CN112979851B - Catalytic system for synthesizing polyacrylamide and synthesis method of polyacrylamide - Google Patents

Catalytic system for synthesizing polyacrylamide and synthesis method of polyacrylamide Download PDF

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CN112979851B
CN112979851B CN202110196716.3A CN202110196716A CN112979851B CN 112979851 B CN112979851 B CN 112979851B CN 202110196716 A CN202110196716 A CN 202110196716A CN 112979851 B CN112979851 B CN 112979851B
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polyacrylamide
polymerization
water
acrylamide
otf
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CN112979851A (en
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蒋建国
陈伟峰
程爱民
郭静
张睿
刘岳树
顾晓龙
薛梅
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Yangzhou Product Quality Supervision And Inspection Institute
Yangzhou Polytechnic College Yangzhou Radio and TV University
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Yangzhou Product Quality Supervision And Inspection Institute
Yangzhou Polytechnic College Yangzhou Radio and TV University
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F120/00—Homopolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride, ester, amide, imide or nitrile thereof
    • C08F120/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
    • C08F120/52—Amides or imides
    • C08F120/54—Amides, e.g. N,N-dimethylacrylamide or N-isopropylacrylamide
    • C08F120/56—Acrylamide; Methacrylamide
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F4/00—Polymerisation catalysts
    • C08F4/42—Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors
    • C08F4/44—Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors selected from light metals, zinc, cadmium, mercury, copper, silver, gold, boron, gallium, indium, thallium, rare earths or actinides
    • C08F4/52—Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors selected from light metals, zinc, cadmium, mercury, copper, silver, gold, boron, gallium, indium, thallium, rare earths or actinides selected from boron, aluminium, gallium, indium, thallium or rare earths
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F4/00—Polymerisation catalysts
    • C08F4/42—Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors
    • C08F4/44—Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors selected from light metals, zinc, cadmium, mercury, copper, silver, gold, boron, gallium, indium, thallium, rare earths or actinides
    • C08F4/54—Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors selected from light metals, zinc, cadmium, mercury, copper, silver, gold, boron, gallium, indium, thallium, rare earths or actinides together with other compounds thereof
    • C08F4/545—Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors selected from light metals, zinc, cadmium, mercury, copper, silver, gold, boron, gallium, indium, thallium, rare earths or actinides together with other compounds thereof rare earths being present, e.g. triethylaluminium + neodymium octanoate
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F6/00—Post-polymerisation treatments
    • C08F6/02—Neutralisation of the polymerisation mass, e.g. killing the catalyst also removal of catalyst residues
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2438/00—Living radical polymerisation
    • C08F2438/01—Atom Transfer Radical Polymerization [ATRP] or reverse ATRP

Abstract

The invention discloses a catalytic system for synthesizing polyacrylamide and a method for synthesizing polyacrylamide. The catalytic system comprises a catalyst with a molar ratio of 1: (0.5-2.5): (2.5-5): (0.8-1.5): chloroacetic acid, (1.5-2.5) Y (OTf)3、AlCl3、Cu2O and tetramethylethylenediamine. The invention establishes that chloroacetic acid is used as an initiator and matched with a catalyst Cu2O and complexing agent tetramethyl ethylenediamine to form an ATRP polymerization system suitable for acrylamide monomer, and two Lewis acids Y (OTf) are introduced3And AlCl3The polyacrylamide which is used as a directional polymerization control agent and has narrow molecular weight distribution and certain stereoregularity is synthesized by adjusting the use ratio of the directional polymerization control agent.

Description

Catalytic system for synthesizing polyacrylamide and synthesis method of polyacrylamide
Technical Field
The invention relates to a synthesis method of a polymer, in particular to a catalytic system for synthesizing polyacrylamide based on an acrylamide monomer and a synthesis method of the polyacrylamide.
Background
Polyacrylamide and its derivatives have been widely used in the fields of drinking water purification, mineral and wastewater treatment, oil extraction, soil improvement, cosmetics, agriculture and biopharmaceuticals because of their unique biocompatibility, nontoxicity and water solubility. Based on the concept of macromolecular design and in order to further expand the application field thereof to obtain more typical application functions, attention has been focused in recent years on synthesizing polyacrylamide compounds with narrow molecular weight distribution width, determined molecular weight and certain stereoregularity because the primary structure of the polymer determined by the molecular weight, molecular weight distribution and stereoregularity of the polymer determines the physical and chemical properties of the material, thereby greatly affecting the practical application thereof.
In order to synthesize a polyacrylamide compound having both a narrow molecular weight distribution width, a definite molecular weight and a definite stereoregularity, the first report of the use of CuCl/Me6-TREN [ tris- (N, N-dimethylaminoethyl) amine in Matyjaszewski et al in 2003 was]As active catalyst, Lewis acid Y (OTf)3Or Yb (OTf)3Polymerization of N, N-Dimethylacrylamide (DMAA) and N-methyl-methacrylamide as stereocontrol agents yields polymers with controlled molecular weight and high isotacticity. In 2006, Okamoto et al introduced Yb (OTf) into an ATRP polymerization system (atom transfer radical polymerization) of N, N-Dimethylacrylamide (DMAA) using an iron catalyst system3And Yb (NTf)2)3Poly (N, N-dimethylacrylamide) (isotacticity m) having very high isotacticity was obtained as a stereocontrol agent>80%) but the molecular weight distribution of the product is very broad, reaching 1.87 and 2.03 respectively. 2019 Yue Sun et al in photo-initiated ATRP polymerization of the monomer N- (2-hydroxyethyl) acrylamide with Lewis acid Y (OTf)3As a stereocontrol agent, under the best polymerization conditions, a polymerization product with the isotacticity m of 42-80% and the molecular weight distribution breadth index of 1.22 is obtained. The monomers for which control studies of polymer tacticity in these ATRP polymerization systems have been made are mainly acrylamide derivatives such as N, N-dimethylacrylamide, N-methyl-methacrylamide, etc., and only polyacrylamide derivatives can be synthesized, whereas polyacrylamide can be synthesized only by acrylamide monomers.
The synthesis of acrylamide polymers with narrow molecular weight distribution width and defined molecular weight by anionic polymerization is difficult to realize due to the presence of hydrogen protons on the amine groups of the acrylamide monomers, and a controllable/'living' free radical polymerization method is needed. Since chemoselectivity (reaction rate), orientation (head-to-head ratio) and stereoselectivity (tacticity) in controlled/"living" radical polymerization are similar to those of conventional radical polymerization, i.e., the SP2 hybrid carbon radical has a nearly planar configuration, both meso and racemic addition can occur, the "living"/controlled radical polymerization fails to get rid of the limitations of conventional radical polymerization and cannot obtain stereoregular polymers of specified structure. In recent years, based on the successful synthesis of polymers with controlled molecular weight and narrow molecular weight distribution, Atom Transfer Radical Polymerization (ATRP) has been a major method for controlled/"living" radical polymerization, and has made significant progress in the research of designing and synthesizing random copolymers, block and graft copolymers, star polymers, hyperbranched polymers, and end-functionalized polymers. Compared with other active polymerization methods or other vinyl monomers, the active amine group in the acrylamide monomer molecule is easy to cause the deactivation reaction of the ATRP catalyst, so that the activation process in the activation-deactivation balance is slowed down, and the ring formation side reaction is easy to occur in an ATRP system, therefore, the ATRP polymerization of the acrylamide monomer is more challenging and difficult to obtain the ideal polymerization result. For example, introduction of a polar solvent of the polyfluorool type or a Lewis acid into a polymerization system of most monomers can control the addition direction of a growing chain during polymerization by hydrogen bonding between the monomer or growing species and the polyfluorool or chelation between the monomer or growing species and the Lewis acid, so as to realize stereocontrolled polymerization of the polymer.
For example, Jewrajka and Mandal achieved ATRP polymerization of acrylamide in aqueous media in 2003. Despite their additional addition of CuX to the polymerization system2Or halides, but the molecular weight of the polyacrylamide obtained by polymerizationThe distribution is wide (1.6-1.7), and a GPC spectrogram shows a shoulder peak. Later, they improved the ATRP polymerization result of acrylamide by adjusting the catalytic system, and obtained a first order kinetic curve, but the molecular weight distribution breadth index of the product still reached 1.51. In 2006 and 2007, a method that a cuprous chloride is used as a catalyst, 2, 2' -bipyridine is used as a ligand, benzyl chloride or 2-chloropropionamide is used as an initiator, polyacrylamide and hydrogel thereof are synthesized through ATRP (atom transfer radical polymerization) when a Jangseng and a Jiangxing of university of Chongqing are successively reported, and in a polymerization system, the pH value of a solution needs to be adjusted to be neutral; the polymerization reaction has a significant induction period at certain temperatures (e.g., 70 ℃); the molecular weight distribution breadth index of the polymerization product polyacrylamide still reaches 1.5-2.0 under the condition that the conversion rate is less than 43.9%.
Therefore, there is a need to develop an initiated catalytic synthesis system suitable for ATRP polymerization of acrylamide monomers to achieve synthesis of polyacrylamide having both narrow molecular weight distribution and a certain stereoregularity.
Disclosure of Invention
In order to solve the problems, the invention provides a catalytic system for synthesizing polyacrylamide based on an acrylamide monomer and a synthesis method of the polyacrylamide, and the polyacrylamide with narrow molecular weight distribution and certain stereoregularity can be obtained by catalyzing the acrylamide monomer by using the catalytic system.
In order to achieve the above object, the present invention provides a catalytic system for synthesizing polyacrylamide, wherein the catalytic system comprises a catalyst with a molar ratio of 1: (0.5-2.5): (2.5-5): (0.8-1.5): chloroacetic acid, (1.5-2.5) Y (OTf)3、AlCl3、Cu2O and tetramethylethylenediamine.
The second aspect of the present invention provides a method for synthesizing polyacrylamide, which comprises the following steps: sequentially adding Cu2O, tetramethylethylenediamine, acrylamide, Y (OTf)3、AlCl3Mixing the solvent and chloroacetic acid, performing freezing-vacuum pumping-nitrogen introducing circulation process for 2-4 times, performing closed reaction at 80-100 ℃ for 40-60 hours to obtain a polymerization product,
wherein the chloroacetic acid,The Y (OTf)3The AlCl3The Cu2The molar ratio of the used amounts of O, the tetramethylethylenediamine, the acrylamide and the solvent is 1: (0.5-2.5): (2.5-5): (0.8-1.5): (1.5-2.5): (45-55): (40-60).
Specifically, the solvent is water; or the solvent is a mixed solvent of water and glycerol and/or ethylene glycol.
Further, the molar ratio of water in the mixed solvent is 50% or more.
Specifically, the freezing adopts liquid nitrogen freezing.
Specifically, the mixture is subjected to a sealed reaction in a constant-temperature oil bath at 80-100 ℃ for 40-60 hours.
Further, the method also comprises the following processing steps after the polymerization product is obtained:
s1, dissolving the polymerization product in water in an atmospheric environment, precipitating with methanol, centrifuging, and dissolving the separated substance in water again;
s2, removing the copper complex;
and S3, precipitating with methanol again, and drying the precipitate to obtain the polyacrylamide.
Specifically, in step S1, the conditions of the centrifugal separation are: separating in a centrifuge at 2000-3000 rpm for 5-10 min.
Preferably, in step S2, the copper complex is removed by a cation exchange column.
Preferably, in step S3, the drying conditions are: vacuum drying at 40-50 deg.C for 20-30 hr.
Through the technical scheme, the invention has the following beneficial effects:
1. the invention establishes that chloroacetic acid is used as an initiator and matched with a catalyst Cu2O and complexing agent tetramethyl ethylenediamine to form an ATRP polymerization system suitable for acrylamide monomer, and two Lewis acids Y (OTf) are introduced3And AlCl3The polyacrylamide with narrow molecular weight distribution and certain stereoregularity is synthesized by being used as a directional polymerization control agent and adjusting the use ratio of the directional polymerization control agent;
2. the invention selects alpha-halogenated carboxylic acid chloroacetic acid as an ATRP (atom transfer radical polymerization) initiator of an acrylamide monomer, the acid has strong acidity, and a Cl-C bond in a molecular structure has high activity, so that the provided acidic initiation system can effectively prevent a complexing side reaction or a ring formation side reaction which may occur in the polymerization process of acrylamide, thereby realizing ideal ATRP polymerization of the acrylamide;
3. in water-soluble ATRP polymerization systems of acrylamide monomers, Cu is compared with other cuprous salts such as CuCl, CuBr and the like2O has stable property and higher catalytic activity; compared with bipyridine compounds, the tetramethylethylenediamine is used as a catalytic complexing agent, and the linear structure of the tetramethylethylenediamine similar to that of an acrylamide monomer can effectively improve the Cu catalyst2The solubility of O, thus making the whole system more uniform.
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
The invention provides a catalytic system for synthesizing polyacrylamide, which comprises the following components in a molar ratio of 1: (0.5-2.5): (2.5-5): (0.8-1.5): chloroacetic acid, (1.5-2.5) Y (OTf)3、AlCl3、Cu2O and tetramethylethylenediamine.
Suitable initiators are an important factor in determining the progress of the ATRP polymerization. Practice has shown that various organic compounds such as halogenated hydrocarbons, halogenated alkylbenzenes, halogenated ketones, halogenated acid esters, sulfonyl chlorides, etc. successfully initiate polymerization of the relevant monomers in atom transfer radical polymerization. For acrylamide monomers, chloroacetic acid in the alpha-halogenated carboxylic acid series is selected as an ATRP initiator of the acrylamide monomers. Chloroacetic acid is cheap and easily available, is easily dissolved in water, and has high activity of Cl-C bond. Meanwhile, compared with other halogenated carboxylic acids, the halogenated carboxylic acid has strong acidity. The acidic initiation system provided by chloroacetic acid is different from the traditional neutral ATRP polymerization, so that the complexation side reaction or cyclization side reaction which may occur in the acrylamide polymerization process can be effectively prevented. On the other hand, chloroacetic acid has two functional groups-Cl and-COOH, when acrylamide ATRP polymerization is initiated by chloroacetic acid, the chloroacetic acid can be grafted to two ends of the product polyacrylamide, and a very convenient way is provided for further preparing the functionalized polymer.
The invention firstly establishes that chloroacetic acid is used as an initiator and is matched with Cu2O and complexing agent tetramethylethylenediamine are used as catalytic complexing agents, and the ATRP aqueous solution polymerization system is suitable for acrylamide monomers. On the basis, in consideration of the molecular structure characteristics of the acrylamide monomer, Lewis acid is further introduced into a water-soluble ATRP polymerization system of the monomer as a directional polymerization control agent. Tetrafluoromethane sulfonates of rare earth metals, e.g. Y (OTf)3Is a particular Lewis acid, since it has a strong Lewis acidity, a high coordination number, is tolerant to protic solvents and water, and is therefore described by Y (OTf)3Is one of the most effective additives in controlling the regularity of the polymerization product in the polymerization reaction. AlCl3As a Lewis acid with moderate acidity, the acid is cheap and easy to obtain. Based on AlCl3Into the polymerization reaction of the present system, the Lewis acid AlCl3Possibly reacting with alkene chain hydrocarbon with electron-withdrawing groups, increasing the complexation of the alkene chain hydrocarbon with monomers or growing high molecular chain segments, and being capable of generating positive effect on the improvement of the isotacticity of products in the ATRP polymerization reaction of acrylamide; simultaneously, AlCl3Partial hydrolysis is possible in the water system and further increases the acidity of the reaction system, thereby making the acrylamide ATRP reaction milder.
The acidic polymerization condition provided by chloracetic acid as an ATRP initiator is utilized, so that the complexation or cyclization side reaction in the ATRP process of acrylamide is effectively prevented, and the possibility that the complexation of the ATRP and an ATRP metal catalyst is influenced by the transfer of a complexing agent used by the ATRP to Lewis acid is reduced, thereby obtaining the polyacrylamide with controllable molecular weight distribution and certain stereoregularity.
The second aspect of the present invention provides a method for synthesizing polyacrylamide, which comprises the following steps: sequentially adding Cu2O, tetramethylethylenediamine, acrylamide, Y (OTf)3、AlCl3Mixing the solvent and chloroacetic acid, performing freezing-vacuum pumping-nitrogen introducing circulation process for 2-4 times, performing closed reaction at 80-100 ℃ for 40-60 hours to obtain a polymerization product,
wherein said chloroacetic acid, said Y (OTf)3The AlCl3The Cu2The molar ratio of the used amounts of O, the tetramethylethylenediamine, the acrylamide and the solvent is 1: (0.5-2.5): (2.5-5): (0.8-1.5): (1.5-2.5): (45-55): (40-60).
The solvent is water; or the solvent is a mixed solvent of water and glycerol and/or ethylene glycol, and the molar ratio of water in the mixed solvent is more than 50%.
Specifically, the freezing is performed by adopting liquid nitrogen freezing, after a polymerization system is solidified, a vacuum system is connected to extract air and remove oxygen, the vacuum degree is generally required to be not less than 80KPa, and then a nitrogen bag is connected to introduce nitrogen.
Specifically, the mixture is subjected to a sealed reaction in a constant-temperature oil bath at 80-100 ℃ for 40-60 hours.
Further, the method also comprises the following processing steps after the polymerization product is obtained:
s1, dissolving the polymerization product in water in an atmospheric environment, then pouring the solution into pure methanol to precipitate a polymer, performing centrifugal separation, and dissolving the separated substance in water again;
s2, removing the copper complex;
and S3, precipitating with methanol again, and drying the precipitate to obtain the polyacrylamide.
Specifically, in step S1, the conditions of the centrifugal separation are: separating in a centrifuge at 2000-3000 rpm for 5-10 min.
Preferably, in step S2, the copper complex is removed by a cation exchange column.
Preferably, in step S3, the drying conditions are: vacuum drying at 40-50 deg.C for 20-30 hr.
The present invention is further illustrated by the following examples.
The reagents used in the following examples are all commercially available products.
Example 1
The following method is adopted to prepare polyacrylamide:
(1) 0.8mmol of Cu are sequentially added2O, 1.5mmol of tetramethylethylenediamine, 45mmol of acrylamide, 0.5mmol of Y (OTf)3、2.5mmol AlCl3Adding 40mmol of water and 1mmol of chloroacetic acid into a clean reaction tube for mixing, placing the sealed reaction tube into a constant-temperature oil bath at 80 ℃ for sealed reaction for 60 hours after 2 liquid nitrogen freezing-vacuum air extraction-nitrogen introduction circulation processes, taking out the reaction tube and opening a sealing plug to expose a polymerization system in the air to stop polymerization reaction to obtain a polymerization product;
(2) dissolving the polymerization product in water, then pouring into methanol to precipitate the polymer, separating in a centrifuge of 2000rpm for 10min, and re-dissolving the separated substance in water;
(3) passing the solution through a cation exchange column to remove the copper complex;
(4) the solution after passing through the column was further precipitated with methanol, and the resulting product was dried in a vacuum oven at 40 ℃ for 30 hours.
Example 2
The following method is adopted to prepare polyacrylamide:
(1) sequentially adding 1.5mmol of Cu2O, 2.5mmol of tetramethylethylenediamine, 55mmol of acrylamide, 2.5mmol of Y (OTf)3、5mmol AlCl3Adding 30mmol of water, 20mmol of glycerol, 10mmol of ethylene glycol and 1mmol of chloroacetic acid into a clean reaction tube for mixing, placing the sealed reaction tube into a constant-temperature oil bath at 100 ℃ for sealed reaction for 40 hours after 4 liquid nitrogen freezing-vacuum air extraction-nitrogen introduction circulation processes, taking out the reaction tube, opening a sealing plug, and exposing a polymerization system in the air to stop polymerization reaction to obtain a polymerization product;
(2) dissolving the polymer product in water, then pouring into methanol to precipitate the polymer, separating in a centrifuge of 3000rpm for 5min, and dissolving the separated substance in water again;
(3) passing the solution through a cation exchange column to remove the copper complex;
(4) the solution after passing through the column was further precipitated with methanol, and the resulting product was dried in a vacuum oven at 50 ℃ for 20 hours.
Example 3
The following method is adopted to prepare polyacrylamide:
(1) sequentially adding 1mmol of Cu2O, 2mmol of tetramethylethylenediamine, 50mmol of acrylamide, 0.5mmol of Y (OTf)3、5mmol AlCl3Adding 50mmol of water and 1mmol of chloroacetic acid into a clean reaction tube for mixing, placing the sealed reaction tube into a constant-temperature oil bath at 80 ℃ for sealed reaction for 48 hours after 3 times of liquid nitrogen freezing-vacuum air extraction-nitrogen introduction circulation processes, taking out the reaction tube and opening a sealing plug to expose a polymerization system in the air to stop polymerization reaction to obtain a polymerization product;
(2) dissolving the polymerization product in water, then pouring into methanol to precipitate the polymer, separating in a centrifuge of 2400rpm for 8min, and re-dissolving the separated substance in water;
(3) passing the solution through a cation exchange column to remove the copper complex;
(4) the solution after passing through the column was further precipitated with methanol, and the resulting product was dried in a vacuum oven at 40 ℃ for 24 hours.
Example 4
The following method is adopted to prepare polyacrylamide:
(1) sequentially adding 1.2mmol of Cu2O, 1.8mmol of tetramethylethylenediamine, 48mmol of acrylamide, 1mmol of Y (OTf)3、3mmol AlCl3Adding 25mmol of water, 20mmol of glycerol and 1mmol of chloroacetic acid into a clean reaction tube for mixing, placing the sealed reaction tube into a constant-temperature oil bath at 90 ℃ for sealed reaction for 50 hours after 2 liquid nitrogen freezing-vacuum air extraction-nitrogen introduction circulation processes, taking out the reaction tube, opening a sealing plug, and exposing a polymerization system in the air to stop polymerization reaction to obtain a polymerization product;
(2) dissolving the polymerization product in water, then pouring into methanol to precipitate the polymer, separating in a centrifuge of 2400rpm for 8min, and re-dissolving the separated substance in water;
(3) passing the solution through a cation exchange column to remove the copper complex;
(4) the solution after the column chromatography was further precipitated with methanol, and the resulting product was dried in a vacuum oven at 45 ℃ for 25 hours.
Example 5
The following method is adopted to prepare polyacrylamide:
(1) sequentially adding 1.5mmol of Cu2O, 2.2mmol of tetramethylethylenediamine, 52mmol of acrylamide, 2mmol of Y (OTf)3、4mmol AlCl3Adding 40mmol of water, 15mmol of ethylene glycol and 1mmol of chloroacetic acid into a clean reaction tube for mixing, placing the sealed reaction tube into a constant-temperature oil bath at 95 ℃ for sealed reaction for 45 hours after 3 liquid nitrogen freezing-vacuum air extraction-nitrogen introduction circulation processes, taking out the reaction tube and opening a sealing plug to expose a polymerization system in the air to stop the polymerization reaction to obtain a polymerization product;
(2) dissolving the polymer product in water, then pouring into methanol to precipitate the polymer, separating in a centrifuge at 2800rpm for 6min, and redissolving the isolate in water;
(3) passing the solution through a cation exchange column to remove the copper complex;
(4) the solution after passing through the column was further precipitated with methanol, and the resulting product was dried in a vacuum oven at 42 ℃ for 28 hours.
Example 6
The following method is adopted to prepare polyacrylamide:
(1) 0.9mmol of Cu2O, 2.3mmol of tetramethylethylenediamine, 50mmol of acrylamide, 2.5mmol of Y (OTf)3、4.5mmol AlCl3Adding 53mmol of water and 1mmol of chloroacetic acid into a clean reaction tube for mixing, placing the sealed reaction tube into a constant-temperature oil bath at 85 ℃ for sealed reaction for 48 hours after 4 circulation processes of liquid nitrogen freezing, vacuum air extraction and nitrogen introduction, taking out the reaction tube, opening a sealing plug, exposing a polymerization system in the air, and stopping polymerization to obtain the polymerA product;
(2) dissolving the polymer product in water, then pouring into methanol to precipitate the polymer, separating in a centrifuge of 2900rpm for 8min, and dissolving the separated substance in water again;
(3) passing the solution through a cation exchange column to remove the copper complex;
(4) the solution after the column was further precipitated with methanol, and the resulting product was dried in a vacuum oven at 48 ℃ for 22 hours.
Comparative example 1
The following method is adopted to prepare polyacrylamide:
(1) sequentially adding 1mmol of Cu2Adding O, 2mmol of tetramethylethylenediamine, 50mmol of acrylamide, 50mmol of water and 1mmol of chloroacetic acid into a clean reaction tube, mixing, performing circulation processes of liquid nitrogen freezing, vacuum pumping and nitrogen introduction for 3 times, placing the sealed reaction tube in a constant-temperature oil bath at 80 ℃ for sealed reaction for 48 hours, taking out the reaction tube, opening a sealing plug, and exposing a polymerization system in the air to stop polymerization reaction to obtain a polymerization product;
(2) dissolving the polymerization product in water, then pouring into methanol to precipitate the polymer, separating in a centrifuge of 2400rpm for 8min, and re-dissolving the separated substance in water;
(3) passing the solution through a cation exchange column to remove the copper complex;
(4) the solution after passing through the column was further precipitated with methanol, and the resulting product was dried in a vacuum oven at 40 ℃ for 24 hours.
Comparative example 2
The following method is adopted to prepare polyacrylamide:
(1) sequentially adding 1mmol of Cu2O, 2mmol of tetramethylethylenediamine, 50mmol of acrylamide, 5.5mmol of Y (OTf)3Adding 50mmol of water and 1mmol of chloroacetic acid into a clean reaction tube for mixing, placing the sealed reaction tube into a constant-temperature oil bath at 80 ℃ for sealed reaction for 48 hours after 3 times of liquid nitrogen freezing-vacuum air extraction-nitrogen introduction circulation processes, taking out the reaction tube and opening a sealing plug to expose a polymerization system in the air to stop polymerization reaction to obtain a polymerization product;
(2) dissolving the polymerization product in water, then pouring into methanol to precipitate the polymer, separating in a centrifuge of 2400rpm for 8min, and re-dissolving the separated substance in water;
(3) passing the solution through a cation exchange column to remove the copper complex;
(4) the solution after passing through the column was further precipitated with methanol, and the resulting product was dried in a vacuum oven at 40 ℃ for 24 hours.
Comparative example 3
The following method is adopted to prepare polyacrylamide:
(1) sequentially adding 1mmol of Cu2O, 2mmol of tetramethylethylenediamine, 50mmol of acrylamide and 5.5mmol of AlCl3Adding 50mmol of water and 1mmol of chloroacetic acid into a clean reaction tube for mixing, placing the sealed reaction tube into a constant-temperature oil bath at 80 ℃ for sealed reaction for 48 hours after 3 times of liquid nitrogen freezing-vacuum air extraction-nitrogen introduction circulation processes, taking out the reaction tube and opening a sealing plug to expose a polymerization system in the air to stop polymerization reaction to obtain a polymerization product;
(2) dissolving the polymerization product in water, then pouring into methanol to precipitate the polymer, separating in a centrifuge of 2400rpm for 8min, and re-dissolving the separated substance in water;
(3) passing the solution through a cation exchange column to remove the copper complex;
(4) the solution after passing through the column was further precipitated with methanol, and the resulting product was dried in a vacuum oven at 40 ℃ for 24 hours.
Comparative example 4
The following method is adopted to prepare polyacrylamide:
(1) sequentially adding 1mmol of Cu2O, 2mmol of tetramethylethylenediamine, 50mmol of acrylamide, 0.5mmol of Y (OTf)3、5mmol AlCl3Adding 50mmol of water and 1mmol of benzyl chloride into a clean reaction tube for mixing, placing the sealed reaction tube into a constant-temperature oil bath at 80 ℃ for sealed reaction for 48 hours after 3 times of circulation processes of liquid nitrogen freezing, vacuum air extraction and nitrogen introduction, taking out the reaction tube and opening a sealing plug to expose a polymerization system in the air to stop polymerization reaction to obtain a polymerization product;
(2) dissolving the polymerization product in water, then pouring into methanol to precipitate the polymer, separating in a centrifuge of 2400rpm for 8min, and re-dissolving the separated substance in water;
(3) passing the solution through a cation exchange column to remove the copper complex;
(4) the solution after passing through the column was further precipitated with methanol, and the resulting product was dried in a vacuum oven at 40 ℃ for 24 hours.
Comparative example 5
The following method is adopted to prepare polyacrylamide:
(1) sequentially adding 1mmol of Cu2O, 2mmol of tetramethylethylenediamine, 50mmol of acrylamide, 0.5mmol of Y (OTf)3、5mmol AlCl3Adding 25mmol of water, 25mmol of glycerol and 1mmol of chloroacetic acid into a clean reaction tube for mixing, placing the sealed reaction tube in a constant-temperature oil bath at 130 ℃ for sealed reaction for 4 hours after 3 liquid nitrogen freezing-vacuum air extraction-nitrogen introduction circulation processes, taking out the reaction tube and opening a sealing plug to expose a polymerization system in the air to stop polymerization reaction to obtain a polymerization product;
(2) dissolving the polymerization product in water, then pouring into methanol to precipitate the polymer, separating in a centrifuge of 2400rpm for 8min, and re-dissolving the separated substance in water;
(3) passing the solution through a cation exchange column to remove the copper complex;
(4) the solution after passing through the column was further precipitated with methanol, and the resulting product was dried in a vacuum oven at 40 ℃ for 24 hours.
Performance detection
The conversion rate of the polymerization reaction is obtained by a weighing method;
the tacticity (Meso content) is obtained by analyzing an HNMR spectrum obtained by a 500-MHz INOVA nuclear magnetic resonance instrument, the HNMR spectrum is obtained by the 500-MHz INOVA nuclear magnetic resonance instrument, DMSO-d6 (dimethyl sulfoxide-d 6) is used as a solvent, the chemical shift unit ppm is adopted, and tetramethylsilane is used as an internal standard;
polymer molecular weight and breadth of molecular weight distribution were determined by Wyatt gel chromatography (GPC) equipped with TRI STAR MINIDAWN light scattering detector and SHOWA DENKOK. K. shodex R1-71 differential refractometerTwo Shodex Ohpak SB-806M HQ columns; PEG and PEO (supplied by Wyatt Corp.) as standards; 0.1mol/dm3 NaNO3/CH3CN (V/V is 3:1) solution is mobile phase, flow rate is 0.5 ml/min; all samples were tested at 25 ℃. The measurement results are shown in table 1.
TABLE 1 results of measurement of properties of products of examples and comparative examples
Figure BDA0002947066610000141
As can be seen from table 1: comparative example 1 with chloroacetic acid as ATRP initiator, Cu2O is a catalyst, tetramethylethylenediamine is a catalytic complexing agent, the polymerization conversion rate is 35.6 percent under the condition of no Lewis acid, the molecular weight of the polyacrylamide is 136,800, the product molecular weight distribution breadth index is 1.18, compared with the reported ATRP polymerization of acrylamide monomers, the polymerization system presents the most ideal ATRP polymerization result of the acrylamide so far, but the polymer isotacticity is only 0.49 and is far lower than the scheme using the Lewis acid; the invention uses Lewis acid Y (OTf) with a certain proportion3And AlCl3The mixture as the stereocontrol agent of the ATRP polymerization reaction of the acrylamide can obtain the most ideal stereoregularity polymerization product, the stereoregularity (meso content) of the polymerization product polyacrylamide can reach up to 0.83, and is obviously higher than that of the single use of Lewis acid Y (OTf) in comparative example 2 and comparative example 33Or AlCl3The stereoregularity of the product obtained as a directional control agent; mixed Lewis acid Y (OTf)3And AlCl3The addition of the (A) is beneficial to the mediation of the polymerization process of the ATRP of the acrylamide, so that the polymerization speed is mild and stable; mixed Lewis acid Y (OTf)3And AlCl3The participated polymerization reactions are all in a controllable state, the molecular weight distribution breadth index of the obtained product polyacrylamide is between 1.16 and 1.26, and the characteristics of living radical polymerization are embodied; in addition, by comparison with comparative example 5, an appropriate reaction temperature is also an essential factor for securing the reaction result, because when the reaction temperature is too high, the reaction speed is caused to be fast (in comparative example 5, polymerization after 4 hours of reactionThe mixed system becomes gel-like), which is unfavorable for the index of the width of the molecular weight distribution of the product.
The preferred embodiments of the present invention have been described in detail with reference to the examples, but the present invention is not limited to the details of the above embodiments, and various simple modifications can be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.
It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.
In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.

Claims (7)

1. A method for synthesizing polyacrylamide is characterized by comprising the following steps: 0.8mmol of Cu are sequentially added2O, 1.5mmol of tetramethylethylenediamine, 45mmol of acrylamide, 0.5mmol of Y (OTf)3、2.5mmolAlCl3Mixing 40mmol of water and 1mmol of chloroacetic acid, performing freezing-vacuum pumping-nitrogen introduction circulation process for 2-4 times, and performing closed reaction at 80-100 ℃ for 40-60 hours to obtain a polymerization product; or
Sequentially adding 1mmol of Cu2O, 2mmol of tetramethylethylenediamine, 50mmol of acrylamide, 0.5mmol of Y (OTf)3、5mmol AlCl3Mixing 50mmol of water and 1mmol of chloroacetic acid, performing freezing-vacuum pumping-nitrogen introduction circulation process for 2-4 times, and performing closed reaction at 80-100 ℃ for 40-60 hours to obtain a polymerization product; or
Sequentially adding 1.2mmol of Cu2O, 1.8mmol of tetramethylethylenediamine, 48mmol of acrylamide, 1mmol of Y (OTf)3、3mmolAlCl3Mixing 25mmol of water, 20mmol of glycerol and 1mmol of chloroacetic acid, and performing a cycle of freezing, vacuum pumping and nitrogen introducing for 2-4 timesAnd carrying out closed reaction for 40-60 hours at the temperature of 80-100 ℃ to obtain a polymerization product.
2. The method for synthesizing polyacrylamide as claimed in claim 1, wherein the freezing is liquid nitrogen freezing.
3. The method for synthesizing polyacrylamide as claimed in claim 1, wherein the mixture is subjected to a closed reaction in a constant temperature oil bath at 80-100 ℃ for 40-60 hours.
4. The method for synthesizing polyacrylamide as claimed in any one of claims 1 to 3, wherein the method further comprises the following steps after the polymerization product is obtained:
s1, dissolving the polymerization product in water in an atmospheric environment, precipitating with methanol, centrifuging, and dissolving the separated substance in water again;
s2, removing the copper complex;
and S3, precipitating with methanol again, and drying the precipitate to obtain the polyacrylamide.
5. The method for synthesizing polyacrylamide according to claim 4, wherein in step S1, the conditions of centrifugal separation are as follows: separating in a centrifuge at 2000-3000 rpm for 5-10 min.
6. The method for synthesizing polyacrylamide according to claim 4, wherein in step S2, the copper complex is removed by a cation exchange column.
7. The method for synthesizing polyacrylamide according to claim 6, wherein in step S3, the drying conditions are as follows: vacuum drying at 40-50 deg.C for 20-30 hr.
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