CN118126268A - Ester-terminated polyethersulfone block copolymer and preparation method and use thereof - Google Patents

Abstract

The invention provides an ester-terminated polyethersulfone block copolymer and a preparation method and use thereof, belonging to the technical field of polyethersulfone block copolymers. The invention prepares polyethersulfone by polymerization of bisphenol S and bis(4-fluorophenyl)sulfone, and terminates the polyethersulfone by introducing 2-bromoisobutyryl bromide to obtain a modified polyethersulfone, and then prepares an ester-terminated polyethersulfone block copolymer by polymerization of an acrylate monomer and the modified polyethersulfone, wherein the ester-terminated polyethersulfone block copolymer has a high molecular weight and a uniform molecular weight distribution, so the ultrafiltration membrane prepared has high strength, and the ultrafiltration membrane has good selective permeability and high water flux, and the biochemical oxygen demand, total suspended solids, dissolved oxygen and coliform count in the water after filtering seawater are low, indicating that the ultrafiltration membrane has a good separation effect.

Description

Ester-terminated polyethersulfone block copolymer and preparation method and use thereof

Technical Field

The invention relates to the technical field of polyethersulfone block copolymers, and in particular to an ester-terminated polyethersulfone block copolymer and a preparation method and application thereof.

Background technique

Block copolymers are special polymer materials formed by connecting two or more polymer segments with different properties through chemical polymerization. Due to the different number of segments, they can be divided into diblock copolymers, triblock copolymers and multiblock copolymers. These segments can be different molecular structures of the same type or different types of molecular structures. Linear copolymers formed by alternating polymerization of different types of molecular structures can combine the excellent properties of multiple polymers to obtain functional polymer materials with relatively superior performance. The molecular weight of block copolymers is controllable, the molecular weight distribution is narrow, and the molecular structure and composition can be designed. The glass transition temperature is determined by the segment with lower temperature, while the softening point is determined by the segment with higher temperature. Therefore, the temperature range of the highly elastic state is wide, and it is often used as a membrane material in the field of membrane technology.

The block copolymers of membrane materials are often amphiphilic block copolymers, which refer to block copolymers that contain both hydrophilic and hydrophobic segments in the same polymer and have affinity for both water and oil phases. Amphiphilic block copolymers with clear structures can be prepared by many polymerization methods, such as anionic polymerization, living free radical polymerization, etc. Polyethersulfone, as a high-performance polymer material, has chemical stability, thermal stability, strong rigidity, high strength, good heat resistance, acid and alkali resistance, and chlorine resistance.

CN106731909B discloses an ATRP-based polyethersulfone ultrafiltration membrane for oil-water separation, and a preparation method and application thereof, comprising the following steps: performing an acyl bromide reaction on polyoxyethylene polyoxypropylene ether (F127) under the catalysis of 4-dimethylaminopyridine by 2-bromoisobutyryl bromide to generate an initiator F127-Br; then subjecting the initiator to atom transfer free radical polymerization with monomer hydroxyethyl methacrylate (HEMA) and a complex, and reacting at 50°C for 3-24h to generate F127-b-PHEMA in different proportions, thereby achieving control over the degree of polymerization reaction; then taking the synthesized F127-b-PHEMA as a modified substance, adding it to the casting solution for blending modification; and finally scraping out an organic membrane of 220 μm on a flat film scraping machine.

CN102803341A discloses an aromatic polyethersulfone block copolymer, which consists of polyethersulfone units and polyphenylsulfone units. The obtained block copolymer is then selectively sulfonated using aqueous concentrated sulfuric acid, and the sulfonated block copolymer has a strong separation advantage in the range of 10 to 100 nm; therefore, the block copolymer can simultaneously obtain advantages such as mechanical stability, low swelling of thin plates in water/methanol, high water permeability or high ionic conductivity.

Polyethersulfone is composed of polymer chains and cross-linked structures, so polyethersulfone ultrafiltration membranes are usually porous polymer materials with a molecular weight cutoff range of 1 kDa to 500 kDa, which can remove proteins, viruses, bacteria, colloids, etc. in liquids while allowing smaller molecules and solvents to pass through. However, polyethersulfone itself is a highly hydrophobic compound, which means it repels water and other polar solvents, so polyethersulfone needs to be modified by adding functional groups or coatings that attract water molecules.

CN106310959A discloses a method for preparing a hydrophilic polyarylethersulfone membrane, wherein a deprotonating agent is added to promote direct reaction between polyarylethersulfone and a hydrophilic hydroxyl-containing polymer, thereby generating a hydrophilic polyarylethersulfone block copolymer in situ, and the reaction solution is used to prepare a hydrophilic polyarylethersulfone membrane by a phase inversion method. The method eliminates the steps of precipitation, filtration and drying in the preparation of a traditional hydrophilic modifier.

CN101219350B discloses a method for producing a hydrophilic polyethersulfone microporous filter membrane, comprising dissolving a polyethersulfone solid polymer material in a highly polar organic solvent, and adding a polymer material mixture of polyvinyl pyrrolidone-vinyl acetate and polyoxazoline as a specific additive, and then spreading the solution on a continuously rotating roller or conveyor belt, contacting conditioned air with the solution, and then placing the primary filter membrane on the roller or conveyor belt into a 5-80°C water bath for final molding, and finally washing the molded microporous filter membrane, and performing post-processing and drying steps to produce a dry final product.

In summary, the properties of block copolymers have a decisive influence on the ultrafiltration membrane prepared therefrom. The hydrophilicity and hydrophobicity of block copolymers will also affect the separation selectivity of the ultrafiltration membrane. Therefore, in the prior art, the strength and separation selectivity of the ultrafiltration membrane prepared by polyethersulfone block copolymers are poor, which is still a technical problem that needs to be solved urgently.

Summary of the invention

In view of the above problems, the present invention provides an ester-terminated polyethersulfone block copolymer and a preparation method and use thereof. The ester-terminated polyethersulfone block copolymer has a high molecular weight and a uniform molecular weight distribution. An ultrafiltration membrane prepared from the ester-terminated polyethersulfone block copolymer has high separation selectivity and high water flux. The biochemical oxygen demand, dissolved oxygen content and bacterial population of seawater after filtration through the ultrafiltration membrane are low, and the separation effect is good.

The present invention provides an ester-terminated polyethersulfone block copolymer, wherein the ester-terminated polyethersulfone block copolymer is prepared by atom transfer radical polymerization of acrylate monomers and modified polyethersulfone; the molecular weight of the ester-terminated polyethersulfone block copolymer is 25000-35000, and the molecular weight distribution index is 2.5-2.8; the ester-terminated polyethersulfone block copolymer is a linear block copolymer; the structural formula of the ester-terminated polyethersulfone block copolymer is:

, where R is/> 、/> 、/> One of the following, wherein n and m are positive integers greater than or equal to 1, and n and m are equal or unequal.

The present invention also provides a method for preparing the ester-terminated polyethersulfone block copolymer, comprising the following steps:

Step 1, under continuous stirring conditions, dissolving bisphenol S and bis(4-fluorophenyl)sulfone in an organic solvent 1, and performing a polymerization reaction under a nitrogen atmosphere to obtain a mixed solution 1, adding a neutralizing agent to adjust the pH value of the mixed solution 1, and then adding 2-bromoisobutyryl bromide and a catalyst 1 to perform a catalytic reaction to obtain a mixed solution 2, and filtering and evaporating to obtain a modified polyethersulfone;

Step 2: dissolving the modified polyethersulfone, acrylate monomer and chelating agent in organic solvent 2 under continuous stirring, adding catalyst 2 to catalyze the reaction to obtain mixed solution 3, filtering and evaporating to obtain the ester-terminated polyethersulfone block copolymer.

Furthermore, the speed of continuous stirring in step 1 is 300-500 r/min.

Furthermore, in step 1, the molar ratio of bisphenol S to bis(4-fluorophenyl)sulfone is 1.01:1.

Furthermore, in step 1, the ratio of the organic solvent 1 to the total mass of bisphenol S and bis(4-fluorophenyl)sulfone is 4:1.

Furthermore, in step 1, the organic solvent 1 is one or more of dimethyl sulfone or cyclopentane.

Furthermore, in step 1, the polymerization reaction temperature is 100-120° C., and the polymerization reaction time is 2-3 hours.

Furthermore, in step 1, the mass ratio of the neutralizing agent to the mixed solution 1 is 0.1:1.

Furthermore, in step 1, the neutralizing agent is potassium carbonate.

Furthermore, in step 1, the pH value of the mixed solution 1 is adjusted to 6-7.

Furthermore, in step 1, the molar ratio of 2-bromoisobutyryl bromide, catalyst 1 and bisphenol S is 0.3:0.1:0.06.

Furthermore, in step 1, the catalyst 1 is 4-dimethylaminopyridine.

Furthermore, in step 1, the temperature of the catalytic reaction is 20-30° C., and the time of the catalytic reaction is 24-48 hours.

Furthermore, in step 1, the evaporation temperature is 120° C. and the evaporation time is 6 hours.

Furthermore, the speed of continuous stirring in step 2 is 300-500 r/min.

Furthermore, in step 2, the mass ratio of the modified polyethersulfone, the acrylate monomer and the chelating agent is 0.5:1:0.001.

Furthermore, in step 2, the mass ratio of catalyst 2 to chelating agent is 0.1:1.

Furthermore, in step 2, the mass volume ratio of the modified polyethersulfone to the organic solvent 2 is 0.5:24.

Furthermore, in step 2, the acrylate monomer is one or more of n-hexyl acrylate, 2-ethylhexyl acrylate, and ethylene glycol phenyl ether acrylate.

Furthermore, in step 2, the second catalyst is cuprous bromide (CuBr).

Furthermore, in step 2, the chelating agent is N,N,N',N",N"-pentamethyldiethylenetriamine (PMDETA).

Furthermore, in step 2, the second organic solvent is dichloromethane.

Furthermore, in step 2, the reaction temperature is 50-100° C., and the reaction time is 18-24 hours.

Furthermore, in step 2, the evaporation temperature is 120° C. and the evaporation time is 6 hours.

The present invention also provides a use of the ester-terminated polyethersulfone block copolymer, wherein the ester-terminated polyethersulfone block copolymer is used to prepare an ultrafiltration membrane, wherein the ultrafiltration membrane has a thickness of 50-99 μm, an average surface pore size of 11-13 nm, and a porosity of 85-88%; the separation selectivity of the ultrafiltration membrane is 80-90%, the breaking strength of the ultrafiltration membrane is 2.0-2.2 MPa, the water flux of the ultrafiltration membrane is 400-1500 LMH, and the enrichment multiple is 50-100; after the ultrafiltration membrane filters seawater, the BOD ₅ content in the seawater is 2-3 mg/L, the total suspended matter content is 4 mg/L, the dissolved oxygen content is 5 mg/L, and the total number of Escherichia coli groups is 112-115.

Furthermore, the method for preparing the ultrafiltration membrane comprises the following steps:

Step (1), stirring and dissolving the ester-terminated polyethersulfone block copolymer in organic solution three, standing at room temperature, vacuum degassing to obtain a casting solution, pouring the casting solution on a glass plate, and scraping it flat with a scraper, and placing the scraped casting solution into deionized water for phase inversion to obtain the ultrafiltration membrane.

Furthermore, in step (1), the organic solution three is N,N-dimethylacetamide.

Furthermore, in the step (1), the ester-terminated block copolymer accounts for 15-18 wt% of the total casting solution, and the organic solution three accounts for 82-85 wt% of the total casting solution.

Furthermore, in the step (1), the stirring and dissolving speed is 100-300 r/min, the stirring and dissolving temperature is 30-50° C., and the stirring and dissolving time is 12-24 h.

Furthermore, the degassing time in step (1) is 12 hours and the vacuum degree is -0.1 MPa.

Furthermore, the film scraping thickness of the film scraping machine in step (1) is 100-200 μm.

Furthermore, in the step (1), the temperature of the deionized water is 30-40° C., and the phase inversion time is 1-5 min.

Beneficial effects of the present invention:

1. The present invention prepares polyethersulfone by polymerizing bisphenol S and bis(4-fluorophenyl)sulfone, and end-caps the polyethersulfone by introducing 2-bromoisobutyryl bromide to obtain modified polyethersulfone, and then prepares an ester-terminated polyethersulfone block copolymer by polymerizing an acrylic ester monomer and the modified polyethersulfone. The ester-terminated polyethersulfone block copolymer has a high molecular weight and a uniform molecular weight distribution. Therefore, the prepared ultrafiltration membrane has high strength, good selective permeability, high water flux, and low biochemical oxygen demand, total suspended solids, dissolved oxygen and coliform count in water after filtering seawater, indicating that the ultrafiltration membrane has a good separation effect;

2. The process for preparing the ester-terminated polyethersulfone block copolymer in the present invention is simple and easy to operate, and the raw materials used are non-toxic and harmless, and have no environmental pollution, thereby ensuring the safety of production. In addition, the ultrafiltration membrane in the present application has a wide range of applications, and can be used not only in the field of seawater separation, but also in the field of domestic or industrial sewage treatment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a thermogravimetric analysis curve of the materials in Example 1 and Comparative Example 2;

FIG. 2 is a gel permeation chromatography (GPC) curve of the materials in Example 1 and Comparative Example 2.

Detailed ways

The invention is described in detail below with reference to the embodiments:

The invention provides an ester-terminated polyethersulfone block copolymer and a preparation method and use thereof. An ultrafiltration membrane prepared from the ester-terminated polyethersulfone block copolymer has high porosity, high separation selectivity, high water flux, low biochemical oxygen demand, dissolved oxygen content and bacterial population of seawater after filtration through the ultrafiltration membrane, and good separation effect.

Example 1

The present embodiment provides an ester-terminated polyethersulfone block copolymer, wherein the ester-terminated polyethersulfone block copolymer is prepared by atom transfer radical polymerization of an acrylate monomer and a modified polyethersulfone; the molecular weight of the ester-terminated polyethersulfone block copolymer is 25,000, and the molecular weight distribution index is 2.5; the ester-terminated polyethersulfone block copolymer is a linear block copolymer.

This embodiment also provides a method for preparing the ester-terminated polyethersulfone block copolymer, comprising the following steps:

Step 1, under continuous stirring at 300r/min, 62.57g of bisphenol S and 62.93g of bis(4-fluorophenyl)sulfone were dissolved in 502g of dimethyl sulfone, and polymerized for 2h in a nitrogen atmosphere at 100°C to obtain a mixed solution 1, 62.75g of potassium carbonate was added to adjust the pH value of the mixed solution 1 to 6, and then 287.39g of 2-bromoisobutyryl bromide and 51.53g of 4-dimethylaminopyridine were added, and the mixture was catalyzed at 20°C for 24h to obtain a mixed solution 2, which was filtered and evaporated at 120°C for 6h to obtain a modified polyether sulfone;

Step 2: Under continuous stirring at 300 r/min, 150 g of the modified polyethersulfone, 300 g of n-hexyl acrylate and 0.3 g of N,N,N',N",N"-pentamethyldiethylenetriamine are dissolved in 7200 mL of dichloromethane, 0.03 g of cuprous bromide is added, and the mixture is reacted at 50° C. for 24 h to obtain a mixed solution three. After filtering, the mixture is evaporated at 120° C. for 6 h to obtain the ester-terminated polyethersulfone block copolymer.

The present embodiment also provides a use of the ester-terminated polyethersulfone block copolymer, wherein the ester-terminated polyethersulfone block copolymer is used to prepare an ultrafiltration membrane, wherein the ultrafiltration membrane has a thickness of 50 μm, an average surface pore size of 13 nm, and a porosity of 85%; the separation selectivity of the ultrafiltration membrane is 85%, the breaking strength of the ultrafiltration membrane is 2.0 MPa, the water flux of the ultrafiltration membrane is 1500 LMH, and the enrichment factor is 100; after the ultrafiltration membrane filters seawater, the BOD ₅ content in the seawater is 3 mg/L, the total suspended matter content is 4 mg/L, the dissolved oxygen content is 5 mg/L, and the total number of Escherichia coli is 115.

This embodiment also provides a method for preparing the ultrafiltration membrane, comprising the following steps:

Step (1), stirring 15g of the ester-terminated polyethersulfone block copolymer at 30°C and 100r/min for 12h, dissolving it in 85g of N,N-dimethylacetamide, and standing it for degassing at room temperature and -0.1MPa vacuum for 12h to obtain a casting solution; pouring the casting solution onto a glass plate and scraping it into a casting solution with a thickness of 100μm using a scraping machine, placing the scraped casting solution into deionized water at 30°C for phase inversion for 1min to obtain the ultrafiltration membrane.

Example 2

The present embodiment provides an ester-terminated polyethersulfone block copolymer, wherein the ester-terminated polyethersulfone block copolymer is prepared by an atom transfer radical polymerization reaction of an acrylate monomer and a modified polyethersulfone; the molecular weight of the ester-terminated polyethersulfone block copolymer is 35,000, and the molecular weight distribution index is 2.8; the ester-terminated polyethersulfone block copolymer is a linear block copolymer.

This embodiment also provides a method for preparing the ester-terminated polyethersulfone block copolymer, comprising the following steps:

Step 1, under continuous stirring at 500r/min, 62.57g of bisphenol S and 62.93g of bis(4-fluorophenyl)sulfone were dissolved in 502g of cyclopentane sulfone, and polymerized for 3h in a nitrogen atmosphere at 110°C to obtain a mixed solution 1, 62.75g of potassium carbonate was added to adjust the pH value of the mixed solution 1 to 7, and then 287.39g of 2-bromoisobutyryl bromide and 51.13g of 4-dimethylaminopyridine were added, and the mixture was catalyzed at 30°C for 48h to obtain a mixed solution 2, which was filtered and evaporated at 120°C for 6h to obtain a modified polyethersulfone;

Step 2: Under continuous stirring at 500 r/min, 150 g of the modified polyethersulfone, 300 g of 2-ethylhexyl acrylate and 0.3 g of N,N,N',N",N"-pentamethyldiethylenetriamine were dissolved in 7200 mL of dichloromethane, 0.03 g of cuprous bromide was added, and the mixture was reacted at 100° C. for 18 h to obtain a mixed solution three. After filtering, the mixture was evaporated at 120° C. for 6 h to obtain the ester-terminated polyethersulfone block copolymer.

The present embodiment also provides a use of the ester-terminated polyethersulfone block copolymer, wherein the ester-terminated polyethersulfone block copolymer is used to prepare an ultrafiltration membrane, wherein the ultrafiltration membrane has a thickness of 99 μm, an average surface pore size of 11 nm, and a porosity of 88%; the separation selectivity of the ultrafiltration membrane is 90%, the breaking strength of the ultrafiltration membrane is 2.2 MPa, the water flux of the ultrafiltration membrane is 400 LMH, and the enrichment multiple is 50; after the ultrafiltration membrane filters seawater, the BOD ₅ content in the seawater is 2 mg/L, the total suspended matter content is 4 mg/L, the dissolved oxygen content is 5 mg/L, and the total number of Escherichia coli groups is 112.

This embodiment also provides a method for preparing the ultrafiltration membrane, comprising the following steps:

Step (1), stirring 18g of the ester-terminated polyethersulfone block copolymer at 50°C and 200r/min for 18h, dissolving it in 82g of N,N-dimethylacetamide, and standing it for degassing at room temperature and -0.1MPa vacuum for 12h to obtain a casting solution; pouring the casting solution onto a glass plate and scraping it into a casting solution with a thickness of 200μm using a scraping machine, placing the scraped casting solution into deionized water at 40°C for phase inversion for 3min to obtain the ultrafiltration membrane.

Example 3

The present embodiment provides an ester-terminated polyethersulfone block copolymer, wherein the ester-terminated polyethersulfone block copolymer is prepared by atom transfer radical polymerization of an acrylate monomer and a modified polyethersulfone; the molecular weight of the ester-terminated polyethersulfone block copolymer is 26,000, and the molecular weight distribution index is 2.6; the ester-terminated polyethersulfone block copolymer is a linear block copolymer.

This embodiment also provides a method for preparing the ester-terminated polyethersulfone block copolymer, comprising the following steps:

Step 1, under continuous stirring at 400r/min, 62.57g of bisphenol S and 62.93g of bis(4-fluorophenyl)sulfone were dissolved in 502g of dimethyl sulfone, and polymerized for 2.5h in a nitrogen atmosphere at 120°C to obtain a mixed solution 1, 62.75g of potassium carbonate was added to adjust the pH value of the mixed solution 1 to 6, and then 287.39g of 2-bromoisobutyryl bromide and 51.13g of 4-dimethylaminopyridine were added, and the mixture was catalyzed for 36h at 25°C to obtain a mixed solution 2, which was filtered and evaporated at 120°C for 6h to obtain a modified polyether sulfone;

Step 2: Under continuous stirring at 400 r/min, 150 g of the modified polyethersulfone, 300 g of ethylene glycol phenyl ether acrylate and 0.3 g of N,N,N',N",N"-pentamethyldiethylenetriamine are dissolved in 7200 mL of dichloromethane, 0.03 g of cuprous bromide is added, and the mixture is reacted at 80° C. for 20 h to obtain a mixed solution three. After filtering, the mixture is evaporated at 120° C. for 6 h to obtain the ester-terminated polyethersulfone block copolymer.

The present embodiment also provides a use of the ester-terminated polyethersulfone block copolymer, wherein the ester-terminated polyethersulfone block copolymer is used to prepare an ultrafiltration membrane, wherein the ultrafiltration membrane has a thickness of 75 μm, an average surface pore size of 12 nm, and a porosity of 86%; the separation selectivity of the ultrafiltration membrane is 85%, the breaking strength of the ultrafiltration membrane is 2.1 MPa, the water flux of the ultrafiltration membrane is 700 LMH, and the enrichment factor is 80; after the ultrafiltration membrane filters seawater, the BOD ₅ content in the seawater is 3 mg/L, the total suspended matter content is 4 mg/L, the dissolved oxygen content is 5 mg/L, and the total number of Escherichia coli is 113.

This embodiment also provides a method for preparing the ultrafiltration membrane, comprising the following steps:

Step (1), stirring 15g of the ester-terminated polyethersulfone block copolymer at 40°C and 300r/min for 24h, dissolving it in 85g of N,N-dimethylacetamide, and standing it for degassing at room temperature and -0.1MPa vacuum for 12h to obtain a casting solution; pouring the casting solution onto a glass plate and scraping it into a casting solution with a thickness of 200μm using a scraping machine, placing the scraped casting solution into deionized water at 35°C for phase inversion for 5min to obtain the ultrafiltration membrane.

Comparative Example 1

This comparative example provides a block copolymer, which is prepared by reacting an acrylate monomer with bisphenol S and bis(4-fluorophenyl)sulfone; the molecular weight of the block copolymer is 20,000, and the molecular weight distribution index is 2.5.

This comparative example also provides a method for preparing the block copolymer, comprising the following steps:

Step 1, under continuous stirring at 400 r/min, 62.57 g of bisphenol S and 62.93 g of bis(4-fluorophenyl)sulfone were dissolved in 502 g of dimethyl sulfone, and polymerized for 2.5 h at 150° C. in a nitrogen atmosphere to obtain a mixed solution 1, 62.75 g of potassium carbonate was added to adjust the pH value of the mixed solution 1 to 6, and after filtering and evaporating at 120° C. for 6 h, polyether sulfone was obtained;

Step 2: Under continuous stirring at 400 r/min, 150 g of the polyethersulfone, 300 g of ethylene glycol phenyl ether acrylate and 0.3 g of N,N,N',N",N"-pentamethyldiethylenetriamine are dissolved in 7200 mL of dichloromethane, 0.03 g of cuprous bromide is added, and the mixture is reacted at 80° C. for 20 h to obtain a mixed solution three, which is then filtered and evaporated at 120° C. for 6 h to obtain the block copolymer.

This comparative example also provides a use of the block copolymer, wherein the block copolymer is used to prepare an ultrafiltration membrane, wherein the ultrafiltration membrane has a thickness of 50 μm, an average surface pore size of 13 nm, and a porosity of 70%; the separation selectivity of the ultrafiltration membrane is 80%, the breaking strength of the ultrafiltration membrane is 2.0 MPa, the water flux of the ultrafiltration membrane is 150 LMH, and the enrichment multiple is 10; after the ultrafiltration membrane filters seawater, the BOD ₅ content in the seawater is 4 mg/L, the total suspended matter content is 4 mg/L, the dissolved oxygen content is 5 mg/L, and the total number of Escherichia coli groups is 118.

This comparative example also provides a method for preparing the ultrafiltration membrane, comprising the following steps:

Step (1), stirring 15g of the block copolymer at 40°C and 300r/min for 24h, dissolving it in 85g of N,N-dimethylacetamide, and standing it for degassing at room temperature and -0.1MPa vacuum for 12h to obtain a casting solution, pouring the casting solution onto a glass plate, and scraping it into a casting solution with a thickness of 100μm with a scraping machine, placing the scraped casting solution into deionized water at 35°C for phase inversion for 5min to obtain the ultrafiltration membrane.

Comparative Example 2

This comparative example provides a polyethersulfone prepared by reacting bisphenol S and bis(4-fluorophenyl)sulfone; the molecular weight of the polyethersulfone is 20,000, and the molecular weight distribution index is 2.5.

This comparative example also provides a method for preparing the polyethersulfone, comprising the following steps:

Step 1. Under continuous stirring at 400 r/min, 62.57 g of bisphenol S and 62.93 g of bis(4-fluorophenyl)sulfone were dissolved in 502 g of dimethyl sulfone, and polymerized for 2.5 h at 150° C. in a nitrogen atmosphere to obtain a mixed solution 1. 62.75 g of potassium carbonate was added to adjust the pH value of the mixed solution 1 to 6. After filtering and evaporating at 120° C. for 6 h, modified polyethersulfone was obtained.

This comparative example also provides a use of the polyethersulfone, which is used to prepare an ultrafiltration membrane. The ultrafiltration membrane has a thickness of 80 μm, an average surface pore size of 11 nm, and a porosity of 60%; the separation selectivity of the ultrafiltration membrane is 85%, the breaking strength of the ultrafiltration membrane is 2.0 MPa, the water flux of the ultrafiltration membrane is 50 LMH, and the enrichment factor is 10; after the ultrafiltration membrane filters seawater, the BOD ₅ content in the seawater is 3 mg/L, the total suspended matter content is 4 mg/L, the dissolved oxygen content is 5 mg/L, and the total number of Escherichia coli is 117.

This comparative example also provides a method for preparing the ultrafiltration membrane, comprising the following steps:

Step (1), stirring 18g of the polyethersulfone at 40°C and 300r/min for 24h, dissolving it in 82g of N,N-dimethylacetamide, and standing it for degassing at room temperature and -0.1MPa vacuum for 12h to obtain a casting solution, pouring the casting solution onto a glass plate, and scraping it into a casting solution with a thickness of 200μm with a scraping machine, placing the scraped casting solution into deionized water at 35°C for phase inversion for 5min to obtain the ultrafiltration membrane.

FIG1 is a thermogravimetric analysis curve of the materials in Example 1 and Comparative Example 2, wherein the abscissa is temperature and the ordinate is mass percentage. As shown in the figure, the thermal decomposition temperature of the polyethersulfone in Comparative Example 2 is 500-600°C, and the thermal decomposition temperature of the ester-terminated polyethersulfone block copolymer in Example 1 is 400-500°C. The thermal decomposition temperature of the material decreases, indicating that the ester group is successfully connected to the polyethersulfone block copolymer.

FIG2 is a gel permeation chromatography (GPC) curve of the materials in Example 1 and Comparative Example 2, wherein the horizontal axis is the elution time. As shown in the figure, the elution time of the polyethersulfone in Comparative Example 2 is 18 minutes, and the elution time of the ester-terminated polyethersulfone block copolymer in Example 1 is 17 minutes. Since the ester-terminated polyethersulfone block copolymer introduces an ester group, the molecular weight of the ester-terminated polyethersulfone block copolymer is increased, and the elution time is reduced.

Table 1 Comparison of properties of the block copolymers described in Examples 1-3 and Comparative Examples 1-2

As shown in Table 1, the molecular weight of the ester-terminated polyethersulfone block copolymer of the present invention is 25,000-35,000, and the molecular weight distribution is 2.5-2.8. After the modified polyethersulfone is terminated by the ester group, the molecular weight becomes larger.

Table 2 Comparison of properties of the ultrafiltration membranes described in Examples 1-3 and Comparative Examples 1-2

As shown in Table 2, the ultrafiltration membrane in the present invention has a high porosity, and thus has a good ultrafiltration effect, good separation selectivity, and high water flux and enrichment multiple.

Table 3 Comparison of data before and after ultrafiltration membrane separation of seawater in Example 1-3 and Comparative Example 1-2

As shown in Table 3, the ultrafiltration membrane of the present invention has a better ultrafiltration effect on the five-day biochemical oxygen demand (BOD ₅ ) content in seawater, and a better ultrafiltration effect on the total number of Escherichia coli.

The molecular weight and molecular weight distribution of the ester-terminated polyethersulfone block copolymer described in the present invention are tested by gel permeation chromatography (GPC) under the following conditions: column temperature of 25°C, mobile phase of tetrahydrofuran, flow rate of 0.6 mL/min, and flow cell temperature of 25°C.

The test conditions for the separation selectivity, water flux and enrichment multiple of the ultrafiltration membrane in the present invention are 25° C. and 0.2 MPa.

In the data test of the ultrafiltration membrane before and after the separation of seawater in the present invention, the analysis method of the five-day biochemical oxygen demand ( _BOD5 ) content is the five-day culture method, the analysis method of the total suspended solids content is the weight method, the detection limit is 2 mg/L, and the analysis standard complies with "HY 003.4-91"; the analysis method of the dissolved oxygen content is the iodine titration method, the detection limit is 0.042 mg/L, and the analysis standard complies with "GB 12763.4-91"; the analysis method of the total Escherichia coli group is the filter membrane method, and the analysis standard complies with "HY 003.9-91".

Based on the above, it can be seen that the ultrafiltration membrane prepared from the ester-terminated polyethersulfone block copolymer in this patent application has a wide range of applications, low cost, and extremely high market prospects.

The above description is only a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any modification or equivalent change made based on the technical essence of the present invention still falls within the scope of protection required by the present invention.

Claims (10)

1. An ester-terminated polyethersulfone block copolymer, characterized in that the ester-terminated polyethersulfone block copolymer is prepared by atom transfer radical polymerization of acrylate monomers and modified polyethersulfone; the molecular weight of the ester-terminated polyethersulfone block copolymer is 25000-35000, and the molecular weight distribution index is 2.5-2.8; the ester-terminated polyethersulfone block copolymer is a linear block copolymer; the structural formula of the ester-terminated polyethersulfone block copolymer is: , where R is/> 、/> 、/> One of the following, wherein n and m are positive integers greater than or equal to 1, and n and m are equal or unequal. 2. A method for preparing the ester-terminated polyethersulfone block copolymer according to claim 1, characterized in that it comprises the following steps: Step 1, under continuous stirring conditions, dissolving bisphenol S and bis(4-fluorophenyl)sulfone in an organic solvent 1, and performing a polymerization reaction under a nitrogen atmosphere to obtain a mixed solution 1, adding a neutralizing agent to adjust the pH value of the mixed solution 1, and then adding 2-bromoisobutyryl bromide and a catalyst 1 to perform a catalytic reaction to obtain a mixed solution 2, and filtering and evaporating to obtain a modified polyethersulfone; Step 2: dissolving the modified polyethersulfone, acrylate monomer and chelating agent in organic solvent 2 under continuous stirring, adding catalyst 2 to catalyze the reaction to obtain mixed solution 3, filtering and evaporating to obtain ester-terminated polyethersulfone block copolymer. 3. The preparation method according to claim 2, characterized in that the molar ratio of bisphenol S to bis(4-fluorophenyl)sulfone in step 1 is 1.01:1. 4. The preparation method according to claim 2, characterized in that the organic solvent 1 in step 1 is one or more of dimethyl sulfone or cyclopentane. 5. The preparation method according to claim 2, characterized in that the polymerization reaction temperature in step 1 is 100-120°C and the polymerization reaction time is 2-3h. 6. The preparation method according to claim 2, characterized in that the molar ratio of 2-bromoisobutyryl bromide, catalyst 1 and bisphenol S in step 1 is 0.3:0.1:0.06. 7. The preparation method according to claim 2, characterized in that the mass ratio of the modified polyethersulfone, the acrylate monomer and the chelating agent in step 2 is 0.5:1:0.001. 8. The preparation method according to claim 2, characterized in that the acrylate monomer in step 2 is one or more of n-hexyl acrylate, 2-ethylhexyl acrylate, and ethylene glycol phenyl ether acrylate. 9. The preparation method according to claim 2, characterized in that the reaction temperature in step 2 is 50-100°C and the reaction time is 18-24h. 10. A use of the ester-terminated polyethersulfone block copolymer according to claim 1, characterized in that the ester-terminated polyethersulfone block copolymer is used to prepare an ultrafiltration membrane, the ultrafiltration membrane has a thickness of 50-99 μm, an average surface pore size of 11-13 nm, and a porosity of 85-88%; the separation selectivity of the ultrafiltration membrane is 80-90%, the breaking strength of the ultrafiltration membrane is 2.0-2.2 MPa, the water flux of the ultrafiltration membrane is 400-1500 LMH, and the enrichment multiple is 50-100; after the ultrafiltration membrane filters seawater, the BOD ₅ content in the seawater is 2-3 mg/L, the total suspended matter content is 4 mg/L, the dissolved oxygen content is 5 mg/L, and the total number of Escherichia coli is 112-115.