CN201610894414.2A CN201610894414A CN107051215B CN 107051215 B CN107051215 B CN 107051215B CN 201610894414 A CN201610894414 A CN 201610894414A CN 107051215 B CN107051215 B CN 107051215B
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马文中
潘霁
李玉雪
赵宇辰
夏艳平
龚方红
刘春林
陶国良
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Changzhou University
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Abstract

The invention belongs to the field of nanofiltration membrane preparation, and particularly relates to a preparation method and a method for synthesizing an amphiphilic polymer brush carbon nanotube/PVDF nanofiltration membrane by click chemistry. Firstly, synthesizing a novel macroinitiator capable of carrying out click chemical reaction and initiating azide reaction, grafting the clickable macroinitiator to the surface of a single-walled carbon nanotube through the click chemical reaction, and selecting a proper hydrophilic modifier monomer to prepare the amphiphilic polymer brush carbon nanotube. Blending, extruding and casting the prepared amphiphilic polymer brush carbon nanotube chemically synthesized by click and PVDF according to a certain proportion, and adjusting the double-drawing process, controlling the double-drawing temperature and speed and adjusting the aperture size of the microporous membrane; and coating a layer of ultrathin thin layer with a nano-scale aperture on the prepared microporous membrane in a compounding way to prepare the amphiphilic polymer brush carbon nanotube/PVDF nanofiltration membrane.

Description

Amphiphilic polymer brush carbon nanotube/PVDF nanofiltration membrane and preparation method thereof
Technical Field
The invention belongs to the field of nanofiltration membrane preparation, and particularly relates to a preparation method and a method for synthesizing an amphiphilic polymer brush carbon nanotube/PVDF nanofiltration membrane by click chemistry.
Background
In the 60 s of the 20 th century, the membrane separation technology is rapidly developed as a new separation technology, and has the advantages of high efficiency, energy conservation, environmental protection and the like, so that the membrane separation technology is widely applied to the fields of food, biology and the like. According to the size of the molecular weight cut-off, the membrane can be divided into a reverse osmosis membrane, a nanofiltration membrane, an ultrafiltration membrane, a microfiltration membrane and the like. The nanofiltration membrane is used as a separation membrane with a nanoscale charge as a pore structure, the pore diameter is about 1-3 nm, the cut-off molecular weight is 200-1000, the operation pressure is low, the water outlet efficiency is high, the discharge of concentrated water is less, and the like, so that the nanofiltration membrane has incomparable advantages compared with other types of membranes in the field of water treatment, and gradually replaces the traditional water treatment membrane in the current market.
How to develop a nanofiltration membrane with good performance and stability is very important in material selection. The material for preparing the nanofiltration membrane has the following characteristics: (1) the flux and the removal rate are higher; (2) good chemical stability, hydrolysis resistance and chemical cleaning resistance; (3) good pollution resistance. Polyvinylidene fluoride (PVDF) has a unique structure, so that the PVDF has the advantages of very stable chemical property, strong radiation resistance, high thermal stability and the like, and is an ideal membrane substrate for a nanofiltration membrane. The Carbon Nano Tube (CNT) is a seamless hollow tube rolled by a graphite sheet with a laminated structure, the diameter of a single-walled carbon tube is 0.4-2 nm, the strength and the toughness of the single-walled carbon tube are extremely high, the elastic modulus exceeds 1Tpa, and the ultimate specific surface area can reach 2630m2The adsorption capacity of the activated carbon per gram of fluorine ions in the aqueous solution can reach more than 4.5 mg/g. Therefore, the carbon nano tube and PVDF are blended and modified to obtain the ultrafiltration membrane, such as Chinese patent CN105107392A<Multi-walled carbon nanotube surface embedded modified polyvinylidene fluoride and preparation method thereof>In the method, the multi-walled carbon nano-tube is subjected to silane treatment, so that the affinity of the multi-walled carbon nano-tube on the surface of the PVDF membrane is improved, and the interception effect of the multi-walled carbon nano-tube on heavy metal ions is improved. The invention mainly adopts the preparation and the method for synthesizing the amphiphilic polymer brush carbon nano tube/PVDF nano-filtration membrane by click chemistry, and the nano-filtration membrane prepared by the method realizes the effective control of carbon nanoThe dispersibility of the rice tube in PVDF realizes that the carbon tube is not sealed, the types of amphiphilic polymers on the tube wall are adjusted, the quantity of the amphiphilic polymers is controllable, the structure and the performance of the amphiphilic polymers brushed with the carbon nanotube/PVDF nanofiltration membrane are effectively adjusted, and ionic salts with small relative molecular weight, nano-grade particle size and other low-molecular-weight substances such as saccharides, inorganic salt ions, metal ions and the like are intercepted.
Disclosure of Invention
The invention aims to provide an amphiphilic polymer brush carbon nanotube/PVDF nanofiltration membrane synthesized by click chemistry and a preparation method thereof.
The invention is realized by the following technical scheme: the preparation method of the click chemistry synthesis amphiphilic polymer brush carbon nanotube/PVDF nanofiltration membrane comprises the following steps:
(1) click chemistry synthesis of amphiphilic polymer brush carbon nanotubes: the functionalization of the carbon nano tube is realized, the hydrophilic polymer is effectively and selectively grafted on the surface of the carbon nano tube, and the performance of the PVDF nano-filtration membrane is improved. Firstly, synthesizing a novel macroinitiator capable of carrying out click chemical reaction and initiating azide reaction, grafting the clickable macroinitiator to the surface of a single-walled carbon nanotube through the click chemical reaction, and selecting a proper hydrophilic modifier monomer to prepare the amphiphilic polymer brush carbon nanotube.
(2) The invention adopts a composite method to prepare the amphiphilic polymer brush carbon nanotube/PVDF nano-filtration membrane:
a. blending, extruding and casting the prepared amphiphilic polymer brush carbon nanotube chemically synthesized by click and PVDF according to a certain proportion, and adjusting the double-drawing process, controlling the double-drawing temperature and speed and adjusting the aperture size of the microporous membrane;
b. and coating a layer of ultrathin thin layer with a nano-scale aperture on the prepared microporous membrane in a compounding way to prepare the amphiphilic polymer brush carbon nanotube/PVDF nanofiltration membrane.
The main preparation process of the amphiphilic polymer brush carbon nanotube disclosed by the invention comprises the following steps:
(1) nitrizing the surface of the carbon nano tube: adding NaN3Mechanically stirring with acetonitrile at 0 deg.C until the solution is milky white, slowly adding ICl dropwise, reacting at 0 deg.C for 20-30 min, and filtering to obtain IN3A solution; dispersing single-arm carbon nanotube IN IN3And (3) uniformly stirring the solution at room temperature, filtering by adopting a PTFE microporous membrane, washing the obtained solid by using deionized water and methanol, and drying in vacuum to obtain the azide single-arm carbon nano tube.
Further, NaN3The mass volume ratio of the acetonitrile to the water is as follows: 1-2 g: 100-; ICl and NaN3The mass ratio of (A) to (B) is as follows: 1-2: 2-4; single-arm carbon nanotubes and IN3The mass-volume ratio of the solution is as follows: 25-50 mg: 10-15 ml.
Furthermore, the pore diameter of the PTFE microporous membrane is 0.45-0.5 um.
Further, the stirring time at room temperature is 30-50 min.
(2) Preparation of amphiphilic Polymer:
(a) mechanically stirring the dodecanethiol, the acetone and the tetrabutylammonium bromide uniformly under the condition of nitrogen; slowly dropwise adding NaOH solution 1, continuously stirring for 15-20 min, and slowly dropwise adding CS2And uniformly stirring the mixed solution with acetone, dropwise adding chloroform and NaOH solution 2, mechanically stirring at room temperature for reaction for 11-13h, dropwise adding HCl and deionized water after the reaction is finished, continuing the reaction for 30-50 min, and carrying out reduced pressure distillation to obtain a product 1.
Further, the molar volume ratio of the dodecanethiol, the acetone and the tetrabutylammonium bromide is 100-200 mmol: 50-100 ml: 4-5 mmol.
Further, the molar mass ratio of the dodecanethiol to the NaOH solution 1 to the NaOH solution 2 is as follows: 20 mmol-40 mmol: 1.5-2.0 g: 8-10 g; the concentration of the NaOH solution 1 and the NaOH solution 2 is 50 wt% -60 wt%.
Further, the volume ratio of acetone, the mixed solution, chloroform, HCl and deionized water is as follows: 10-20: 50-90: 30-50: 5-10: 30-50; CS in the Mixed solution2The volume ratio of the acetone is as follows: 2-4: 3-5; the concentration of HCl is 6-10 mol/L.
(b) Taking the product 1 prepared in the above, 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (EDC-HCl), 4-Dimethylaminopyridine (DMAP) and dried CH2Cl2Stirring uniformly at 0 ℃, slowly dropwise adding propargyl alcohol, reacting for 15-20 min, reacting for 23-25h at room temperature, and washing the product to be neutral by deionized water to obtain a product 2.
Further, the product 1, 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (EDC-HCl), 4-Dimethylaminopyridine (DMAP) and CH2Cl2The molar volume ratio of (1-2 mmol): 2-3 mmol: 2-3 mmol: 4-8ml, CH2Cl2The volume mol ratio of the compound to the propiolic alcohol is 4-8 ml: 2-3 mmol.
(c) And (3) selecting a monomer, a product 2, an initiator and anisole, reacting at 70-80 ℃ for 40-60 min under the condition of nitrogen, and obtaining the hydrophilic polymer.
Further: the molar volume ratio of the monomer, the product 2, the initiator and the anisole is 100-200 mmol: 0.5-1 mmol: 0.05-0.1 mmol: 80-100 ml.
Wherein the monomers in step (c) are essentially: fluorine-containing acrylates such as dodecafluoroheptyl methacrylate, hexafluorobutyl acrylate, hexafluorobutyl methacrylate and the like; methyl methacrylate, 2-propargyl methacrylate, acrylic acid, n-butyl methacrylate, polyethylene glycol, cellulose acetate, cellulose triacetate, polyethylene glycol methacrylate, hydroxyethyl methacrylate, and the like.
The initiator is a compound which is easily decomposed into free radicals (namely primary free radicals) by heating, namely azobisisobutyronitrile, azobisisoheptonitrile, benzoyl peroxide, lauroyl peroxide, cumene hydroperoxide, tert-butyl peroxybenzoate, tert-butyl peroxypivalate, diisopropyl peroxydicarbonate and dicyclohexyl peroxydicarbonate.
(3) Click chemistry synthesis of an amphiphilic polymer brush carbon nanotube material: and (2) dissolving the mixture of the azide single-arm carbon nano tube prepared in the step (1) and the hydrophilic polymer prepared in the step (2) in a dimethylformamide solution, reacting for 24 hours under the condition of nitrogen after ultrasonic dispersion, placing in the air for continuously reacting for 30 minutes, and centrifuging to obtain the amphiphilic polymer brush carbon nano tube material.
Further, the mass ratio of the azide single-arm carbon nanotube to the hydrophilic polymer is 1-10: 100-150; the mass-volume ratio of the hydrophilic polymer to the dimethylformamide is 2-3 g: 2-4 ml.
The preparation method of the amphiphilic polymer brush carbon nanotube/PVDF nanofiltration membrane by click chemistry synthesis comprises the following specific steps:
(1) blending and extruding the prepared amphiphilic polymer brush carbon nanotube material and PVDF, and granulating at the processing temperature of 200-220 ℃; casting the manufactured particles by a casting machine to form a film, performing biaxial tension to form a film, performing longitudinal and transverse 1.5-2 times of tension, and controlling the aperture size of the microporous film; and (3) carrying out heat setting at the temperature of 140-150 ℃ to fix the oriented film structure, and cooling to form the film.
Wherein the PVDF is selected from the following grades: 3208. 740, 1010, 461, 710, CF 10BK, 21216, etc., wherein the amphiphilic polymer brush carbon nanotube material accounts for 5-10 parts, and the PVDF accounts for 90-95 parts.
(2) And (2) coating a layer of ultrathin thin layer with a nano-scale aperture on the prepared microporous membrane in a compounding way, preparing the prepared amphiphilic polymer brush carbon nanotube material and PVDF blend particles into a solution with a certain concentration, and coating the solution on the prepared microporous membrane to ensure that the microporous membrane is deeply inserted into micropores of the base membrane to form a surface layer with a macromolecular reticular structure. And preparing the amphiphilic polymer brush carbon nanotube/PVDF nano-filtration membrane.
The solvent mainly comprises NMP, DMAc, TEF, DMSO, MEK, THF, DMC and the like, and the concentration of blend particles (a blend of an amphiphilic polymer brush carbon nanotube material and PVDF, wherein the amphiphilic polymer brush carbon nanotube material accounts for 5-10 parts, and the PVDF accounts for 90-95 parts) is 1-15 g/mol.
Compared with the prior art, the click chemistry synthesized amphiphilic polymer brush carbon nanotube/PVDF nanofiltration membrane provided by the invention has the following advantages:
(1) the functionalization of the carbon nano tube is realized, the hydrophilic polymer is effectively and selectively grafted on the surface of the carbon nano tube, and the performance of the PVDF nano-filtration membrane is improved.
(2) The preparation method comprises the steps of preparing the amphiphilic polymer brush carbon nanotube/PVDF nanofiltration membrane by adopting a composite coating process, carrying out blending extrusion casting, and adjusting the double-drawing process, controlling the double-drawing temperature and speed and adjusting the aperture size of the microporous membrane. The controllable adjustment of different processing requirements on different occasions is realized; and coating an ultrathin layer with a nanometer aperture on the surface of the microporous base film to enable the ultrathin layer to penetrate into micropores of the base film to form a surface layer with a macromolecular reticular structure.
(3) The prepared amphiphilic polymer brush carbon nanotube/PVDF nanofiltration membrane has a double nanofiltration function, the unsealed structure of the carbon nanotube and the special structure of the single-arm carbon tube enable the carbon tube to have the nanofiltration function, and the subsequent selected matrix material PVDF is subjected to a double-pull coating process to obtain nanofiltration holes, so that the material has the double nanofiltration function, and the successful separation treatment of the water environment with complex components is realized.
Drawings
Table 1 shows the rejection rate of NaCl under the continuous operation of the amphiphilic polymer brush carbon nanotube/PVDF nanofiltration membrane prepared by the invention for 24 hours at 25 ℃ and 0.7Mpa, wherein the initial concentration of NaCl is 170mmol.L-1。
FIG. 1 is a schematic structural diagram of the amphiphilic polymer brush carbon nanotube prepared.
FIG. 2 is a schematic diagram of the structure of the click chemistry synthesized amphiphilic polymer brush carbon nanotube/PVDF nanofiltration membrane prepared in the figure.
FIG. 3 is a cross-sectional view of the prepared click chemistry synthesis amphiphilic polymer brush carbon nanotube/PVDF nano-filtration membrane, wherein white arrows indicate carbon nanotubes.
Detailed Description
Example 1
The main preparation process of the amphiphilic polymer brush carbon nanotube disclosed by the invention comprises the following steps:
(1) nitrizing the surface of the carbon nano tube: adding 0.2g of NaN3Mechanically stirring with 20ml acetonitrile at 0 deg.C until the solution is milky white, slowly adding dropwise 0.1g ICl, reacting at 0 deg.C for 20min, and filtering to obtain IN3And (3) solution. 50mg of single-walled carbon nanotubes were dispersed IN 20ml of IN3And stirring the solution at room temperature for 30min, filtering by using a PTFE (polytetrafluoroethylene) microporous membrane with the diameter of 0.45um, washing the obtained solid for several times by using deionized water and methanol, and drying the obtained solid product in vacuum to obtain the azide single-arm carbon nanotube.
(2) Preparation of amphiphilic Polymer:
(a) 20mmol of dodecyl mercaptan, 10ml of acetone and 0.8mmol of tetrabutylammonium bromide are mechanically stirred uniformly under the condition of nitrogen. Slowly dropwise adding 1.5g (mass fraction of 50 wt%) of NaOH solution, and continuously stirring for 15 min. A mixed solution of 20ml of CS2 and 30ml of acetone is slowly dropped and stirred for 15min until the mixed solution is uniformly stirred. 30ml of chloroform and 8g (mass fraction: 50 wt%) of NaOH solution are added dropwise, and the reaction is carried out for about 12 hours at room temperature by mechanical stirring. After the reaction is finished, 5ml (the molar mass is 6mol/L) of HCl and 30ml of deionized water are added dropwise, the reaction is continued for 30min, and the product 1 is obtained by reduced pressure distillation.
(b) Taking 15mmol of the product prepared above, 10mmol of 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (EDC-HCl), 10mmol of 4-Dimethylaminopyridine (DMAP), and dried CH2Cl240ml, stirring evenly at 0 ℃, slowly dropping 10mmol of propiolic alcohol for reaction for 15 min. Then reacting for about 24 hours at room temperature, and washing the product to be neutral by using deionized water to obtain a product 2.
(c) Selecting 100mmol of monomer fluorine-containing acrylate, reacting with 20.5 mmol of product, 0.05mmol of initiator azobisisobutyronitrile and 80ml of anisole at 70 ℃ for 40min under the condition of nitrogen to obtain the hydrophilic polymer.
(3) Click chemistry synthesis of an amphiphilic polymer brush carbon nanotube material: and (3) dissolving a mixture of 0.1g of the azide single-arm carbon nano tube prepared in the step (1) and 10g of the hydrophilic polymer prepared in the step (2) in 10ml of dimethylformamide solution, carrying out ultrasonic dispersion for 10min, reacting for 24h under the nitrogen condition, then placing in the air for continuing to react for 30min, and centrifuging to obtain the amphiphilic polymer brush carbon nano tube material.
The formula for synthesizing the amphiphilic polymer brush carbon nanotube/PVDF nano-filtration membrane by click chemistry comprises the following steps:
(1) blending and extruding the prepared amphiphilic polymer brush carbon nanotube material and PVDF, and granulating at the processing temperature of about 200 ℃. And (3) casting the manufactured particles by a casting machine to form a film, performing biaxial stretching to form a film, and performing longitudinal and transverse 2-time stretching, wherein the pore size of the microporous film is controlled and uniformly distributed at 5-15 nm. Heat-setting at a certain temperature (150 deg.C) to fix the oriented film structure, and cooling to form the film. Wherein the PVDF is selected from the following grades: 3208. 5 parts of amphiphilic polymer brush carbon nanotube material and 95 parts of PVDF.
(2) And (2) coating an ultrathin thin layer with a nano-scale aperture on the prepared microporous membrane in a composite manner, and preparing the prepared amphiphilic polymer brush carbon nanotube material and PVDF blend particles into a solution with a certain concentration (wherein the adopted solvent is NMP, and the concentration of the blend particle concentrated solution is 2 g/mol). And coating the obtained product on the prepared microporous membrane to enable the microporous membrane to penetrate into micropores of the base membrane to form a surface layer with a macromolecular reticular structure, and preparing the amphiphilic polymer brush carbon nanotube/PVDF nanofiltration membrane.
Example 2
The main preparation process of the amphiphilic polymer brush carbon nanotube disclosed by the invention comprises the following steps:
(1) nitrizing the surface of the carbon nano tube: adding 0.4g of NaN3Mechanically stirring with 30ml acetonitrile at 0 deg.C until the solution is milky white, slowly adding dropwise 0.2g ICl, reacting at 0 deg.C for 30min, and filtering to obtain IN3And (3) solution. 80mg of single-walled carbon nanotubes were dispersed IN 30ml of IN3Stirring the solution at room temperature for 50min, collectingAnd (3) filtering by using a PTFE microporous membrane with the diameter of 0.5um, washing the obtained solid for several times by using deionized water and methanol, and drying the obtained solid product in vacuum to obtain the azide single-arm carbon nanotube.
(2) Preparation of amphiphilic Polymer:
(a) 40mmol of dodecyl mercaptan, 20ml of acetone and 1.0mmol of tetrabutylammonium bromide are mechanically stirred uniformly under the condition of nitrogen. 2.0g (mass fraction: 60 wt%) of NaOH solution was slowly added dropwise, and stirring was continued for 20 min. 40ml of CS is slowly added dropwise2And 50ml of acetone for 20min, and stirring uniformly. 50ml of chloroform and 10g (mass fraction: 55 wt%) of NaOH solution are added dropwise, and the reaction is carried out at room temperature for about 12 hours by mechanical stirring. After the reaction is finished, 10ml (molar mass is 10mol/L) of HCl and 50ml of deionized water are added dropwise, the reaction is continued for 50min, and the product 1 is obtained by reduced pressure distillation.
(b) Taking 15mmol of the product obtained in the preparation, 15mmol of 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (EDC-HCl), 15mmol of 4-Dimethylaminopyridine (DMAP) and dried CH2Cl240ml, stirring evenly at 0 ℃, slowly dropping 15mmol of propiolic alcohol, and reacting for 20 min. Then reacting for about 24 hours at room temperature, and washing the product to be neutral by using deionized water to obtain a product 2.
(c) Selecting 200mmol of monomer hexafluorobutyl methacrylate, reacting with 21 mmol of product, 0.1mmol of initiator azobisisobutyronitrile and 100ml of anisole at 80 ℃ for 60min under the condition of nitrogen, and obtaining the hydrophilic polymer.
(3) Click chemistry synthesis of an amphiphilic polymer brush carbon nanotube material: and (3) dissolving a mixture of 1g of the azide single-arm carbon nano tube prepared in the step (1) and 15g of the hydrophilic polymer prepared in the step (2) in 20ml of dimethylformamide solution, performing ultrasonic dispersion for 10min, reacting for 24h under the nitrogen condition, then placing in the air for continuing to react for 30min, and centrifuging to obtain the amphiphilic polymer brush carbon nano tube material.
The formula for synthesizing the amphiphilic polymer brush carbon nanotube/PVDF nano-filtration membrane by click chemistry comprises the following steps:
(1) blending and extruding the prepared amphiphilic polymer brush carbon nanotube material and PVDF, and granulating at the processing temperature of about 200-220 ℃. And casting the manufactured particles by a casting machine to form a film, performing biaxial stretching to form a film, performing longitudinal and transverse stretching by 1.5 times, and controlling the pore size of the microporous film, wherein the pore size of the microporous film is uniformly distributed at 5-15 nm. Heat-setting at a certain temperature (150 deg.C) to fix the oriented film structure, and cooling to form the film. The PVDF is selected from the trade marks of 21216 and the like, wherein the amphiphilic polymer is used for brushing 10 parts of carbon nanotube material and 90 parts of PVDF.
(2) And (2) coating a layer of ultrathin thin layer with a nano-scale aperture on the prepared microporous membrane in a compounding manner, preparing the amphiphilic polymer brush carbon nanotube material prepared in the step one and PVDF blend particles into a solution with a certain concentration (wherein the adopted solvent is DMF, and the concentration of the blend particle concentrated solution is 10g/mol), coating the solution on the prepared microporous membrane, and enabling the microporous membrane to penetrate into micropores of the base membrane to form a surface layer with a macromolecular net structure, thus preparing the amphiphilic polymer brush carbon nanotube/PVDF nanofiltration membrane.
Example 3
(1) Nitrizing the surface of the carbon nano tube by adding 0.3g of NaN3Mechanically stirring with 30ml acetonitrile at 0 deg.C until the solution is milky white, slowly adding dropwise 0.15g ICl, reacting at 0 deg.C for 25min, and filtering to obtain IN3And (3) solution. 80mg of single-walled carbon nanotubes were dispersed IN 25ml of IN3And stirring the solution at room temperature for 4min, filtering by using a PTFE (polytetrafluoroethylene) microporous membrane with the diameter of 0.5um, washing the obtained solid for several times by using deionized water and methanol, and drying the obtained solid product in vacuum to obtain the azide single-arm carbon nanotube.
(2) Preparation of amphiphilic Polymer:
(a) 30mmol of dodecyl mercaptan, 15ml of acetone and 0.9mmol of tetrabutylammonium bromide are mechanically stirred uniformly under the condition of nitrogen. Slowly dropwise adding 1.80g (mass fraction is 60 wt%) of NaOH solution, and continuously stirring for 18 min. A mixed solution of 30ml of CS2 and 4ml of acetone is slowly dropped and stirred for 20min until the mixed solution is uniformly stirred. 40ml of chloroform and 10g (mass fraction: 55 wt%) of NaOH solution are added dropwise, and the reaction is carried out at room temperature for about 12 hours by mechanical stirring. After the reaction is finished, 10ml (molar mass is 10mol/L) of HCl and 40ml of deionized water are added dropwise, the reaction is continued for 40min, and the product 1 is obtained by reduced pressure distillation.
(b) Taking 18 mmol of the product prepared above, 12mmol of 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (EDC-HCl), 12mmol of 4-Dimethylaminopyridine (DMAP), and dried CH2Cl230ml, stirring evenly at 0 ℃, slowly reacting with 12mmol of propargyl alcohol for 18 min. Then reacting for about 24 hours at room temperature, and washing the product to be neutral by using deionized water to obtain a product 2.
(c) Selecting 150mmol of monomer n-butyl methacrylate, reacting with 20.8 mmol of product, 0.08mmol of initiator diisopropyl peroxydicarbonate and 100ml of anisole at 80 ℃ for 60min under the condition of nitrogen to obtain the hydrophilic polymer.
(3) Click chemistry synthesis of an amphiphilic polymer brush carbon nanotube material: and (3) dissolving 0.1-1 g of azide single-arm carbon nano tube prepared in the step (1) and 10-15 g of hydrophilic polymer prepared in the step (2) in 10-20 ml of dimethylformamide solution, carrying out ultrasonic dispersion for 10min, reacting for 24h under the nitrogen condition, then placing in the air for continuing to react for 30min, and centrifuging to obtain the amphiphilic polymer brush carbon nano tube material.
The formula for synthesizing the amphiphilic polymer brush carbon nanotube/PVDF nano-filtration membrane by click chemistry comprises the following steps:
(1) blending and extruding the prepared amphiphilic polymer brush carbon nanotube material and PVDF, and granulating at the processing temperature of about 200-220 ℃. And (3) casting the manufactured particles by a casting machine to form a film, performing biaxial stretching to form a film, performing longitudinal and transverse stretching by 1.8 times, and controlling the pore size of the microporous film to be about 5-10 nm. Heat-setting at a certain temperature (145 deg.C) to fix the oriented film structure, and cooling to form the film. Wherein the PVDF is selected from the following grades: 740. 8 parts of an amphiphilic polymer brush carbon nanotube material and 92 parts of PVDF.
(2) The method comprises the steps of coating a layer of ultrathin thin layer with a nanoscale aperture on a prepared microporous membrane in a compounding manner, preparing a solution with a certain concentration by the prepared amphiphilic polymer brush carbon nanotube material and PVDF blend particles (wherein the adopted solvent is DMSO, the concentration of the blend particle concentrated solution is 15g/mol), coating the solution on the prepared microporous membrane, enabling the microporous membrane to penetrate into micropores of a base membrane to form a surface layer with a macromolecular net structure, and preparing the amphiphilic polymer brush carbon nanotube/PVDF nanofiltration membrane.
TABLE 1 interception stability results (unit: mmol. L.) of the nanofiltration membranes prepared in examples 1 to 3 on NaCl-1)
Figure BDA0001129886180000091

Claims (7)

1. The preparation method of the amphiphilic polymer brush carbon nanotube/PVDF nanofiltration membrane is characterized by comprising the following steps: firstly, synthesizing a macroinitiator capable of carrying out click chemical reaction and initiating azide reaction, grafting the clickable macroinitiator to the surface of a single-walled carbon nanotube through the click chemical reaction, and selecting a proper hydrophilic modifier monomer to prepare the amphiphilic polymer brush carbon nanotube; blending, extruding and casting the prepared amphiphilic polymer brush carbon nanotube chemically synthesized by click and PVDF according to a certain proportion, and adjusting the double-drawing process, controlling the double-drawing temperature and speed and adjusting the aperture size of the microporous membrane; and coating an ultrathin thin layer with a nano-scale aperture on the prepared microporous membrane to prepare the amphiphilic polymer brush carbon nanotube/PVDF nanofiltration membrane, which comprises the following specific steps:
(1) nitrizing the surface of the carbon nano tube: adding NaN3Mechanically stirring with acetonitrile at 0 deg.C until the solution is milky white, slowly adding ICl dropwise, reacting at 0 deg.C for 20-30 min, and filtering to obtain IN3A solution; dispersing single-arm carbon nanotube IN IN3Uniformly stirring the solution at room temperature, filtering by adopting a PTFE microporous membrane, washing the obtained solid by using deionized water and methanol, and drying in vacuum to obtain an azide single-arm carbon nanotube;
(2) preparation of amphiphilic Polymer:
(a) will tenMechanically stirring dithiol, acetone and tetrabutylammonium bromide uniformly under the condition of nitrogen; slowly dripping NaOH solution 1, continuously stirring for 15-20 min, and then slowly dripping CS2Uniformly stirring the mixed solution with acetone, dropwise adding chloroform and NaOH solution 2, mechanically stirring at room temperature for reaction for 11-13h, dropwise adding HCl and deionized water after the reaction is finished, continuing the reaction for 30-50 min, and carrying out reduced pressure distillation to obtain a product 1;
(b) taking the product 1 prepared in the above, 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (EDC-HCl), 4-Dimethylaminopyridine (DMAP) and dried CH2Cl2Uniformly stirring at 0 ℃, slowly dropwise adding propiolic alcohol, reacting for 15-20 min, reacting for 23-25h at room temperature, and washing the product to be neutral by deionized water to obtain a product 2;
(c) selecting a monomer, a product 2, an initiator and anisole, reacting at 70-80 ℃ for 40-60 min under the condition of nitrogen to obtain a hydrophilic polymer;
(3) click chemistry synthesis of an amphiphilic polymer brush carbon nanotube material: dissolving the mixture of the azide single-arm carbon nano tube prepared in the step (1) and the hydrophilic polymer prepared in the step (2) in a dimethylformamide solution, reacting for 24 hours under the condition of nitrogen after ultrasonic dispersion, placing in the air for continuously reacting for 30 minutes, and centrifuging to obtain an amphiphilic polymer brush carbon nano tube material;
(4) blending and extruding the prepared amphiphilic polymer brush carbon nanotube material and PVDF, and granulating at the processing temperature of 200-220 ℃; casting the manufactured particles by a casting machine to form a film, performing biaxial tension to form a film, performing longitudinal and transverse 1.5-2 times of tension, and controlling the aperture size of the microporous film; carrying out heat setting at the temperature of 140-150 ℃ to fix the oriented film structure, and cooling to form a film;
(5) coating a layer of ultrathin thin layer with a nano-scale aperture on the prepared microporous membrane in a compounding manner, preparing the prepared amphiphilic polymer brush carbon nanotube material and PVDF blend particles into a solution with a certain concentration, coating the solution on the prepared microporous membrane to ensure that the microporous membrane extends into micropores of a base membrane to form a surface layer with a macromolecular net structure, and preparing the amphiphilic polymer brush carbon nanotube/PVDF nanofiltration membrane;
in the step (5), the adopted solvent mainly comprises NMP, DMAc, TEF, DMSO, MEK, THF and DMC, and the concentration of the blend particles is 1-15 g/mol; the blend is a blend of an amphiphilic polymer brush carbon nanotube material and PVDF, wherein the amphiphilic polymer brush carbon nanotube material accounts for 5-10 parts, the PVDF accounts for 90-95 parts, and the selected mark of the PVDF is the same as that in the step (4).
2. The method for preparing the amphiphilic polymer brush carbon nanotube/PVDF nanofiltration membrane according to claim 1, wherein in the step (1), NaN is used as the carrier3The mass volume ratio of the acetonitrile to the water is as follows: 1-2 g: 100-; ICl and NaN3The mass ratio of (A) to (B) is as follows: 1-2: 2-4; single-arm carbon nanotubes and IN3The mass-volume ratio of the solution is as follows: 25-50 mg: 10-15 ml; the pore diameter of the PTFE microporous membrane is 0.45-0.5 mu m; stirring for 30-50 min at room temperature.
3. The method for preparing an amphiphilic polymer brush carbon nanotube/PVDF nanofiltration membrane as claimed in claim 1, wherein in step (a), the molar volume ratio of dodecyl mercaptan, acetone and tetrabutylammonium bromide is 100-200 mmol: 50-100 ml: 4-5 mmol; the molar mass ratio of the dodecanethiol to the NaOH solution 1 to the NaOH solution 2 is as follows: 20 mmol-40 mmol: 1.5-2.0 g: 8-10 g; the concentration of the NaOH solution 1 and the NaOH solution 2 is 50 wt% -60 wt%; acetone, CS2The volume ratio of the mixed solution of the acetone to the chloroform to the HCl to the deionized water is as follows: 10-20: 50-90: 30-50: 5-10: 30-50; CS2And CS in a mixed solution of acetone2The volume ratio of the acetone is as follows: 2-4: 3-5; the concentration of HCl is 6-10 mol/L.
4. The method of claim 1, wherein in step (b), the products 1, 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (EDC-HCl), 4-Dimethylaminopyridine (DMAP) and CH are added to the nanofiltration membrane2Cl2The molar volume ratio of (1-2 mmol):2-3mmol：2-3mmol：4-8ml，CH2Cl2the volume mol ratio of the compound to the propiolic alcohol is 4-8 ml: 2-3 mmol.
5. The method for preparing an amphiphilic polymer brush carbon nanotube/PVDF nanofiltration membrane as claimed in claim 1, wherein in step (c), the molar volume ratio of the monomer, the product 2, the initiator and the anisole is 100-200 mmol: 0.5-1 mmol: 0.05-0.1 mmol: 80-100 ml;
the monomers mainly comprise: fluorine-containing acrylate, methyl methacrylate, 2-propargyl methacrylate, acrylic acid, n-butyl methacrylate, polyethylene glycol, cellulose acetate, cellulose triacetate, polyethylene glycol methacrylate, or hydroxyethyl methacrylate;
the initiator is a compound which is easily decomposed into primary free radicals by heating, and specifically comprises the following components: azobisisobutyronitrile, azobisisoheptonitrile, benzoyl peroxide, lauroyl peroxide, cumene hydroperoxide, tert-butyl peroxybenzoate, tert-butyl peroxypivalate, diisopropyl peroxydicarbonate, or dicyclohexyl peroxydicarbonate.
6. The method for preparing the amphiphilic polymer brush carbon nanotube/PVDF nanofiltration membrane as claimed in claim 1, wherein in the step (3), the mass ratio of the azide single-arm carbon nanotube to the hydrophilic polymer is 1-10: 100-150; the mass-volume ratio of the hydrophilic polymer to the dimethylformamide is 2-3 g: 2-4 ml.
7. The method for preparing the amphiphilic polymer brush carbon nanotube/PVDF nanofiltration membrane according to claim 1, wherein in the step (4), the PVDF is selected from the following brands: 3208. 740, 1010, 461, 710, CF 10BK, 21216, wherein the amphiphilic polymer brush carbon nanotube material accounts for 5-10 parts, and the PVDF accounts for 90-95 parts.
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