CN113480703B - Method for preparing amphiphilic block copolymer by light-controlled free radical polymerization and ring-opening copolymerization - Google Patents
Method for preparing amphiphilic block copolymer by light-controlled free radical polymerization and ring-opening copolymerization Download PDFInfo
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- CN113480703B CN113480703B CN202110773633.6A CN202110773633A CN113480703B CN 113480703 B CN113480703 B CN 113480703B CN 202110773633 A CN202110773633 A CN 202110773633A CN 113480703 B CN113480703 B CN 113480703B
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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
- C08F293/00—Macromolecular compounds obtained by polymerisation on to a macromolecule having groups capable of inducing the formation of new polymer chains bound exclusively at one or both ends of the starting macromolecule
- C08F293/005—Macromolecular compounds obtained by polymerisation on to a macromolecule having groups capable of inducing the formation of new polymer chains bound exclusively at one or both ends of the starting macromolecule using free radical "living" or "controlled" polymerisation, e.g. using a complexing agent
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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
- 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]
Abstract
The invention discloses a method for preparing an amphiphilic block copolymer by light-controlled free radical polymerization and ring-opening copolymerization, which comprises the following preparation steps: and adding a hydroxyl or carboxyl-containing reversible addition chain transfer reagent, a photoinitiator, a hydrophilic vinyl monomer, a Lewis acid base pair catalytic system consisting of Lewis acid and Lewis base, an epoxy compound and cyclic anhydride into the polymerization reaction system. The chain transfer reagent is used as a ring-opening polymerization initiator, and the Lewis acid-base pair is used as a catalyst to catalyze ring-opening copolymerization of cyclic anhydride and epoxide, so that the chain transfer agent is attached to the tail end of polyester. Meanwhile, visible light or ultraviolet light is irradiated, the photoinitiator is decomposed to generate free radicals, free radical polymerization of vinyl monomers is realized, and the hydrophilic polyolefin chain and the polyester chain are added through reversible addition of a chain transfer agent, so that the amphiphilic block polymer is formed. The preparation method provided by the invention is simple and easy to operate, low in production cost, and has a certain biodegradability, the polymerization process is easy to control, and the product structure can be accurately regulated and controlled.
Description
Technical Field
The invention belongs to the technical field of polymer synthesis, relates to a method for synthesizing an amphiphilic polymer, and in particular relates to a method for preparing an amphiphilic block copolymer by a one-pot method through light-controlled reversible addition chain transfer free radical polymerization and Lewis acid-base pairing catalysis cyclic anhydride and epoxide ring-opening copolymerization.
Background
The amphiphilic polymer material is a polymer system containing both hydrophilic segments and hydrophobic segments, has the stability of polymers and the surface activity of low molecules, can be used for preparing polymer brushes, star polymers, polymer NPs, polymer nanofibers, polymer films and the like with nano structures by utilizing the self-assembly performance of the amphiphilic polymer material, and has good applicability in nano material (L-B) films, polymer liquid crystals, drug targeting and slow release, polymer alloys, adhesives, emulsion polymerization, dispersion polymerization and the like in tertiary oil recovery and chemical industry. Typical amphiphilic polymers are generally synthetic amphiphilic block polymers, are prepared by stepwise and repeated polymerization, have more steps and more energy consumption, and are more complicated.
In recent years, a one-pot method for preparing amphiphilic block polymers is gradually reported, and related research work is rapidly developed. At present, a plurality of report systems are emulsion polymerization (Polymer, 2016, 106, 275-284,Macromolecules 2011,44,7584-7593,Macromolecules 2011,44,5590-5598,Macromol.Rapid Commun.2011,32,1270-1276) controlled by a reversible addition chain transfer agent, however, the method is only limited to be carried out in an aqueous phase, the product has poor structural regularity and slightly wide molecular weight distribution, is only suitable for polymerization of olefin monomers, and has no degradation characteristic at all. Another major class of systems uses macromolecular hydrophilic initiators to initiate copolymerization of olefinic monomers or other cyclic aliphatic or cyclic carbonate monomers to give amphiphilic polymers (Biomacromolecules 2013,14,2171-2178,Macromol.Rapid Commun.2007,28,2151-2158). Recently, attention has been paid to the preparation of amphiphilic polymers by simultaneous polymerization of two polymerization forms in one pot, for example, hyun Uk Kang et al, which uses a chain transfer agent (initiator) to achieve simultaneous polymerization of two polymerization forms, namely free radical polymerization and caprolactone ring-opening polymerization, to obtain amphiphilic block polymers of polypyrrolidone and polycaprolactone, however, in this method, both polymerization forms depend on the influence of temperature, only if the temperature satisfies the requirements of both polymerization forms at the same time, the simultaneous polymerization of both polymerization forms can be achieved, and the molecular weight or ratio of both blocks depends severely on the original feed ratioOther approaches fail to achieve regulation of the molecular weight of the two blocks (Macromolecules 2013,46,1291-1295); zhao Junpeng and the like using phosphazene base (t-BuP) 1 ) The catalyst is used for catalyzing the copolymerization of the cyclic anhydride and the ethylene oxide, the copolymerization activity of the cyclic anhydride and the ethylene oxide is extremely high, alternating polyester is obtained firstly, and excessive ethylene oxide is further subjected to ring-opening polymerization under the self-buffering action of the catalyst to obtain hydrophilic polyether, so that the amphiphilic block polymer is obtained. Although there are various forms of the method for preparing the amphiphilic block polymer by one pot method, the above problems are more or less present. Therefore, the development of a novel one-pot polymerization method which is simpler, more efficient, easier to control and adjustable in product structure is still the focus of current research.
Disclosure of Invention
The invention aims to provide a method for preparing an amphiphilic block copolymer by light-controlled free radical polymerization and ring-opening copolymerization, namely a method for preparing the amphiphilic block copolymer by light-controlled reversible addition chain transfer free radical polymerization and Lewis acid base pair catalyzed ring-opening copolymerization of cyclic anhydride and epoxide by a one-pot method, so as to realize the following aims: the preparation method provided by the invention is simple and easy to operate, low in production cost, and has a certain biodegradability, the polymerization process is easy to control, the product structure can be accurately regulated and controlled, and the preparation method has extremely high application value in the fields of nano material films, high polymer liquid crystals, drug targeting and slow release, high polymer alloys, tertiary oil recovery and the like.
In order to achieve the aim, the technical scheme adopted by the invention is that the photo-controlled reversible addition chain transfer free radical polymerization is cooperated with Lewis acid base pair to catalyze ring-opening copolymerization of cyclic anhydride and epoxide to prepare the amphiphilic block copolymer by a one-pot method, and the preparation method comprises the following specific steps:
s1, simultaneously adding a hydroxyl or carboxyl-containing reversible addition chain transfer reagent, a photoinitiator, a hydrophilic vinyl monomer, a Lewis acid base pair catalytic system consisting of Lewis acid and Lewis base, an epoxy compound and cyclic anhydride into a polymerization reaction system;
s2, under a certain temperature condition, using a chain transfer reagent as an initiator, catalyzing ring-opening copolymerization of cyclic anhydride and epoxide by Lewis acid and alkali, attaching a chain transfer agent to the tail end of polyester, simultaneously irradiating visible light or ultraviolet light, decomposing the photoinitiator to generate free radicals, realizing free radical polymerization of vinyl monomers, and adding a hydrophilic polyolefin chain and a polyester chain through reversible addition of the chain transfer agent to form the amphiphilic block polymer.
Preferably, in the step S1, a dry polymerization reaction tube is selected as a polymerization reaction system to react under the nitrogen atmosphere; in the step S2, the polymerization reaction tube is sealed and then placed in an oil bath to react under the irradiation of visible light or ultraviolet light, the reaction mixture taken out from the polymerization reaction tube is poured into a mixed solution of diethyl ether and n-hexane to carry out precipitation, repeated precipitation is carried out for a plurality of times, filtration is carried out, and the obtained polymer is dried in vacuum to obtain the amphiphilic block polymer.
Preferably, the chain transfer agent is at least one of 4-cyano-4- [ (dodecylthiocarbonyl) thiocarbonyl ] pentanoic acid (TTC-COOH), 4-cyano-4- [ (dodecylthiocarbonyl) thiocarbonyl ] pentanol (TTC-OH), 4-cyano-4- (thiobenzoyl) pentanoic acid, 2-methyl-2- (dodecyltrithiocarbonate group) propionic acid, and the chain transfer agent has a structural formula shown below;
R-OH(1)，R-COOH(2)；
the structural formula and the corresponding Chinese names are as follows:
4-cyano-4- [ (dodecylsulfanylthiocarbonyl) thiocarbonyl ] pentanoic acid (TTC-COOH)
4-cyano-4- [ (dodecylsulfanylthiocarbonyl) thiocarbonyl ] pentanol (TTC-OH)
4-cyano-4- (thiobenzoyl) pentanoic acid
2-methyl-2- (dodecyl trithiocarbonate) propanoic acid.
Preferably, the photoinitiator is at least one of methyl benzoylformate, benzoin dimethyl ether, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1- (4-methylthiophenyl) -2-morpholino-1-propanone, (2, 4, 6-trimethylbenzoyl) diphenyl phosphine oxide, ethyl 2,4, 6-trimethylbenzoyl phenyl phosphonate, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butanone, 2-hydroxy-4' - (2-hydroxyethoxy) -2-methylpropenyl propanone, 2-dimethylamino-2- (4-methyl) benzyl-1- [4- (4-morpholino) phenyl ] -1-butanone, benzophenone, tetraethyl midone.
Preferably, the hydrophilic vinyl monomer is at least one of acrylamide, N-isopropyl acrylamide, vinyl pyrrolidone, vinyl imidazole, N, N-dimethyl acrylamide, polyethylene glycol methyl ether methacrylate.
Preferably, in the lewis acid-base pair catalytic system composed of lewis acid and lewis base, the lewis acid is selected from at least one of triethylboron, tributylboron, triphenylboron, tris (pentafluorophenyl) boron, diethylmethoxyborane; the Lewis base is at least one of triphenylphosphine (PPh 3), bis (triphenylphosphine) ammonium chloride (PPNCL), tetraphenylphosphine chloride (PPh 4 CL), 1, 8-diazabicyclo [5.4.0] undec-7-ene (DBU), phosphazene base (t-BuP 1 or t-BuP).
Preferably, the cyclic anhydride is succinic anhydride, 2-methylsuccinic anhydride, glutaric anhydride, diglycolic anhydride, phthalic anhydride, etc., and the anhydride is purified by recrystallization in acetic anhydride and sublimation for a plurality of times; the epoxy compound is propylene oxide, cyclopentane epoxide, styrene oxide, cyclohexane epoxide, cyclohexane oxide, phenyl glycidyl ether, benzyl glycidyl ether, and neither the cyclic anhydride nor the epoxy compound contains unsaturated double bond.
Preferably, in the polymer preparation, the molar ratio of chain transfer agent to photoinitiator: 1 to 10:1, a step of; molar ratio of chain transfer agent to hydrophilic vinyl monomer: 1: 100-500 parts; molar ratio of chain transfer agent to lewis acid: 5:1 to 10; the molar ratio of Lewis acid to Lewis base is 1-5: 1, a step of; the molar ratio of lewis base to epoxide was 1: 100-500 parts; the molar ratio of cyclic anhydride to epoxide was 1:1 to 5; the copolymerization reaction is carried out under the condition of solution, the temperature of the copolymerization reaction is 0-60 ℃, the light reaction time is 0-5 h under the autogenous pressure, and the heating reaction is 0-24 h.
Preferably, in step S2, the irradiation light is ultraviolet light or visible light, the wavelength is one of 365nm, 390nm, 405nm or 440nm, and the light intensity is 0.4mw/cm 2 ～10mw/cm 2 。
The invention utilizes two polymerization modes of special chain transfer agent initiator bridging free radical polymerization and epoxide/cyclic anhydride ring-opening copolymerization, the former depends on photoinitiation, the latter needs to rely on a certain temperature to overcome a polymerization barrier, namely, the two polymerization modes are not interfered with each other, and the effective control of any block polymerization can be realized by controlling any physical auxiliary mode, so that the amphiphilic block polymer with controllable structure is obtained.
The polymerization method adopted by the method has two polymerization modes, and the two polymerization mechanisms are synchronously carried out without mutual interference; all monomer initiator and catalyst are placed in a reaction device and polymerized in one pot; on the one hand, the effective regulation and control of the molecular weight of the hydrophilic block can be realized by adjusting the proportion of the photoinitiator and the vinyl monomer, and the effective regulation and control of the molecular weight of the hydrophobic polyester block can be realized by adjusting the proportion of the chain transfer agent and the epoxide/cyclic anhydride; on the other hand, the molecular weight of the hydrophilic block can be regulated by regulating the illumination time, and the molecular weight of the polyester block can be regulated by heating time, so that the regulation of the polymer structure is simpler and more convenient due to the physical regulation form. In addition, as the two polymerization forms are not interfered with each other, and the types of monomers suitable for the two polymerization are various, the amphiphilic block polymers with different performances can be obtained by changing the types of the monomers, the hydrophilic and hydrophobic properties of the polymers can be changed by adjusting the proportion of the two blocks, and the polymer is endowed with more abundant assembly behaviors. These all lead the synthesized polymer to have wide application prospect
Compared with the prior art, the invention has the beneficial effects that:
(1) According to the invention, the optically-controlled reversible addition chain transfer free radical polymerization and the temperature-controlled nonmetallic Lewis acid-base pair catalytic epoxide and cyclic anhydride ring-opening copolymerization are effectively combined through one-pot reaction for the first time, and the polymerization products corresponding to the two polymerization mechanisms are bridged by creatively utilizing a special chain transfer initiator, so that the amphiphilic block polymer with the chain transfer initiator as a connecting point is obtained. The prior art mainly utilizes emulsion polymerization controlled by a reversible addition chain transfer agent to synthesize, the method is only limited to be carried out in a water phase, the product has poor structural regularity and slightly wide molecular weight distribution, and the method is only suitable for polymerization of olefin monomers and has no degradation characteristic. The other major category uses macromolecular hydrophilic initiator to initiate copolymerization of vinyl monomer or other cyclic ester or cyclic carbonate monomer, thus obtaining amphiphilic polymer, the macromolecular hydrophilic initiator has a slightly expensive price, the special structure needs complex synthesis, and the structure is inaccurate in most cases. In addition, part of systems are used for synchronously preparing the amphiphilic polymer by using two polymerization forms by a one-pot method, however, in the technologies, the two polymerization forms depend on a single physical source such as the influence of temperature, only if the two polymerization forms simultaneously meet the requirements of the two polymerization forms, the two polymerization forms can be synchronously carried out, the molecular weight or the proportion of the two blocks is seriously dependent on the original feeding ratio, and the regulation and control of the molecular weight and the structure of the two blocks can not be realized by simply changing the external conditions. The polymerization method adopted by the method has two polymerization modes, and the two polymerization mechanisms are synchronously carried out without mutual interference; all monomer initiator and catalyst are placed in a reaction device and polymerized in one pot; the molecular weight of the hydrophilic block can be simply and conveniently regulated by regulating the illumination time, and the molecular weight of the polyester block can be regulated by regulating the heating time, so that the regulation of the polymer structure becomes simpler and more convenient by the physical regulation form. In addition, as the two polymerization forms are not interfered with each other, and the types of monomers suitable for the two polymerization are various, the amphiphilic block polymers with different performances can be obtained by changing the types of the monomers, the hydrophilic and hydrophobic properties of the polymers can be changed by adjusting the proportion of the two blocks, and the polymer is endowed with more abundant assembly behaviors. The synthesis method is simpler and more convenient in general, high in efficiency, easy to control and adjustable in product structure. The synthetic polymer has wide application prospect.
(2) In addition, a metal initiator or a metal catalyst is not used in the polymerization system, so that toxic heavy metal ion residues in the synthesized polymer can be avoided, and the application of the polymer in the fields of biological materials and the like is facilitated; the epoxide and the cyclic anhydride are rich in species and low in cost, and meanwhile, the chemical modification of the epoxide and the cyclic anhydride is simple and convenient, so that the late functionalization is easy; the hydrophilic monomers are various in variety and different in performance, so that the properties of the amphiphilic block polymer prepared by construction are more abundant; the method has the advantages that the ring-opening copolymerization of epoxide and anhydride is catalyzed by using the nonmetallic Lewis acid-base pair which is low in cost, easy to prepare and good in stability, the polyester hydrophobic structure with controllable sequence and regularity is easy to obtain, meanwhile, the nonmetallic Lewis acid-base pair has higher catalytic activity, the types of the epoxide and the cyclic anhydride which can be catalyzed are more, and the method has good catalytic activity for partial chemically modified monomers, so that the functionalization of the material is facilitated; the hydrophobic aliphatic polyester block can be obtained by ring-opening copolymerization of partial epoxide and anhydride, and can be gradually degraded into small molecular compounds through hydrolysis, enzymolysis and other processes in a specific environment, so that the hydrophobic aliphatic polyester block has excellent biodegradability, low toxicity and good biocompatibility; the characteristics lead the application field of the block polymer prepared by the method to be greatly expanded.
Drawings
The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate the invention and together with the embodiments of the invention, serve to explain the invention. In the drawings:
FIG. 1 is a graph showing the molecular weight and distribution of amphiphilic block polymers according to the present invention;
FIG. 2 shows the amphiphilic block polymer according to the invention dissolved in deuterated chloroform 1 Nuclear magnetic hydrogen spectrogram after H NMR test;
FIG. 3 is a graph showing particle diameters and particle diameter distribution of an assembled body measured by a dynamic light scattering meter in accordance with an embodiment of the present invention.
Detailed Description
The invention will be further described with reference to the following specific examples.
The molecular weight and structure of the amphiphilic block polymer obtained in the following examples of the present invention were determined by SEC and 1HNMR, respectively. The relative molecular weight and molecular weight distribution of the polymer were determined by gel permeation chromatography (Viscotek 270 hplc pump, viscotek gel chromatography column (G2000H HR, G3000H HR, and G4000H HR), viscotek differential refractive index detector, chromatographic grade Tetrahydrofuran (THF) column temperature 35 ℃, flow rate 1.0mL/min. Nuclear magnetism was determined on Bruker Avance DMX (1H: 400 mhz) instrument, deuterated chloroform (CDCl 3) was used as solvent, tetramethylsilane (TMS) was used as internal standard, and the amphiphilic polymer assembly behavior was detected by Brookhaven 173Plus dynamic light scattering instrument, confirming the formation of amphiphilic structure.
Example 1
Sequentially placing stirring rods into a dry polymerization reaction tube in a glove box filled with nitrogen, and adding a chain transfer agent initiator 4-cyano-4- [ (dodecyl sulfanyl) thiocarbonyl]Valeric acid (TTC-COOH) (80 mg,0.2 mmol), (2, 4, 6-trimethylbenzoyl) diphenyl phosphine oxide (TPO) (17.4 mg,0.05 mmol), N-isopropylacrylamide (1.13 g,10 mmol), cyclopentane oxide (0.44 mL,5 mmol), phthalic anhydride (recrystallised first and then sublimated) (0.74 g,5 mmol), triethylboron (TEB) in THF (10. Mu.L, 0.1 mmol), phosphazene base (t-BuP 1) (10. Mu.L, 0.04 mmol), THF (2 ml). After the material is fed, the vibration is uniform, so that the monomer, the chain transfer agent, the initiator and the catalyst are completely dissolved. Taking out and placing in an oil bath at 60 ℃ to react under magnetic stirring while utilizing 3mw/cm 2 And (3) carrying out blue light irradiation with the intensity of 405nm and heating for 24 hours, and taking a small amount of crude products for nuclear magnetic testing after the reaction is finished, so as to calculate the monomer conversion rate. The crude product was then precipitated three times in diethyl ether to give a purified product which was dried in a vacuum oven. Obtaining amphiphilic block polymer, phthalic anhydride monomer conversion rate>99% of the polymer obtained has a molecular weight of 18.4kDa and a molecular weight distribution of 1.78, the molecular weight and the distribution diagram being shown in data 1 of FIG. 1.
The obtained polymer was dissolved in deuterated chloroform and subjected to 1H NMR test, and nuclear magnetic resonance hydrogen spectrum is shown in figure 2. As can be seen in FIG. 2, chemical shifts of 7.8ppm and 7.5ppm correspond to the hydrogen on the benzene ring in the segment after the phthalic anhydride polymerization has been incorporated into the polymer chain; the chemical shift is 6.3ppm and 6.1ppm respectively correspond to the hydrogen on two CH2 on the outer ring of the cyclopentane epoxide; chemical shifts of 5.85ppm and 5.63ppm correspond to hydrogen on two CH2 obtained by polymerizing cyclopentane in the main chain; chemical shift 4.15ppm corresponds to hydrogen on the last CH2 on cyclopentane epoxide; chemical shift 4.0ppm corresponds to hydrogen on CH on tert-butyl carbon at N position after polymerization of N, N-dimethylacrylamide is introduced into the main chain; chemical shift 1.0-2.0ppm corresponds to hydrogen remaining after polymerization of N, N-dimethylacrylamide incorporated into the backbone. It is known from the integral area calculation that the number of hydrophilic monomer introduction is about five times that of hydrophobic monomer (epoxy or anhydride).
Example two
Other polymerization conditions in this example were the same as in example one, and 4-cyano-4- [ (dodecylsulfanylsulfanylcarbonyl) sulfanyl ] pentanoic acid (TTC-COOH) was used as a chain transfer agent initiator, the different blue light irradiation times were changed to 0h, the heating time was unchanged, the reaction was carried out in an oil bath at 60℃for 24h, the other feed types and ratios were the same, the phthalic anhydride monomer conversion was >99%, the molecular weight of the resulting polymer was 7.8kDa, the molecular weight distribution was 1.56, and the data for heating-free illumination were shown in data 2 in FIG. 1.
Example III
Other polymerization conditions in this example were the same as in example one, but 4-cyano-4- [ (dodecylsulfanylsulfanylcarbonyl) sulfanyl ] pentanoic acid (TTC-COOH) was still used as a chain transfer agent initiator, except that the blue light intensity was changed to 12 hours with constant irradiation time, the heating time was changed, and the reaction was carried out in an oil bath at 60℃for 24 hours, with other feed types and proportions being consistent, with a 92% yield of the resulting polyester. Phthalic anhydride monomer conversion was >99%, and the resulting polymer had a molecular weight of 14.7kDa and a molecular weight distribution of 1.64.
Example IV
Other polymerization conditions in this example were the same as in example one except that 4-cyano-4- [ (dodecylsulfanylsulfanylcarbonyl) sulfanyl ] pentanol (TTC-OH) was used as a chain transfer agent initiator, other dosing types and proportions were the same, blue light of the same power and the same wavelength was irradiated, reacted in an oil bath at 60℃for 24 hours, phthalic anhydride monomer conversion was >99%, and the resulting polymer had a molecular weight of 18.1kDa and a molecular weight distribution of 1.75.
Example five
Other polymerization conditions in this example were the same as in example one, but 4-cyano-4- [ (dodecylsulfanylsulfanylcarbonyl) sulfanyl ] pentanoic acid (TTC-COOH) was still used as a chain transfer agent initiator, except that benzophenone was used as a photoinitiator, the other feeds were of the same type and proportion, the same power and the same wavelength blue light was irradiated, reacted in an oil bath at 60℃for 24 hours with a phthalic anhydride monomer conversion of >99%, and the resulting polymer had a molecular weight of 19.6kDa and a molecular weight distribution of 1.57.
Example six
Other polymerization conditions in this example were the same as in example one, but 4-cyano-4- [ (dodecylsulfanylsulfanylcarbonyl) sulfanyl ] pentanoic acid (TTC-COOH) was still used as a chain transfer agent initiator, except that N, N-dimethylacrylamide was used as a hydrophilic monomer, other charged species and proportions were the same, blue light of the same power and wavelength was irradiated, and reacted in an oil bath at 60℃for 24 hours, with a phthalic anhydride monomer conversion of >99%, and the resulting polymer had a molecular weight of 20.2kDa and a molecular weight distribution of 1.49.
Example seven
Other polymerization conditions in this example were the same as in example one, but 4-cyano-4- [ (dodecylsulfanylsulfanylcarbonyl) sulfanyl ] pentanoic acid (TTC-COOH) was still used as a chain transfer agent initiator, except that the Lewis base was changed to tetraphenylphosphine chloride, the other charged species and proportions were the same, the same power and the same wavelength blue light was irradiated, reacted in an oil bath at 60℃for 24 hours, the phthalic anhydride monomer conversion was >99%, and the resulting polymer had a molecular weight of 18.7kDa and a molecular weight distribution of 1.68.
Example eight
Other polymerization conditions in this example were the same as in example one, and 4-cyano-4- [ (dodecylsulfanylsulfanylcarbonyl) sulfanyl ] pentanoic acid (TTC-COOH) was used as the chain transfer agent initiator, except that the Lewis acid was changed to triphenylboron, the other charge types and proportions were the same, the same power and the same wavelength blue light was irradiated, reacted in an oil bath at 60℃for 24 hours, the phthalic anhydride monomer conversion was 87%, and the resulting polymer had a molecular weight of 15.6kDa and a molecular weight distribution of 1.82.
Example nine
Other polymerization conditions in this example were the same as in example one, and 4-cyano-4- [ (dodecylsulfanylsulfanylcarbonyl) sulfanyl ] pentanoic acid (TTC-COOH) was used as a chain transfer agent initiator, except that the epoxide was changed to cyclohexene oxide, the other feeds were of the same type and proportion, the same power and the same wavelength blue light was irradiated, and reacted in an oil bath at 60℃for 24 hours, with a phthalic anhydride monomer conversion of >99%, and the resulting polymer had a molecular weight of 21.8kDa and a molecular weight distribution of 1.65.
Examples ten
Other polymerization conditions in this example were the same as in example one, and 4-cyano-4- [ (dodecylsulfanylsulfanylcarbonyl) sulfanyl ] pentanoic acid (TTC-COOH) was still used as a chain transfer agent initiator, and the other charged species and proportions were the same, and blue light of the same power and the same wavelength was irradiated for 24 hours, except that the mixture was heated in an oil bath at 60℃for 12 hours (after which it was rapidly cooled to room temperature by cooling water), and the other charged species and proportions were the same, and the phthalic anhydride monomer conversion was 71%, and the resulting polymer had a molecular weight of 16.1kDa and a molecular weight distribution of 1.50.
Example eleven
200mg of the amphiphilic block polymer prepared in the ninth embodiment was dissolved in 0.5mL of N, N-dimethylformamide, and after dissolution, slowly dropped into 80mL of deionized water while stirring. Then, the assembled solution was put into a dialysis bag and dialyzed in water for two days with water changed for 4 times in between to remove N, N-dimethylformamide.
The concentration of the assembly liquid was diluted to 0.5mg/mL, and the particle size and particle size distribution thereof were measured by a dynamic light scattering instrument, as shown in FIG. 3, and the particle size of the assembly was about 119nm and the distribution index was about 0.133 as shown in the dynamic light scattering data, whereby it was confirmed that the method of the present invention can surely produce an amphiphilic block polymer excellent in the assembly property.
Therefore, the synthesis method successfully realizes the effective combination of optically controlled reversible addition chain transfer free radical polymerization and temperature controlled nonmetallic Lewis acid-base pair catalyzed epoxide and cyclic anhydride ring-opening copolymerization through one-pot reaction, creatively utilizes a special chain transfer initiator to bridge polymerization products corresponding to two polymerization mechanisms, and obtains the amphiphilic block polymer with the chain transfer initiator as a connecting point; the polymerization method has two polymerization modes, and the two polymerization mechanisms are synchronously carried out without mutual interference; all monomer initiator and catalyst are placed in a reaction device and polymerized in one pot; the molecular weight of the hydrophilic block can be simply and conveniently regulated by regulating the illumination time, and the molecular weight of the polyester block can be regulated by regulating the heating time, so that the regulation of the polymer structure becomes simpler and more convenient by the physical regulation form. In addition, as the two polymerization forms are not interfered with each other, and the types of monomers suitable for the two polymerization are various, the amphiphilic block polymers with different performances can be obtained by changing the types of the monomers, the hydrophilic and hydrophobic properties of the polymers can be changed by adjusting the proportion of the two blocks, and the polymer is endowed with more abundant assembly behaviors; the polymerization system does not use a metal initiator or a metal catalyst, so that toxic heavy metal ion residues in the synthesized polymer can be avoided, and the application of the polymer in the fields of biological materials and the like is facilitated; the epoxide and the cyclic anhydride are rich in species and low in cost, and meanwhile, the chemical modification of the epoxide and the cyclic anhydride is simple and convenient, so that the late functionalization is easy; the hydrophilic monomers are various in variety and different in performance, so that the properties of the amphiphilic block polymer prepared by construction are more abundant; the catalyst is cheap and easy to obtain, has high catalytic activity, and is easy to obtain a polyester block structure with controllable sequence and regularity; the monomer source is wide and the price is low; because the catalyst chain transfer agent and the initiator are organic compounds, residual toxic heavy metal ions in the synthesized polymer can be effectively avoided, and the biocompatibility is excellent. The synthesis method is simpler and more convenient in general, high in efficiency, easy to control and adjustable in product structure, and the synthetic method has wide application prospect.
The present invention is not limited to the above-mentioned embodiments, and any person skilled in the art, based on the technical solution of the present invention and the inventive concept thereof, can be replaced or changed within the scope of the present invention.
Claims (4)
1. A method for preparing an amphiphilic block copolymer by light-controlled free radical polymerization and ring-opening copolymerization is characterized by comprising the following preparation steps:
in a nitrogen atmosphere, adding a hydroxyl or carboxyl-containing reversible addition chain transfer reagent, a photoinitiator, a hydrophilic vinyl monomer, a Lewis acid base pair catalytic system consisting of Lewis acid and Lewis base, an epoxy compound and cyclic anhydride into a dry polymerization reaction tube simultaneously;
sealing a polymerization reaction tube, placing the polymerization reaction tube in an oil bath, under a certain temperature condition, using a chain transfer reagent as an initiator, using Lewis acid and alkali to catalyze ring-opening copolymerization of cyclic anhydride and an epoxy compound, attaching a chain transfer agent to the tail end of polyester, irradiating visible light or ultraviolet light at the same time, decomposing a photoinitiator to generate free radicals, realizing free radical polymerization of vinyl monomers, and adding a hydrophilic polyolefin chain and a polyester chain through reversible addition of the chain transfer agent to form an amphiphilic block polymer;
pouring the reaction mixture into a mixed solution of diethyl ether and n-hexane for precipitation, repeatedly precipitating for multiple times, filtering, and vacuum drying the product to obtain an amphiphilic block polymer;
the chain transfer agent is 4-cyano-4- [ (dodecyl sulfanyl) thiocarbonyl ] pentanoic acid, 4-cyano-4-
At least one of [ (dodecylsulfanylsulfanyl) sulfanyl ] pentanol, 4-cyano-4- (thiobenzoyl) pentanoic acid, 2-methyl-2- (dodecyltrithiocarbonate group) propionic acid; the Lewis acid is at least one selected from triethylboron, tributylboron, triphenylboron, tris (pentafluorophenyl) boron and diethyl methoxyborane; the Lewis base is at least one of triphenylphosphine (PPh 3), bis (triphenylphosphine) ammonium chloride (PPNCl), tetraphenylphosphine chloride (PPh 4 Cl), 1, 8-diazabicyclo [5.4.0] undec-7-ene (DBU), phosphazene base t-BuP1 or t-BuP; the cyclic anhydride is succinic anhydride, 2-methylsuccinic anhydride, glutaric anhydride, diglycolic anhydride and phthalic anhydride, and the anhydride is purified by recrystallization in acetic anhydride and sublimation for multiple times; the epoxy compound is propylene oxide, cyclopentane epoxide, cyclohexane epoxide, phenyl glycidyl ether and benzyl glycidyl ether;
the hydrophilic vinyl monomer is at least one of acrylamide, N-isopropyl acrylamide, vinyl pyrrolidone, vinyl imidazole, N, N-dimethyl acrylamide and polyethylene glycol methyl ether methacrylate.
2. The method for preparing the amphiphilic block copolymer by light-operated free radical polymerization synergistic ring-opening copolymerization according to claim 1, wherein the photoinitiator is at least one of methyl benzoate, benzoin dimethyl ether, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1- (4-methylthiophenyl) -2-morpholino-1-propanone, (2, 4, 6-trimethylbenzoyl) diphenyl phosphine oxide, ethyl 2,4, 6-trimethylbenzoyl phenylphosphonate, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butanone, 2-hydroxy-4' - (2-hydroxyethoxy) -2-methylbenzophenone, 2-dimethylamino-2- (4-methyl) benzyl-1- [4- (4-morpholinyl) phenyl ] -1-butanone, benzophenone and tetraethyl mione.
3. The method for preparing the amphiphilic block copolymer by light-operated free radical polymerization and collaborative ring-opening copolymerization according to claim 1, wherein in the preparation of the polymer, the mole ratio of chain transfer agent to photoinitiator is as follows: 1 to 10:1, a step of; molar ratio of chain transfer agent to hydrophilic vinyl monomer: 1: 100-500 parts; molar ratio of chain transfer agent to lewis acid: 5:1 to 10; the molar ratio of Lewis acid to Lewis base is 1-5: 1, a step of; the molar ratio of lewis base to epoxide compound is 1: 100-500 parts; the molar ratio of cyclic anhydride to epoxy compound is 1:1 to 5; the copolymerization reaction is carried out under the condition of solution, and the temperature of the copolymerization reaction is 0 to 60 o And C, carrying out a heating reaction for 0-24 h under autogenous pressure and illumination reaction time for 0-5 h.
4. The method for preparing the amphiphilic block copolymer by light-controlled free radical polymerization and collaborative ring-opening copolymerization according to claim 1, wherein the irradiation light is one of ultraviolet light and visible light with the wavelength of 365nm, 390nm, 405nm or 440nm and the light intensity of 0.4mw/cm 2 ～10 mw/cm 2 。
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