Self-assembled block copolymer polymerization method and application of homoporous membrane thereof

Abstract

The invention discloses a self-assembled segmented copolymer polymerization method and application of a homoporous membrane thereof, and the method comprises the following steps: adding a hydrophilic monomer, a chain transfer agent and an initiator into a polar solvent to form a clear solution; heating the clarified solution to 40-90 DEG C under the protection of inert gas, and stirring for reaction; when the conversion rate of the hydrophilic monomer reaches 85-100%, cooling the solution to room temperature, and adding a hydrophobic monomer, a cosolvent and an initiator; heating the solution to 40-90 DEG C under the protection of inert gas, and stirring for reaction; after the reaction is finished, recovering the solvent to obtain a crude product; and cleaning the crude product with a first mixed solvent, filtering, and drying to obtain the self-assembled block copolymer. Controllable synthesis of different molecular weights of the self-assembled block copolymer and block composition regulation and control can be realized, and the method is suitable for preparation of a homoporous membrane.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of special membrane separation material synthesis, and particularly relates to a self-assembled block copolymer, a polymerization method thereof and an application of a uniform pore membrane thereof. BACKGROUND

[0002] Block copolymer is a kind of high molecular material connected by two or more polymer chains with different chemical properties through covalent bond. Due to the incompatibility between the chain segments, the block copolymer has the ability of micro-phase separation and forms different nano-ordered structures to obtain different functional properties. Block copolymer occupies an extremely important position in both basic research and industrial application. In the aspect of separation membrane material, some researchers use the micro-phase separation and self-assembly ability of block copolymer to prepare a uniform pore membrane by using the non-solvent induced phase separation (SNIPS) method of self-assembled block copolymer. In addition, different pore size uniform pore membranes can be obtained by designing the molecular weight and block ratio, so as to realize the precise separation of high value-added drugs, noble catalysts and other substances; in the aspect of nanotechnology, block copolymer can be used as a photoetching template to prepare high-density memory devices (such as Intel uses PS-b-PMMA polymer to prepare a pattern structure with sub-10 nm); in the aspect of biological pharmaceuticals, the micellar particles formed by self-assembly of amphiphilic block copolymer (PEG-b-PLA) can realize drug delivery, significantly improve the solubility and targeting of hydrophobic drugs, and thus realize high activity of the drugs.

[0003] However, to realize the functional application of block copolymer, the core challenge is how to precisely control the molecular structure of block copolymer through controllable polymerization. As shown in Table 1, the traditional synthesis methods of block copolymer include anionic polymerization, atom transfer radical polymerization (ATRP), click chemistry, reversible addition-fragmentation chain transfer polymerization (RAFT), ring-opening polymerization (ROP) and the like. Although anionic polymerization can realize a relatively narrow molecular weight distribution (Mw / Mn≈1.05), the harsh waterless and oxygenless conditions and the polymerization method suitable for very few monomers seriously hinder its application in large-scale industrial production. ATRP polymerization needs to use metal salt as catalyst, which leads to the residual metal ions in the final polymer product, affecting its biological safety. ATRP is limited in use due to the residual metal catalyst. RAFT is a method proposed by Rizzardo et al. in 1998, which has a relatively low reaction temperature (60-80℃) and a relatively narrow molecular weight distribution (Mw / Mn≈1.05) of the obtained polymer. However, the use of sulfur-containing compounds as chain transfer agents may cause the problem of toxicity and environmental pollution. ROP is a method of polymerization by ring-opening reaction of monomers with cyclic structure, which has a relatively narrow molecular weight distribution (Mw / Mn≈1.05) and a relatively high polymerization rate. However, the polymerization method is suitable for very few monomers, and the polymerization reaction needs to be carried out in a solvent, which is not conducive to the industrial production of block copolymer. ​Compared with ATRP, RAFT polymerization does not require the use of metal salt catalysts during the polymerization process, and the product purification and post-processing are simple. For ROP and click chemistry methods, the synthesis method is complex and the operation requirement is high, and it is not suitable for the large-scale production of functional block copolymers. Therefore, the development of an efficient and universal synthesis technology has become the key to the functional application of block copolymers.

[0004] Table 1. Different synthesis methods of block copolymers and their advantages and disadvantages

[0005]

[0006] For the membrane separation process, the traditional membrane separation often faces the problem of "trade-off effect" between permeability and selectivity, which means that when the permeability of ordinary membranes is improved, the selectivity of the separation membrane will decrease, and vice versa. This is limited by the wide pore size distribution of the polymer film surface, and large and small pores affect the decrease of selectivity and permeability, which limits the development of membrane separation technology. The uniform pore membrane can effectively overcome this problem and realize the two-way improvement of selectivity and permeability. At present, the mainstream preparation method of uniform pore membrane is based on the self-assembly phase inversion technology of block copolymer, which uses the microphase separation ability of different chain segments to form an ordered pore structure. By using the non-solvent induced phase separation technology, the block copolymer solution is cast into a film and then immersed in a non-solvent, and a uniform pore structure is formed by solvent evaporation and phase separation. Based on the above point, it is urgent to develop an efficient polymerization method to realize the large-scale controllable synthesis of self-assembled block copolymers to meet the actual needs of large-scale application of uniform pore membranes. SUMMARY

[0007] In view of the shortcomings of the prior art, the present application provides a self-assembled block copolymer polymerization method and its uniform pore membrane application, which realizes the low-cost rapid synthesis of block copolymers and realizes the controllable synthesis of different block copolymer molecular weights (30~150 kg / mol) and composition regulation (pore-forming block ratio 10%~50%). The block copolymer preparation method and the preparation of the uniform pore membrane composite membrane have the characteristics of simple preparation steps, fast preparation speed, wide application range, easy to expand, etc.

[0008] The object of the present application is achieved by the following technical solutions:

[0009] A polymerization method of a self-assembled block copolymer, comprising the following steps:

[0010] Step one: adding a hydrophilic monomer, an initiator and a chain transfer agent into a polar solvent to form a clear solution; wherein the molar ratio of the hydrophilic monomer, the chain transfer agent and the initiator is (50~800): 1: (0.03~0.25);

[0011] Step two: the clear solution is heated to 40-90℃ under inert gas protection, and the reaction is carried out by stirring to obtain a hydrophilic polymer;

[0012] Step three: when the conversion rate of the hydrophilic monomer reaches 85%-100%, the solution is cooled to room temperature, and a hydrophobic monomer, a cosolvent and the initiator are added; the cosolvent needs to meet the requirements of forming a uniform solution with the hydrophilic polymer and being unable to dissolve the self-assembled block copolymer formed in subsequent polymerization; the mass of the hydrophobic monomer added is 0.8-8 times that of the hydrophilic monomer, and the mass ratio of the hydrophobic monomer to the cosolvent is (0.1-0.8):1, and the molar ratio of the hydrophobic monomer to the initiator added in this step is (400-8500):1;

[0013] Step four: the solution obtained in step three is heated to 40-90℃ under inert gas protection, and the reaction is carried out by stirring to fully react; the reaction time is preferably 10-32 h;

[0014] Step five: after the reaction is completed, the solvent in the material liquid is recovered by distillation to obtain a crude polymer product; the crude polymer product is washed with a first mixed solvent for multiple times (preferably 3-4 times), filtered, and dried to obtain a self-assembled block copolymer.

[0015] Further, the hydrophilic monomer is selected from any one or several of acrylic acid, methacrylic acid, hydroxyethyl methacrylate, 4-vinylpyridine, 2-vinylpyridine, N,N-dimethyl acrylamide, isopropyl acrylamide, and hydroxyethyl acrylate in any proportion;

[0016] Further, the thermal initiator used should have the characteristics of high efficiency and wide applicability, and the initiator is selected from any one of dibenzoyl peroxide, diacetyl peroxide, ammonium persulfate, and azo initiator. The azo initiator is preferably any one of azobisdimethylamidinum hydrochloride, azobiscyclohexyl nitrile, azobisimidozoline hydrochloride, azobisdimethyl nitrile, and azobisdiisopropyl nitrile.

[0017] Further, the chain transfer agent used should have the characteristics of high activity, high controllability and wide applicability, and the chain transfer agent is selected from any one of s,s'-bis(α,α'-methyl-α''-acetic acid)trithiocarbonate, 2-[(n)alkylthio(thiocarbonyl)thio]-2-methylpropionic acid, methyl(phenyl)amino dithiocarbamic acid cyanomethyl ester, and 4-cyano-4-[((n)alkylsulfanylthiocarbonyl)sulfanyl]pentanoic acid, wherein n is 5-12.

[0018] Further, the polar solvent used should have good solubility for the product after polymerization of the hydrophilic monomer, and the polar solvent is selected from one or two of ethylene glycol monomethyl ether, propylene glycol monomethyl ether, isopropanol, butanol, water, methanol, ethanol, tert-butanol mixed in any ratio.

[0019] Further, the hydrophobic monomer used should have better hydrophobicity and activity, and the hydrophobic monomer is selected from any one of methyl methacrylate, methyl acrylate, styrene, trifluoromethyl methacrylate, 4-fluorostyrene.

[0020] Further, the cosolvent is selected from any one of a mixed solvent composed of water and ethylene glycol monomethyl ether, water and isopropanol, water and ethanol, water and methanol, water and n-propanol, wherein the volume fraction of water is 5% to 65%.

[0021] Further, the first mixed solvent used should have good solubility for the byproduct of the polymer and very poor solubility for the block copolymer, and the first mixed solvent is a mixed solvent composed of water and alcohol or a mixed solvent composed of alkane and alcohol; the first mixed solvent is selected from any one of water / ethanol solution, n-hexane / isopropanol solution, n-hexane / ethanol solution, n-hexane / methanol solution, cyclopentane-methanol solution, cyclopentane-ethanol solution, n-octane / methanol solution, wherein the volume fraction of the alcohol solvent in the first mixed solvent is 10% to 80%.

[0022] A self-assembled block copolymer prepared by a polymerization method of a self-assembled block copolymer.

[0023] A uniform pore membrane prepared from a self-assembled block copolymer, the self-assembled block copolymer is dissolved in a second mixed solvent to obtain a homogeneous solution, and then the solution is left to stand and defoamed, and then the membrane is scraped and immersed in a coagulation bath after solvent evaporation to obtain a uniform pore membrane.

[0024] The hydrophilic block in the self-assembled block copolymer accounts for 10 to 55 wt%;

[0025] The second mixed solvent is selected from any one of a mixed solution of 1,4-dioxane and N,N-dimethylformamide with a mass percentage of 50 to 100 wt%, a mixed solution of tetrahydrofuran and N,N-dimethylformamide with a mass percentage of 10 to 50 wt%, a mixed solution of tetrahydrofuran and 1,4-dioxane with a mass percentage of 10 to 50 wt%.

[0026] Further, the coagulation bath used should be a non-good solvent of the block copolymer, the film thickness during the preparation of the uniform pore membrane is preferably 25-150 μm, the support cloth is preferably polyester non-woven fabric, polyolefin non-woven fabric, polytetrafluoroethylene microporous membrane, nylon microporous membrane, polyvinylidene fluoride microporous membrane, the solvent evaporation time is preferably 3-27 s, and the coagulation bath is preferably water, ethanol.

[0027] The beneficial effects of the present application are as follows:

[0028] (1) The polymerization method of the self-assembled block copolymer provided by the present application can realize efficient conversion of monomers, realize large-scale rapid preparation of the self-assembled block copolymer, and has simple preparation steps, wide applicability of monomers, high conversion rate, recyclable solvents, and low solvent emission.

[0029] (2) The polymerization method of the self-assembled block copolymer provided by the present application is a heterogeneous polymerization method, which can realize fine customization of the molecular weight and block composition of the self-assembled block copolymer by adding a co-solvent and controlling the amount of hydrophilic monomers and hydrophobic monomers, and realize efficient preparation of a subsequent block copolymer uniform pore membrane.

[0030] (3) When the self-assembled block copolymer provided by the present application is used for the preparation of a uniform pore membrane, the pore size of the uniform pore membrane can be customized by controlling the molecular weight of the block copolymer, and the prepared composite uniform pore membrane has good mechanical strength and is easy to produce on a large scale. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 It is a small test equipment of the block copolymer synthesized in Example 1.

[0032] Figure 2 It is the nuclear magnetic resonance hydrogen spectrum data graph of the block copolymer prepared in Examples 3 and 5, wherein (a) in the graph is the result of Example 3, and (b) in the graph is the result of Example 5.

[0033] Figure 3 It is the gel permeation chromatography data graph of the block copolymer prepared in Example 3.

[0034] Figure 4 It is the SEM graph of the uniform pore membrane prepared by the block copolymer prepared in Examples 1, 3 and 5, wherein (a) in the graph is the result of Example 1, (b) in the graph is the result of Example 3, and (c) in the graph is the result of Example 5.

[0035] Figure 5 It is the block copolymer / PET, block copolymer / PTFE composite membrane real object graph prepared in Examples 3 and 5, wherein (a) in the graph is the result of Example 3, and (b) in the graph is the result of Example 5.

[0036] Figure 6 is the infrared data chart of the uniform pore membrane of Example 1, 3, 5.

[0037] Figure 7 is the water flux and bovine hemoglobin, bovine serum albumin and lysozyme retention data of Example 1, 3, 5. DETAILED DESCRIPTION

[0038] The present application will be described in detail below with reference to the accompanying drawings and preferred embodiments, the purpose and effects of the present application will become more apparent, and it should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application.

[0039] All the following examples use the block copolymer small test equipment as described in Figure 1 to synthesize self-assembled block copolymers.

[0040] Example 1

[0041] (1) 78.9 g of acrylic acid, 0.136 g of azobisisoheptane nitrile, 1 g of 2-[hexane sulfide (thiocarbonyl) sulfide]-2-methylpropionic acid were added to a reaction kettle containing 260 ml of tert-butyl alcohol solution to form a homogeneous solution;

[0042] (2) The residual oxygen in the reaction homogeneous solution and the reaction kettle was removed by gas replacement, and heated to 75°C under nitrogen protection, and the stirring reaction was started to obtain a hydrophilic polymer;

[0043] (3) After the conversion rate of acrylic acid monomer reached 90%, the reaction solution was cooled to room temperature, then 290 g of styrene monomer, 2100 ml of a mixed solution of water and n-propanol with a volume percentage of 30% and 0.136 g of azobisisoheptane nitrile were added to the homogeneous solution according to the set block ratio, the residual oxygen was replaced by nitrogen, and the reaction was started by heating to 75°C and stirring;

[0044] (4) After the reaction was completed, the reaction kettle was connected with a reduced pressure distillation device, and the residual n-propanol and water in the feed liquid were recovered by distillation to obtain the crude product particles of the polymer;

[0045] (5) The solid product was taken out, washed 4 times with a mixed solution of n-hexane and methanol with a volume percentage of 90%, filtered and dried to obtain the self-assembled block copolymer. Nuclear magnetic resonance hydrogen spectrum was used on the dried self-assembled block copolymer to determine the block ratio of the block copolymer. Gel permeation chromatography was used to analyze the molecular weight of the block copolymer, which proved to have good molecular weight distribution.

[0046] (6) The self-assembled block copolymer was dissolved in a 100 wt% 1,4-dioxane solution with a concentration of 22 wt% to obtain a homogeneous solution. The solution was allowed to stand for 24 h to defoam. The film was scraped and the solvent evaporated for 7 s before being immersed in water to obtain a uniform porous membrane with a thickness of 35 μm and a support fabric of polyolefin non-woven fabric.

[0047] Subsequently, electron microscopy was used to characterize the structure of the prepared isoporous membrane, such as Figure 4 As shown in Figure 2, the prepared isoporous membrane exhibits a good isoporous structure. The isoporous membrane prepared by infrared analysis of the block copolymer is shown in Figure 2. Figure 6 As shown, it is at 1645 cm -1 There is an obvious carbonyl peak at 3400 cm -1 There is a clear hydroxyl peak at the bottom. The water flux of the uniform pore membrane was then measured using a Millipore ultrafiltration cup and was 7.7 L·m -2 ·h -1 bar -1 The retention rates of bovine hemoglobin, bovine serum albumin and lysozyme were 99%, 97% and 63% respectively. Figure 7 shown.

[0048] Example 2

[0049] (1) 10.4 g of methacrylic acid, 0.02 g of azobisisobutyramidine hydrochloride, and 1 g of 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid were added to a 60 ml reaction vessel containing a 20% by volume mixed solution of isopropanol and propylene glycol monomethyl ether to form a homogeneous solution;

[0050] (2) Residual oxygen in the homogeneous reaction solution and the reactor was removed by gas replacement, and the mixture was heated to 70°C under nitrogen protection and stirred to start the reaction to obtain a hydrophilic polymer;

[0051] (3) After the conversion rate of the hydrophilic monomer reached 93%, the reaction solution was cooled to room temperature. Then, 83.2 g of styrene monomer, 70 ml of a 20% by volume mixed solution of water and isopropanol, and 0.026 g of azobisisobutylamidine hydrochloride were added to the homogeneous solution according to the set block ratio. Nitrogen was introduced to replace the residual oxygen. The reaction was heated to 70 °C and stirred to start the reaction.

[0052] (4) After the reaction is completed, the reactor is connected to a vacuum distillation device to remove the residual propylene glycol monomethyl ether, isopropyl alcohol and water in the feed liquid by distillation to obtain crude polymer particles;

[0053] (5) The solid product is taken out, washed 3 times with a mixed solution of n-octane and methanol with a volume fraction of 95%, filtered, and dried to obtain a self-assembled block copolymer; first, nuclear magnetic resonance hydrogen spectrum is used to determine the block ratio of the block copolymer after the dried polymer. Gel permeation chromatography is used to analyze the molecular weight of the block copolymer, which proves to have a good molecular weight distribution.

[0054] (6) The self-assembled block copolymer is dissolved in a mixed solution of 1,4-dioxane and tetrahydrofuran with a mass fraction of 90wt%, a concentration of 24wt% is configured to obtain a homogeneous solution, and the solution is left to stand for 24 hours to defoam. After the film is scraped and the solvent is volatilized for 3 seconds, it is immersed in a mixed solution of ethanol and water with a volume fraction of 50% to obtain a uniform pore membrane with a thickness of 75 μm and a supporting cloth of nylon microporous membrane.

[0055] Subsequently, the structure of the uniform pore membrane after preparation is characterized by electron microscopy. The prepared uniform pore membrane exhibits a good uniform pore structure. The uniform pore membrane prepared by the block copolymer is analyzed by infrared. It has a clear carbonyl peak at 1645 cm -1 and a clear hydroxyl peak at 3400 cm -1 . The water flux of the uniform pore membrane is determined by using a Millipore ultrafiltration cup, and the rejection rate is determined by using bovine hemoglobin, bovine serum albumin, and lysozyme.

[0056] Example 3

[0057] (1) 60 g of 4-vinylpyridine, 0.1 g of azobisisobutyronitrile, and 1 g of s,s'-bis(α,α'-methyl-α''-acetic acid)trithiocarbonate are added to a reaction kettle containing 300 ml of ethylene glycol monomethyl ether polar solvent to form a homogeneous solution;

[0058] (2) The residual oxygen in the reaction homogeneous solution and the reaction kettle is removed by gas replacement, and the reaction is heated to 80°C under nitrogen protection and stirred to start the reaction to obtain a hydrophilic polymer;

[0059] (3) After the conversion rate of the hydrophilic monomer reaches 92%, the reaction solution is cooled to room temperature. Then, 170 g of styrene monomer, 1200 ml of a mixed solution of ethylene glycol monomethyl ether and water with a volume fraction of 60%, and 0.1 g of azobisisobutyronitrile are added to the homogeneous solution according to the set block ratio. Inert gas is introduced to replace the residual oxygen, heated to 71°C, and stirred to start the reaction;

[0060] (4) After the reaction is completed, the reaction kettle is connected with a reduced pressure distillation device, and the residual ethylene glycol monomethyl ether and water in the feed liquid are removed by distillation to obtain a crude product particle of the polymer;

[0061] (5) The solid product was taken out and washed 4 times with a mixed solution of n-hexane and isopropanol with a volume fraction of 80%, filtered, and dried to obtain a self-assembled block copolymer. First, the dried polymer was subjected to nuclear magnetic resonance hydrogen spectrum, as shown in Figure 2 , it was determined that the P4VP block of the block copolymer accounted for 25wt%. As shown in Figure 3 , the molecular weight of the block copolymer was analyzed by gel permeation chromatography, and it was proved to have a good molecular weight distribution.

[0062] (6) The self-assembled block copolymer was dissolved in a mixed solution of 1,4-dioxane and N,N-dimethylformamide with a mass fraction of 90wt% to obtain a homogeneous solution, and a homogeneous solution with a concentration of 20wt% was prepared. After standing for 24 hours to defoam, scraping the film, and briefly evaporating the solvent for 20s, it was immersed in a mixed solution of ethanol and water with a volume fraction of 20% to obtain a uniform pore membrane with a film thickness of 50μm and a support cloth of polyester non-woven fabric, and the actual figure is as shown in Figure 5

[0063] Subsequently, the structure of the uniform pore membrane after preparation was characterized by electron microscopy, and the prepared uniform pore membrane exhibited a good uniform pore structure, as shown in Figure 4 . The uniform pore membrane prepared by the block copolymer was analyzed by infrared, and the results are shown in Figure 6 . The uniform pore membrane prepared in Example 3 has a clear C=N peak at 1550 cm -1 , and the peaks in the range of 1400 cm -1 -1200 cm -1 mainly correspond to the C=C stretching vibration of benzene ring and pyridine ring, and the stretching vibration of C-H on benzene ring and pyridine ring in the range of 3000 cm -1 -2800 cm -1 . The water flux of the uniform pore membrane was determined by Millipore ultrafiltration cup to be 40 L·m -2 ·h -1 ·bar -1 , and the rejection rates of bovine hemoglobin, bovine serum albumin and lysozyme were 98%, 86% and 35% respectively, and the results are shown in Figure 7 .

[0064] Example 4

[0065] (1) 230 g of 2-vinylpyridine, 0.166 g of dibenzoyl peroxide, and 1 g of 4-cyano-4-[(heptane sulfanyl thio carbonyl) sulfanyl] pentanoic acid were added to a reaction kettle containing 1200 ml of t-butyl alcohol polar solvent to form a homogeneous solution;

[0066] ​(2) Remove the residual oxygen in the reaction homogeneous solution and the reaction kettle by gas replacement, heat to 80°C under nitrogen protection, and start the reaction under stirring to obtain a hydrophilic polymer;

[0067] (3) After the conversion rate of the hydrophilic monomer reaches 95%, cool the reaction solution, then in the homogeneous solution, add 1840 g of styrene monomer, 2300 ml of an 80% volume fraction ethylene glycol monomethyl ether and water mixed solution, and 5.32 g of dibenzoyl peroxide according to the set block ratio, replace the residual oxygen with inert gas, heat to 70°C, and start the reaction under stirring;

[0068] (4) After the reaction is completed, connect the reaction kettle with the vacuum distillation equipment, and recover the residual tert-butyl alcohol, ethylene glycol monomethyl ether, and water in the feed liquid by distillation to obtain the crude product particles of the polymer;

[0069] (5) Take out the solid product, wash it 4 times with a 60% volume fraction water and ethanol mixed solution, filter and dry to obtain the self-assembled block copolymer. First, use nuclear magnetic resonance hydrogen spectrum on the dried polymer to determine the block ratio of the block copolymer. Use gel permeation chromatography to analyze the molecular weight of the block copolymer to prove that it has a good molecular weight distribution.

[0070] (6) Dissolve the self-assembled block copolymer in a 50wt% mass fraction tetrahydrofuran and N,N-dimethylformamide mixed solution, configure a concentration of 25wt% to obtain a homogeneous solution, stand for 24 hours to defoam, scrape the film, briefly evaporate the solvent for 20s, and then immerse it in water to obtain a uniform pore membrane with a film thickness of 30 μm and a polyester non-woven fabric as the support cloth.

[0071] Then, use electron microscopy to characterize the structure of the prepared uniform pore membrane. The prepared uniform pore membrane exhibits a good uniform pore structure. Use infrared analysis to analyze the uniform pore membrane prepared from the block copolymer. Use Millipore ultrafiltration cups to determine the water flux of the uniform pore membrane, and use bovine hemoglobin, bovine serum albumin, and lysozyme to determine its rejection rate.

[0072] Example 5

[0073] (1) Add 52 g of 4-vinylpyridine, 0.07 g of dibenzoyl peroxide, and 1 g of 2-[pentane sulfenyl (thiocarbonyl) sulfenyl]-2-methylpropionic acid to a 250 ml reaction kettle containing a 25% volume fraction ethylene glycol monomethyl ether and methanol polar solvent to form a homogeneous solution;

[0074] (2) Remove the residual oxygen in the reaction homogeneous solution and the reaction kettle by gas replacement, heat to 72°C under nitrogen protection, and start the reaction under stirring to obtain a hydrophilic polymer;

[0075] (3) After the hydrophilic monomer reaches a conversion rate of 88%, the reaction solution is cooled, and then 260 g of styrene monomer, 900 ml of a mixed solution of methanol with a volume fraction of 70% and water, and 0.07 g of dibenzoyl peroxide are added according to the set block ratio in the homogeneous solution, the residual oxygen is replaced by inert gas, and the reaction is started by heating to 72°C and stirring;

[0076] (4) After the reaction is completed, the reaction kettle is connected to a vacuum distillation device, and the residual methanol, ethylene glycol monomethyl ether and water in the feed liquid are removed by distillation to obtain the crude product particles of the polymer;

[0077] (5) The solid product is taken out, washed 3 times with a mixed solution of cyclopentane and ethanol with a volume fraction of 70%, filtered, and dried to obtain a self-assembled block copolymer. As shown in FIG. 5, the dried self-assembled block copolymer is analyzed by nuclear magnetic resonance hydrogen spectrum, and it is determined that the P4VP block ratio is 15% of the total molecular weight. The molecular weight of the block copolymer is analyzed by gel permeation chromatography, and it is proved that it has a good molecular weight distribution. Figure 2

[0078] (6) The self-assembled block copolymer is dissolved in a mixed solution of 1,4-dioxane and N,N-dimethylformamide with a mass fraction of 70wt%, and a concentration of 25wt% is configured to obtain a homogeneous solution. After standing for 24 hours to defoam, scraping the film, and briefly evaporating the solvent for 15 seconds, the homogeneous membrane with a thickness of 25 μm and a support cloth of polytetrafluoroethylene microporous membrane is obtained, and the actual figure is shown in FIG. 6. Figure 5

[0079] Then, the structure of the prepared homogeneous membrane is characterized by electron microscopy, Figure 4 as shown in FIG. 7, the prepared homogeneous membrane exhibits a good homogeneous structure. The homogeneous membrane prepared by the block copolymer is analyzed by infrared, Figure 6 as shown in FIG. 8, and it can be seen from Figure 6 that the homogeneous membrane prepared in Example 5 has a clear C=N peak at 1550 cm -1 -1200 cm -1 -1200 cm -1 , and the peaks in the range of 3000 cm -1 -2800 cm -1 correspond to the C-H stretching vibration of the benzene ring and the pyridine ring. Finally, the water flux of the homogeneous membrane is measured by a Millipore ultrafiltration cup, which is 180 L·m -2 ·h -1 ·bar -1 , and the rejection rates of bovine hemoglobin, bovine serum albumin and lysozyme are 12.6%, 9.2% and 3% respectively, and the results are shown in FIG. 9. Figure 7 as shown in FIG. 9.​​

[0080] Example 6

[0081] (1) 58.6 g of hydroxyethyl methacrylate, 0.22 g of azobiscyclohexylcarbonitrile, 1 g of methyl(phenyl) aminodithiocarbonic acid cyanomethyl ester were added into a reaction kettle containing 300 ml of methanol polar solvent to form a homogeneous solution;

[0082] (2) The residual oxygen in the reaction homogeneous solution and the reaction kettle was removed by gas replacement, and the temperature was raised to 70°C under nitrogen protection. The reaction was started by stirring, and a hydrophilic polymer was obtained;

[0083] (3) After the conversion rate of the hydrophilic monomer reached 92%, the reaction solution was cooled, and then 126 g of methyl methacrylate monomer, 1200 ml of 80% volume fraction of n-propanol and water mixed solution, and 0.22 g of azobiscyclohexylcarbonitrile were added into the homogeneous solution according to the set block ratio. The residual oxygen was replaced by inert gas, heated to 70°C, and the reaction was started by stirring;

[0084] (4) After the reaction was completed, the reaction kettle was connected with a reduced pressure distillation device, and the residual methanol and water in the feed liquid were removed by distillation to obtain the crude product particles of the polymer;

[0085] (5) The solid product was taken out, washed 3 times with a 70% volume fraction of n-hexane and ethanol mixed solution, filtered, and dried to obtain a self-assembled block copolymer. First, the dried self-assembled block copolymer was subjected to nuclear magnetic resonance hydrogen spectrum to determine the block ratio of the block copolymer. Gel permeation chromatography was used to analyze the molecular weight of the block copolymer, which proved to have a good molecular weight distribution.

[0086] (6) The final product was dissolved in a 70% mass fraction of 1,4-dioxane and N,N-dimethylformamide mixed solution to prepare a homogeneous solution with a concentration of 22wt%. After standing for 24 hours to defoam, the film was scraped and the solvent was evaporated for 5 seconds. Then the film was immersed in water to obtain a uniform pore membrane with a thickness of 70 μm and a support cloth of polyvinylidene fluoride microporous membrane.

[0087] Then, the structure of the prepared uniform pore membrane was characterized by electron microscopy. The prepared uniform pore membrane exhibited a good uniform pore structure. The uniform pore membrane prepared by the block copolymer was analyzed by infrared. The water flux of the uniform pore membrane was measured by Millipore ultrafiltration cup, and the rejection rate was measured by bovine hemoglobin, bovine serum albumin and lysozyme.

[0088] Example 7

[0089] (1) 135 g N,N-dimethylacrylamide, 0.1 g ammonium persulfate, 1 g 2-[dodecylsulfanyl(thiocarbonyl)thio]-2-methylpropanoic acid were added into a reaction kettle containing 700 ml of ethanol polar solvent to form a homogeneous solution;

[0090] (2) The residual oxygen in the reaction homogeneous solution and the reaction kettle was removed by gas replacement, and the temperature was raised to 75°C under nitrogen protection. The reaction was started by stirring to obtain a hydrophilic polymer;

[0091] (3) After the conversion rate of the hydrophilic monomer reached 93%, the reaction solution was cooled, and then 190 g of methyl acrylate monomer, 4000 ml of a 40% volume fraction of water and ethanol mixed solution, and 0.2 g of azobisisobutyronitrile were added into the homogeneous solution according to the set block ratio. The residual oxygen was replaced by inert gas, and the temperature was raised to 72°C. The reaction was started by stirring;

[0092] (4) After the reaction was completed, the reaction kettle was connected with a reduced pressure distillation device. The residual ethanol and water in the feed liquid were removed by distillation to obtain the crude product particles of the polymer;

[0093] (5) The solid product was taken out and washed 3 times with a 65% volume fraction of a cyclopentane and ethanol mixed solution. After filtration and drying, a self-assembled block copolymer was obtained. First, the dried polymer was subjected to nuclear magnetic resonance hydrogen spectrum to determine the block ratio of the block copolymer. Gel permeation chromatography was used to analyze the molecular weight of the block copolymer, which proved to have a good molecular weight distribution.

[0094] (6) The self-assembled block copolymer was dissolved in a 70wt% 1,4-dioxane and N,N-dimethylformamide mixed solution to obtain a homogeneous solution with a concentration of 17wt%. After standing for 24 hours to defoam, the film was scraped and the solvent was evaporated for 27 seconds. Then the film was immersed in ethanol to obtain a uniform pore membrane with a thickness of 25 μm and a support cloth of nylon microporous membrane.

[0095] Then, the structure of the prepared uniform pore membrane was characterized by electron microscopy. The prepared uniform pore membrane exhibited a good uniform pore structure. The uniform pore membrane prepared by the block copolymer was analyzed by infrared. The water flux of the uniform pore membrane was measured by Millipore ultrafiltration cup, and the rejection rate was measured by bovine hemoglobin, bovine serum albumin and lysozyme.

[0096] Example 8

[0097] (1) 105 g of hydroxyethyl acrylate, 0.165 g of azobiscyclohexyl cyanide, and 1 g of methyl(phenyl) aminodithiocarbonyl cyanomethyl ether were added into a reaction kettle containing 500 ml of tert-butyl alcohol polar solvent to form a homogeneous solution;

[0098] (2) Remove the residual oxygen in the reaction homogeneous solution and the reaction kettle by gas replacement, heat to 72°C under nitrogen protection, and start the reaction under stirring to obtain a hydrophilic polymer;

[0099] (3) After the conversion rate of the hydrophilic monomer reaches 98%, cool the reaction solution, then add 240 g of trifluoromethyl methacrylate monomer, 2000 ml of a mixed solution of ethylene glycol monomethyl ether with a volume fraction of 30% and tert-butyl alcohol, and 0.165 g of azobiscyclohexyl carbonitrile in the homogeneous solution according to the set block ratio, replace the residual oxygen with inert gas, heat to 72°C, and start the reaction under stirring;

[0100] (4) After the reaction is completed, connect the reaction kettle with a vacuum distillation device to remove the residual tert-butyl alcohol and ethylene glycol monomethyl ether in the feed liquid by distillation to obtain the crude product particles of the polymer;

[0101] (5) Take out the solid product, wash it with a mixed solution of cyclopentane and isopropanol with a volume fraction of 90% for 3 times, filter and dry to obtain a self-assembled block copolymer. First, use nuclear magnetic resonance hydrogen spectrum to determine the block ratio of the block copolymer after drying. Use gel permeation chromatography to analyze the molecular weight of the block copolymer to prove that it has a good molecular weight distribution.

[0102] (6) Dissolve the self-assembled block copolymer in a mixed solution of 1,4-dioxane and N,N-dimethylformamide with a mass fraction of 65wt% to obtain a homogeneous solution with a concentration of 22wt%. After standing for 24 hours to defoam, scrape the film, briefly evaporate the solvent for 15 s, and then immerse it in water to obtain a uniform pore membrane with a film thickness of 75 μm and a support cloth of polyester non-woven fabric.

[0103] Then, use electron microscopy to characterize the structure of the prepared uniform pore membrane. The prepared uniform pore membrane exhibits a good uniform pore structure. Use infrared analysis to analyze the uniform pore membrane prepared from the block copolymer. Use Millipore ultrafiltration cup to determine the water flux of the uniform pore membrane, and use bovine hemoglobin, bovine serum albumin and lysozyme to determine its rejection rate.

[0104] Example 9

[0105] (1) Add 87.8 g of hydroxyethyl methacrylate, 0.1 g of ammonium persulfate, and 1 g of methyl(phenyl) aminodithiocarbamic cyanomethyl ester to a reaction kettle containing isopropanol polar solvent to form a homogeneous solution;

[0106] (2) Remove the residual oxygen in the reaction homogeneous solution and the reaction kettle by gas replacement, heat to 72°C under nitrogen protection, and start the reaction under stirring to obtain a hydrophilic polymer;

[0107] (3) After the hydrophilic monomer reaches a conversion rate of 97%, the reaction solution is cooled, then 260 g of 4-fluorostyrene monomer, 1800 ml of a 20% by volume ethylene glycol monomethyl ether and water mixed solution, and 0.1 g of ammonium persulfate are added according to the set block ratio, the residual oxygen is replaced by inert gas, and the reaction is started by heating to 75°C and stirring;

[0108] (4) After the reaction is completed, the reaction kettle is connected to a vacuum distillation device, and the residual ethanol and water in the feed liquid are removed by distillation to obtain the crude product particles of the polymer;

[0109] (5) The solid product is taken out and washed 4 times with a 50% by volume n-octane and t-butyl alcohol mixed solution, filtered and dried to obtain the self-assembled block copolymer. Nuclear magnetic resonance hydrogen spectrum is used on the dried polymer to determine the block ratio of the block copolymer. Gel permeation chromatography is used to analyze the molecular weight of the block copolymer, which proves to have a good molecular weight distribution.

[0110] (6) The self-assembled block copolymer is dissolved in a 50wt% 1,4-dioxane and N,N-dimethylformamide mixed solution to obtain a homogeneous solution with a concentration of 23wt%, and is left to stand for 24 hours to remove bubbles. After scraping the film and briefly evaporating the solvent for 25 s, it is immersed in water to obtain a membrane with a thickness of 75 μm and a support cloth of nylon microporous membrane to obtain a uniform pore membrane.

[0111] Then, the structure of the uniform pore membrane after preparation is characterized by electron microscopy. The prepared uniform pore membrane exhibits a good uniform pore structure. The uniform pore membrane prepared by the block copolymer is analyzed by infrared. The water flux of the uniform pore membrane is measured by a Millipore ultrafiltration cup, and the rejection rate is measured by bovine hemoglobin, bovine serum albumin and lysozyme.

[0112] Those skilled in the art can understand that the above description is only a preferred example of the application and is not intended to limit the application, although the application has been described in detail with reference to the foregoing examples, those skilled in the art can still modify the technical solutions described in the foregoing examples or make equivalent replacements for part of the technical features. Any modification, equivalent replacement, etc. made within the spirit and principles of the application shall be included in the protection scope of the application.

Claims

1. A polymerization process for self-assembling block copolymers, characterized in that, The method comprises the following steps: Step one: hydrophilic monomer, initiator and chain transfer agent are added into polar solvent to form a clear solution; the molar ratio of the hydrophilic monomer, chain transfer agent and initiator is (50-800): 1: (0.03-0.25); Step two: the clear solution is heated to 40-90 DEG C under inert gas protection, and stirring is performed to make it react, so that a hydrophilic polymer is obtained; Step three: when the conversion rate of the hydrophilic monomer reaches 85%-100%, the solution is cooled to room temperature, and hydrophobic monomer, cosolvent and the initiator are added; the cosolvent needs to satisfy the condition of forming a homogeneous solution with the hydrophilic polymer and being unable to dissolve the self-assembled block copolymer formed by subsequent polymerization; The mass of the hydrophobic monomer added is 0.8-8 times that of the hydrophilic monomer, the mass ratio of the hydrophobic monomer and the cosolvent is (0.1-0.8): 1, and the molar ratio of the hydrophobic monomer and the initiator added in this step is (400-8500): 1; Step four: the solution obtained in step three is heated to 40-90 DEG C under inert gas protection, and stirring is performed to make it fully react; Step five: after the reaction is completed, the solvent in the material liquid is recovered by distillation, so that a polymer crude product is obtained; the polymer crude product is washed with a first mixed solvent for multiple times, and is filtered and dried, so that a self-assembled block copolymer is obtained.

2. The polymerization process of self-assembling block copolymers according to claim 1, characterized in that, The hydrophilic monomer is selected from any one or several of acrylic acid, methacrylic acid, hydroxyethyl methacrylate, 4-vinylpyridine, 2-vinylpyridine, N, N-dimethyl acrylamide, isopropyl acrylamide and hydroxyethyl acrylate in any proportion.

3. The polymerization process of self-assembling block copolymers according to claim 1, characterized in that, The initiator is selected from any one of benzoyl peroxide, diacetyl peroxide, ammonium persulfate and azo initiator; the azo initiator is selected from any one of azobisdimethylamidinum hydrochloride, azobiscyclohexyl nitrile, azobisdimethylimidazoline hydrochloride, azobisdimethyl nitrile and azobisdiisopropyl nitrile.

4. The polymerization process of self-assembling block copolymers according to claim 1, characterized in that, The chain transfer agent is selected from any one of s, s'-di(alpha, alpha'-methyl-alpha''-acetic acid)trithiocarbonate, 2-[(n)alkylthio(thiocarbonyl)thio]-2-methylpropionic acid, methyl(phenyl)amino dithiocarbamic acid cyanomethyl ester and 4-cyano-4-[((n)alkylsulfanylthiocarbonyl)sulfanyl]pentanoic acid, wherein n is 5-12.

5. The polymerization process of self-assembling block copolymers according to claim 1, characterized in that, The polar solvent is selected from one or two of ethylene glycol monomethyl ether, propylene glycol monomethyl ether, isopropyl alcohol, butanol, water, methanol, ethanol and tert-butyl alcohol in any proportion.

6. The polymerization process of self-assembling block copolymers according to claim 1, characterized in that, The hydrophobic monomer is selected from any one of methyl methacrylate, methyl acrylate, styrene, trifluoromethyl methacrylate and 4-fluorostyrene.

7. The polymerization process of self-assembling block copolymers according to claim 1, characterized in that, The cosolvent is selected from any one of mixed solvents composed of water and ethylene glycol monomethyl ether, water and isopropyl alcohol, water and ethanol, water and methanol, and water and n-propanol, wherein the volume fraction of water is 5%-65%.

8. The polymerization process of self-assembling block copolymers according to claim 1, characterized in that, The first mixed solvent is a mixed solvent composed of water and alcohol, or a mixed solvent composed of alkane and alcohol; the first mixed solvent is selected from any one of water / ethanol solution, n-hexane / isopropyl alcohol solution, n-hexane / ethanol solution, n-hexane / methanol solution, cyclopentane-methanol solution, cyclopentane-ethanol solution, n-octane / methanol solution, wherein the volume percentage of the alcohol solvent in the first mixed solvent is 10% to 80%.

9. A self-assembled block copolymer prepared by a polymerization method of the self-assembled block copolymer of any one of claims 1-8.

10. A uniform pore membrane prepared from the self-assembled block copolymer of claim 9, characterized in that, The self-assembled block copolymer is dissolved in a second mixed solvent to obtain a homogeneous solution, and then is left to stand to remove bubbles, scraped to form a film, and then immersed in a coagulation bath after solvent evaporation to obtain a uniform pore membrane; The hydrophilic block in the self-assembled block copolymer accounts for 10-55wt%; The second mixed solvent is selected from any one of a mixed solution of 1,4-dioxane and N,N-dimethylformamide with a mass percentage of 50-100wt%, a mixed solution of tetrahydrofuran and N,N-dimethylformamide with a mass percentage of 10-50wt%, and a mixed solution of tetrahydrofuran and 1,4-dioxane with a mass percentage of 10-50wt%.

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