CN118184913A - Antibacterial double-block functional polyvinylidene fluoride material, ultrafiltration membrane, preparation method and application thereof - Google Patents
Antibacterial double-block functional polyvinylidene fluoride material, ultrafiltration membrane, preparation method and application thereof Download PDFInfo
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- 239000012528 membrane Substances 0.000 title claims abstract description 243
- 238000000108 ultra-filtration Methods 0.000 title claims abstract description 179
- 239000002033 PVDF binder Substances 0.000 title claims abstract description 156
- 229920002981 polyvinylidene fluoride Polymers 0.000 title claims abstract description 156
- 230000000844 anti-bacterial effect Effects 0.000 title claims abstract description 74
- 239000000463 material Substances 0.000 title claims abstract description 57
- 238000002360 preparation method Methods 0.000 title claims abstract description 36
- 150000003242 quaternary ammonium salts Chemical class 0.000 claims abstract description 33
- 239000000178 monomer Substances 0.000 claims abstract description 28
- 238000000034 method Methods 0.000 claims abstract description 23
- 238000010560 atom transfer radical polymerization reaction Methods 0.000 claims abstract description 20
- YOCIJWAHRAJQFT-UHFFFAOYSA-N 2-bromo-2-methylpropanoyl bromide Chemical compound CC(C)(Br)C(Br)=O YOCIJWAHRAJQFT-UHFFFAOYSA-N 0.000 claims abstract description 17
- JKNCOURZONDCGV-UHFFFAOYSA-N 2-(dimethylamino)ethyl 2-methylprop-2-enoate Chemical compound CN(C)CCOC(=O)C(C)=C JKNCOURZONDCGV-UHFFFAOYSA-N 0.000 claims abstract description 16
- 230000008569 process Effects 0.000 claims abstract description 13
- 238000006243 chemical reaction Methods 0.000 claims description 34
- ZMANZCXQSJIPKH-UHFFFAOYSA-N Triethylamine Chemical compound CCN(CC)CC ZMANZCXQSJIPKH-UHFFFAOYSA-N 0.000 claims description 27
- 239000002904 solvent Substances 0.000 claims description 23
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- CIWBSHSKHKDKBQ-JLAZNSOCSA-N Ascorbic acid Chemical compound OC[C@H](O)[C@H]1OC(=O)C(O)=C1O CIWBSHSKHKDKBQ-JLAZNSOCSA-N 0.000 claims description 14
- 125000000217 alkyl group Chemical group 0.000 claims description 13
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- JUJWROOIHBZHMG-UHFFFAOYSA-N Pyridine Chemical compound C1=CC=NC=C1 JUJWROOIHBZHMG-UHFFFAOYSA-N 0.000 claims description 8
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 8
- 229920002313 fluoropolymer Polymers 0.000 claims description 8
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- 239000007788 liquid Substances 0.000 description 17
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- GDTBXPJZTBHREO-UHFFFAOYSA-N bromine Substances BrBr GDTBXPJZTBHREO-UHFFFAOYSA-N 0.000 description 4
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- HHKDBXNYWNUHPL-UHFFFAOYSA-N 2-bromobutanoyl bromide Chemical compound CCC(Br)C(Br)=O HHKDBXNYWNUHPL-UHFFFAOYSA-N 0.000 description 2
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- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 1
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- Separation Using Semi-Permeable Membranes (AREA)
Abstract
The invention provides an antibacterial double-block functional polyvinylidene fluoride material, an ultrafiltration membrane and preparation methods and applications thereof, wherein the preparation method of the functional polyvinylidene fluoride material can comprise the following steps: reacting bromoalkane with dimethylaminoethyl methacrylate to obtain a quaternary ammonium salt monomer DMAEMA-C m; PVDF is reacted in alkali liquor, and the obtained powder is reacted with H 2O2 or NaHSO 3 to obtain PVDF-g-OH; reacting PVDF-g-OH with bromoisobutyryl bromide to obtain PVDF-g-Br powder; and carrying out atom transfer radical polymerization reaction on PVDF-g-Br powder, DMAEMA-C m solid and SBMA to obtain the diblock polyvinylidene fluoride material. The functional ultrafiltration membrane provided by the invention has the dual performances of hydrophilicity and bacteriostasis; in the applied wastewater filtering process, bacteria can be effectively prevented from adhering and killed, so that the problem of biological pollution on the surface of the membrane is relieved.
Description
Technical Field
The invention relates to the field of polyvinylidene fluoride films, in particular to an antibacterial double-block functional polyvinylidene fluoride material and a preparation method thereof, and an antibacterial double-block surface functional ultrafiltration membrane, a preparation method and application thereof.
Background
Polyvinylidene fluoride (PVDF, also called polyvinylidene fluoride) is a common polymer membrane material, mainly consists of C-F bonds, and has the characteristics of high bond energy, stable chemical property, high mechanical strength, good processing characteristics and the like. In addition, PVDF has better solubility in common polar organic solvents, and is therefore often used for preparing ultrafiltration and microfiltration membrane materials. The PVDF ultrafiltration membrane has higher capability of removing organic matters, bacteria and viruses, and is considered as one of membrane separation materials with great development prospect for treating water bodies such as drinking water, industrial water, wastewater and the like.
However, during water treatment, organic or biological contaminants in water are easily adsorbed by the membrane surface and even clog the membrane pores due to the strong hydrophobicity of PVDF ultrafiltration membranes. The bacterial is adhered on the surface of the membrane and greatly breeds to form biological pollution, which is very complex, difficult to completely remove and seriously damages the performance of the PVDF ultrafiltration membrane. In addition, researchers have isolated some conditionally pathogenic bacteria, such as pseudomonas aeruginosa, from membrane filters of domestic water purifiers. Meanwhile, the dense and complex biological film on the surface of the film provides protection for resistant bacteria, and can induce drug-resistant gene transfer in a biological film community through horizontal gene transfer. Therefore, the antibacterial film with the function of inhibiting or killing bacteria can effectively relieve the problem of biological pollution in the film filtering process.
In recent years, the antimicrobial ability of the film has been improved by surface coating, bioadhesion, physical blending, surface grafting, and the like. Wherein, the antibacterial agent grafted on the surface of the membrane not only has the activity of inactivating bacteria, but also has the characteristics of long-term effectiveness, good stability and the like. However, how to prepare ultrafiltration membranes with both bactericidal and anti-adhesive properties remains a challenge.
Disclosure of Invention
Aiming at the technical problems, the invention provides an antibacterial double-block functional polyvinylidene fluoride material, an ultrafiltration membrane, and a preparation method and application thereof.
The invention provides an antibacterial double-block functional polyvinylidene fluoride material, which has a structure shown in formula I:
in the formula I, a, b and n are all polymerization degrees; r is selected from straight-chain alkyl with 8-16 carbon atoms.
The invention provides a preparation method of the antibacterial double-block functional polyvinylidene fluoride material, which comprises the following steps: performing atom transfer radical polymerization reaction on a fluorine-containing polymer, a quaternary ammonium salt monomer and methacrylic acid sulfobetaine to obtain an antibacterial double-block functional polyvinylidene fluoride material shown in a formula I;
The fluoropolymer has the structure of formula 1, wherein n is the degree of polymerization;
The quaternary ammonium salt monomer has a structure shown in a formula 2, wherein R is selected from linear alkyl with 8-16 carbon atoms;
the sulfobetaine methacrylate has a structure of formula 3;
The Quaternary Ammonium Salt (QACs) has broad-spectrum antibacterial performance, has a cationic and hydrophobic structure similar to that of natural antibacterial peptide, can jointly exert the bactericidal effect through the charge effect and alkyl puncture, and has great application potential in the construction process of antibacterial film materials. Whereas Sulfobetaines (SBMA) can regulate the surface charge balance, build neutral charge surface to attenuate interactions with contaminants, and form strong hydration layers by electrostatic and hydrogen bonding.
The invention provides a double-block polyvinylidene fluoride material with a structure of formula I, which comprises an SBMA structure and a quaternary ammonium salt structure with a certain carbon chain length, endows polymer molecules with excellent antibacterial performance, and is easy to combine with a hydration layer. According to the embodiment of the invention, the quaternary ammonium salt monomer (shown as the formula 2) and the sulfobetaine are selected as functional monomers participating in the reaction, SBMA with a strong hydration layer and quaternary ammonium salt with good antibacterial effect are grafted on a polyvinylidene fluoride molecular chain through Atom Transfer Radical Polymerization (ATRP) to synthesize a series of uniformly distributed random polymer brushes, so that polymer molecules have excellent antibacterial and antibacterial properties and certain hydrophilic properties, and the preparation of an ultrafiltration membrane is facilitated.
Preferably, the fluoropolymer represented by formula 1 is obtained according to the following steps:
reacting polyvinylidene fluoride with an alkaline substance to obtain a hydroxylated polymer;
reacting the hydroxylated polymer with 2-bromoisobutyryl bromide to obtain the fluoropolymer;
The hydroxylated polymer has the structure of formula 4, wherein n is the degree of polymerization; the 2-bromoisobutyryl bromide has a structure of formula 5;
preferably, the reaction of the hydroxylated polymer with 2-bromoisobutyryl bromide is carried out in the presence of an acid-binding agent selected from one or more of triethylamine, pyridine and sodium carbonate.
Preferably, the quaternary ammonium salt monomer shown in the formula 2 is obtained by reacting dimethylaminoethyl methacrylate with halogenated alkane, wherein the halogenated alkane is linear halogenated alkane with 8-16 carbon atoms, and preferably bromododecane.
Preferably, the atom transfer radical polymerization is carried out under the action of a reducing agent which is L-ascorbic acid and a catalytic system selected from cuprous bromide and 2, 2-bipyridine.
The invention provides an antibacterial double-block surface functional ultrafiltration membrane which is prepared from the antibacterial double-block functional polyvinylidene fluoride material and polyvinylidene fluoride through a phase inversion method.
The invention provides a preparation method of an antibacterial double-block surface functional ultrafiltration membrane, which comprises the following steps:
A) The antibacterial double-block functional polyvinylidene fluoride material, the pore-forming agent and the polyvinylidene fluoride are fused in a first solvent to obtain a casting solution;
b) Coating the casting solution on the surface of a substrate, and forming a film to obtain a film;
C) And drying the film, and then placing the film in a second solvent to obtain the antibacterial double-block surface functionalized ultrafiltration membrane.
Preferably, the mass ratio of the antibacterial diblock functionalized polyvinylidene fluoride material to the polyvinylidene fluoride is 3-7: 9 to 13; the temperature of the film forming is 20-30 ℃; the first solvent and the second solvent are respectively selected from N, N-2-methylacetamide.
The invention provides application of the antibacterial double-block surface functionalized ultrafiltration membrane in membrane separation.
Compared with the prior art, the embodiment of the invention uses the introduced double-block polyvinylidene fluoride material (shown as the formula I) as a functionalization reagent, and prepares a membrane with polyvinylidene fluoride through a phase inversion method, so that the double-block PVDF ultrafiltration membrane with hydrophilicity and bacteriostasis can be obtained, and the double-block PVDF ultrafiltration membrane is a stable ultrafiltration membrane with sterilization performance. The membrane prepared by the embodiment of the invention balances the 'attack' and 'defense' capabilities of two functional monomers, has good antibacterial and bactericidal properties and anti-adhesion properties, and is beneficial to application in membrane separation technology. Experiments show that the ultrafiltration membrane can kill escherichia coli and enterococcus faecalis adhered to the surface of the membrane, and the anti-pollution performance is obviously improved.
In addition, the preparation method of the ultrafiltration membrane provided by the application can finish the preparation and surface modification of the membrane at one time, avoids additional processing steps, and ensures that the copolymer can segregate to the membrane separation surface and the inner pore surface preferentially in the phase conversion process, thereby forming higher porosity and permeability and having an antifouling surface; in another aspect, the surface sterilizing and antifouling layer of the ultrafiltration membrane provided by the application is stable for a long time.
Drawings
FIG. 1 is a schematic illustration of a preparation route for a diblock polyvinylidene fluoride and film material provided in some embodiments of the invention;
FIG. 2 is a Fourier infrared transform spectrum (ATR-FTIR) of PVDF-g-x% SBMA ultrafiltration membranes obtained in examples 1 to 3, PVDF ultrafiltration membrane obtained in comparative example 1, and PVDF-g-C 12 ultrafiltration membrane obtained in comparative example 2 of the present invention;
FIG. 3 is an XPS chart of the PVDF-g-x% SBMA ultrafiltration membrane obtained in examples 1-3, the PVDF ultrafiltration membrane obtained in comparative example 1, and the PVDF-g-C 12 ultrafiltration membrane obtained in comparative example 2 of the present invention;
FIG. 4 is a graph showing the surface morphology of PVDF-g-x% SBMA ultrafiltration membranes in examples 1-3, PVDF ultrafiltration membrane obtained in comparative example 1, and PVDF-g-C 12 ultrafiltration membrane obtained in comparative example 2 of the present invention;
FIG. 5 is a graph showing the porosity and pure water flux of the PVDF-g-x% SBMA ultrafiltration membranes obtained in examples 1 to 3, the PVDF ultrafiltration membrane obtained in comparative example 1, and the PVDF-g-C 12 ultrafiltration membrane obtained in comparative example 2 of the present invention;
FIG. 6 is a surface roughness and AFM image of the PVDF-g-x% SBMA ultrafiltration membrane obtained in examples 1-3, the PVDF ultrafiltration membrane obtained in comparative example 1, and the PVDF-g-C 12 ultrafiltration membrane obtained in comparative example 2 of the present invention;
FIG. 7 is a Zeta potential diagram of the PVDF-g-x% SBMA ultrafiltration membrane of examples 1-3, the PVDF ultrafiltration membrane of comparative example 1, and the PVDF-g-C 12 ultrafiltration membrane of comparative example 2 of the present invention;
FIG. 8 is a graph showing water contact angles of PVDF-g-x% SBMA ultrafiltration membranes in examples 1-3, PVDF ultrafiltration membrane obtained in comparative example 1, and PVDF-g-C 12 ultrafiltration membrane obtained in comparative example 2 of the present invention;
FIG. 9 is a graph showing the adsorption amounts of BSA protein of PVDF-g-x% SBMA ultrafiltration membranes obtained in examples 1 to 3, PVDF ultrafiltration membrane obtained in comparative example 1, and PVDF-g-C 12 ultrafiltration membrane obtained in comparative example 2 of the present invention;
FIG. 10 is a graph showing antibacterial effects of PVDF-g-50% SBMA ultrafiltration membrane in example 1, PVDF ultrafiltration membrane obtained in comparative example 1 and PVDF-g-C 12 ultrafiltration membrane obtained in comparative example 2 of the present invention;
FIG. 11 is a graph showing normalized flux changes of the PVDF-g-50% SBMA ultrafiltration membrane obtained in example 1, the PVDF ultrafiltration membrane obtained in comparative example 1, and the PVDF-g-C 12 ultrafiltration membrane obtained in comparative example 2 of the present invention in a simulated biological pollution long-term filtration experiment.
Detailed Description
In order that those skilled in the art will better understand the technical solution of the present invention, the following detailed description of the present invention with reference to specific embodiments thereof is provided by way of example and explanation only, and should not be construed as limiting the scope of the present invention in any way.
The ultrafiltration membrane separation technology is widely applied to the fields of water treatment, chemical industry, food processing, medicine and the like at present, but most of the ultrafiltration membranes used at present have no antibacterial capability, and the ultrafiltration membranes are easy to be infringed by bacteria in feed liquid to cause irreversible biological pollution in the use process, so that the permeability of the membranes is reduced, and the separation efficiency and the service life of the ultrafiltration membranes are seriously influenced. In view of the above, the present application provides a diblock polyvinylidene fluoride, a method for preparing the same, a method for preparing an ultrafiltration membrane using the same, and the like.
The invention provides an antibacterial double-block functional polyvinylidene fluoride material, which has a structure shown in a formula I, wherein a, b and n are polymerization degrees; r is selected from linear alkyl with 8-16 carbon atoms;
In the double-block functional polyvinylidene fluoride material molecule shown in the formula I, brush-shaped quaternary ammonium salt and sulfobetaine structures are connected to a carbon main chain, so that the double-block functional polyvinylidene fluoride material has excellent antibacterial and antibacterial properties and a certain hydrophilic property, and is beneficial to the preparation of a subsequent functional ultrafiltration membrane. Wherein, R is selected from linear alkyl (-C nH2n+1, n=8, 12,16, etc.) with 8-16 carbon atoms, preferably linear alkyl (-C 12H25) with 12 carbon atoms, and has better performance. N in formula I is the degree of polymerization, which results in a PVDF structure of 100kDa in molecular weight. In addition, a may represent the polymerization degree of QAC after ATRP, and b represents the polymerization degree of SBMA after ATRP. In addition, bromine (Br) can theoretically be replaced with other halogen elements.
The invention provides a preparation method of the antibacterial double-block functional polyvinylidene fluoride material, which comprises the following steps: performing atom transfer radical polymerization reaction on a fluorine-containing polymer, a quaternary ammonium salt monomer and methacrylic acid sulfobetaine to obtain an antibacterial double-block functional polyvinylidene fluoride material shown in a formula I;
the fluoropolymer has the structure of formula 1, wherein n is the degree of polymerization; the quaternary ammonium salt monomer has a structure shown in a formula 2, wherein R is selected from linear alkyl with 8-16 carbon atoms; the sulfobetaine methacrylate has a structure of formula 3;
In the preparation method provided by the embodiment of the invention, the quaternary ammonium salt monomer is prepared firstly: the precursor material, namely dimethylaminoethyl methacrylate (DMAEMA), is selected to react with halogenated alkane, and the quaternary ammonium salt monomer DMAEMA-C m solid (see the formulas 2, m=8, 12,16 and the like, preferably DMAEMA-C 12) is obtained after filtration for standby.
Wherein the haloalkane is preferably bromoalkane; the DMAEMA has lower commercial price and is beneficial to the film material with lower production cost. Specifically, bromoalkane can be placed in an acetonitrile and dimethylaminoethyl methacrylate system for reaction, then the bromoalkane is washed by anhydrous diethyl ether, and finally the quaternary ammonium salt monomer DMAEMA-C m, preferably DMAEMA-C 12, is obtained after vacuum drying. In this step, preferably, the molar ratio of the bromoalkane, the acetonitrile and the dimethylaminoethyl methacrylate is 1.1:1:1, a step of; the molar ratio of the bromoalkane to the dimethylaminoethyl methacrylate can be in the range of (1.1-1.5): 1. The reaction temperature of the system is preferably 40-60 ℃, more preferably 50-60 ℃; the reaction time may be 10 to 24 hours, preferably 12 hours. The Acetonitrile (ACN) is a solvent medium for the above reaction, and an organic solvent such as dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), and Dichloromethane (DCM) may be used. Filtering after the reaction, washing with anhydrous diethyl ether and the like, and vacuum drying for 24-36 h to obtain the quaternary ammonium salt monomer DMAEMA-C m solid with the structure shown in the formula 2.
Before the reaction, the specific embodiment of the application can place acetonitrile and dimethylaminoethyl methacrylate in a three-neck flask connected with a thermometer, a serpentine condenser pipe and a constant pressure dropping funnel according to the volume ratio of 3:1, and the temperature of the system is controlled to be 50-60 ℃, and the application can adopt a water bath kettle to heat and adjust the temperature of the system; in the reaction, bromoalkane is preferably added dropwise to the system according to a reaction molar ratio of 1.1:1, and the reaction is carried out for 10 to 12 hours, wherein nucleophilic substitution reaction occurs in the three-necked flask. After the reaction is finished, the system is cooled to room temperature, then the liquid in the three-neck flask is concentrated to be sticky by using a rotary evaporator, and white solid can be obtained by repeatedly cleaning by using diethyl ether. The white solid can be dried in vacuum for 24 hours to obtain the required quaternary ammonium salt monomer.
The above process specifically occurs in a reaction wherein n in the formula of bromoalkane represents an alkyl chain length;
In addition, the fluoropolymer shown in the formula 1 is prepared according to the embodiment of the invention, wherein n in the formula 1 is the polymerization degree. Specifically, polyvinylidene fluoride Powder (PVDF) is reacted in alkali liquor, and the obtained powder is reacted with H 2O2 (or NaHSO 3) to obtain hydroxylated polymer PVDF-g-OH powder; and then reacting PVDF-g-OH powder with bromoisobutyryl bromide under the action of an acid binding agent, and vacuum drying to obtain the fluorine-containing polymer PVDF-g-Br powder.
The hydroxylated polymer has a structure of formula 4, wherein n is the degree of polymerization; the 2-bromo-isobutyryl bromide has a structure shown in a formula 5, namely bromo-isobutyryl bromide, wherein bromine can be theoretically replaced by other halogen elements, and can be collectively called as 2-halo-isobutyryl halide;
In the examples of the present invention, polyvinylidene fluoride powder (PVDF, structural formula above, n is the degree of polymerization) was purchased from ALFA AESAR and molecular weight 100kDa. The alkali liquor can be selected from ethanol solution of sodium hydroxide or potassium hydroxide with the concentration of 7.0-9.0 mol/L; the NaOH used was dissolved in ethanol for the purpose of the hydroxylation process. The reaction temperature in the alkali liquor is preferably 70-80 ℃, more preferably 70-75 ℃ and the time is 1-2 h. The obtained powder is stirred with hydrogen peroxide or sodium bisulfate solution for reaction, preferably for 8-12h, more preferably for 12h; the addition of hydrogen peroxide or sodium bisulphite is continued mainly for the purpose of washing away residual lye, while hydroxyl groups continue to be produced. The reaction of the hydroxylated polymer with 2-bromoisobutyryl bromide is carried out in the presence of an acid-binding agent selected from one or more of triethylamine, pyridine and sodium carbonate. The reaction time is 12-24 hours; the ratio of PVDF-g-OH powder, the acid binding agent and the bromoisobutyryl bromide is (1.5-3) g (2.5-4.5) mL (1.5-4.0) mL.
Specifically, polyvinylidene fluoride powder is reacted in alkali liquor, and the obtained powder is reacted with H 2O2 or NaHSO 3 to obtain PVDF-g-OH; before the reaction, the polyvinylidene fluoride monomer is dried, and the drying is carried out in a baking oven at 50-60 ℃; stirring the dried PVDF powder in a sodium hydroxide solution or a potassium hydroxide solution at 70-80 ℃ for 1-2 h; the concentration of the sodium hydroxide solution or the potassium hydroxide solution is 7.0-9.0 mol/L, more specifically 7.5-8.5 mol/L. After the reaction was completed, ethanol was used for washing to remove potassium hydroxide or sodium hydroxide therefrom. The centrifuged powder may then be reacted with H 2O2 to generate sufficient hydroxyl groups on the PVDF surface (noted PVDF-g-OH).
Reacting PVDF-g-OH powder with bromoisobutyryl bromide under the action of an acid binding agent, and vacuum drying to obtain PVDF-g-Br powder; more specifically, PVDF-g-OH powder is added into dichloromethane or tetrahydrofuran and then stirred with an acid binding agent under nitrogen atmosphere, and then bromine isobutyryl bromide is added under ice bath condition (0 ℃) for reaction. In the process, the bromoisobutyryl bromide first undergoes a substitution reaction with PVDF-g-OH powder, thereby preparing PVDF-g-Br powder. In the present application, the acid-binding agent is selected from triethylamine, pyridine or sodium carbonate, and in a specific embodiment, the acid-binding agent is selected from triethylamine. The PVDF-g-OH powder, the acid-binding agent and the bromine isobutyryl bromide are in a proportion of (1.5-3) g (2.5-4.5) mL (1.5-4.0) mL, more specifically, the PVDF-g-OH powder, the acid-binding agent and the bromine isobutyryl bromide are in a proportion of (2.0-2.5) g (2.6-4.0) mL (1.9-3.8) mL. The stirring time is 30-40 min, and the reaction time is 18-24 h. And after the reaction, adopting methanol for centrifugal washing, and vacuum drying to obtain PVDF-g-Br powder.
In the embodiment of the invention, the obtained PVDF-g-Br powder, DMAEMA-C m solid (QAC) and sulfobetaine methacrylate SBMA (shown as formula 3) are subjected to atom transfer radical polymerization under the action of a reducing agent and a catalytic system to obtain the diblock polyvinylidene fluoride material. Wherein the reducing agent is preferably L-ascorbic acid, and the catalytic system is preferably selected from cuprous bromide CuBr and 2, 2-bipyridine. Preferably, the ratio of PVDF-g-Br powder, DMAEMA-C m solid and SBMA is (1-1.2) g (3.0-3.5) mmol.
According to the application, PVDF-g-Br powder, QAC and SBMA are subjected to Atom Transfer Radical Polymerization (ATRP) under the action of a reducing agent and a catalytic system to obtain the double-block polyvinylidene fluoride material shown in the formula I; in the above process, the reducing agent is L-ascorbic acid, the catalytic system is selected from CuBr and 2, 2-bipyridine, and the system solvent is selected from isopropanol. Atom Transfer Radical Polymerization (ATRP), which is generally to use simple organic halide as initiator and transition metal complex as halogen Atom carrier, establishes reversible dynamic balance between active species and dormant species through oxidation-reduction reaction, thereby realizing control of Polymerization reaction. In the ATRP reaction process, the rapid conversion between the low-valence copper and the high-valence copper is favorable for keeping the concentration of active species, the dosage of copper salt is reduced, and the L-ascorbic acid in the system reduces the high-valence copper to the low-valence copper. In the present application, the ratio of the PVDF-g-Br powder, the QAC and the SBMA is preferably (1 to 1.2) g (3 to 3.5) mmol, more specifically, the ratio of the PVDF-g-Br powder, the QAC and the SBMA is 1.0g:3.5mmol:3.5mmol. The temperature of the ATRP is 20-40 ℃ and the time is 12-24 h, and specifically, the temperature of the ATRP is 25-35 ℃ and the time is 15-24 h.
The invention provides an antibacterial double-block surface functional ultrafiltration membrane which is prepared from the antibacterial double-block functional polyvinylidene fluoride material and polyvinylidene fluoride through a phase inversion method.
The invention prepares the ultrafiltration membrane by using the double-block polyvinylidene fluoride, and the ultrafiltration membrane can have a interception effect on bacteria in water and further improve the capability of resisting biological pollution in a long-term dynamic filtration experiment; meanwhile, the surface structure of the film is modified, so that the hydrophilicity of the film is increased, and the anti-adhesion performance is improved. Specifically, the embodiment of the invention discloses a preparation method of a double-block polyvinylidene fluoride material and an ultrafiltration membrane, as shown in fig. 1; the method specifically comprises the following steps:
S1, reacting bromoalkane with dimethylaminoethyl methacrylate (DMAEMA), washing with anhydrous diethyl ether, and vacuum drying to obtain a quaternary ammonium salt monomer DMAEMA-C m;
S2, reacting polyvinylidene fluoride Powder (PVDF) in alkali liquor, and reacting the obtained powder with H 2O2 to obtain PVDF-g-OH powder (corresponding to (a) hydroxylation);
reacting PVDF-g-OH powder with bromoisobutyryl bromide under the action of an acid binding agent, and vacuum drying to obtain PVDF-g-Br powder (corresponding to (b) bromine initiation);
S3, performing ATRP reaction on PVDF-g-Br, DMAEMA-C m and SBMA under the action of a reducing agent and a catalytic system to obtain a diblock polyvinylidene fluoride material;
s4, preparing the antibacterial double-block surface functional ultrafiltration membrane by phase inversion of the double-block polyvinylidene fluoride material and polyvinylidene fluoride.
The last step corresponds to a specific preparation method of the antibacterial double-block surface functionalized ultrafiltration membrane provided by the embodiment of the application; after the preparation of the diblock polyvinylidene fluoride material, the preparation of the diblock antibacterial ultrafiltration membrane is carried out by using the diblock polyvinylidene fluoride material, and specifically comprises the following steps:
A) The antibacterial double-block functional polyvinylidene fluoride material, the pore-forming agent and the polyvinylidene fluoride are fused in a first solvent to obtain a casting solution;
b) Coating the casting solution on the surface of a substrate, and forming a film to obtain a film;
c) And drying the film, and then placing the film in a second solvent to obtain the antibacterial double-block surface functionalized ultrafiltration membrane (abbreviated as antibacterial ultrafiltration membrane).
In an embodiment of the present invention, the diblock polyvinylidene fluoride material is a diblock polyvinylidene fluoride material prepared by the preparation method described above, the pore-forming agent is preferably polyvinylpyrrolidone, and the first solvent and the second solvent are preferably N, N-dimethylacetamide. The mass ratio of the antibacterial diblock functionalized polyvinylidene fluoride material to the polyvinylidene fluoride is preferably 3-7: 9 to 13; the mass ratio of the antibacterial double-block functional polyvinylidene fluoride material to the pore-foaming agent to the polyvinylidene fluoride (molecular weight 100 kDa) to the first solvent can be (3-7): 1-2): 9-13): 80-85. The film forming temperature is preferably 20-30 ℃, and the humidity can be 50-60%.
The diblock antibacterial ultrafiltration membrane disclosed by the embodiment of the application is prepared by a phase inversion method: firstly, mixing the diblock polyvinylidene fluoride material, a pore-forming agent and polyvinylidene fluoride in a solvent according to the proportion to obtain a casting solution; the solvent is selected from N, N-2-methylacetamide, and the pore-forming agent is selected from polyvinylpyrrolidone. Then, coating the casting solution on the surface of a substrate, and forming a film to obtain a film; in this process, the substrate is a substrate well known to those skilled in the art, and in a specific embodiment, the substrate is selected from the group consisting of nonwoven fabrics, and the film forming temperature is 20 to 30 ℃ and the humidity is 50 to 60%. According to the embodiment of the application, finally, the film is dried and then placed in a solvent, so that the antibacterial ultrafiltration membrane is obtained; the solvent is likewise selected from N, N-2-methylacetamide.
Specifically, the preparation method of the antibacterial ultrafiltration membrane disclosed by the application is carried out in the following manner:
Dissolving a diblock polyvinylidene fluoride material in N, N-2-methylacetamide (DMAc) and stirring for 12-24 hours under the water bath condition of 50-70 ℃, adding PVP and PVDF powder, continuously stirring for 6-24 hours in a water bath kettle of 60 ℃, and defoaming the obtained casting film liquid at room temperature for 24-48 hours;
pouring the casting solution on the surface of the non-woven fabric sprayed with ethanol, scraping the film by a scraper at 25 ℃ and 40-60% RH, evaporating the film in air for 10-15 s, and immediately placing the film in 10% DMAc to form an ultrafiltration membrane with uniform pores; finally, the ultrafiltration membrane can be soaked in deionized water for 48 hours, residual solvents are filtered off, and the ultrafiltration membrane is stored in a refrigerator at 4 ℃.
Furthermore, the invention also provides application of the antibacterial double-block surface functionalized ultrafiltration membrane in membrane separation. In some embodiments, the ultrafiltration membrane has a porosity of 12% -15%, an average roughness of 35-50nm, a water contact angle of 75-80 °, and a Zeta potential of between-10 and-20 mV.
In summary, the embodiment of the application discloses a double-block polyvinylidene fluoride material for preparing an anti-pollution ultrafiltration membrane, a preparation method thereof, a preparation method of a double-block surface functionalized antibacterial ultrafiltration membrane and the like; according to the embodiment of the application, based on PVDF molecules, a polyion liquid brush (corresponding to a quaternary ammonium salt structure) with antibacterial property and a substance with hydrophilic group are grafted on a PVDF molecular chain to prepare PVDF-g-50% SBMA powder, and then an anti-biological pollution ultrafiltration membrane is prepared by a phase inversion method. The ultrafiltration membrane prepared by the method can finish membrane preparation and surface modification at one time, and extra processing steps are avoided. The polyion liquid brush on the surface of the membrane material can damage a bacterial phospholipid bilayer through an alkyl chain, and positive charges carried by quaternary ammonium salt can disturb the electric potential of the surface of negatively charged bacteria, so that bacteria adhered to the surface of the membrane can be killed; in addition, the hydrophilic groups on the surface of the membrane material improve the hydrophilicity of the membrane, so that bacteria are less likely to adhere. Therefore, the ultrafiltration membrane provided by the application has a main effect of killing bacteria adhered to the surface of the membrane and preventing bacteria from adhering as a novel antibacterial membrane material. In the actual wastewater filtering process, bacteria and resistant bacteria trapped on the surface of the membrane can be effectively killed, so that the problem of biological pollution on the surface of the membrane and the risk of resistant gene transfer are relieved.
The invention will now be described in further detail with reference to the following examples, which are described herein to aid in understanding the invention and are not intended to limit the scope of the invention. Wherein, the raw materials related to the embodiment of the invention are commercially available, and the molecular weight of the polyvinylidene fluoride powder is 100kDa.
Examples 1-3: double-block polyvinylidene fluoride material for preparing anti-pollution ultrafiltration membrane
The preparation method of the double-block polyvinylidene fluoride material and the ultrafiltration membrane comprises the following steps:
(1) Nucleophilic substitution to prepare quaternary ammonium salt: bromododecane was added dropwise to 30mL of acetonitrile and 10mL of dimethylaminoethyl methacrylate and stirred at 50 ℃ for 12h; after the reaction is finished, cooling to room temperature, washing with a large amount of anhydrous diethyl ether to obtain white solid DMAEMA-C 12, and drying overnight under vacuum at 30 ℃;
(2) PVDF hydroxylation: adding fully dried polyvinylidene fluoride powder (PVDF, molecular weight 100 kDa) into 40mL of 7.5M NaOH solution, and stirring for 1-2 h at 70-75 ℃; after the reaction is finished, centrifuging with 50% ethanol for multiple times at 5000rpm for 3min to remove NaOH; stirring the centrifuged powder with 10% H 2O2 solution overnight to generate sufficient hydroxyl on the surface of PVDF powder, thus obtaining PVDF-g-OH;
(3) PVDF-g-OH bromine initiation: 1.5g PVDF-g-OH powder and 2.6mL Triethylamine (TEA) are added into a 20mL methylene dichloride system, the mixture is stirred for 30 minutes under the nitrogen atmosphere, and then 1.9mL 2-bromobutyryl bromide (BIBB) is added dropwise under the ice bath condition for reaction for 18 hours; after the reaction is finished, the obtained PVDF-g-Br powder is centrifuged by 50% methanol, repeatedly washed for three times, and dried overnight under vacuum at 30 ℃ to obtain PVDF-g-Br;
(3) ATRP reaction functionalized PVDF-g-Br: 3.5mmolSBMA and 1.8mmol DMAEMA-C 12 (ratio see Table below), 1.5mmol ascorbic acid, 20mL of 50% isopropyl alcohol by volume fraction, stirring at room temperature under N 2 for 30min, adding PVDF-g-Br, continuing stirring uniformly, rapidly adding 2-4 mL of a mixture containing 30 mu molCuBr and 60 mu mol of 2, 2-bipyridine (Bpy) to the system, and continuing stirring at room temperature for 12h under sealed conditions; respectively obtaining diblock polyvinylidene fluoride powder (PVDF-g-x% SBMA, wherein x is 20, 50, 80 and 100 respectively), centrifuging for 3min at 5000rpm, and drying the separated powder in a vacuum oven for later use.
Wherein, example 1 is PVDF-g-50% SBMA, example 2 is PVDF-g-20% SBMA, example 3 is PVDF-g-80% SBMA, PVDF-g-100% SBMA is control group.
TABLE 1 graft Polymer brush monomer molar ratio
(4) Dissolving the diblock polyvinylidene fluoride powder in N, N-2-methylacetamide (DMAc) and stirring for 12 hours under the water bath condition of 50 ℃, adding PVP and original PVDF powder (molecular weight 100 kDa), and continuously stirring for 12 hours in a water bath kettle of 50 ℃ to obtain uniform functionalized copolymer casting solution; in the casting film liquid, the mass ratio of the diblock polyvinylidene fluoride material to the pore-forming agent to the polyvinylidene fluoride to the solvent is 3.2:1:12.8:83;
(5) Standing and defoaming the obtained casting film liquid for 24 hours, and then carefully pouring the casting film liquid on the surface of the non-woven fabric sprayed with ethanol; scraping a film with the thickness of 150 mu m by using a scraper under the conditions of 25 ℃ and 50-60% RH; after the film is evaporated in the air for 10 seconds, the film is immediately placed in 10% DMAc for phase inversion for 5 minutes to form PVDF-g-x% SBMA ultrafiltration membrane with uniform pores; finally, the membrane is soaked in deionized water for 24 hours, residual solvent is filtered off fully, and the membrane is preserved in a refrigerator at 4 ℃.
Comparative example 1: blank PVDF ultrafiltration membrane
The PVDF ultrafiltration membrane is prepared by the following steps:
(1) Dispersing fully dried polyvinylidene fluoride Powder (PVDF) and pore-forming agent polyvinylpyrrolidone (PVP) in solvent N, N-dimethylacetamide (DMAc), wherein the mass ratio of the polyvinylidene fluoride is 16% and the mass ratio of the polyvinylpyrrolidone is 1%; stirring and dissolving in a water bath at 50 ℃ for 12 hours to form uniform and stable polyvinylidene fluoride (PVDF) casting film liquid;
(2) Standing and defoaming the casting solution prepared in the step (1) for 24 hours, and then carefully pouring the casting solution prepared in the step (1) on the surface of the non-woven fabric sprayed with ethanol; scraping a film with the thickness of 150 mu m by using a scraper under the conditions of 25 ℃ and 50-60% RH; immediately placing the film in 10% DMAc for 5min for image conversion after evaporating the film in the air for 10s to form a PVDF ultrafiltration membrane with uniform pores; finally, the membrane is soaked in deionized water for 24 hours, residual solvent is filtered off fully, and the membrane is preserved in a refrigerator at 4 ℃.
Comparative example 2: PVDF ultrafiltration membrane modified by quaternary ammonium salt only
The preparation method of the quaternary ammonium salt modified PVDF ultrafiltration membrane comprises the following steps:
(1) Dropwise adding bromododecane into 30mL of acetonitrile and 10mL of dimethylaminoethyl methacrylate, and stirring for 12h at 50-60 ℃; after the reaction is finished, cooling to room temperature, washing with a large amount of anhydrous diethyl ether to obtain white solid DMAEMA-C 12, and drying overnight under vacuum at 30 ℃;
(2) Adding fully dried polyvinylidene fluoride Powder (PVDF) into 40mL of 7.5MNaOH solution, and stirring for 1-2 h at 70-75 ℃; after the reaction is finished, centrifuging with 50% ethanol for multiple times at 5000rpm for 3min to remove NaOH; stirring the centrifuged powder with 10% H 2O2 solution overnight to generate sufficient hydroxyl on the surface of PVDF powder, thus obtaining PVDF-g-OH;
(3) 1.5g PVDF-g-OH powder and 2.6mL Triethylamine (TEA) are added into a 20mL solvent methylene dichloride system, the mixture is stirred for 30 minutes under the nitrogen atmosphere, and then 1.9mL 2-bromobutyryl bromide (BIBB) is added dropwise under the ice bath condition for reaction for 18 hours; after the reaction is finished, the obtained PVDF-g-Br powder is centrifuged by 50% methanol, repeatedly washed for three times and dried in vacuum at 30 ℃ overnight;
(3) 3.6mmolDMAEMA-C 12, 1.5mmol of ascorbic acid, 20mL of 50% isopropyl alcohol by volume fraction, stirring at room temperature for 30min under the atmosphere of N 2, adding PVDF-g-Br, continuously stirring uniformly, rapidly adding 2-4 mL of a mixture containing 30 mu molCuBr and 60 mu mol of 2, 2-bipyridine (Bpy) into the system, and continuously stirring at room temperature in a sealing way for 12h; centrifuging the obtained quaternized polyvinylidene fluoride powder for 3min at 5000rpm, and drying the separated powder in a vacuum oven for later use;
(4) Dissolving the quaternized polyvinylidene fluoride powder in N, N-2-methylacetamide (DMAc), stirring for 12 hours under the water bath condition of 50 ℃, adding PVP and original PVDF powder, and continuously stirring for 12h in the water bath kettle of 50 ℃ to obtain uniform functionalized copolymer casting solution; in the casting solution, the mass ratio of the quaternized polyvinylidene fluoride material to the pore-forming agent to the polyvinylidene fluoride to the solvent is 3.2:1:12.8:83;
(5) Standing and defoaming the obtained casting film liquid for 24 hours, and then carefully pouring the casting film liquid on the surface of the non-woven fabric sprayed with ethanol; scraping a film with the thickness of 150 mu m by using a scraper under the conditions of 25 ℃ and 50-60% RH; after the film is evaporated in the air for 10 seconds, the film is immediately placed in 10 percent DMAc for phase inversion for 5 minutes to form PVDF-g-C 12 ultrafiltration membrane with uniform pores; finally, the membrane is soaked in deionized water for 24 hours, residual solvent is filtered off fully, and the membrane is preserved in a refrigerator at 4 ℃.
Example 4
And qualitatively analyzing the chemical groups of the prepared modified powder by attenuated total reflection-Fourier transform infrared (ATR-FTIR).
Directly performing ATR-FTIR test on the PVDF powder obtained in comparative example 1, the PVDF-g-C 12 powder obtained in comparative example 2 and the PVDF-g-x% SBMA powder obtained in example 1 to obtain a Fourier infrared transformation spectrogram shown in figure 2; as can be seen from FIG. 2, the PVDF-g-50% SBMA film prepared in example 1, the PVDF-g-C 12 film prepared in comparative example 2 had a pair of-CH 2 -characteristic absorption peaks at 2923cm -1 and 2848cm -1, which are derived from-CH 2 -asymmetric and symmetric stretching vibrations, respectively, of the alkyl groups in the prepared powder; DMAEMA monomer has a characteristic absorption peak of-O-C=O-at 1726cm -1, whereas SBMA can be prepared by ring-opening reaction of DMAEMA with 1, 3-propylsultone, which is the same as the main raw material used to prepare quaternary ammonium salt monomer, so SBMA has a characteristic absorption peak of-O-C=O-at 1726cm -1.
Example 5
And (3) qualitatively analyzing the element composition of the surface of the prepared ultrafiltration membrane by adopting X-ray photoelectron spectroscopy (XPS).
The PVDF ultrafiltration membrane obtained in comparative example 1, the PVDF-g-C 12 ultrafiltration membrane obtained in comparative example 2 and the PVDF-g-50% SBMA ultrafiltration membrane obtained in example 1 are cut into proper sizes, washed with deionized water and dried in vacuum for 24 hours, and sample feeding tests are carried out to obtain a full spectrum shown in fig. 3 (a), a C1s spectrum and an O1s spectrum of the PVDF ultrafiltration membrane shown in fig. 3 (b) and fig. 3 (d) and a C1s spectrum and an O1s spectrum of the PVDF-g-C 12 ultrafiltration membrane shown in fig. 3 (C) and fig. 3 (e).
From FIG. 3 (a), it is understood that the PVDF-g-50% SBMA film prepared in example 1 detected the S2p characteristic peak in the 174-164eV interval, which indicates that sulfonate groups were successfully introduced into the film surface; compared to fig. 3 (b), the PVDF-g-50% sbma film prepared in example 1 in fig. 3 (C) exhibits new characteristic peaks at 288.6eV and 286.6eV of element C1S, corresponding to O-c=o bond and C-O-C bond, respectively, and C-S bond overlaps characteristic peaks due to close binding energy with C-N bond; compared to fig. 3 (d), the PVDF-g-50% sbma film prepared in example 1 in fig. 3 (e) exhibited a new characteristic peak at 532.2eV of element O1s, corresponding to O-c=o bond. The new characteristic peaks appearing in the C peak and the O peak prove that the modified antibacterial film successfully introduces the acrylic ester structure contained in both functional monomers.
Example 6
And (3) characterizing the surface morphology structure of the prepared antibacterial ultrafiltration membrane by adopting a Scanning Electron Microscope (SEM), primarily judging the pore size and distribution condition of the membrane surface, and analyzing and calculating the porosity of the ultrafiltration membrane. And measuring the pure water flux of the prepared antibacterial ultrafiltration membrane by adopting a cross-flow filter device, and judging the water flux change condition of the ultrafiltration membrane after the diblock polymer is introduced.
The PVDF ultrafiltration membrane obtained in comparative example 1, the PVDF-g-C 12 ultrafiltration membrane obtained in comparative example 2 and the PVDF-g-x% SBMA ultrafiltration membrane obtained in example 1 were cut into a size of 1cm by 1cm, the surface was washed with deionized water to adsorb impurities, and the samples were dried under vacuum at room temperature to remove the water. And (3) flatly pasting the prepared sample on a sample table by using conductive adhesive, carrying out metal spraying (Pt) treatment on the surface of the sample, endowing the sample with excellent conductive performance, and measuring by using SEM to obtain the surface morphology structural diagram of (a) PVDF, (b) PVDF-g-C 12 film, (C) PVDF-g-20% SBMA film, (d) PVDF-g-50% SBMA film, (e) PVDF-g-80% SBMA film and (f) PVDF-g-100% SBMA film shown in figure 4.
As can be seen from fig. 4, the PVDF-g-50% sbma membrane prepared in example 1, the PVDF membrane prepared in comparative example 1 and the PVDF-g-C 12 membrane prepared in comparative example 2 have uniform pore channels, wherein the PVDF-g-C 12 membrane prepared in comparative example 2 has a larger pore diameter than the other two membranes, because the hydrophobic long carbon chain structure of the quaternary ammonium salt monomer is easily entangled and folded when the quaternary ammonium salt monomer is grafted and grown on the PVDF side chain, and the dispersion and dissolution properties are reduced during the preparation of the casting solution, so that a part of macroporous structure is easily formed; after SBMA is introduced to participate in the grafting modification of PVDF, the phenomenon of carbon chain stacking in the double-functional layer can be relieved, so that the macroporous structure of PVDF-g-50% SBMA is reduced compared with that of PVDF-g-C 12 film, and the performance is better.
After obtaining the ultrafiltration membrane SEM images, the porosity of the membrane was obtained by ImageJ software analysis. Calibrating the size of a scale by using software, and then adjusting a threshold value for a selected area to obtain film surface porosity information, wherein each film is subjected to shooting analysis by selecting 3 positions under the same magnification; the PVDF ultrafiltration membrane obtained in comparative example 1, the PVDF-g-C 12 ultrafiltration membrane obtained in comparative example 2, and the PVDF-g-50% SBMA ultrafiltration membrane obtained in example 1 were cut to a size suitable for the filtration system (effective area is 3.14cm 2), the system flow rate was controlled at 60LPH at the time of test, the temperature was controlled at 25 ℃, the membrane was pressed at 0.2MPa for 1 hour until the flux drop became stable, and the pure water flux was measured at 0.1 MPa.
FIG. 5 is a graph showing the porosity and pure water flux of the PVDF ultrafiltration membrane obtained in comparative example 1, the PVDF-g-C 12 ultrafiltration membrane obtained in comparative example 2, and the PVDF-g-x% SBMA ultrafiltration membrane obtained in example 1 of the present invention; as can be seen from fig. 5, the porosity results of the PVDF-g-50% sbma film prepared in example 1, the PVDF film prepared in comparative example 1 and the PVDF-g-C 12 film prepared in comparative example 2 are substantially the same as the surface morphology, and the partial macroporous structure is advantageous to improve the porosity of the ultrafiltration membrane to some extent; the porosity basically determines the pure water flux of the membrane, the pure water flux of the PVDF-g-C 12 membrane is maximum, the PVDF-g-50% SBMA membrane is smaller, and the PVDF-g-100% SBMA membrane is minimum.
Example 7
The surface morphology of the prepared ultrafiltration membrane was more finely characterized by Atomic Force Microscopy (AFM), and the change in the surface roughness of the membrane was evaluated.
The PVDF ultrafiltration membrane obtained in comparative example 1, the PVDF-g-C 12 ultrafiltration membrane obtained in comparative example 2 and the PVDF-g-x% SBMA ultrafiltration membrane obtained in example 1 were cut into a size of 1cm by 1cm, the surface was washed with deionized water to adsorb impurities, and the samples were dried under vacuum at room temperature to remove the water. And (3) flatly adhering the prepared sample on a sample table by using conductive adhesive, and carrying out metal spraying (Pt) treatment on the surface of the sample to endow the sample with excellent conductive performance. And then the prepared sample is flatly stuck on a glass slide by double-sided adhesive tape, and is lightly pressed and fixed by a cover glass, and 3 different area ranges are selected for shooting and analyzing each membrane. After obtaining the AFM surface image, the average roughness was calculated by selecting an area of 5 μm by 5 μm, respectively.
FIG. 6 is a graph showing, in the upper part, the average surface roughness of the PVDF ultrafiltration membrane obtained in comparative example 1, the PVDF-g-C 12 ultrafiltration membrane obtained in comparative example 2, and the PVDF-g-x% SBMA ultrafiltration membrane obtained in example 1 of the present invention; the lower parts (a), (b), (C), (d), (e) and (f) of FIG. 6 are AFM images of the PVDF ultrafiltration membrane obtained in comparative example 1, the PVDF-g-C 12 ultrafiltration membrane obtained in comparative example 2, the PVDF-g-20% SBMA ultrafiltration membrane obtained in example 1, the PVDF-g-50% SBMA ultrafiltration membrane, the PVDF-g-80% SBMA ultrafiltration membrane and the PVDF-g-100% SBMA ultrafiltration membrane, respectively. As can be seen from FIG. 6, the PVDF-g-50% SBMA ultrafiltration membrane prepared in example 1 has no obvious change in the fluctuation degree of the surface peak-valley structure compared with the PVDF ultrafiltration membrane prepared in comparative example 1 and the PVDF-g-C 12 ultrafiltration membrane prepared in comparative example 2, which shows that the fluctuation degree of the surface of the ultrafiltration membrane is hardly influenced by adopting PVDF bulk modification. The PVDF-g-C 12 ultrafiltration membrane prepared in comparative example 2 has a partially macroporous structure, so that the surface roughness is slightly improved. Compared with the PVDF film prepared in comparative example 1, the PVDF-g-50% SBMA ultrafiltration film prepared in example 1 has the average roughness increased by 2.2nm, and is beneficial to improving the wettability of the film surface to a certain extent.
Example 8
And testing the Zeta potential change of the surface of the prepared antibacterial ultrafiltration membrane by adopting SurPASS electric solid surface analyzer.
PVDF ultrafiltration membrane obtained in comparative example 1, PVDF-g-C 12 ultrafiltration membrane obtained in comparative example 2 and PVDF-g-x% SBMA ultrafiltration membrane obtained in example 1 are cut into standard sizes according to the size of a sample preparation device and stuck on a sample cell, and a cleaning cell is opened to run a clean-empty program. After the cleaning is finished, the sample cell is replaced by a sample cell (the solution of the sample cell is 1mM KCl), the distance between the inner membranes of the sample cell is adjusted to be 90-110 mu m, the pH test range and each change value of the sample cell test are set, a 'pH scan' program is operated, and the parallel test is carried out for 3 times under each pH condition.
FIG. 7 is a graph showing the Zeta potential change of the PVDF ultrafiltration membrane obtained in comparative example 1, the PVDF-g-C 12 ultrafiltration membrane obtained in comparative example 2, and the PVDF-g-x% SBMA ultrafiltration membrane obtained in example 1 of the present invention; as can be seen from FIG. 7, the PVDF membrane prepared in comparative example 1 exhibits electronegativity in the pH range of 3-11, the surface electrical property of the PVDF-g-C 12 ultrafiltration membrane prepared in comparative example 2 is positively biased as the positively charged quaternary ammonium salt monomer QAC-C 12 is introduced, and the degree of forward bias of the PVDF-g-50% SBMA ultrafiltration membrane prepared in example 1 is reduced as SBMA is introduced, because SBMA has sulfonate negatively charged groups, and thus the Zeta potential of the zwitterionic-introduced PVDF-g-50% SBMA ultrafiltration membrane is between the original PVDF membrane and PVDF-g-C 12 membrane. Compared with the PVDF ultrafiltration membrane of comparative example 1, the PVDF-g-50% SBMA ultrafiltration membrane prepared in example 1 is positively shifted by 15.7mV at pH=7, and the electronegativity of the membrane surface is weakened, which is beneficial to reducing the adsorption of pollutants on the ultrafiltration membrane surface through electrostatic action.
Example 9
And (3) testing the water contact angle of the surface of the prepared antibacterial ultrafiltration membrane by adopting a domestic HARKE-SPCA contact angle tester, so as to analyze the hydrophilicity and hydrophobicity of a membrane sample.
And (3) fully drying PVDF ultrafiltration membranes obtained in comparative example 1, PVDF-g-C 12 ultrafiltration membranes obtained in comparative example 2 and PVDF-g-x% SBMA ultrafiltration membrane samples obtained in example 1 for the same time, contacting liquid drops with the same volume with the membrane surface by adopting a hanging drop method, calibrating the contact angle in the acquired image by adopting a computer software angulation method until the contact time interval is 3s, and selecting at least 5 membranes for parallel test analysis, thereby obtaining a static water contact angle graph of the three ultrafiltration membranes shown in figure 8. As is clear from FIG. 8, the ultrafiltration membrane such as PVDF-g-50% SBMA prepared in example 1 has improved hydrophilic performance due to the presence of hydrophilic sulfonic acid groups, and has reduced water contact angle.
Example 10
The antifouling property of the surface of the prepared antibacterial ultrafiltration membrane is evaluated by a protein adsorption experiment.
The PVDF ultrafiltration membrane obtained in comparative example 1, the PVDF-g-C 12 ultrafiltration membrane obtained in comparative example 2, and the PVDF-g-x% SBMA ultrafiltration membrane obtained in example 1 were cut into 1cm by 1cm size, immersed in 1mL of 50mg/L Bovine Serum Albumin (BSA) solution, and shake-adsorbed in a 180rmp shaker at 37℃for 2 h. The residual protein content in the solution was measured by coomassie brilliant blue method, and the reduction of BSA concentration in the solution was calculated from the BSA standard curve, and converted into the adsorption amount per unit membrane area BSA, to obtain the adsorption amount shown in fig. 9. As can be seen from FIG. 9, the antibacterial ultrafiltration membrane such as PVDF-g-50% SBMA prepared in example 1 has unique hydrophilicity and electroneutrality due to the introduction of zwitterions, and the adhesion resistance of the membrane is improved; the PVDF-g-C 12 ultrafiltration membrane prepared in comparative example 2 has poor adhesion resistance because of the reduced wettability of the membrane surface due to the hydrophobic carbon chain structure of the quaternary ammonium salt.
Example 11
And (5) measuring the sterilization performance of the prepared antibacterial ultrafiltration membrane by adopting a colony forming unit counting method.
Culturing Escherichia coli (E.coli) or enterococcus faecalis (E.faecalis) in Luria-Bertani (LB) liquid medium, culturing for 12h in a 180rmp shaker at 37 ℃ to the logarithmic bacterial growth phase, centrifuging and washing for 3 times by using sterile Phosphate Buffer Solution (PBS), and diluting the four bacteria to fresh bacterial liquid with the concentration of 2 x 10 5 CFU/mL; cutting three film samples into 1cm×1cm, soaking in 75% alcohol for 10min to wash out surface impurities and bacteria, and washing with sterile water or sterile PBS buffer solution for 3 times; dropping 40 mu L of fungus on the surface of a film sample and standing at 37 ℃ for culturing 6 h; after the culture is finished, putting the contacted membrane into PBS buffer solution for ultrasonic cleaning for 10min, so that bacteria on the surface of the membrane are dispersed into the solution as much as possible; 100 mu L of the cleaned bacterial liquid is evenly coated on LB solid medium, the number of viable bacterial colonies is recorded after the bacterial liquid is cultured for 24 hours at 37 ℃, and the average value of parallel counting results is selected for each film, so that the bacterial liquid is shown in figure 10.
As can be seen from fig. 10, the PVDF-g-C 12 ultrafiltration membrane prepared in comparative example 2 and the PVDF-g-50% sbma ultrafiltration membrane prepared in example 1 significantly improved antibacterial performance compared to the PVDF ultrafiltration membrane of comparative example 1 due to the inactivation of negatively charged bacteria by the alkyl long chain structure of the quaternary ammonium salt, while the PVDF-g-50% sbma ultrafiltration membrane of example 1 was reduced in antibacterial performance compared to the PVDF-g-C 12 ultrafiltration membrane of comparative example 2 due to the reduction of the quaternary ammonium salt. The PVDF-g-C 12 ultrafiltration membrane prepared in comparative example 2 and the PVDF-g-50% SBMA ultrafiltration membrane prepared in example 1 have smaller bactericidal activity on enterococcus faecalis than E.coli, and the surface of enterococcus faecalis has thicker peptidoglycan lamellar structure, so that cells can be protected from external interference to a certain extent.
Example 12
And the antibacterial ultrafiltration membrane prepared by the test is improved in anti-biological pollution performance by adopting a cross-flow filtration device mode.
The PVDF ultrafiltration membrane obtained in comparative example 1, the PVDF-g-C 12 ultrafiltration membrane obtained in comparative example 2 and the PVDF-g-50% SBMA ultrafiltration membrane obtained in example 1 are cut into a size (effective area is 3.14cm 2) suitable for a filtration system, and the filtration system is stabilized by pre-pressing with deionized water under the pressure of 0.2MPa for 1.5h; the simulated wastewater with 1.16mM C6H5Na3O7、0.94mM NH4Cl、0.45mM KH2PO4、0.5mM CaCl2,0.5mM NaHCO3、2.0mM NaCl、0.6mM MgSO4, initial escherichia coli concentration of 10 5 CFU/mL is used as a feed solution, the initial flux is consistent by regulating the system pressure at about 0.1MPa under the condition of 30 ℃ and 60LPH flow rate, the filtration is stable for 10 hours, and the membrane flux change is recorded. As shown in FIG. 11, it is understood from FIG. 11 that the PVDF-g-50% SBMA ultrafiltration membrane prepared in example 1 is further relieved in terms of biological contamination compared with the PVDF ultrafiltration membrane obtained in comparative example 1 and the PVDF-g-C 12 ultrafiltration membrane obtained in comparative example 2 due to the improvement of sterilization performance and anti-adhesion performance.
The following are the properties of PVDF-g-50% SBMA ultrafiltration membranes prepared in example 1:
TABLE 2 Properties of PVDF-g-50% SBMA ultrafiltration membrane prepared in example 1
In addition, the embodiment of the invention realizes different double-block ultrafiltration membrane performances by changing the proportion of betaine and quaternary ammonium salt functional monomers.
From the above examples, the embodiment of the present application uses the introduced diblock polyvinylidene fluoride material (shown in formula I) as a functionalizing agent, and prepares a membrane with polyvinylidene fluoride by a phase inversion method, so as to obtain a diblock PVDF ultrafiltration membrane having both hydrophilicity and bacteriostasis. The film prepared by the embodiment of the application balances the 'attack' and 'defense' capabilities of two functional monomers, and has good antibacterial and bactericidal properties and anti-adhesion properties. In addition, the preparation method of the ultrafiltration membrane can finish the preparation and the surface modification of the membrane at one time, and is simple, convenient and easy to implement; the copolymer can segregate to the membrane separation surface and the inner pore surface preferentially in the phase inversion process, so that higher porosity and permeability are formed, and the copolymer has an antifouling surface. On the other hand, the surface sterilization and antifouling layer of the ultrafiltration membrane provided by the application is stable for a long time and is beneficial to application in membrane separation technology.
The above description of the embodiments is only for aiding in the understanding of the method of the present invention and its core ideas. It should be noted that it will be apparent to those skilled in the art that various modifications and adaptations of the invention can be made without departing from the principles of the invention and these modifications and adaptations are intended to be within the scope of the invention as defined in the following claims.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. An antibacterial diblock functionalized polyvinylidene fluoride material characterized by having the structure of formula I:
in the formula I, a, b and n are all polymerization degrees; r is selected from straight-chain alkyl with 8-16 carbon atoms.
2. The method for preparing the antibacterial double-block functionalized polyvinylidene fluoride material according to claim 1, comprising the following steps:
Performing atom transfer radical polymerization reaction on a fluorine-containing polymer, a quaternary ammonium salt monomer and methacrylic acid sulfobetaine to obtain an antibacterial double-block functional polyvinylidene fluoride material shown in a formula I;
The fluoropolymer has the structure of formula 1, wherein n is the degree of polymerization;
The quaternary ammonium salt monomer has a structure shown in a formula 2, wherein R is selected from linear alkyl with 8-16 carbon atoms;
the sulfobetaine methacrylate has a structure of formula 3;
3. the preparation method according to claim 2, wherein the fluoropolymer represented by formula 1 is obtained by the following steps:
reacting polyvinylidene fluoride with an alkaline substance to obtain a hydroxylated polymer;
reacting the hydroxylated polymer with 2-bromoisobutyryl bromide to obtain the fluoropolymer;
The hydroxylated polymer has the structure of formula 4, wherein n is the degree of polymerization; the 2-bromoisobutyryl bromide has a structure of formula 5;
4. A method of preparation according to claim 3, wherein the reaction of the hydroxylated polymer with 2-bromoisobutyryl bromide is carried out in the presence of an acid binding agent selected from one or more of triethylamine, pyridine and sodium carbonate.
5. The preparation method according to claim 2, wherein the quaternary ammonium salt monomer represented by formula 2 is obtained by reacting dimethylaminoethyl methacrylate with a halogenated alkane, wherein the halogenated alkane is a linear halogenated alkane having 8 to 16 carbon atoms.
6. The process according to any one of claims 2 to 5, wherein the atom transfer radical polymerization is carried out under the action of a reducing agent which is L-ascorbic acid and a catalytic system selected from the group consisting of cuprous bromide and 2, 2-bipyridine.
7. An antibacterial double-block surface functional ultrafiltration membrane, which is characterized by being prepared from the antibacterial double-block functional polyvinylidene fluoride material and polyvinylidene fluoride according to claim 1 by a phase inversion method.
8. The preparation method of the antibacterial double-block surface functionalized ultrafiltration membrane is characterized by comprising the following steps of:
A) Fusing the antibacterial diblock functionalized polyvinylidene fluoride material, the pore-forming agent and the polyvinylidene fluoride according to claim 1 in a first solvent to obtain a casting solution;
b) Coating the casting solution on the surface of a substrate, and forming a film to obtain a film;
C) And drying the film, and then placing the film in a second solvent to obtain the antibacterial double-block surface functionalized ultrafiltration membrane.
9. The preparation method of claim 8, wherein the mass ratio of the antibacterial diblock functionalized polyvinylidene fluoride material to the polyvinylidene fluoride is 3-7: 9 to 13; the temperature of the film forming is 20-30 ℃; the first solvent and the second solvent are respectively selected from N, N-2-methylacetamide.
10. Use of an antimicrobial diblock surface functionalized ultrafiltration membrane according to claim 7 in membrane separation.
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