A self-assembled block copolymer polymerization method and its application in uniformly porous membranes

Abstract

This invention discloses a method for polymerizing self-assembled block copolymers and their application in homogeneous porous membranes. The method includes: adding a hydrophilic monomer, a chain transfer agent, and an initiator to a polar solvent to form a clear solution; heating the clear solution to 40-90°C under inert gas protection and stirring the reaction; after the hydrophilic monomer conversion reaches 85%-100%, cooling the solution to room temperature, and adding a hydrophobic monomer, a co-solvent, and an initiator; heating the solution to 40-90°C under inert gas protection and stirring the reaction; after the reaction is complete, recovering the solvent to obtain a crude product; washing the crude product with a first mixed solvent, filtering, and drying to obtain the self-assembled block copolymer. This invention enables the controllable synthesis of self-assembled block copolymers with different molecular weights and the regulation of block composition, making it suitable for the preparation of homogeneous porous membranes.

Description

Technical Field

[0001] This invention belongs to the field of special membrane separation material synthesis, and specifically relates to a self-assembled block copolymer, its polymerization method, and its application as a uniformly porous membrane. Background Technology

[0002] Block copolymers are a class of polymeric materials composed of two or more chemically distinct polymer chains linked by covalent bonds. Due to the incompatibility between the chain segments, block copolymers possess the ability to separate microphases and form different ordered nanostructures, thereby acquiring diverse functional properties. Block copolymers occupy an extremely important position in both basic research and industrial applications. In the field of separation membrane materials, some researchers have utilized the microphase separation and self-assembly capabilities of block copolymers, employing the solvent-inducible phase inversion (SNIPS) method to prepare uniformly porous membranes. Furthermore, homogeneous porous membranes with different pore sizes can be designed by adjusting molecular weight and block ratio to achieve precise separation of high-value-added drugs, expensive catalysts, and other substances. In nanotechnology, block copolymers can be used as photolithography templates to prepare high-density memory devices (e.g., Intel uses PS-b-PMMA polymers to prepare sub-10 nm patterned structures). In biopharmaceuticals, micelles formed by the self-assembly of amphiphilic block copolymers (PEG-b-PLA) can be used to deliver drugs, significantly improving the solubility and targeting of hydrophobic drugs, thereby achieving high drug activity.

[0003] However, the core challenge in realizing the functional applications of block copolymers lies in how to precisely control the molecular structure of block copolymers through controlled polymerization. As shown in Table 1, traditional methods for synthesizing block copolymers include anionic polymerization, atom transfer radical polymerization (ATRP), click chemistry, reversible addition-fragmentation chain transfer polymerization (RAFT), and ring-opening polymerization (ROP). Although anionic polymerization can achieve a narrower molecular weight distribution (…),… ≈1.05), but the harsh anhydrous and oxygen-free conditions and the fact that the polymerization method is suitable for very few monomers severely hinder its application in large-scale industrial production. ATRP polymerization requires the use of metal salts as catalysts, resulting in residual metal ions in the final polymer product, affecting its biosafety. The use of ATRP is limited by the metal catalyst residue. RAFT, proposed by Rizzardo et al. in 1998, is a method with a lower reaction temperature (60~80℃) and a narrower molecular weight distribution of the resulting polymer (…). < 1.3) Controlled polymerization methods. Compared with ATRP, RAFT polymerization does not require metal salt catalysts, and product purification and post-processing are simpler. ROP and click chemistry methods are complex to synthesize and have high operational requirements, making them unsuitable for the large-scale production of functional block copolymers. Therefore, developing efficient and universal synthesis technologies is crucial for the functionalization of block copolymers.

[0004] Table 1. Synthesis methods of different block copolymers and their advantages and disadvantages

[0005]

[0006] In membrane separation processes, traditional membrane separation often faces a "trade-off effect" between permeability and selectivity. This means that increasing the permeability of a conventional membrane often leads to a decrease in selectivity, and vice versa. This is limited by the wide pore size distribution on the polymer film surface; macropores and micropores respectively affect the decrease in selectivity and permeability, thus restricting the development of membrane separation technology. Uniformly porous membranes can effectively overcome this problem, achieving a dual improvement in selectivity and permeability. Currently, the mainstream preparation method for uniformly porous membranes is based on the self-assembly phase inversion technology of block copolymers, utilizing the microphase separation capabilities of different chain segments to form an ordered pore structure. The block polymer solution is cast into a membrane using a self-assembly non-solvent-induced phase separation technique and then immersed in a non-solvent, forming a uniformly porous structure through solvent evaporation and phase separation. Based on the above, there is an urgent need to develop an efficient polymerization method to achieve the large-scale, controllable synthesis of self-assembled block copolymers to meet the practical needs of large-scale applications of uniformly porous membranes. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a self-assembled block copolymer polymerization method and its application in uniformly porous membranes. This method enables low-cost and rapid synthesis of block copolymers, as well as controllable synthesis and compositional regulation of different block copolymer molecular weights (30~150 kg / mol) (with porous block content ranging from 10% to 50%). Furthermore, the block copolymer preparation method and the uniformly porous membrane composite membrane preparation method are characterized by simple preparation steps, fast preparation speed, wide applicability, and ease of expansion.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] A polymerization method for a self-assembled block copolymer includes the following steps:

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

[0011] Step 2: Heat the clarified solution to 40~90℃ under inert gas protection and stir to allow it to react, thereby obtaining a hydrophilic polymer;

[0012] Step 3: When the conversion rate of the hydrophilic monomer reaches 85%-100%, cool the solution to room temperature, and add the hydrophobic monomer, cosolvent, and initiator; wherein, the cosolvent must be able to form a homogeneous solution with the hydrophilic polymer and cannot dissolve the self-assembled block copolymer formed by subsequent polymerization; the mass of the hydrophobic monomer added is 0.8 to 8 times that of the hydrophilic monomer, 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 4: Under inert gas protection, heat the solution obtained in Step 3 to 40~90 ℃ and stir to allow it to react completely; the reaction time is preferably 10~32 h;

[0014] Step 5: After the reaction is completed, the solvent in the feed solution is recovered by distillation to obtain the crude polymer product; the crude polymer product is washed multiple times (preferably 3 to 4 times) with the first mixed solvent, filtered and dried to obtain the self-assembled block copolymer.

[0015] Furthermore, the hydrophilic monomer is selected from any one or more of acrylic acid, methacrylic acid, hydroxyethyl methacrylate, 4-vinylpyridine, 2-vinylpyridine, N,N-dimethylacrylamide, isopropylacrylamide, and hydroxyethyl acrylate, mixed in any proportion;

[0016] Furthermore, the thermal initiator used should be selected for its high efficiency and wide applicability. The initiator is selected from benzoyl peroxide, diacetyl peroxide, ammonium persulfate, and azo initiators. Preferably, the azo initiator is any one of azobisisobutyramidine hydrochloride, azobiscyclohexylformonitrile, azobisisobutyramidazole hydrochloride, azobisisobutyronitrile, or azobisisoheptanenitrile.

[0017] Furthermore, the chain transfer agent used should be selected to have high activity, high controllability, and wide applicability. 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)aminodithiocarbamate, and 4-cyano-4-[((n)alkylthioalkylthiocarbonyl)thioalkyl]valerate, wherein n is 5 to 12.

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

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

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

[0021] Furthermore, the first mixed solvent should have good solubility for polymer byproducts and extremely poor solubility for block copolymers. 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, and n-octane / methanol solution, wherein the volume percentage of alcohol solvent in the first mixed solvent is 10% to 80%.

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

[0023] A uniformly porous membrane prepared from a self-assembled block copolymer is obtained by dissolving the self-assembled block copolymer in a second mixed solvent to obtain a homogeneous solution, allowing it to stand to defoam, scraping the membrane, evaporating the solvent, and then immersing it in a coagulation bath to obtain a uniformly porous membrane.

[0024] The hydrophilic blocks in the self-assembled block copolymer account for 10~55 wt%;

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

[0026] Furthermore, the coagulation bath should be a non-good solvent for block copolymers. During the preparation of the uniformly porous membrane, the membrane thickness is preferably 25~150 μm, the support cloth is preferably polyester nonwoven fabric, polyolefin nonwoven fabric, polytetrafluoroethylene microporous membrane, nylon microporous membrane, or polyvinylidene fluoride microporous membrane, the solvent evaporation time is preferably 3~27 s, and the coagulation bath is preferably water or ethanol.

[0027] The beneficial effects of this invention are as follows:

[0028] (1) The polymerization method of self-assembled block copolymers provided by the present invention can achieve efficient conversion of monomers, realize the large-scale rapid preparation of self-assembled block copolymers, and the preparation steps are simple, the monomers are widely applicable, the conversion rate is high, the solvent can be recycled and reused, and the solvent emission is low.

[0029] (2) The polymerization method of self-assembled block copolymer provided by the present invention is a heterogeneous polymerization method. By adding a co-solvent and controlling the amount of hydrophilic and hydrophobic monomers, the molecular weight and block composition of the self-assembled block copolymer can be precisely customized to achieve efficient preparation of the subsequent block copolymer homoporous membrane.

[0030] (3) When the self-assembled block copolymer provided by the present invention is used to prepare a uniformly porous membrane, the pore size of the uniformly porous membrane can be customized by controlling the molecular weight of the block copolymer. The prepared composite uniformly porous membrane has good mechanical strength and is easy to mass-produce. Attached Figure Description

[0031] Figure 1 This is a physical image of the equipment used for the small-scale test of the block copolymer synthesized in Example 1.

[0032] Figure 2 These are the 1H NMR data of the block copolymers prepared in Examples 3 and 5, where (a) is the result of Example 3 and (b) is the result of Example 5.

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

[0034] Figure 4 These are SEM images of the uniformly porous membranes prepared from the block copolymers in Examples 1, 3, and 5. In the image, (a) is the result of Example 1, (b) is the result of Example 3, and (c) is the result of Example 5.

[0035] Figure 5 These are physical images of the block copolymer / PET and block copolymer / PTFE composite films prepared in Examples 3 and 5, respectively. In the figure, (a) is the result of Example 3 and (b) is the result of Example 5.

[0036] Figure 6 These are infrared data images of the uniformly porous membranes of Examples 1, 3, and 5.

[0037] Figure 7 The data are the water flux, bovine hemoglobin, bovine serum albumin, and lysozyme retention data for Examples 1, 3, and 5. Detailed Implementation

[0038] The present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. The purpose and effects of the present invention will become clearer. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0039] All the following embodiments adopt the following... Figure 1 The block copolymer pilot-scale equipment described above is used to synthesize self-assembled block copolymers.

[0040] Example 1

[0041] (1) 78.9 g of acrylic acid, 0.136 g of azobisisoheptanenitrile, and 1 g of 2-[hexanethio(thiocarbonyl)thio]-2-methylpropionic acid were added to a reaction vessel containing 260 ml of tert-butanol solution to form a homogeneous solution;

[0042] (2) The oxygen in the homogeneous reaction solution and the reaction vessel was removed by gas replacement. The mixture was heated to 75°C under nitrogen protection and stirred to start the reaction, thus obtaining a hydrophilic polymer.

[0043] (3) After the acrylic monomer reaches a conversion rate of 90%, the reaction solution is cooled to room temperature. Then, in the homogeneous solution, 290 g of styrene monomer, 2100 ml of a mixture of water and n-propanol with a volume percentage of 30% and 0.136 g of azobisisoheptanenitrile are added according to the set block ratio. Nitrogen gas is introduced to replace the residual oxygen, and the mixture is heated to 75°C and stirred to start the reaction.

[0044] (4) After the reaction is completed, the reactor is connected to a vacuum distillation device to recover the residual n-propanol and water in the feed liquid by distillation, and crude polymer particles are obtained.

[0045] (5) The solid product was removed and washed four times with a mixed solution of 90% hexane and methanol (by volume). After filtration and drying, the self-assembled block copolymer was obtained. The block ratio of the self-assembled block copolymer was determined by 1H NMR spectroscopy. The molecular weight of the block copolymer was analyzed by gel permeation chromatography, which proved that it had a good molecular weight distribution.

[0046] (6) The self-assembled block copolymer was dissolved in a 1,4-dioxane solution with a mass fraction of 100wt% to prepare a homogeneous solution with a concentration of 22wt%. The solution was allowed to stand for 24 hours to defoam, and after the film was scraped and the solvent evaporated for 7 seconds, it was immersed in water to obtain a uniformly porous membrane with a thickness of 35 μm and a support cloth of polyolefin nonwoven fabric.

[0047] Subsequently, the structure of the uniformly porous membrane was characterized using electron microscopy, such as... Figure 4 As shown, the prepared uniformly porous membrane exhibits a good uniform pore structure. The uniformly porous membrane prepared using block copolymers was analyzed by infrared spectroscopy. Figure 6 As shown, it is at 1645 cm -1 It has a distinct carbonyl peak at 3400 cm⁻¹ -1 A distinct hydroxyl peak was observed at the point. Subsequently, the water flux of the uniformly pore membrane was determined to be 7.7 L·m using a Millipore ultrafiltration cup. -2 ·h -1 ·bar -1 The retention rates of bovine hemoglobin, bovine serum albumin, and lysozyme were determined to be 99%, 97%, and 63%, respectively. The results are as follows: Figure 7 As 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-[(dodecylthioalkylthiocarbonyl)thioalkyl]valeric acid were added to a reaction vessel containing a 60 ml mixture of 20% isopropanol and propylene glycol monomethyl ether to form a homogeneous solution;

[0050] (2) The oxygen in the homogeneous reaction solution and the reaction vessel was removed by gas replacement. The mixture was heated to 70°C under nitrogen protection and stirred to start the reaction, thus obtaining a hydrophilic polymer.

[0051] (3) After the hydrophilic monomer reaches a conversion rate of 93%, the reaction solution is cooled to room temperature. Then, in the homogeneous solution, 83.2 g of styrene monomer, 70 ml of a 20% water and isopropanol mixed solution and 0.026 g of azobisisobutyramidine hydrochloride are added according to the set block ratio. Nitrogen gas is introduced to replace the residual oxygen, and the solution is 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 apparatus to remove the residual propylene glycol monomethyl ether, isopropanol and water in the feed liquid by distillation to obtain crude polymer particles.

[0053] (5) The solid product was removed and washed three times with a 95% (v / v) mixture of n-octane and methanol. After filtration and drying, the self-assembled block copolymer was obtained. First, the dried polymer was subjected to 1H NMR spectroscopy to determine the block ratio of the block copolymer. The molecular weight of the block copolymer was analyzed by gel permeation chromatography, which proved that it had a good molecular weight distribution.

[0054] (6) The self-assembled block copolymer was dissolved in a mixed solution of 1,4-dioxane and tetrahydrofuran with a mass fraction of 90 wt% to prepare a homogeneous solution with a concentration of 24 wt%. The solution was allowed to stand for 24 hours to defoam, and after scraping and brief solvent evaporation for 3 s, it was immersed in a mixed solution of ethanol and water with a volume fraction of 50% to obtain a uniformly porous membrane with a membrane thickness of 75 μm and a nylon microporous membrane as the support cloth.

[0055] Subsequently, the structure of the prepared uniformly porous membrane was characterized by electron microscopy. The prepared uniformly porous membrane exhibited a good uniform pore structure. Infrared analysis was performed on the uniformly porous membrane prepared using block copolymers, which showed a pore size of 1645 cm⁻¹. -1 It has a distinct carbonyl peak at 3400 cm⁻¹ -1 A distinct hydroxyl peak was observed at the site. The water flux of the uniformly porous membrane was determined using a Millipore ultrafiltration cup, and its rejection rate was determined 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 were added to a reaction vessel containing 300 ml of ethylene glycol monomethyl ether polar solvent to form a homogeneous solution;

[0058] (2) The oxygen in the homogeneous reaction solution and the reaction vessel was removed by gas replacement. The mixture was heated to 80°C under nitrogen protection and stirred to start the reaction, thus obtaining a hydrophilic polymer.

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

[0060] (4) After the reaction is completed, the reactor is connected to a vacuum distillation apparatus to remove the residual ethylene glycol monomethyl ether and water in the feed liquid by distillation, and crude polymer particles are obtained.

[0061] (5) The solid product was removed and washed four times with a mixed solution of 80% hexane and isopropanol. It was then filtered and dried to obtain the self-assembled block copolymer. The dried polymer was first subjected to 1H NMR spectroscopy, such as... Figure 2 As shown, the proportion of P4VP blocks in the block copolymer was determined to be 25 wt%. Figure 3 As shown, gel permeation chromatography analysis revealed that the molecular weight of the block copolymer was 65,000 g / mol, demonstrating 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 90 wt% to obtain a homogeneous solution. A homogeneous solution with a concentration of 20 wt% was prepared, and the solution was allowed to stand for defoaming for 24 hours. After scraping the film and allowing the solvent to evaporate briefly for 20 s, the film was immersed in a mixed solution of ethanol and water with a volume fraction of 20% to obtain a uniformly porous membrane with a thickness of 50 μm and a support fabric of polyester nonwoven fabric. The actual product is shown in the figure. Figure 5 As shown.

[0063] Subsequently, the structure of the prepared uniformly porous membrane was characterized by electron microscopy. The prepared uniformly porous membrane is shown in the figure. Figure 4 As shown, it exhibits a good uniform porous structure. The uniformly porous membrane prepared by infrared analysis of the block copolymer yielded the following results: Figure 6 As shown, the uniformly porous membrane prepared in Example 3 has a porosity of 1550 cm⁻¹. -1 It has a distinct C=N peak at 1400 cm⁻¹. -1 -1200 cm -1 The peak values ​​within this range mainly correspond to the C=C stretching vibrations of the benzene and pyridine rings, 3000 cm⁻¹. -1 -2800 cm -1 This range corresponds to the stretching vibrations of CH on the benzene and pyridine rings. The water flux of the uniform-pore membrane, measured using a Millipore ultrafiltration cup, was 40 L·m⁻¹. -2 ·h -1 ·bar -1 The retention rates were determined using bovine hemoglobin, bovine serum albumin, and lysozyme, and were 98%, 86%, and 35%, respectively. The results are as follows: Figure 7 As shown.

[0064] Example 4

[0065] (1) 230 g of 2-vinylpyridine, 0.166 g of benzoyl peroxide and 1 g of 4-cyano-4-[(heptylthioalkylthiocarbonyl)thioalkyl]valeric acid were added to a reaction vessel containing 1200 ml of tert-butanol as a polar solvent to form a homogeneous solution;

[0066] (2) The oxygen in the homogeneous reaction solution and the reaction vessel was removed by gas replacement. The mixture was heated to 80°C under nitrogen protection and stirred to start the reaction, thus obtaining a hydrophilic polymer.

[0067] (3) After the hydrophilic monomer reaches a conversion rate of 95%, the reaction solution is cooled. Then, in the homogeneous solution, 1840 g of styrene monomer, 2300 ml of a mixed solution of ethylene glycol monomethyl ether and water with a volume fraction of 80% and 5.32 g of benzoyl peroxide are added according to the set block ratio. Inert gas is introduced to replace the residual oxygen, and the mixture is heated to 70°C and stirred to start the reaction.

[0068] (4) After the reaction is completed, the reactor is connected to a vacuum distillation device to recover the residual tert-butanol, ethylene glycol monomethyl ether and water in the feed liquid by distillation to obtain crude polymer particles.

[0069] (5) The solid product was removed and washed four times with a 60% (v / v) water and ethanol mixture. After filtration and drying, the self-assembled block copolymer was obtained. First, the dried polymer was subjected to 1H NMR spectroscopy to determine the block ratio of the copolymer. Gel permeation chromatography was used to analyze the molecular weight of the block copolymer, demonstrating its good molecular weight distribution.

[0070] (6) The self-assembled block copolymer was dissolved in a mixed solution of tetrahydrofuran and N,N-dimethylformamide with a mass fraction of 50wt% to prepare a homogeneous solution with a concentration of 25wt%. The solution was allowed to stand for 24 hours to defoam, and after scraping and short-term solvent evaporation for 20s, it was immersed in water to obtain a uniformly porous membrane with a thickness of 30 μm and a support fabric of polyester nonwoven fabric.

[0071] Subsequently, the structure of the prepared uniformly porous membrane was characterized by electron microscopy, and the prepared uniformly porous membrane exhibited a good uniform pore structure. Infrared spectroscopy was used to analyze the uniformly porous membrane prepared from the block copolymer. The water flux of the uniformly porous membrane was determined using a Millipore ultrafiltration cup, and its rejection rate was determined using bovine hemoglobin, bovine serum albumin, and lysozyme.

[0072] Example 5

[0073] (1) 52 g of 4-vinylpyridine, 0.07 g of benzoyl peroxide and 1 g of 2-[pentanethio(thiocarbonyl)thio]-2-methylpropionic acid were added to a 250 ml reactor containing 25% by volume ethylene glycol monomethyl ether and methanol as a polar solvent to form a homogeneous solution;

[0074] (2) The oxygen in the homogeneous reaction solution and the reaction vessel was removed by gas replacement. The mixture was heated to 72°C under nitrogen protection and stirred to start the reaction, thus obtaining a hydrophilic polymer.

[0075] (3) After the hydrophilic monomer reaches a conversion rate of 88%, the reaction solution is cooled. Then, in the homogeneous solution, 260 g of styrene monomer, 900 ml of a 70% methanol and water mixture and 0.07 g of benzoyl peroxide are added according to the set block ratio. Inert gas is introduced to replace the residual oxygen, and the mixture is heated to 72°C and stirred to start the reaction.

[0076] (4) After the reaction is completed, the reactor is connected to a vacuum distillation apparatus to remove the residual methanol, ethylene glycol monomethyl ether and water in the feed liquid by distillation, and crude polymer particles are obtained.

[0077] (5) The solid product was removed, washed three times with a 70% (v / v) cyclopentane and ethanol mixed solution, filtered, and dried to obtain the self-assembled block copolymer; the dried self-assembled block copolymer was subjected to 1H NMR spectroscopy, such as... Figure 2 As shown, the P4VP block was determined to account for 15% of the total molecular weight. Gel permeation chromatography analysis of the block copolymer confirmed its good molecular weight distribution.

[0078] (6) The self-assembled block copolymer was dissolved in a 70 wt% mixed solution of 1,4-dioxane and N,N-dimethylformamide to prepare a 25 wt% homogeneous solution. After standing for 24 hours to defoam, the membrane was scraped, and after a brief solvent evaporation of 15 s, it was immersed in water to obtain a uniformly porous membrane with a thickness of 25 μm and a polytetrafluoroethylene microporous membrane as the support fabric. The actual image is shown below. Figure 5 As shown.

[0079] Subsequently, the structure of the uniformly porous membrane was characterized using electron microscopy. Figure 4 As shown, the prepared uniformly porous membrane exhibits a good uniform pore structure. Infrared analysis of the uniformly porous membrane prepared using block copolymers yielded the following results: Figure 6 As shown, from Figure 6 It can be seen from the image that the uniformly porous membrane prepared in Example 5 has a porosity of 1550 cm⁻¹. -1 It has a distinct C=N peak at 1400 cm⁻¹. -1 -1200 cm -1 The peak values ​​within this range mainly correspond to the C=C stretching vibrations of the benzene and pyridine rings, 3000 cm⁻¹. -1 -2800 cm -1 This corresponds to the CH stretching vibrations on the benzene and pyridine rings within this range. Finally, the water flux of the uniform pore membrane was determined using a Millipore ultrafiltration cup and was 180 L·m⁻¹. -2 ·h -1 ·bar -1 The retention rates were determined using bovine hemoglobin, bovine serum albumin, and lysozyme, and were 12.6%, 9.2%, and 3%, respectively. The results are as follows: Figure 7 As shown.

[0080] Example 6

[0081] (1) Add 58.6 g of hydroxyethyl methacrylate, 0.22 g of azodicyclohexyl formonitrile and 1 g of methyl cyanomethyl methyl (phenyl)aminodithiocarbamate to a reaction vessel containing 300 ml of methanol as a polar solvent to form a homogeneous solution;

[0082] (2) The oxygen in the homogeneous reaction solution and the reaction vessel was removed by gas replacement. The mixture was heated to 70°C under nitrogen protection and stirred to start the reaction, thus obtaining a hydrophilic polymer.

[0083] (3) After the hydrophilic monomer reaches a conversion rate of 92%, the reaction solution is cooled. Then, in the homogeneous solution, 126 g of methyl methacrylate monomer, 1200 ml of a mixed solution of 80% n-propanol and water and 0.22 g of azobiscyclohexyl formonitrile are added according to the set block ratio. Inert gas is introduced to replace the residual oxygen, and the mixture is heated to 70°C and stirred to start the reaction.

[0084] (4) After the reaction is completed, the reactor is connected to a vacuum distillation apparatus to remove the residual methanol and water in the feed liquid by distillation, and crude polymer particles are obtained.

[0085] (5) The solid product was removed and washed three times with a 70% hexane-ethanol mixture, filtered, and dried to obtain the self-assembled block copolymer. First, the dried self-assembled block copolymer was subjected to 1H NMR spectroscopy to determine the block ratio. Gel permeation chromatography was used to analyze the molecular weight of the block copolymer, demonstrating that it had a good molecular weight distribution.

[0086] (6) Dissolve the final product in a 70% mass fraction mixed solution of 1,4-dioxane and N,N-dimethylformamide to prepare a 22wt% concentration solution to obtain a homogeneous solution. Let it stand for 24 hours to defoam, scrape the membrane, let the solvent evaporate briefly for 5 seconds, and then immerse it in water to obtain a uniformly porous membrane with a thickness of 70 μm and a support cloth of polyvinylidene fluoride microporous membrane.

[0087] Subsequently, the structure of the prepared uniformly porous membrane was characterized by electron microscopy, and the prepared uniformly porous membrane exhibited a good uniform pore structure. Infrared spectroscopy was used to analyze the uniformly porous membrane prepared from the block copolymer. The water flux of the uniformly porous membrane was determined using a Millipore ultrafiltration cup, and its rejection rate was determined using bovine hemoglobin, bovine serum albumin, and lysozyme.

[0088] Example 7

[0089] (1) 135 g N,N-dimethylacrylamide, 0.1 g ammonium persulfate and 1 g 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid were added to a reaction vessel containing 700 ml of ethanol as a polar solvent to form a homogeneous solution;

[0090] (2) The oxygen in the homogeneous reaction solution and the reaction vessel was removed by gas replacement. The mixture was heated to 75°C under nitrogen protection and stirred to start the reaction, thus obtaining a hydrophilic polymer.

[0091] (3) After the hydrophilic monomer reaches a conversion rate of 93%, the reaction solution is cooled. Then, in the homogeneous solution, 190 g of methyl acrylate monomer, 4000 ml of a 40% water and ethanol mixed solution and 0.2 g of azobisisobutyronitrile are added according to the set block ratio. Inert gas is introduced to replace the residual oxygen, and the mixture is heated to 72°C and stirred to start the reaction.

[0092] (4) After the reaction is completed, the reactor is connected to a vacuum distillation apparatus to remove the residual ethanol and water in the feed liquid by distillation, and crude polymer particles are obtained.

[0093] (5) The solid product was removed and washed three times with a 65% (v / v) cyclopentane and ethanol mixture. After filtration and drying, the self-assembled block copolymer was obtained. First, the dried polymer was subjected to 1H NMR spectroscopy to determine the block ratio of the copolymer. Gel permeation chromatography was used to analyze the molecular weight of the block copolymer, demonstrating its good molecular weight distribution.

[0094] (6) The self-assembled block copolymer was dissolved in a 70 wt% N,N-dimethylformamide mixed solution of 1,4-dioxane to prepare a 17 wt% homogeneous solution. After standing for 24 hours to defoam, the membrane was scraped and briefly evaporated for 27 seconds before being immersed in ethanol to obtain a uniformly porous membrane with a thickness of 25 μm and a nylon microporous membrane as the support fabric.

[0095] Subsequently, the structure of the prepared uniformly porous membrane was characterized by electron microscopy, and the prepared uniformly porous membrane exhibited a good uniform pore structure. Infrared spectroscopy was used to analyze the uniformly porous membrane prepared from the block copolymer. The water flux of the uniformly porous membrane was determined using a Millipore ultrafiltration cup, and its rejection rate was determined using bovine hemoglobin, bovine serum albumin, and lysozyme.

[0096] Example 8

[0097] (1) 105 g of hydroxyethyl acrylate, 0.165 g of azodicyclohexyl formonitrile and 1 g of methyl cyanomethyl methyl (phenyl)aminodithiocarbamate were added to a reaction vessel containing 500 ml of tert-butanol as a polar solvent to form a homogeneous solution.

[0098] (2) The oxygen in the homogeneous reaction solution and the reaction vessel was removed by gas replacement. The mixture was heated to 72°C under nitrogen protection and stirred to start the reaction, thus obtaining a hydrophilic polymer.

[0099] (3) After the hydrophilic monomer reaches a conversion rate of 98%, the reaction solution is cooled. Then, in the homogeneous solution, 240 g of trifluoromethyl methacrylate monomer, 2000 ml of a mixed solution of 30% ethylene glycol monomethyl ether and tert-butanol and 0.165 g of azobiscyclohexyl formonitrile are added according to the set block ratio. Inert gas is introduced to replace the residual oxygen, and the mixture is heated to 72°C and stirred to start the reaction.

[0100] (4) After the reaction is completed, the reactor is connected to a vacuum distillation apparatus to remove the residual tert-butanol and ethylene glycol monomethyl ether in the feed liquid by distillation, and crude polymer particles are obtained.

[0101] (5) The solid product was removed and washed three times with a 90% (v / v) cyclopentane and isopropanol mixed solution. After filtration and drying, the self-assembled block copolymer was obtained. First, the dried polymer was subjected to 1H NMR spectroscopy to determine the block ratio of the block copolymer. The molecular weight of the block copolymer was analyzed by gel permeation chromatography, which proved that it had a good molecular weight distribution.

[0102] (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 65 wt% to prepare a homogeneous solution with a concentration of 22 wt%. The solution was allowed to stand for 24 hours to defoam, and after scraping and a brief solvent evaporation of 15 s, it was immersed in water to obtain a uniformly porous membrane with a thickness of 75 μm and a support fabric of polyester nonwoven fabric.

[0103] Subsequently, the structure of the prepared uniformly porous membrane was characterized by electron microscopy, and the prepared uniformly porous membrane exhibited a good uniform pore structure. Infrared spectroscopy was used to analyze the uniformly porous membrane prepared from the block copolymer. The water flux of the uniformly porous membrane was determined using a Millipore ultrafiltration cup, and its rejection rate was determined using bovine hemoglobin, bovine serum albumin, and lysozyme.

[0104] Example 9

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

[0106] (2) The oxygen in the homogeneous reaction solution and the reaction vessel was removed by gas replacement. The mixture was heated to 75°C under nitrogen protection and stirred to start the reaction, thus obtaining a hydrophilic polymer.

[0107] (3) After the hydrophilic monomer reaches a conversion rate of 97%, the reaction solution is cooled. Then, in the homogeneous solution, 260 g of 4-fluorostyrene monomer, 1800 ml of a mixed solution of 20% ethylene glycol monomethyl ether and water and 0.1 g of ammonium persulfate are added according to the set block ratio. Inert gas is introduced to replace the residual oxygen, and the mixture is heated to 75°C and stirred to start the reaction.

[0108] (4) After the reaction is completed, the reactor is connected to a vacuum distillation apparatus to remove the residual ethanol and water in the feed liquid by distillation, and crude polymer particles are obtained.

[0109] (5) The solid product was removed and washed four times with a 50% (v / v) mixed solution of n-octane and tert-butanol. After filtration and drying, the self-assembled block copolymer was obtained. The block ratio of the block copolymer was determined by 1H NMR spectroscopy. The molecular weight of the block copolymer was analyzed by gel permeation chromatography, which proved that it had a good molecular weight distribution.

[0110] (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 50 wt% to prepare a homogeneous solution with a concentration of 23 wt%. The solution was allowed to stand for 24 hours to defoam, and after scraping and short-term solvent evaporation for 25 s, it was immersed in water to obtain a membrane with a thickness of 75 μm. The support cloth was a nylon microporous membrane to obtain a uniformly porous membrane.

[0111] Subsequently, the structure of the prepared uniformly porous membrane was characterized by electron microscopy, and the prepared uniformly porous membrane exhibited a good uniform pore structure. Infrared spectroscopy was used to analyze the uniformly porous membrane prepared from the block copolymer. The water flux of the uniformly porous membrane was determined using a Millipore ultrafiltration cup, and its rejection rate was determined using bovine hemoglobin, bovine serum albumin, and lysozyme.

[0112] It will be understood by those skilled in the art that the above descriptions are merely preferred examples of the invention and are not intended to limit the invention. Although the invention 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 substitutions for some of the technical features. All modifications and equivalent substitutions made within the spirit and principles of the invention should be included within the scope of protection of the invention.

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 uniform solution with the hydrophilic polymer and being unable to dissolve the self-assembled block copolymer formed in subsequent polymerization; the cosolvent is selected from any one of the mixed solvents of water and glycol monomethyl ether, water and isopropanol, water and ethanol, water and methanol, and water and n-propanol, wherein the volume fraction of water is 5%-65%; 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, filtered, and dried, so that a self-assembled block copolymer is obtained; 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; The hydrophobic monomer is selected from any one of methyl methacrylate, methyl acrylate, styrene, trifluoromethyl methacrylate, and 4-fluorostyrene.

2. The polymerization process of self-assembling block copolymers according to claim 1, characterized in that, The initiator is selected from any one of dibenzoyl peroxide, diacetyl peroxide, ammonium persulfate, azobisimidoform hydrochloride, azobiscyclohexylnitrile, azobisisobutylimidazoline hydrochloride, azobisisobutyronitrile, and azobisisoheptyl nitrile.

3. 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)aminodithiocarbamic cyanomethyl ester, and 4-cyano-4-[((n)alkylsulfanylthiocarbonyl)sulfanyl]pentanoic acid, wherein n is 5-12.

4. 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 glycol monomethyl ether, propylene glycol monomethyl ether, isopropanol, butanol, water, methanol, ethanol, and tert-butanol in any proportion.

5. The polymerization process of self-assembling block copolymers according to claim 1, characterized in that, 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%.

6. A self-assembled block copolymer prepared by a polymerization method of the self-assembled block copolymer according to any one of claims 1 to 5.

7. A uniform pore membrane prepared from the self-assembled block copolymer of claim 6, 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 is 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 to 55 wt%. 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%, and a mixed solution of tetrahydrofuran and 1,4-dioxane with a mass percentage of 10 to 50 wt%.

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