Bottle brush type polymer with poly-alpha-glutamic acid with pH responsiveness on side chain as well as preparation method and application of bottle brush type polymer

Abstract

The invention discloses a bottle brush type polymer of poly-alpha-glutamic acid with pH responsiveness on a side chain, and belongs to the technical field of high-molecular compounds, the structural formula of the polymer is as follows: # imgabs0 #, and a preparation method comprises the following specific steps: (1) taking L-glutamic acid-NCA protected by gamma-carboxyl as a monomer, adding primary amine containing polymerizable double bonds, and reacting for 1-2 hours; initiating a ring-opening polymerization reaction of the monomer to obtain a macromolecular monomer of gamma-carboxyl protected L-glutamic acid containing polymerizable double bonds at the tail end; and (2) reacting the macromonomer under the action of a catalyst or an initiator to obtain the bottle brush type polymer with the pH-responsive poly-alpha-glutamic acid on the side chain. The high-density side chain modified bottle brush type polymer prepared by the invention has zero shear viscosity and low entanglement platform modulus, and presents unique mechanical and rheological properties, and the stimuli-responsive polypeptide is adopted as the side chain of the bottle brush type polymer, so that the biocompatibility of the bottle brush type polymer can be improved, and the functionality of the bottle brush type polymer can be enriched.

Description

Technical Field

[0001] The present invention belongs to the technical field of macromolecular compounds, and particularly relates to a bottlebrush polymer with pH-responsive poly-α-glutamic acid in the side chain, a preparation method thereof, and an application thereof. Background Art

[0002] Bottlebrush polymers are highly branched macromolecules, and their linear side chains are attached to the polymer main chain in a very dense manner. Due to their unique properties, bottlebrush polymers have attracted extensive research in many aspects. In dilute solutions, bottlebrush polymers exhibit a worm-like morphology; in semi-dilute solutions, when the concentration exceeds the critical value, bottlebrush polymers will grow in one direction, forming liquid crystal-like structures, and even conformational transitions of crystals may occur. The behavior of bottlebrush macromolecules in solution is not only related to their concentration, but also closely related to the grafting density of the polymer, the size and length of the side chains, the flexibility of the main and side chains, etc. In the melt, due to the high grafting degree of the side chains of bottlebrush polymers, they exhibit different properties from linear polymers. Through design, super-soft elastomers with good viscoelastic properties and polymer films with excellent ductility can be prepared. The viscoelastic properties of bottlebrush macromolecules also play an important role in the normal functioning of the physiological functions of some human tissues, such as the stress absorption and lubrication of articular cartilage, and the cleaning function of the cilia of the lung airway mucosa. It is precisely because bottlebrush polymers exhibit some unique physical properties in both solutions and melts that they have good application prospects in many aspects, such as new energy, pollutant control, catalyst carriers, nanoscale sensors, drug delivery, etc. The synthesis and design of such polymers are attracting more and more attention.

[0003] Currently, there are mainly three methods for synthesizing bottlebrush polymers: polymerization of macromonomers, grafting of branched chains, and polymerization of macromolecular initiator side chains. However, the related methods have problems such as complex synthesis steps, inability to ensure that each initiation site can initiate the ring-opening polymerization of NCA monomers during the synthesis process, and uncontrollability of the side chain grafting density and length.

[0004] Therefore, it is an urgent problem for those skilled in the art to provide a bottlebrush polymer that can ensure the modification of polyamino acids in the side chain on each monomer unit of the main chain, while the side chain density, length, and polypeptide type are also controllable, and a preparation method thereof. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a bottlebrush polymer with pH-responsive poly-α-glutamic acid in the side chain, a preparation method thereof, and an application thereof.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A bottlebrush polymer with a pH-responsive poly-α-glutamic acid in the side chain, and the structural formula of the polymer is as follows:

[0008]

[0009] Among them, the R is selected from

[0010]

[0011] any one of;

[0012] Among them, the R 1 is selected from

[0013] any one of.

[0014] The bottlebrush polymer with high-density side-chain modification prepared by the present invention has zero-shear viscosity and low entanglement plateau modulus, showing unique mechanical and rheological properties. Using polypeptides as the side chains of the bottlebrush polymer can improve the biocompatibility of the bottlebrush polymer and enrich the functionality of the bottlebrush polymer.

[0015] The preparation method of a bottlebrush polymer with a pH-responsive poly-α-glutamic acid in the side chain as described above includes the following specific steps:

[0016] (1) Using γ-carboxyl-protected L-glutamic acid-NCA as a monomer, adding a primary amine containing a polymerizable double bond, and initiating the ring-opening polymerization reaction of the monomer to obtain a γ-carboxyl-protected L-glutamic acid macromonomer with a polymerizable double bond at the end;

[0017] (2) Reacting the macromonomer under the action of a catalyst or an initiator to obtain a bottlebrush polymer with a pH-responsive poly-α-glutamic acid in the side chain.

[0018] The present invention can effectively control the length of the side chain through the ring-opening polymerization of NCA monomers initiated by a primary amine containing an unsaturated double bond, and the reaction conditions are mild. The double bond at the end of the macromonomer can further synthesize BBPs through the "grafting through" strategy to ensure high-density modification of the side chain.

[0019] Preferably, in step (1), the mass ratio of the γ-carboxyl-protected L-glutamic acid-NCA to the primary amine containing a polymerizable double bond is 1-50:0.02-0.18;

[0020] The primary amine containing a polymerizable double bond is at least one of 5-norbornene-2-methylamine, 2-methylallylamine, 3-buten-1-amine, allylamine, 4-vinylbenzylamine, 2-aminoethyl acrylate, and 2-aminoethyl acrylamide;

[0021] The conditions for the ring-opening polymerization reaction are as follows: reacting at room temperature for 3 - 12 h.

[0022] Preferably, in step (1), the ring-opening polymerization reaction further includes a solvent, and the solvent is DMF or tetrahydrofuran (THF). Using DMF and THF with high dielectric constants as solvents can ensure that the polypeptide segments are in a random coil state, so that the polymerization reaction is not affected.

[0023] The mass ratio of the solvent to the γ-carboxyl-protected L-glutamic acid-NCA is 6 - 200:1 - 50.

[0024] Preferably, the preparation method of the γ-carboxyl-protected L-glutamic acid-NCA in step (1) is to uniformly mix γ-carboxyl-protected L-glutamic acid, triphosgene, and a solvent, and then add epichlorohydrin to react to obtain γ-carboxyl-protected L-glutamic acid-NCA. Using solid phosgene (triphosgene) can reduce the hazards in the synthesis process of NCA monomers, and epichlorohydrin can absorb hydrogen chloride gas generated during the reaction, thus avoiding equipment corrosion and environmental pollution.

[0025] Preferably, the mass ratio of the γ-carboxyl-protected L-glutamic acid, the triphosgene, the solvent, and the epichlorohydrin is 1 - 8:1 - 5:6 - 100:1 - 5;

[0026] The conditions for the reaction are as follows: reacting at 25 - 66 °C for 0.5 - 2 h;

[0027] The solvent is tetrahydrofuran;

[0028] The γ-carboxyl-protected L-glutamic acid is at least one of γ-carboxyl-tert-butyl-protected L-glutamic acid and γ-carboxyl-benzyl-protected L-glutamic acid.

[0029] Preferably, in step (2), the mass ratio of the macromonomer to the catalyst is 1 - 60:0.004 - 0.01, and the mass ratio of the macromonomer to the initiator is 1 - 60:0.002 - 0.012;

[0030] The conditions for the reaction are as follows: reacting at 50 - 80 °C for 0.5 - 8 h;

[0031] The catalyst is at least one of Grubbs second generation and third generation;

[0032] The initiator is at least one of organic azo compounds and peroxides.

[0033] Preferably, the organic azo compounds include azobisisobutyronitrile and / or azobisisoheptonitrile, and the peroxides include benzoyl peroxide and / or tert-butyl hydroperoxide.

[0034] Preferably, the reaction in step (2) further includes a solvent, the solvent is tetrahydrofuran, and the mass ratio of the solvent to the macromonomer is 1-14:1-50;

[0035] The bottle-brush polymer further includes a step of obtaining a pure bottle-brush polymer by reacting to remove the protecting group on the side-chain carboxyl group under the action of a mixed solvent of trifluoroacetic acid and dichloromethane or trifluoroacetic acid, acetic acid and anisole;

[0036] Among them, the mass ratio of the bottle-brush polymer, the trifluoroacetic acid and the dichloromethane is 2-6:1-6:1-8; the reaction conditions are to react at room temperature for 1-3 h

[0037] The mass ratio of the bottle-brush polymer, the trifluoroacetic acid, the acetic acid and the anisole is 1:1-2:1-3:0.5-1; the reaction conditions are to react at room temperature for 16-24 h.

[0038] Application of the bottle-brush polymer prepared according to the bottle-brush polymer described above or the preparation method described above in the fields of super-soft elastomers, dynamic adaptive networks, biological friction and lubrication, and nano-drug carriers.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] The present invention uses a primary amine containing a polymerizable double bond as an initiator, and through the primary amine mechanism, initiates the ring-opening polymerization reaction of γ-carboxyl-protected L-glutamic acid NCA monomer, and controls the length of the side chain by controlling the feeding ratio of the monomer and the primary amine; in addition, the present invention uses olefin metathesis catalyzed by Grubbs catalyst or thermal-initiated polymerization to synthesize bottle-brush polymers through the "grafting through" strategy. The double bond at the end of the macromonomer can ensure that each monomer unit on the main chain can be modified with a side chain, ensuring a 100% side-chain grafting density. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0042] Figure 1 Schematic diagram of the synthesis route of the bottle-brush polymer of the present invention;

[0043] Figure 21H NMR spectrum of the bottle-brush polymer macromonomer of Example 1 of the present invention;

[0044] Figure 3 CD spectrum of the bottle-brush polymer macromonomer of Example 1 of the present invention. Detailed implementation manners

[0045] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0046] Example 1

[0047] As Figure 1 , the present invention provides a preparation method of a bottle-brush polymer with pH-responsive poly-α-glutamic acid on the side chain, including the following specific steps:

[0048] (1) First, in a thick-walled pressure-resistant bottle, L-glutamic acid with γ-carboxyl tert-butyl protection, triphosgene and tetrahydrofuran (THF) are mixed according to the mass ratio of 2:1:9, and then 5 times the mass of epichlorohydrin is added. Immediately seal the pressure-resistant bottle and stir the reaction at room temperature to ensure that all components are evenly mixed; as the reaction proceeds, the temperature of the reaction system gradually rises until the THF solvent boils. As the reaction gradually completes (0.5 h), the heat release of the system decreases, and the temperature of the reaction bottle gradually returns to room temperature to obtain a mixed solution; according to the volume ratio of n-hexane to ethyl acetate of 2:1, and the sum of the volumes of n-hexane and ethyl acetate is 10 times the volume of THF, the mixed solution obtained in step (1) is gradually added dropwise to a flask containing a mixed solvent of n-hexane and ethyl acetate; after the addition is completed, the flask is placed in a 4°C refrigerator and left to stand overnight, and a white solid gradually precipitates. After suction filtration, a white crystal is obtained. The recrystallization step is repeated 2 times, and after suction filtration and drying, the final product, γ-carboxyl tert-butyl protected L-glutamic acid NCA monomer, is obtained;

[0049] (2) Mix 5-norbornene-2-methylamine, γ-carboxyl tert-butyl protected L-glutamic acid NCA and THF evenly according to the mass ratio of 0.1:2.5:10, and place them in a two-necked round-bottom flask. React at 25°C for 12 h. After the reaction is completed, precipitate with ether and use a suction filtration device to separate the product from the solvent, and then perform vacuum drying treatment at 50°C to remove the residual solvent and moisture, that is, a macromonomer of γ-carboxyl tert-butyl protected L-glutamic acid containing a polymerizable double bond at the end is obtained;

[0050] (3) Mix evenly a macromonomer of γ-carboxy-tert-butyl-protected L-glutamic acid with a terminal polymerizable double bond, Grubbs catalyst, and dichloromethane in a mass ratio of 1:0.02:1, place it in a two-necked round-bottom flask, react at 50 °C for 8 h, after the reaction is completed, precipitate with diethyl ether and use a suction filtration device to separate the product from the solvent, and then perform vacuum drying treatment at 50 °C to remove residual solvent and moisture to obtain a bottlebrush polymer;

[0051] (4) Dissolve one mass portion of the obtained bottlebrush polymer in ten mass portions of dichloromethane, add ten mass portions of trifluoroacetic acid, stir at room temperature for 2 h, then rotary evaporate to remove the solvent, add the obtained residual solid to 0.1 M hydrochloric acid solution, dialyze in a dialysis bag for 48 h, and freeze-dry to obtain a pure bottlebrush polymer with a main chain polymerization degree of 200 and a side chain polymerization degree of 20;

[0052] Among them, the bottlebrush polymer based on poly-L-glutamic acid obtained in this example has very good water solubility and biocompatibility. Figure 2 The nuclear magnetic resonance hydrogen spectrum accurately characterizes the chemical structure of the bottlebrush polymer macromonomer. Through Figure 3 It can confirm its α-helix and random coil conformation transitions; the bottlebrush polymer synthesized by the "grafting through" strategy in this example has unique configurational characteristics, with a low entanglement plateau elastic modulus and shear modulus. The pH responsiveness and biocompatibility of the polypeptide side chains can meet the usage requirements of super soft elastomers and biomaterials, and can be used as bio-inspired soft tissue structures, nano drug carriers, etc.

[0053] Example 2

[0054] The present invention provides a preparation method of a bottlebrush polymer with a pH-responsive poly-α-glutamic acid side chain, including the following specific steps:

[0055] (1) The preparation method of γ-carboxy-tert-butyl-protected L-glutamic acid NCA monomer is the same as that in step (1) of the example;

[0056] (2) Mix evenly 2-methylallylamine, γ-carboxy-tert-butyl-protected L-glutamic acid NCA, and THF in a mass ratio of 0.06:2.5:10, place it in a two-necked round-bottom flask, react at 25 °C for 12 h, after the reaction is completed, precipitate with diethyl ether and use a suction filtration device to separate the product from the solvent, and then perform vacuum drying treatment at 50 °C to remove residual solvent and moisture, that is, obtain a macromonomer of γ-carboxy-tert-butyl-protected L-glutamic acid with a terminal polymerizable double bond.

[0057] (3) Mix uniformly a macromonomer of γ-carboxy-tert-butyl-protected L-glutamic acid with a terminal polymerizable double bond, azobisisobutyronitrile, and dichloromethane in a mass ratio of 1:0.006:1, place the mixture in a two-necked round-bottom flask, react at 50 °C for 3 h, after the reaction is completed, precipitate with diethyl ether and use a suction filtration device to separate the product from the solvent, and then perform vacuum drying treatment at 50 °C to remove residual solvent and moisture to obtain a bottlebrush polymer;

[0058] (4) Dissolve one mass portion of the obtained bottlebrush polymer in one mass portion of dichloromethane, then add 1.5 mass portions of trifluoroacetic acid, stir at room temperature for 1 h, neutralize with 0.1 M hydrochloric acid solution to pH 7.4, dialyze in a dialysis bag for 48 h, and freeze-dry to obtain a pure bottlebrush polymer with a main chain polymerization degree of 200 and a side chain polymerization degree of 30.

[0059] Example 3

[0060] The present invention provides a preparation method of a bottlebrush polymer with a side chain having pH-responsive poly-α-glutamic acid, including the following specific steps:

[0061] (1) First, mix L-glutamic acid γ-benzyl ester, triphosgene, and tetrahydrofuran (THF) in a mass ratio of 2:1:9 in a thick-walled pressure-resistant bottle, then add 5 times the mass of epichlorohydrin, immediately seal the pressure-resistant bottle, and stir and react at room temperature to ensure that all components are uniformly mixed; as the reaction proceeds, the temperature of the reaction system gradually increases until the tetrahydrofuran solvent boils, as the reaction gradually completes (0.5 h), the heat release of the system decreases, and the temperature of the reaction bottle gradually returns to room temperature to obtain a mixed solution; according to the volume ratio of n-hexane to ethyl acetate of 2:1, and the sum of the volumes of n-hexane and ethyl acetate is 10 times the volume of tetrahydrofuran, gradually add the mixed solution obtained in step (1) dropwise to a flask containing a mixed solvent of n-hexane and ethyl acetate; after the dropping is completed, place the flask in a 4 °C refrigerator and let it stand overnight, gradually precipitate a white solid, filter by suction to obtain a white crystal, repeat the recrystallization step 2 times, and filter and dry to obtain the final product γ-carboxybenzyl-protected L-glutamic acid NCA monomer;

[0062] (2) Mix uniformly 5-norbornene-2-methylamine, γ-carboxybenzyl-protected L-glutamic acid NCA monomer, and THF in a mass ratio of 0.1:2:9, place the mixture in a two-necked round-bottom flask, react at 25 °C for 12 h, after the reaction is completed, precipitate with diethyl ether and use a suction filtration device to separate the product from the solvent, and then perform vacuum drying treatment at 50 °C to remove residual solvent and moisture to obtain a macromonomer of γ-carboxybenzyl-protected L-glutamic acid with a terminal polymerizable double bond;

[0063] (3) Mix uniformly a macromonomer of γ-carboxybenzyl-protected L-glutamic acid with a polymerizable double bond at the end, azodiisobutyronitrile, and dichloromethane in a mass ratio of 1:0.005:1, place the mixture in a two-necked round-bottom flask, react at 50 °C for 3 h. After the reaction is completed, precipitate with diethyl ether and use a suction filtration device to separate the product from the solvent, and then perform vacuum drying at 50 °C to remove residual solvent and moisture to obtain a bottlebrush polymer;

[0064] (4) Dissolve one mass portion of the obtained bottlebrush polymer in one mass portion of trifluoroacetic acid, one mass portion of acetic acid, and one mass portion of anisole. After stirring at room temperature for 16 h, remove anisole, add two mass portions of 1 M sodium hydroxide solution, and dialyze the aqueous phase in a dialysis bag for 48 h. After freeze-drying, obtain a pure bottlebrush polymer with a main chain polymerization degree of 500 and a side chain polymerization degree of 20.

[0065] Each embodiment is described in a progressive manner. What each embodiment focuses on explaining is the difference from other embodiments. For the same or similar parts among the embodiments, reference can be made to each other.

[0066] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A bottle brush polymer having a pH-responsive poly-α-glutamic acid side chain, characterized in that: The structural formula of the polymer is as follows: Wherein, the R is selected from Any of the following: Wherein, the R1 is selected from Any one of .

2. A method for preparing a bottle brush polymer having a pH-responsive poly-α-glutamic acid side chain as claimed in claim 1, characterized in that: The specific steps include: (1) using γ-carboxyl protected L-glutamic acid-NCA as a monomer, adding a primary amine containing a polymerizable double bond, initiating a ring-opening polymerization reaction of the monomer, and obtaining a macromolecular monomer of γ-carboxyl protected L-glutamic acid containing a polymerizable double bond at the end; (2) The macromonomer is reacted under the action of a catalyst or an initiator to obtain a bottle brush polymer having a pH-responsive poly-α-glutamic acid side chain.

3. The method for preparing a bottle brush type polymer having a pH responsive poly-α-glutamic acid side chain according to claim 2, characterized in that: The mass ratio of the γ-carboxyl protected L-glutamic acid-NCA to the primary amine containing a polymerizable double bond in step (1) is 1-50:0.02-0.18; The primary amine containing a polymerizable double bond is at least one of 5-norbornene-2-methylamine, 2-methylallylamine, 3-butene-1-amine, allylamine, 4-vinylbenzylamine, 2-aminoethyl acrylate and 2-aminoethyl acrylamide; The conditions of the ring-opening polymerization reaction are: reacting at room temperature for 3-12 hours.

4. The method for preparing a bottle brush type polymer having a pH responsive poly-α-glutamic acid side chain according to claim 2, characterized in that: The ring-opening polymerization reaction in step (1) further comprises a solvent, wherein the solvent is DMF or tetrahydrofuran, and the mass ratio of the solvent to the γ-carboxyl-protected L-glutamic acid-NCA is 6-200:1-50.

5. The method for preparing a bottle brush polymer having a pH-responsive poly-α-glutamic acid side chain according to claim 2, characterized in that: The preparation method of the γ-carboxyl-protected L-glutamic acid-NCA in step (1) is to uniformly mix the γ-carboxyl-protected L-glutamic acid, triphosgene and a solvent, and then add epichlorohydrin to react to obtain the γ-carboxyl-protected L-glutamic acid-NCA.

6. The method for preparing a bottle brush polymer having a pH-responsive poly-α-glutamic acid side chain according to claim 5, characterized in that: The mass ratio of the γ-carboxyl protected L-glutamic acid, the triphosgene, the solvent and the epichlorohydrin is 1-8:1-5:6-100:1-5; The reaction conditions are: reacting at 25-66°C for 0.5-2h; The solvent is tetrahydrofuran; The γ-carboxyl protected L-glutamic acid is at least one of γ-carboxyl tert-butyl protected L-glutamic acid and γ-carboxyl benzyl protected L-glutamic acid.

7. The method for preparing a bottle brush polymer having a pH-responsive poly-α-glutamic acid side chain according to claim 2, characterized in that: In step (2), the mass ratio of the macromonomer to the catalyst is 1-60:0.004-0.01, and the mass ratio of the macromonomer to the initiator is 1-60:0.002-0.012; The reaction conditions are: reacting at 50-80°C for 0.5-8h; The catalyst is at least one of the second generation and third generation of Grubbs; The initiator is at least one of an organic azo initiator and a peroxide initiator.

8. The method for preparing a bottle brush polymer having a pH-responsive poly-α-glutamic acid side chain according to claim 7, characterized in that: The organic azo compounds include azobisisobutyronitrile and / or azobisisoheptanenitrile, and the peroxide compounds include benzoyl peroxide and / or tert-butyl hydroperoxide.

9. The method for preparing a bottle brush polymer having a pH-responsive poly-α-glutamic acid side chain according to claim 2, characterized in that: The reaction in step (2) further comprises a solvent, wherein the solvent is tetrahydrofuran, and the mass ratio of the solvent to the macromonomer is 1-18:1-60; The bottle brush polymer further comprises a step of removing the protecting group on the side chain carboxyl group by reaction under the action of a mixed solvent of trifluoroacetic acid and dichloromethane or trifluoroacetic acid, acetic acid and anisole to obtain a pure bottle brush polymer; Wherein, the mass ratio of the bottle brush polymer, the trifluoroacetic acid and the dichloromethane is 2-6:1-6:1-8, and the reaction condition is to react at room temperature for 1-3h; The mass ratio of the bottle brush polymer, the trifluoroacetic acid, the acetic acid and the anisole is 1:1-2:1-3:0.5-1; and the reaction condition is to react at room temperature for 16-24 hours.

10. Application of the bottle brush polymer according to claim 1 or the bottle brush polymer prepared by the preparation method according to any one of claims 2 to 9 in the fields of ultra-soft elastomers, dynamic adaptive networks, biofriction and lubrication, and nano drug carriers.

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