CN112812228B - UCST enhanced acrylamide copolymer and preparation method thereof - Google Patents

UCST enhanced acrylamide copolymer and preparation method thereof Download PDF

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CN112812228B
CN112812228B CN202110085297.6A CN202110085297A CN112812228B CN 112812228 B CN112812228 B CN 112812228B CN 202110085297 A CN202110085297 A CN 202110085297A CN 112812228 B CN112812228 B CN 112812228B
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CN112812228A (en
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张明明
孙佳琳
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Institute of Biomedical Engineering of CAMS and PUMC
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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
    • C08F220/00—Copolymers 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
    • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
    • C08F220/52—Amides or imides
    • C08F220/54—Amides, e.g. N,N-dimethylacrylamide or N-isopropylacrylamide
    • C08F220/56—Acrylamide; Methacrylamide
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    • 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
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    • 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
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    • 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
    • C08F2438/03—Use of a di- or tri-thiocarbonylthio compound, e.g. di- or tri-thioester, di- or tri-thiocarbamate, or a xanthate as chain transfer agent, e.g . Reversible Addition Fragmentation chain Transfer [RAFT] or Macromolecular Design via Interchange of Xanthates [MADIX]
    • 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
    • C08F2800/00—Copolymer characterised by the proportions of the comonomers expressed
    • C08F2800/10—Copolymer characterised by the proportions of the comonomers expressed as molar percentages

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Abstract

The invention relates to the technical field of copolymers with critical dissolution temperature, in particular to a UCST (highest critical dissolution temperature) enhanced acrylamide copolymer and a preparation method thereof, wherein a side chain structure of the acrylamide copolymer comprises an acrylamide monomer, a succinimide monomer and a carboxylic acid monomer. The polymer of the invention is mainly acrylamide, contains a small amount of succinimide monomer and carboxylic acid monomer, and enhances the acting force in and between polymer chains by means of the hydrophobic action of the succinimide monomer and the hydrogen bonding action between the succinimide monomer and the acrylamide and the carboxylic acid monomer, so that the copolymer has excellent UCST performance, and can obtain higher T cp (cloud point temperature) at a lower concentration. The resulting polymer has better UCST performance than existing acrylamide-based polymers, as reflected in: higher T cp is obtained at low concentration of 0.2-3 mg/mL.

Description

UCST enhanced acrylamide copolymer and preparation method thereof
Technical Field
The invention relates to the technical field of copolymers with critical dissolution temperature, in particular to a UCST enhanced acrylamide copolymer and a preparation method thereof.
Background
Polymers with the highest critical dissolution temperature (upper critical solution temperature, UCST) are capable of undergoing a phase transition in a solvent at a certain critical temperature, also known as the cloud point temperature (T cp, cloud point temperature), exhibiting low temperature insoluble high temperature dissolution properties. In general, two important forces forming UCST polymers are electrostatic interactions or hydrogen bonding. Electrostatic interactions are susceptible to ions and pH in solvents, resulting in the disappearance of UCST properties, in contrast to hydrogen bonding based UCST polymers that can accommodate more complex solution environments. Common hydrogen bond-based UCST polymers typically contain both proton donor and proton acceptor structures, such as: amide-, ureido-, or imidazolyl-based polymers, and the like. Polyacrylamide (PAAm) is a common water-soluble polymer, and an amide structure is not only a hydrogen bond donor but also a hydrogen bond acceptor, so that the PAAm can form intramolecular and intermolecular hydrogen bonds, and is copolymerized with other monomers containing the hydrogen bond donor and acceptor structures to obtain UCST-type polymers, and the PAAm has important application value in the fields and directions of drug delivery, cell culture, protein separation, catalysis, sensors and the like.
However, existing UCST polymers based on PAAm often have weaker UCST performance due to low strength of hydrogen bond acting force, mainly characterized in that the polymers are difficult to generate higher T cp at lower concentration, so that the application of the polymers is greatly limited.
In order to improve UCST performance of the polymer, the following method is generally adopted: 1. adding a hydrophobic monomer unit into the copolymer, inducing a polymer chain to enhance aggregation tendency through hydrophobic action, and pulling in the distance between a hydrogen bond donor and an acceptor so as to further improve T cp; 2. the molar ratio of the proton donor to the proton acceptor is regulated to enable the molar ratio of the proton donor to the proton acceptor to be close, and the strength of the formed hydrogen bond is highest at the moment, so that T cp is improved; 3. The molecular weight of the polymer is increased, so that the inter-chain force of the polymer is higher. However, the above method still has certain limitations, such as: the type and proportion of the hydrophobic monomer can only be adjusted to T cp within a certain range, too high proportion can lead the copolymer to be completely insoluble in water, and too low proportion can lead the copolymer to be incapable of undergoing phase transition; the polymer has no influence on T cp after the molecular weight is increased to a certain degree. Based on the above factors, existing acrylamide-based UCST polymers are often difficult to achieve a T cp at 70-80 ℃ or require very high polymer concentrations to achieve a higher T cp. For example, 500mg/mL of poly (acrylamide-acrylic acid) copolymer (P (AAm-AAc)), T cp reaches a maximum at AAc/aam=6/4, only 24 ℃ (Macromolecules, 2010,10645). 10mg/mL of the poly (acrylamide-acrylonitrile) copolymer (P (AAm-AN)) had a T cp of 34 ℃ (Soft Matter,2015,7059). 2-10 mg/mL of poly (acrylamide-styrene) copolymer (P (AAm-St)), T cp of the polymer being 61-66 ℃ (Journal of Polymer SCIENCE PART A: polymer Chemistry,2014,1878) at St/aam=14/86. Thus, there is a need for an acrylamide-based UCST copolymer having a higher cloud point temperature at low concentrations.
Disclosure of Invention
Aiming at the problem of poor UCST performance of the existing acrylamide copolymer, the invention designs a brand-new structure of the acrylamide copolymer, so that the UCST performance is greatly improved.
One of the technical solutions of the present invention is a UCST reinforced acrylamide copolymer, the side chain structure of which comprises an acrylamide monomer (AAm), a succinimide monomer (NHSM), and a Carboxylic Acid Monomer (CAM), wherein the acrylamide monomer: succinimide monomer: the molar ratio of the carboxylic acid monomer is (70-90): (1-11): (8-25).
Further, the succinimide monomer is any alkenyl monomer containing a succinimide structure, such as N-acryloxysuccinimide (NAS), N-Methacryloxysuccinimide (MAS), allyl succinimidyl carbonate (NACSI), N-succinimide para-vinyl benzoate (NSVB), and the like.
Further, the acrylamide copolymer may be constructed in one or more of linear, branched and crosslinked structures.
Further, when the acrylamide copolymer is in a linear or branched structure, the molecular weight distribution is 1.1-3.0, the number average molecular weight is 1-20 ten thousand, the reversible phase transition of low-temperature insoluble-high-temperature soluble can occur in pure water, and the phase transition temperature is 40-90 ℃; when the acrylamide copolymer is in a crosslinking structure, the crosslinking degree is less than 5%, the water absorption multiple is more than 80%, the acrylamide copolymer can undergo low-temperature water loss shrinkage-high-temperature swelling reversible transformation in pure water, and the transformation temperature is 40-90 ℃.
The structure of the copolymer of the invention comprises 3 essential components: AAm, NHSM, and CAM monomers, wherein CAM is obtained by partial hydrolysis NHSM (because the polymer is purified by a trace amount of water in the purification precipitant, allowing a quantitative controlled hydrolysis reaction of NHSM during precipitation). NHSM general structure and structure examples (including but not limited to the following structures):
Further, the acrylamide copolymer is a crosslinked polymer, and the structure of the acrylamide copolymer also comprises a crosslinking agent monomer, wherein the crosslinking agent monomer is any multi-alkenyl monomer, such as N, N '-methylene Bisacrylamide (BIS), N' -BIS (acryl) cystamine (BAC), polyethylene glycol dimethacrylate (PEGDMA), BIS (2-methacryloyl) oxyethyl disulfide (DSDMA) and the like; examples of general structures and structures of the multi-alkenyl crosslinking agents include, but are not limited to, the following:
The invention also provides a preparation method of the UCST enhanced acrylamide copolymer, which takes an acrylamide monomer and a succinimide monomer as raw materials and is prepared by a free radical polymerization method, a reversible addition-fragmentation chain transfer polymerization method (RAFT) or an atom transfer free radical polymerization method (ATRP).
The invention adopts common free radical polymerization, RAFT, ATRP and other methods, and does not affect UCST properties of the product polymer. When the RAFT method is used, the system also comprises a certain proportion of chain transfer agent; when the ATRP method is used, a certain proportion of catalyst is also included in the system.
Further, when the acrylamide copolymer is a linear polymer, the method for preparing the acrylamide copolymer by using the free radical polymerization method comprises the following steps: dissolving an initiator and a monomer in an anhydrous polar organic solvent, removing oxygen, polymerizing, removing unreacted monomer, and freeze-drying to obtain an acrylamide copolymer;
further, when the acrylamide copolymer is a linear polymer, the method for preparing the polymer by using the reversible addition-fragmentation chain transfer polymerization method comprises the following steps: dissolving a monomer, a chain transfer agent and an initiator in an anhydrous polar organic solvent, performing liquid nitrogen freezing-vacuumizing-argon introducing-defrosting circulation on the solution for 3 times to remove oxygen, polymerizing, removing unreacted monomers, and freeze-drying to obtain an acrylamide copolymer;
further, when the acrylamide copolymer is a linear polymer, the method for preparing the acrylamide copolymer by using the atom transfer radical polymerization method comprises the following steps: dissolving a monomer, an initiator and a copper catalyst in an anhydrous polar organic solvent, performing liquid nitrogen freezing-vacuumizing-argon introducing-defrosting circulation on the solution for 3 times to remove oxygen, polymerizing, removing the copper catalyst, removing unreacted monomers, and freeze-drying to obtain an acrylamide copolymer;
Further, when the acrylamide copolymer is a branched polymer, the method for preparing the polymer by using the reversible addition-fragmentation chain transfer polymerization method comprises the following steps: dissolving a monomer, a chain transfer agent with a branched structure and an initiator in an anhydrous polar organic solvent, performing liquid nitrogen freezing-vacuumizing-argon introducing-defrosting circulation on the solution for 3 times to remove oxygen, polymerizing, removing unreacted monomers, and freeze-drying to obtain an acrylamide copolymer;
further, when the acrylamide copolymer is a branched polymer, the method for preparing the acrylamide copolymer by adopting the atom transfer radical polymerization method comprises the following steps: dissolving a monomer, an initiator with a branched structure and a copper catalyst in an anhydrous polar organic solvent, performing liquid nitrogen freezing-vacuumizing-argon-defrosting circulation on the solution for 3 times to remove oxygen, polymerizing, removing the copper catalyst, removing unreacted monomers, and freeze-drying to obtain an acrylamide copolymer;
Further, when the acrylamide copolymer is a crosslinked polymer, the preparation step using radical polymerization comprises: dissolving an initiator, a monomer and a crosslinking agent monomer in an anhydrous polar organic solvent, removing oxygen, polymerizing, removing unreacted monomer, and freeze-drying to obtain the crosslinked acrylamide copolymer.
The reaction solvent of the present invention must be an anhydrous reagent because the succinimide monomer is strongly hydrolyzable, and the aqueous reagent can cause excessive hydrolysis of the monomer, resulting in a product copolymer that loses UCST properties. The solvent must be a strong polar organic solvent that can dissolve both the monomer and the polymer, otherwise, it is easy to make the reaction system heterogeneous, affecting the yield and molecular weight of the product.
Further, the anhydrous polar organic solvent is dimethyl sulfoxide, N-dimethylformamide, tetrahydrofuran or dioxane, and strict anhydrous purification treatment is required before use.
Further, the concentration of the monomer in the anhydrous polar organic solvent is 0.01-0.5 g/mL, and the molar ratio of the acrylamide monomer to the succinimide monomer in the monomer is 20:1-3:1; the unreacted monomers are removed, specifically, the reaction solution is precipitated into a precipitant for further purification. The molar ratio of AAm to NHSM is adjusted to be between 20/1 and 3/1 when the materials are fed, so that the molar ratio of AAm to NHSM to CAM in the product is = (70-90): (1-11): (8-25). The above protocol allows the product to produce UCST properties with better performance. The precipitant can be absolute ethyl alcohol, acetone, absolute methyl alcohol, diethyl ether, even cold water and other solvents capable of precipitating the polymer, the purity of the precipitant is of an analytical grade, and no special pretreatment is needed.
Further, the addition amount of the initiator is 0.02-0.3% of the mole number of the monomer;
Further, in the free radical polymerization process, the polymerization temperature is 60-70 ℃ and the polymerization time is 5-10 h;
Further, in the reversible addition-fragmentation chain transfer polymerization process, the polymerization temperature is 60-70 ℃ and the polymerization time is 10-20 h;
further, in the atom transfer radical polymerization process, the polymerization temperature is 60-90 ℃ and the polymerization time is 10-48 h.
Compared with the prior art, the invention has the following beneficial effects:
the polymer of the invention is mainly acrylamide (AAm), contains a small amount of succinimide monomer (NHSM) and Carboxylic Acid Monomer (CAM), and can obviously enhance the acting force in and among polymer chains by means of the hydrophobic effect of NHSM and the hydrogen bonding effect between NHSM and AAm and CAM, so that the copolymer has excellent UCST performance, and can obtain higher T cp at a lower concentration. The polymer obtained by the monomer combination and the preparation method has better UCST performance than the existing polymer, and is characterized in that: higher T cp (60-90 ℃) is obtained at lower concentrations (e.g., 0.2-3 mg/mL).
Drawings
FIG. 1 is a 1 H NMR spectrum of a copolymer prepared in example 1 of the present invention;
FIG. 2 is a graph showing the transmittance of the polymer according to temperature in example 13 of the present invention;
FIG. 3 is a graph showing the transmittance of the second polymer in example 14 according to the concentration of the second polymer;
FIG. 4 is a plot of cloud point temperature versus concentration for Polymer two of example 14 of the present invention.
Detailed Description
Various exemplary embodiments of the invention will now be described in detail, which should not be considered as limiting the invention, but rather as more detailed descriptions of certain aspects, features and embodiments of the invention.
It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In addition, for numerical ranges in this disclosure, it is understood that each intermediate value between the upper and lower limits of the ranges is also specifically disclosed. Every smaller range between any stated value or stated range, and any other stated value or intermediate value within the stated range, is also encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.
It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the application described herein without departing from the scope or spirit of the application. Other embodiments will be apparent to those skilled in the art from consideration of the specification of the present application. The specification and examples of the present application are exemplary only.
As used herein, the terms "comprising," "including," "having," "containing," and the like are intended to be inclusive and mean an inclusion, but not limited to.
The monomer materials used in the following examples of the present invention were subjected to a severe anhydrous purification treatment with the polymerization solvent before use;
Example 1:
By adopting a RAFT polymerization method, firstly, 2- (dodecyl trithiocarbonate group) -2-methylpropanoic acid (DDMAP) (chain transfer agent), azodiisobutyronitrile (AIBN) (initiator), acrylamide (AAm) and N-acryloyloxy succinimide (NAS) are dissolved in anhydrous DMSO, the total concentration of monomers is 0.3g/mL, the molar ratio of DDMAP:AIBN to AAm to NAS is 1:0.2:400:60, and the reaction solution is subjected to liquid nitrogen freezing-vacuumizing-argon filling-defrosting circulation for 3 times to remove oxygen in a reaction system. Then the reaction solution is sealed and placed in a water bath at 60 ℃ for reaction for 10 hours. Then, the reaction solution is precipitated in 10 times of absolute ethyl alcohol with volume of analytical purity (without hydration treatment), washed for 3 times, NAS is hydrolyzed by trace amount of water in the absolute ethyl alcohol to generate acrylic acid (AAc) with a specific proportion, and the linear polymer I is obtained by vacuum drying. The reaction structural formula:
The polymer was characterized by gel permeation chromatography to give a polymer weight average molecular weight of 41800 and a molecular weight distribution of 1.36. FIG. 1 is a 1 H NMR spectrum of the polymer, chemical shifts 6.9 and 7.1 are hydrogen (a) on the amide nitrogen of AAm; chemical shift 2.9 is succinimidyl methine hydrogen (b) of NAS; chemical shift 10.6 is carboxyhydrogen (c) of AAc, and the above attribution indicates that the polymer is a copolymer of AAm, NAS and AAc, and the molar ratio of AAm, NAS and AAc in the copolymer is 81.9:2.8:15.3.
Example 2:
By adopting a RAFT polymerization method, firstly, 2- (dodecyl trithiocarbonate group) -2-methylpropanoic acid (DDMAP), azodiisobutyronitrile (AIBN), acrylamide (AAm) and N-acryloyloxy succinimide (NAS) are dissolved in anhydrous DMSO, the total monomer concentration is 0.3g/mL, the molar ratio of DDMAP to AIBN to AAm to NAS is 1:0.2:400:80, and the reaction solution is subjected to liquid nitrogen freezing-vacuumizing-argon filling-thawing cycle for 3 times to remove oxygen in a reaction system. Then the reaction solution is sealed and placed in a water bath at 60 ℃ for reaction for 20 hours. Then, the reaction solution is precipitated in 10 times volume of absolute ethyl alcohol with analytical purity, washed for 3 times, NAS is hydrolyzed by trace water in the absolute ethyl alcohol (without anhydrous treatment) to generate acrylic acid (AAc) with a specific proportion, and the linear polymer II is obtained by vacuum drying. The polymer was characterized by gel permeation chromatography to give a polymer weight average molecular weight 35400, a molecular weight distribution of 1.19, and a molar ratio of AAm, NAS and AAc in the copolymer of 77.1:4.8:18.1.
Example 3:
by adopting a RAFT polymerization method, firstly, 2- (dodecyl trithiocarbonate group) -2-methylpropanoic acid (DDMAP), azodiisobutyronitrile (AIBN), acrylamide (AAm) and N-acryloyloxy succinimide (NAS) are dissolved in anhydrous DMSO, the total monomer concentration is 0.3g/mL, the molar ratio of DDMAP to AIBN to AAm to NAS is 1:0.2:400:100, and the reaction solution is subjected to liquid nitrogen freezing-vacuumizing-argon filling-thawing cycle for 3 times to remove oxygen in a reaction system. Then the reaction solution is sealed and placed in a water bath at 60 ℃ for reaction for 10 hours. Then, the reaction solution is precipitated in 10 times volume of absolute ethyl alcohol with analytical purity, washed for 3 times, NAS is hydrolyzed by trace amount of water in the absolute ethyl alcohol (without anhydrous treatment), acrylic acid (AAc) with a specific proportion is generated, and the linear polymer is obtained by vacuum drying. The polymer was characterized by gel permeation chromatography to give a polymer weight average molecular weight 38300, a molecular weight distribution of 1.17, and a molar ratio of AAm, NAS and AAc in the copolymer of 70.5:6.9:22.6.
Example 4:
Azobisisobutyronitrile (AIBN), acrylamide (AAm) and N-acryloyloxysuccinimide (NAS) were dissolved in anhydrous DMSO using a radical polymerization method so that the ratio of AIBN to AAm to NAS was 1:378:59 and the total monomer concentration was 0.3g/mL. The reaction solution was bubbled with argon for 30min to remove oxygen in the reaction system. Then the reaction solution was sealed and placed in a water bath at 60℃for reaction for 6 hours. Then, the reaction solution is precipitated in 10 times of absolute ethyl alcohol with volume of analytical purity (without hydration treatment), washed for 3 times, NAS is hydrolyzed by trace amount of water in the absolute ethyl alcohol to generate acrylic acid (AAc) with a specific proportion, and the linear polymer is obtained by vacuum drying. The polymer was characterized by gel permeation chromatography to give a polymer weight average molecular weight 191900, a molecular weight distribution of 2.30, and a molar ratio of AAm, NAS and AAc in the copolymer of 72.6:10.2:17.2.
Example 5:
Azobisisobutyronitrile (AIBN), acrylamide (AAm) and N-acryloyloxysuccinimide (NAS) were dissolved in anhydrous DMSO using a radical polymerization method so that the ratio of AIBN to AAm to NAS was 1:378:79 and the total monomer concentration was 0.3g/mL. The reaction solution was bubbled with argon for 30min to remove oxygen in the reaction system. Then the reaction solution is sealed and placed in a water bath at 60 ℃ for reaction for 5 hours. The reaction was then precipitated in absolute ethanol, washed 3 times and dried in vacuo to give the linear polymer five.
Example 6:
Azobisisobutyronitrile (AIBN), acrylamide (AAm) and N-acryloyloxysuccinimide (NAS) were dissolved in anhydrous DMSO using a radical polymerization method so that the ratio of AIBN to AAm to NAS was 1:378:99 and the total monomer concentration was 0.3g/mL. The reaction solution was bubbled with argon for 30min to remove oxygen in the reaction system. Then the reaction solution was sealed and placed in a water bath at 60℃for reaction for 6 hours. The reaction was then precipitated in absolute ethanol, washed 3 times and dried in vacuo to give linear polymer six.
Example 7:
Using ATRP polymerization, ethyl 2-bromo-2-methylpropionate (EBriB) (initiator), cuprous chloride (CuCl), N', N "-Pentamethyldiethylenetriamine (PMDETA) (CuCl and PMDETA are complexed to form a catalyst system), acrylamide (AAm) and N-acryloyloxysuccinimide (NAS) were dissolved in anhydrous DMSO to give a total monomer concentration of 0.5g/mL at a ratio of EBriB:cucl to PMDETA to AAm to NAS of 1:1:2:378:79. The reaction liquid is subjected to liquid nitrogen freezing, vacuumizing, argon filling and defrosting circulation for 3 times to remove oxygen in the reaction system. Then the reaction solution is sealed and placed in a water bath at 60 ℃ for reaction for 24 hours. The polymer was purified by passing through a silica gel column, then precipitated in absolute ethanol, washed 3 times, and dried in vacuo to give linear polymer seven.
Example 8:
brominated cyclodextrins (CD-Br, 17 Br per cyclodextrin, i.e., 17 ATRP initiation sites), cuprous chloride (CuCl), N, N, N' -Pentamethyldiethylenetriamine (PMDETA), acrylamide (AAm) and N-acryloyloxysuccinimide (NAS) were dissolved in anhydrous DMSO using an ATRP polymerization method to give a ratio of Br: cuCl: PMDETA: AAm: NAS of 1:1:2:378:79, and a total monomer concentration of 0.1g/mL. The reaction liquid is subjected to liquid nitrogen freezing, vacuumizing, argon filling and defrosting circulation for 3 times to remove oxygen in the reaction system. Then the reaction solution was sealed and placed in a water bath at 60℃for 48 hours. The polymer was purified by passing through a silica gel column, then precipitated in absolute ethanol, washed 3 times and dried in vacuo to give branched polymer eight.
Example 9:
azobisisobutyronitrile (AIBN), acrylamide (AAm) and N-Methacryloyloxysuccinimide (MAS) were dissolved in anhydrous DMSO using a radical polymerization method so that the ratio of AIBN to AAm to MAS was 1:400:30 and the total monomer concentration was 0.5g/mL. The reaction solution was bubbled with argon for 30min to remove oxygen in the reaction system. Then the reaction solution was sealed and placed in a water bath at 60℃for reaction for 6 hours. The reaction was then precipitated in absolute ethanol, washed 3 times and dried in vacuo to give the linear polymer nine.
Example 10:
Azobisisobutyronitrile (AIBN), acrylamide (AAm) and allylsuccinimidyl carbonate (NACSI) were dissolved in anhydrous DMSO using a free radical polymerization to give a AIBN: AAm: NACSI ratio of 1:380:30 and a total monomer concentration of 0.2g/mL. The reaction solution was bubbled with argon for 30min to remove oxygen in the reaction system. Then the reaction solution was sealed and placed in a water bath at 60℃for reaction for 6 hours. The reaction was then precipitated in absolute ethanol, washed 3 times and dried in vacuo to give the linear polymer ten.
Example 11:
azobisisobutyronitrile (AIBN), acrylamide (AAm) and N-succinimidyl para-vinylbenzoate (NSVB) were dissolved in anhydrous DMSO using a free radical polymerization method to give a AIBN: AAm: NSVB ratio of 1:400:20 and a total monomer concentration of 0.2g/mL. The reaction solution was bubbled with argon for 30min to remove oxygen in the reaction system. Then the reaction solution is sealed and placed in a water bath at 60 ℃ for reaction for 10 hours. The reaction was then precipitated in absolute ethanol, washed 3 times and dried in vacuo to give the linear polymer eleven.
Example 12:
Azobisisobutyronitrile (AIBN), acrylamide (AAm), N-acryloyloxysuccinimide (NAS) and N, N' -methylenebisacrylamide (BIS) were dissolved in anhydrous DMSO using a radical polymerization method so that the ratio of AIBN to AAm to NAS to BIS was 1:378:79:9 and the total monomer concentration was 0.03g/mL. The reaction solution was bubbled with argon for 30min to remove oxygen in the reaction system. Then the reaction solution was sealed and placed in a water bath at 60℃for reaction for 6 hours. And (3) obtaining a crosslinked copolymer, soaking the crosslinked copolymer in fresh DMSO to remove unreacted monomers, transferring the solution to absolute ethyl alcohol to replace DMSO solvent, and drying in vacuum to obtain the crosslinked polymer twelve.
Example 13:
determination of UCST
Solution transmittance was measured using an ultraviolet-visible spectrophotometer (UV-vis): the polymer with the concentration of 0.2-10 mg/mL is dissolved in hot water, the change of the transmissivity (T%) of the polymer solution along with the temperature is detected by using UV-vis, the temperature changing speed is 0.5-2 ℃/min, and the temperature corresponding to 50% of the change of the T% is defined as the cloud point temperature (T cp).
The above polymer one, polymer two and polymer three were weighed into 1mg to 1mL deionized water, heated to be completely dissolved, and the change of the transmittance (T%) of the solution with temperature (T) was measured at a wavelength of 600nm using an ultraviolet spectrophotometer to obtain a curve as shown in fig. 2, which shows that the polymer had UCST properties, 50% of the transmittance change was defined as T cp, T cp of polymer one was measured to be 46 ℃, T cp of polymer two was measured to be 72 ℃, and T cp of polymer three was measured to be 76 ℃.
Example 14:
The polymers were respectively formulated as aqueous solutions at concentrations of 0.5,0.8,1.0,2.0,3.0mg/mL, heated to dissolve completely, and the change in transmittance (T%) of the solution with temperature (T) was measured using an ultraviolet spectrophotometer at a wavelength of 600nm to give a curve as shown in fig. 3, indicating that the polymer had UCST properties, 50% of the change in transmittance was defined as T cp, and T cp at concentrations of 0.5,0.8,1.0,2.0,3.0mg/mL was measured as 60, 63, 72, 80, 86 ℃ (as shown in fig. 4), respectively.
The polymers prepared in examples 4-12 were subjected to the same test as in examples 13-14 to verify that polymer tetra-polymer twelve was able to give a higher T cp (60-90 ℃) at a lower concentration (e.g., 0.2-3 mg/mL), polymer tetra-polymer eleven had a molecular weight distribution of 1.1-3.0, a number average molecular weight of 1-20 ten thousand, a polymer twelve crosslinking degree of 2%, and a water absorption multiple of 98%.
The foregoing description of the preferred embodiments of the invention is not intended to limit the invention to the particular embodiments disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Claims (1)

1. A UCST-reinforced acrylamide copolymer, prepared in one of the following ways:
a. Firstly, dissolving 2- (dodecyl trithiocarbonate group) -2-methylpropanoic acid DDMAP, azodiisobutyronitrile AIBN, acrylamide AAm and N-acryloyloxy succinimide (NAS) in anhydrous DMSO (non-aqueous DMSO), wherein the total monomer concentration is 0.3g/mL, and the molar ratio of DDMAP AIBN to AAm to NAS is 1:0.2:400:80, and performing liquid nitrogen freezing-vacuumizing-argon filling-defrosting cycle on the reaction solution for 3 times to remove oxygen in the reaction system; then sealing the reaction liquid, and placing the reaction liquid in a water bath at 60 ℃ for reaction for 20 hours; then precipitating the reaction solution in 10 times of absolute ethyl alcohol with analytical purity by volume, washing for 3 times, hydrolyzing NAS by depending on trace water in the absolute ethyl alcohol to generate acrylic acid AAc with a specific proportion, and vacuum drying to obtain a linear polymer II;
b. Firstly, dissolving 2- (dodecyl trithiocarbonate group) -2-methylpropanoic acid DDMAP, azodiisobutyronitrile AIBN, acrylamide AAm and N-acryloyloxy succinimide NAS in anhydrous DMSO (non-aqueous DMSO) by adopting a RAFT polymerization method, wherein the total monomer concentration is 0.3g/mL, and the molar ratio of DDMAP AIBN to AAm to NAS is 1:0.2:400:100, and performing liquid nitrogen freezing-vacuumizing-argon filling-thawing cycle on the reaction solution for 3 times to remove oxygen in the reaction system; then sealing the reaction liquid, and placing the reaction liquid in a water bath at 60 ℃ for reaction for 10 hours; then precipitating the reaction solution in 10 times of absolute ethyl alcohol with analytical purity, washing for 3 times, hydrolyzing NAS by depending on trace water in the absolute ethyl alcohol to generate acrylic acid AAc with a specific proportion, and drying in vacuum to obtain the linear polymer III.
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