A polyamino acid-polyester-polycarbonate triblock copolymer and a method for synthesizing the same

Abstract

The application belongs to the technical field of polymer synthesis, and discloses a kind of polyamino acid-polyester-polycarbonate tri-block copolymer and synthesis method thereof, the mixture of organic lewis acid and steric hindrance organic lewis base is used as catalyst in the application, combined with self-accelerating polymerization and copolymerization strategy, realize the four-copolymerization of N-carboxyl cyclic anhydride, epoxide, cyclic anhydride and carbon dioxide, polyamino acid-polyester-polycarbonate tri-block copolymer is synthesized by one-step method with high selectivity and high catalytic efficiency.The block copolymer obtained by the application has more rich structure type, and its glass transition temperature can be adjusted;The polyamino acid block synthesized by ring-opening polymerization of N-carboxyl cyclic anhydride is a mimic of natural polymer and protein, which can significantly improve the medical function of biodegradable polyester block;And the secondary structure of the application promotes the ring-opening of cyclic anhydride and carbon dioxide, thereby improving the ring-opening copolymerization reaction rate.

Description

Technical Field

[0001] This invention belongs to the field of polymer synthesis technology, and more specifically, relates to a polyamino acid-polyester-polycarbonate triblock copolymer and its synthesis method. Background Technology

[0002] Polyamino acids (polypeptides) possess excellent biocompatibility, bioactivity, and biodegradability, and have been widely used in drug and gene delivery, tissue engineering, and antibacterial applications. However, polyamino acids have poor mechanical properties, high melting points, and are difficult to process. Compared to polyamino acid homopolymers, copolymers formed from amino acids and other comonomers can have their physical and chemical properties adjusted and improved at the molecular scale, effectively improving mechanical properties, lowering processing temperatures, and enhancing biocompatibility and biodegradability. By rationally designing and introducing biodegradable blocks such as polyester and polycarbonate, the polymer can possess two glass transition temperatures: one below room temperature, imparting a highly elastic rubbery state, and the other above room temperature, imparting an easily processable plastic state. However, such polyamino acid-polyester-polycarbonate triblock copolymers have not yet been reported.

[0003] Ring-opening polymerization of N-carboxylated intracyclic anhydrides is a classic strategy in peptide synthesis. Over the past century, numerous research groups internationally have reported various methods for initiating polymerization, among which primary amine-initiated ring-opening polymerization of N-carboxylated intracyclic anhydrides remains the most widely used method. The primary amine initiators commonly used in N-carboxylated intracyclic anhydride ring-opening polymerization undergo an additional decarboxylation step to generate reaction centers for continuous chain growth. This decarboxylation step significantly slows down the polymerization rate (typically requiring 2-3 days to complete) and makes it difficult to prepare large molecular weight peptides. Furthermore, because N-carboxylated intracyclic anhydride monomers generally have poor stability, prolonged reactions may lead to side reactions.

[0004] In recent years, anionic ring-opening living polymerization systems such as bis(trimethylsilyl)amine lithium and tetraalkylammonium carboxyl salts have developed rapidly. This living polymerization can conveniently achieve homopolymerization, blending, and block polymerization of NCA (Nat. Commun. 2018, 9, 5297; Angew. Chem. Int. Ed. 2021, 60, 26063-26071). However, these methods can only yield peptides, not hybrid peptide multi-block copolymers. Furthermore, due to limitations in polymerization methods and structures, hybrid peptide block copolymers mainly employ a "multi-step method," i.e., a strategy of sequentially adding monomers. However, this method requires stepwise feeding and indirect purification, which is time-consuming and labor-intensive.

[0005] The inventors of this invention previously obtained a method for preparing polyester I-polyester II-polycarbonate triblock copolymer (see Chinese patent document CN115584018A). Although it discloses a "one-step" process (no need to add monomers in sequence), all four components are ring-opening copolymerization reactions of oxyheterocyclic monomers. Summary of the Invention

[0006] To address the aforementioned deficiencies or improvement needs of existing technologies, the present invention aims to provide a polyamino acid-polyester-polycarbonate triblock copolymer and its synthesis method. Using a mixture of organic Lewis acids and sterically hindered organic Lewis bases as catalysts, and combining self-accelerated polymerization and copolymerization strategies, a quaternary copolymerization of N-carboxylic acid anhydride, epoxy compound, cyclic anhydride, and carbon dioxide is achieved in a one-step process with high selectivity and high catalytic efficiency, synthesizing a polyamino acid-polyester-polycarbonate triblock copolymer. This solves the technical problem of limited structural types of hybrid peptide block copolymers prepared by existing technologies. The block copolymers synthesized in this invention have a richer variety of structural types, and their glass transition temperatures can be adjusted. The polyamino acid blocks synthesized by ring-opening polymerization (ROP) of N-carboxylic acid anhydrides are natural polymer and protein mimics, which can significantly improve the medical functions of biodegradable polyester blocks. Furthermore, the ortho-hydrogen bonding of its secondary structure promotes the ring-opening of cyclic anhydrides and carbon dioxide, thereby increasing the rate of ring-opening copolymerization (that is, based on the invention, the unique hydrogen bonding of polyamino acid blocks can increase the reaction rate of ring-opening copolymerization ROCOP).

[0007] To achieve the above objectives, according to one aspect of the present invention, a polyamino acid-polyester-polycarbonate triblock copolymer is provided, characterized in that it is synthesized in one step using a mixture of N-carboxylic acid anhydride, epoxy compound, cyclic anhydride and carbon dioxide as raw materials, under the action of a catalyst and an initiator;

[0008] Wherein, polyamino acid is the ring-opening polymerization product of the N-carboxyl intracyclic anhydride; polyester is the ring-opening copolymer of the epoxy compound and the cyclic anhydride; and polycarbonate is the ring-opening copolymer of the carbon dioxide and the epoxy compound.

[0009] The catalyst includes a main catalyst and a co-catalyst, wherein the main catalyst is an organic Lewis acid catalyst and the co-catalyst is a sterically hindered organic Lewis basic catalyst.

[0010] As a further preferred embodiment of the present invention, the general structural formula of the polyamino acid-polyester-polycarbonate triblock copolymer is as follows:

[0011]

[0012] Wherein, R1 is one of the following structural formulas:

[0013]

[0014] R2 is one of the following structural formulas:

[0015] *-H*-CH3

[0016] R3 is one of the following structural formulas:

[0017]

[0018] R4 is one of the following structural formulas:

[0019]

[0020] Furthermore, n = 5–30, m = 20–50, and z = 10–30.

[0021] As a further preferred embodiment of the present invention, the polyamino acid-polyester-polycarbonate triblock copolymer has two glass transition temperatures, one of which is -20°C to 20°C and the other is 50°C to 70°C.

[0022] According to another aspect of the present invention, the present invention provides a method for synthesizing the above-mentioned polyamino acid-polyester-polycarbonate triblock copolymer, characterized in that it includes the following steps:

[0023] (1) Under a protective atmosphere and under oxygen-free and anhydrous conditions, the three monomers, namely N-carboxylic acid anhydride, cyclic anhydride and epoxy compound, are first thoroughly mixed with the initiator and the main catalyst in the reactor for 1 to 4 hours.

[0024] (2) After adding the co-catalyst to the reactor of step (1), carbon dioxide is introduced into the reactor to obtain a reaction mixture;

[0025] (3) React the reaction mixture from step (2) at room temperature for 4 to 10 hours. After the reaction is complete, release the carbon dioxide in the reactor and quench the reaction to obtain crude product A.

[0026] (4) Purify the crude product A obtained in step (3) to obtain polyamino acid-polyester-polycarbonate triblock copolymer;

[0027] Preferably, the molar ratio of the N-carboxylic acid anhydride to the initiator in step (1) is 5 to 30:1.

[0028] As a further preferred embodiment of the present invention, the N-carboxyl ring anhydride has a structure as shown in formula (I):

[0029]

[0030] Wherein, R1 is one of the following structural formulas:

[0031]

[0032] R2 is one of the following structural formulas:

[0033] *-H*-CH3;

[0034] Preferably, the N-carboxyl ring anhydride has the structure shown in any one of formulas (I) to (VIII):

[0035]

[0036] As a further preferred embodiment of the present invention, the main catalyst is one or more selected from triethylborane, tributylborane, triphenylborane, and tris(pentafluorophenyl)borane;

[0037] The pK of the co-catalyst in acetonitrile a The value is greater than 24 and less than 35, preferably one or more of the following: phosphazene ligand P1-tert-butyl, phosphazene ligand P2-tert-butyl, 7-methyl-1,5,7-triazabicyclo(4.4.0)dec-5-ene, 1,5,7-triazidobicyclo(4.4.0)dec-5-ene, and 1,8-diazabicyclo(5.4.0)undec-7-ene.

[0038] As a further preferred embodiment of the present invention, the epoxy compound is one or more selected from ethylene oxide, propylene oxide, 1,2-epoxybutane, n-butyl glycidyl ether and tert-butyl glycidyl ether;

[0039] The cyclic anhydride is one or more of phthalic anhydride, norbornene anhydride, tetrahydrophthalic anhydride, succinic anhydride, glutaric anhydride, and diethylene glycol anhydride;

[0040] The initiator is a terminal hydroxyl or carboxyl compound, preferably one or more of benzyl alcohol and benzoic acid.

[0041] As a further preferred embodiment of the present invention, the molar ratio of the cyclic anhydride to the initiator is 20 to 50:1; and the molar ratio of the epoxide to the initiator is 300 to 500:1.

[0042] As a further preferred embodiment of the present invention, the molar ratio of the main catalyst to the co-catalyst is 1:1 to 5:1;

[0043] In step (2), the pressure of carbon dioxide is 1-4 MPa.

[0044] Compared with the prior art, the above-conceptual technical solution of this invention utilizes the synergistic catalytic effect of organic Lewis acids / organic Lewis bases, using terminal hydroxyl or carboxyl compounds as initiators, and combines chemically selective polymerization and copolymerization strategies to carry out a quaternary copolymerization reaction of N-carboxylic acid anhydride, epoxy compound, cyclic anhydride and carbon dioxide. By optimizing the feed ratio of the main catalyst and co-catalyst and the structure of the N-carboxylic acid anhydride, a one-step method with high selectivity and high catalytic efficiency can synthesize biodegradable and biocompatible polyamino acid-polyester-polycarbonate triblock copolymers.

[0045] The polyamino acid-polyester-polycarbonate triblock copolymer obtained in this invention has a glass transition temperature (T0) of either the polyester block or the polycarbonate block. g The glass transition temperature (T) of polyamino acids is no more than room temperature and ranges from -20℃ to 20℃. g Above room temperature (50℃~70℃), polyester or polycarbonate blocks are miscible with each other but immiscible with polyamino acid blocks, resulting in triblock copolymers having two glass transition temperatures (T0). g One of them has a glass transition temperature below room temperature, giving the material a highly elastic rubber state, while the other has a glass transition temperature above room temperature, giving the material a easily processable plastic state. The phase separation of the soft and hard segments can form thermoplastic elastomer materials. The thermodynamically reversible physical crosslinking generated by block separation means that these elastomers are recyclable and reprocessable, retaining the thermoplastic characteristics of plastics. They are especially suitable for constructing medical elastomers, with high biocompatibility and adjustable biodegradability.

[0046] The copolymerization reaction mechanism diagram of this invention is shown below. Figure 1As shown, the organo-Lewis base is a non-nucleophilic base that removes the hydroxyl hydrogen from benzyl alcohol, which acts as an initiator, via hydrogen bonding to form an alkoxyl active species 1. Simultaneously, the alkoxyl active species 1 attacks the N-carboxyl anhydride monomer to form complex 2. Under the action of the organo-Lewis base, complex 2 undergoes both N-carboxyl anhydride addition and carbon dioxide decarboxylation simultaneously to produce complex 3. The organo-Lewis base-promoted ring-opening polymerization of N-carboxyl anhydrides initiated by benzyl alcohol differs from the traditional primary amine initiation method, which requires hydrogen transfer to release carbon dioxide in the additional decarboxylation step. Furthermore, the steric hindrance of the organo-Lewis base can stabilize the terminal alkylamino active center. Next, the terminal alkylamino active center initiates a ring-opening copolymerization (ROCOP) reaction between the cyclic anhydride and the epoxy compound, producing complex 4, where the active center changes from alkylamino to alkoxy. Simultaneously, the amide bond on the polyamino acid forms hydrogen bonds with the cyclic anhydride and carbon dioxide, accelerating the ring-opening copolymerization (ROCOP) rate of the cyclic anhydride / epoxide and epoxy / carbon dioxide reactions. Finally, the terminal alkoxy active center initiates a ring-opening cocyclic polymerization (ROCOP) reaction between carbon dioxide and the epoxy compound, producing complex 5, which is the final product, a polyamino acid-polyester-polycarbonate triblock copolymer. The organic Lewis acid plays two roles: one is to activate the poorly electrophilic epoxy monomer, and the other is to coordinate with the terminal oxygen atom, inhibiting the occurrence of two side reactions: transesterification and backbiting.

[0047] In this invention, the polyamino acid blocks are synthesized via ring-opening polymerization of N-carboxylic acid anhydrides. Polyamino acids (polypeptides) prepared through the ring-opening polymerization of N-carboxylic acid anhydrides, combining the advantages of peptides and polymers, have become the most attractive protein mimics. Furthermore, the hydrogen bonding of the polyamino acid blocks can simultaneously increase the ring-opening copolymerization rate of epoxides and cyclic anhydrides, as well as the ring-opening copolymerization rate of carbon dioxide and epoxides. In this invention, the polyester is obtained through ring-opening copolymerization of epoxides and cyclic anhydrides. Epoxides and cyclic anhydrides are abundant and inexpensive, allowing for the preparation of polyesters containing various functionalized groups. For example, reactive groups such as double bonds can be introduced into the polyester, enabling further post-modification of the polymer; therefore, the polyester has strong functionalization potential. In this invention, polycarbonate is obtained by ring-opening copolymerization of epoxy compound and carbon dioxide. Carbon dioxide, a "greenhouse gas", is actually an abundant, non-toxic, and low-cost monomer, and is considered to be a very attractive one. Therefore, carbon dioxide-based polymers can solve the problem of carbon dioxide recycling, capture carbon dioxide, lock the recovered carbon dioxide in the polymer, effectively mitigate the greenhouse effect, and greatly promote the realization of carbon neutrality.

[0048] In summary, the technical solutions conceived by this invention have the following beneficial effects compared with the prior art:

[0049] (1) The block copolymers synthesized in this invention have a richer variety of structural types. The polyamino acid blocks synthesized by ring-opening polymerization (ROP) of N-carboxylic acid anhydrides are natural polymers and protein analogs, which can significantly improve the medical function of biodegradable polyester blocks. Moreover, the unique hydrogen bonding effect of polyamino acid blocks can simultaneously improve the reaction rate of ring-opening copolymerization (ROCOP) of epoxy compounds / cyclic acid anhydrides and the reaction rate of ring-opening copolymerization (ROCOP) of carbon dioxide / epoxy compounds.

[0050] The repeating units of the polyamino acid block are preferably between 5 and 30 (this can be ensured by controlling the molar ratio of the N-carboxylic anhydride to the initiator in the reaction system to 5–30:1). This allows for both α-helical and β-sheet secondary conformations and maintains the solubility of the polyamino acid. The ortho-hydrogen bonding in the secondary conformation of the polyamino acid promotes the ring-opening of the cyclic anhydride and carbon dioxide. The reason for prioritizing 5–30 repeating units is that fewer than 5 repeating units result in no secondary structure, while more than 30 repeating units cause the polyamino acid to precipitate from the epoxy compound. Therefore, neither fewer than 5 nor more than 30 repeating units can increase the rate of ring-opening copolymerization (ROCOP) of the epoxy compound / cyclic anhydride nor the rate of ring-opening copolymerization (ROCOP) of the carbon dioxide / epoxide compound.

[0051] (2) The present invention utilizes carbon dioxide as a cheap and renewable carbon monomer, which can effectively regulate the kinetic / thermal properties of block copolymers and reduce the carbon footprint of materials.

[0052] (3) This invention uses a mixture of N-carboxylic acid anhydride, epoxy compound, cyclic anhydride and carbon dioxide as raw materials to synthesize a polyamino acid-polyester-polycarbonate triblock copolymer in one step under the action of an initiator and a catalyst. The main catalyst in this invention is a weakly Lewis acid, which has two functions: one is to stabilize the terminal alkoxy or carboxyl active species of the polymer, and the other is to activate the N-carboxylic acid anhydride or epoxy compound. Furthermore, the co-catalyst is a sterically hindered organic Lewis basic catalyst; the organic base activates the initiator through hydrogen bonding to form active species. Next, the N-carboxyl anhydride undergoes ring-opening polymerization. After the N-carboxyl anhydride is completely consumed, the epoxy compound and the cyclic anhydride undergo ring-opening copolymerization. After the cyclic anhydride is completely consumed, the remaining epoxy compound undergoes ring-opening copolymerization with carbon dioxide gas. Finally, the reaction stops after the carbon dioxide is released into the air, thus synthesizing a fully biodegradable and biocompatible polyamino acid-polyester-polycarbonate triblock copolymer. The synthesized copolymer can be widely used in biomedical and chemical fields.

[0053] This invention utilizes the coordination effect of organic Lewis acids and organic Lewis bases to synergistically catalyze the quaternary copolymerization reaction of N-carboxylated intracyclic anhydride, epoxy compound, cyclic anhydride, and carbon dioxide (which can be further optimized by adjusting the feed ratio of the main catalyst and co-catalyst, as well as the structure of the N-carboxylated intracyclic anhydride). At room temperature, the hydrogen bonding effect of the polyamino acid blocks synthesized in the first step can simultaneously improve the ring-opening copolymerization (ROCOP) reaction rate of epoxy compound and cyclic anhydride and the ring-opening copolymerization (ROCOP) reaction rate of carbon dioxide and epoxy compound, avoiding the side reactions that may occur due to prolonged reaction. Thus, a one-step synthesis of polyamino acid-polyester-polycarbonate triblock copolymers can be achieved with high selectivity and high catalytic efficiency.

[0054] Taking Example 1 below as an example, Example 1 uses triethylborane as the main catalyst, 1,8-diazabicyclo(5.4.0)undec-7-ene as the co-catalyst, and benzyl alcohol as the initiator to carry out a quaternary copolymerization reaction of N-carboxylic intracyclic anhydride (Formula I), propylene oxide, phthalic anhydride, and carbon dioxide. The specific reaction mechanism is as follows:

[0055] In the first stage, the polymerization reaction is the ring-opening polymerization (ROP) of N-carboxylic acid anhydride (Formula I), and the specific reaction process is as follows:

[0056]

[0057] After the N-carboxyl anhydride (Formula I) monomer is completely consumed, the polymerization reaction enters the second stage. The second stage polymerization reaction is a ring-opening copolymerization (ROCOP) of propylene oxide and phthalic anhydride. The specific reaction process is as follows:

[0058]

[0059] Once the phthalic anhydride monomer is completely consumed, the polymerization reaction enters the third stage, which is a ring-opening copolymerization of propylene oxide and carbon dioxide (ROCOP). The specific reaction process is as follows:

[0060]

[0061] During the experimental process, this invention discovered that the N-carboxyl cyclic anhydride involved in this invention, due to its high monomer activity, first forms polyamino acid blocks in the first stage. Once the N-carboxyl cyclic anhydride is completely consumed, the polymerization reaction enters the second stage. Notably, the ring-opening copolymerization rate of epoxy compounds / cyclic anhydrides is much greater than that of epoxy compounds / carbon dioxide, resulting in the formation of polyester blocks first in the second stage. After the cyclic anhydride is completely consumed, the polymerization reaction enters the third stage, namely the ring-opening copolymerization of epoxy compounds and carbon dioxide, producing polycarbonate blocks. However, at room temperature, the ring-opening copolymerization rates of epoxy compounds / cyclic anhydrides and epoxy compounds / carbon dioxide are both relatively slow (generally exceeding 24 hours). It is worth noting that macromolecular structures such as enzymes in the human body accelerate intracellular protein polymerization reactions through supramolecular interactions. To date, no literature or patents have reported using chemical synthesis methods to self-accelerate ring-opening copolymerization reactions, i.e., using the reaction products as catalysts for the ring-opening copolymerization reaction. In this invention, the polyamino acid block synthesized in the first stage acts as a self-accelerator. The ortho-hydrogen bonding of the secondary conformation of the polyamino acid block promotes the ring-opening of cyclic anhydrides and carbon dioxide, thereby increasing the rate of ring-opening copolymerization (ROCOP) of epoxides and cyclic anhydrides, and the rate of ROCOP of carbon dioxide and epoxides, thus avoiding side reactions that may occur due to prolonged reaction. Furthermore, different substituents in the N-carboxyl anhydride significantly affect the hydrogen bonding acceleration. By optimizing the structure of the N-carboxyl anhydride, the hydrogen bonding acceleration can be greatly enhanced, thereby significantly reducing the polymerization time required for the second and third stages, and consequently greatly increasing the catalyst conversion frequency (the amount of reactants converted per unit active site per unit time).

[0062] In summary, this invention utilizes an organic Lewis acid as the main catalyst and a sterically hindered organic base as the co-catalyst to carry out a quaternary copolymerization reaction of N-carboxylic acid anhydride, epoxy compound, cyclic anhydride and carbon dioxide. By optimizing the feed ratio of the main catalyst and co-catalyst and the structure of the N-carboxylic acid anhydride, a polyamino acid-polyester-polycarbonate triblock copolymer can be synthesized with high selectivity and high catalytic efficiency. The beneficial effects of the present invention are as follows: (1) The present invention adopts a "one-step method" and successfully realizes three different catalytic processes in one step, which reduces the types and quantities of catalysts, simplifies the production process, and ultimately reduces the production cost; (2) The present invention can solve the problem of carbon dioxide recycling, capture carbon dioxide, lock the recovered carbon dioxide in the polymer, effectively alleviate the greenhouse effect, and greatly promote the realization of carbon neutrality; (3) The block copolymers synthesized by the present invention have more diverse structural types. The polyamino acid blocks synthesized by the ring-opening polymerization of N-carboxylic acid anhydrides are natural polymers and protein analogs, which can significantly improve the medical function of biodegradable polyester blocks; (4) The adjacent hydrogen bonding of the polyamino acid blocks synthesized in the first stage of the present invention can improve the reaction rate of ring-opening copolymerization. Attached Figure Description

[0063] Figure 1 This is a copolymerization mechanism diagram of the polyamino acid-polyester-polycarbonate triblock copolymer synthesized in the embodiments of the present invention.

[0064] Figure 2 This is a schematic diagram of the synthesis reaction of the block copolymer in Example 1.

[0065] Figure 3 The image shows the 1H NMR spectrum of the block copolymer in Example 1.

[0066] Figure 4 This is a gel permeation chromatogram of the block copolymer in Example 1.

[0067] Figure 5 This is a gel permeation chromatogram of the block copolymer in Comparative Example 3. Detailed Implementation

[0068] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0069] In general, the polyamino acid-polyester-polycarbonate triblock copolymer of the present invention has the following general formula structure:

[0070]

[0071] The preparation method uses a mixture of organic Lewis acids and organic Lewis bases as catalysts, and in the presence of an initiator (such as a terminal hydroxyl or carboxyl compound), combines chemically selective polymerization and copolymerization strategies to carry out a quaternary copolymerization reaction of N-carboxylic acid anhydride, epoxy compound, cyclic anhydride and carbon dioxide. This method can synthesize biodegradable and biocompatible polyamino acid-polyester-polycarbonate triblock copolymers in one step with high selectivity and high catalytic efficiency.

[0072] The following are specific examples, in which N-carboxylic acid anhydrides represented by any one of formulas (I), (II), (III), (IV), (V), (VI), (VII), and (VIII) are used as reactants:

[0073]

[0074]

[0075] Example 1

[0076] A type of -[NH-CO]5-[COO] 20 -[OCO] 10 - A triblock copolymer, wherein the polyamino acid block has 5 repeating units; the polyester block has 20 repeating units; and the polycarbonate block has 10 repeating units. The number-average relative molecular mass of the block copolymer was determined to be 6400 by gel permeation chromatography, and the molecular weight distribution index was 1.27. The amount of epoxide converted per unit active site per unit time was calculated by proton nuclear magnetic resonance spectroscopy, i.e., the catalyst conversion frequency was 15 h⁻¹. -1 T was measured by differential scanning calorimetry. g1 The temperature is 15℃, T g2 At a temperature of 65℃, the structure of this block copolymer is shown below (where n = 5, m = 20, z = 10):

[0077]

[0078] The synthesis steps of this block copolymer are as follows:

[0079] (1) Add benzyl alcohol, phthalic anhydride, N-carboxylate anhydride (Formula I), propylene oxide and triethylborane sequentially into the high-pressure reactor in a molar ratio of 1:20:5:300:2; use an oil pump to evacuate and fill with argon gas to ensure that oxygen and water vapor in the high-pressure reactor are completely removed; mix thoroughly in the reactor for 1 hour to completely dissolve the N-carboxylate anhydride.

[0080] (2) After adding 1 equivalent of 1,8-diazabicyclo(5.4.0)undec-7-ene to the high-pressure reactor described in step (1), carbon dioxide at 3 MPa is introduced into the high-pressure reactor to obtain a reaction mixture;

[0081] (3) React the reaction mixture described in step (2) at room temperature for 4 hours. After the reaction is completed, slowly release the carbon dioxide in the reactor and quench the reaction to obtain crude product A.

[0082] (4) Purify the crude product A obtained in step (3) to obtain a polyamino acid-polyester-polycarbonate triblock copolymer. Take a small amount of the crude product A obtained in step (3) for... 1 1H NMR analysis revealed that the remaining crude product A was first diluted with dichloromethane and then precipitated in frozen methanol. The polymer product obtained by precipitation was dried overnight in a vacuum oven to synthesize a polyamino acid-polyester-polycarbonate triblock copolymer.

[0083] Figure 2 This is a schematic diagram of the reaction in Example 1 to synthesize a polyamino acid-polyester-polycarbonate triblock copolymer in one step from a mixture of N-carboxylic acid anhydride (Formula I), propylene oxide, phthalic anhydride and carbon dioxide, under the action of the main catalyst triethylborane and the co-catalyst 1,8-diazabicyclo(5.4.0)undec-7-ene.

[0084] Figure 3 The image shows the 1H NMR spectrum of the polyamino acid-polyester-polycarbonate triblock copolymer synthesized in Example 1. The 1H NMR spectrum clearly shows the characteristic proton signal peaks of the polyamino acid block (3.80-4.00 ppm), polyester block (5.36-5.54 ppm), and polycarbonate block (4.90-5.10 ppm), and no characteristic signal peaks of other polymers are present.

[0085] Figure 4 The image shows a gel permeation chromatogram of the polyamino acid-polyester-polycarbonate triblock copolymer synthesized in Example 1 with tetrahydrofuran as the mobile phase. The curve in the gel permeation chromatogram shows a narrow single peak distribution with a molecular weight distribution of 1.27, indicating that the polyester and polycarbonate blocks increase the solubility of the polyamino acid blocks in tetrahydrofuran, and that the synthesized quaternary copolymer is a block copolymer.

[0086] Example 2

[0087] A type of -[NH-CO] 30 -[COO] 50 -[OCO] 30A triblock copolymer, wherein the polyamino acid block contains 30 repeating units; the polyester block contains 50 repeating units; and the polycarbonate block contains 30 repeating units. The number-average molecular weight of this block copolymer was determined to be 22,700 and the molecular weight distribution index was 1.30 by gel permeation chromatography. Notably, by optimizing the R1 structure of the N-carboxyl anhydride, the catalyst switching frequency calculated by 1H NMR spectroscopy was increased to 21 h compared to Example 1. -1 The catalytic efficiency increased by 40%, as measured by differential scanning calorimetry (T). g1 The temperature is 12℃, T g2 The structure of this block copolymer is shown below (where n = 30, m = 50, z = 30) at a temperature of 62℃:

[0088]

[0089] The synthesis steps of this block copolymer are as follows:

[0090] (1) Add benzyl alcohol, phthalic anhydride, N-carboxylate anhydride (Formula II), ethylene oxide and triethylborane sequentially into the high-pressure reactor in a molar ratio of 1:50:30:500:1; use an oil pump to evacuate and fill with argon gas to ensure that oxygen and water vapor in the high-pressure reactor are completely removed; mix thoroughly in the reactor for 2 hours to completely dissolve the N-carboxylate anhydride.

[0091] (2) After adding 1 equivalent of 1,8-diazabicyclo(5.4.0)undec-7-ene to the high-pressure reactor described in step (1), carbon dioxide at 3 MPa is introduced into the high-pressure reactor to obtain a reaction mixture;

[0092] (3) React the reaction mixture described in step (2) at room temperature for 8 hours. After the reaction is completed, slowly release the carbon dioxide in the reactor and quench the reaction to obtain crude product A.

[0093] (4) Purify the crude product A obtained in step (3) to obtain a polyamino acid-polyester-polycarbonate triblock copolymer. Take a small amount of the crude product A obtained in step (3) for... 1 1H NMR analysis revealed that the remaining crude product A was first diluted with dichloromethane and then precipitated in frozen methanol. The polymer product obtained by precipitation was dried overnight in a vacuum oven to synthesize a polyamino acid-polyester-polycarbonate triblock copolymer.

[0094] Example 3

[0095] A type of -[NH-CO]5-[COO] 20 -[OCO] 10A triblock copolymer, wherein the polyamino acid block has 5 repeating units; the polyester block has 20 repeating units; and the polycarbonate block has 10 repeating units. The number-average molecular weight of this block copolymer was determined to be 5800 by gel permeation chromatography, and the molecular weight distribution index was 1.25. The catalyst switching frequency was calculated to be 11.8 h⁻¹ by proton nuclear magnetic resonance spectroscopy. -1 Compared to Example 1, replacing the N-carboxylic acid anhydride (I) with (V) resulted in a 21% decrease in catalytic efficiency, as measured by differential scanning calorimetry (T). g1 The temperature is 14℃, T g2 The temperature is 64℃. The structure of this block copolymer is shown below (where n = 5, m = 20, z = 10):

[0096]

[0097] The synthesis steps of this block copolymer are as follows:

[0098] (1) Add benzyl alcohol, phthalic anhydride, N-carboxylate anhydride (Formula V), propylene oxide and triethylborane sequentially into the high-pressure reactor in a molar ratio of 1:20:5:300:5; use an oil pump to evacuate and fill with argon gas to ensure that oxygen and water vapor in the high-pressure reactor are completely removed; mix thoroughly in the reactor for 3 hours to completely dissolve the N-carboxylate anhydride.

[0099] (2) After adding 1 equivalent of 1,8-diazabicyclo(5.4.0)undec-7-ene to the high-pressure reactor described in step (1), carbon dioxide at 3 MPa is introduced into the high-pressure reactor to obtain a reaction mixture;

[0100] (3) React the reaction mixture described in step (2) at room temperature for 5 hours. After the reaction is completed, slowly release the carbon dioxide in the reactor and quench the reaction to obtain crude product A.

[0101] (4) Purify the crude product A obtained in step (3) to obtain a polyamino acid-polyester-polycarbonate triblock copolymer. Take a small amount of the crude product A obtained in step (3) for... 1 1H NMR analysis revealed that the remaining crude product A was first diluted with dichloromethane and then precipitated in frozen methanol. The polymer product obtained by precipitation was dried overnight in a vacuum oven to synthesize a polyamino acid-polyester-polycarbonate triblock copolymer.

[0102] Example 4

[0103] A type of -[NH-CO] 10 -[COO] 35 -[OCO] 20A triblock copolymer, wherein the polyamino acid block has 10 repeating units; the polyester block has 35 repeating units; and the polycarbonate block has 20 repeating units. The number-average molecular weight of this block copolymer was determined to be 11500 and the molecular weight distribution index to be 1.25 by gel permeation chromatography. The catalyst switching frequency was calculated to be 14 h⁻¹ by proton nuclear magnetic resonance spectroscopy. -1 T was measured by differential scanning calorimetry. g1 At 20℃, T g2 At 70℃, the structure of this block copolymer is shown below (where n = 10, m = 35, z = 20):

[0104]

[0105] The synthesis steps of this block copolymer are as follows:

[0106] (1) Add benzoic acid, norbornene anhydride, N-carboxylate anhydride (Formula III), propylene oxide and tributylborane sequentially into the high-pressure reactor in a molar ratio of 1:35:10:400:2; use an oil pump to evacuate and fill with argon gas to ensure that oxygen and water vapor in the high-pressure reactor are completely removed; mix thoroughly in the reactor for 1 hour to completely dissolve the N-carboxylate anhydride.

[0107] (2) After adding 1 equivalent of 1,5,7-triazidobicyclo(4.4.0)dec-5-ene to the high-pressure reactor described in step (1), carbon dioxide at 3 MPa is introduced into the high-pressure reactor to obtain the reaction mixture;

[0108] (3) React the reaction mixture described in step (2) at room temperature for 7.5 hours. After the reaction is completed, slowly release the carbon dioxide in the reactor and quench the reaction to obtain crude product A.

[0109] (4) Purify the crude product A obtained in step (3) to obtain a polyamino acid-polyester-polycarbonate triblock copolymer. Take a small amount of the crude product A obtained in step (3) for... 1 1H NMR analysis revealed that the remaining crude product A was first diluted with dichloromethane and then precipitated in frozen methanol. The polymer product obtained by precipitation was dried overnight in a vacuum oven to synthesize a polyamino acid-polyester-polycarbonate triblock copolymer.

[0110] Example 5

[0111] A type of -[NH-CO] 10 -[COO] 20 -[OCO] 10A triblock copolymer, wherein the polyamino acid block has 10 repeating units; the polyester block has 20 repeating units; and the polycarbonate block has 10 repeating units. The number-average molecular weight of this block copolymer was determined to be 4200 and the molecular weight distribution index to be 1.32 by gel permeation chromatography. The catalyst switching frequency was calculated to be 10.9 h⁻¹ by proton nuclear magnetic resonance spectroscopy. -1 T was measured by differential scanning calorimetry. g1 -5℃, T g2 The temperature is 58℃. The structure of this block copolymer is shown below (where n = 10, m = 20, z = 10):

[0112]

[0113] The synthesis steps of this block copolymer are as follows:

[0114] (1) Add benzoic acid, succinic anhydride, N-carboxylate anhydride (Formula IV), propylene oxide and triphenylborane sequentially into the high-pressure reactor in a molar ratio of 1:20:10:300:2; use an oil pump to evacuate and fill with argon gas to ensure that oxygen and water vapor in the high-pressure reactor are completely removed; mix thoroughly in the reactor for 4 hours to completely dissolve the N-carboxylate anhydride.

[0115] (2) After adding 1 equivalent of 7-methyl-1,5,7-triazabicyclo(4.4.0)dec-5-ene to the high-pressure reactor described in step (1), carbon dioxide at 4 MPa is introduced into the high-pressure reactor to obtain the reaction mixture;

[0116] (3) React the reaction mixture described in step (2) at room temperature for 5.5 hours. After the reaction is completed, slowly release the carbon dioxide in the reactor and quench the reaction to obtain crude product A.

[0117] (4) Purify the crude product A obtained in step (3) to obtain a polyamino acid-polyester-polycarbonate triblock copolymer. Take a small amount of the crude product A obtained in step (3) for... 1 1H NMR analysis revealed that the remaining crude product A was first diluted with dichloromethane and then precipitated in frozen methanol. The polymer product obtained by precipitation was dried overnight in a vacuum oven to synthesize a polyamino acid-polyester-polycarbonate triblock copolymer.

[0118] Example 6

[0119] A type of -[NH-CO] 10 -[COO] 30 -[OCO] 20A triblock copolymer, wherein the polyamino acid block has 10 repeating units; the polyester block has 30 repeating units; and the polycarbonate block has 20 repeating units. The number-average molecular weight of this block copolymer was determined to be 9500 by gel permeation chromatography, and the molecular weight distribution index was 1.35. The catalyst switching frequency was calculated to be 15.5 h⁻¹ by proton nuclear magnetic resonance spectroscopy. -1 T was measured by differential scanning calorimetry. g1 At 5℃, T g2 The structure of this block copolymer is shown below (where n = 10, m = 30, z = 20) at a temperature of 62℃:

[0120]

[0121] The synthesis steps of this block copolymer are as follows:

[0122] (1) Add benzyl alcohol, tetrahydrophthalic anhydride, N-carboxylate anhydride (Formula V), propylene oxide and tris(pentafluorophenyl)borane sequentially to the high-pressure reactor in a molar ratio of 1:30:10:400:2; use an oil pump to evacuate and fill with argon gas to ensure that oxygen and water vapor in the high-pressure reactor are completely removed; mix thoroughly in the reactor for 1 hour to completely dissolve the N-carboxylate anhydride.

[0123] (2) After adding 1 equivalent of phosphazene ligand P1-tert-butyl to the high-pressure reactor described in step (1), carbon dioxide at 3 MPa is introduced into the high-pressure reactor to obtain a reaction mixture;

[0124] (3) React the reaction mixture described in step (2) at room temperature for 6.5 hours. After the reaction is completed, slowly release the carbon dioxide in the reactor and quench the reaction to obtain crude product A.

[0125] (4) Purify the crude product A obtained in step (3) to obtain a polyamino acid-polyester-polycarbonate triblock copolymer. Take a small amount of the crude product A obtained in step (3) for... 1 1H NMR analysis revealed that the remaining crude product A was first diluted with dichloromethane and then precipitated in frozen methanol. The polymer product obtained by precipitation was dried overnight in a vacuum oven to synthesize a polyamino acid-polyester-polycarbonate triblock copolymer.

[0126] Example 7

[0127] A type of -[NH-CO] 12 -[COO] 20 -[OCO] 10A triblock copolymer, wherein the polyamino acid block has 12 repeating units; the polyester block has 20 repeating units; and the polycarbonate block has 10 repeating units. The number-average molecular weight of this block copolymer was determined to be 6000 and the molecular weight distribution index to be 1.22 by gel permeation chromatography. The catalyst switching frequency was calculated to be 8.3 h⁻¹ by proton nuclear magnetic resonance spectroscopy. -1 T was measured by differential scanning calorimetry. g1 -10℃, T g2 At 55℃, the structure of this block copolymer is shown below (where n = 12, m = 20, z = 10):

[0128]

[0129] The synthesis steps of this block copolymer are as follows:

[0130] (1) Add benzyl alcohol, glutaric anhydride, N-carboxylate anhydride (formula VII), 1,2-epoxybutane and triphenylborane sequentially to the high-pressure reactor in a molar ratio of 1:20:12:300:2; use an oil pump to evacuate and fill with argon gas to ensure that oxygen and water vapor in the high-pressure reactor are completely removed; mix thoroughly in the reactor for 3 hours to completely dissolve the N-carboxylate anhydride.

[0131] (2) After adding 1 equivalent of phosphazene ligand P2-tert-butyl to the high-pressure reactor described in step (1), 2 MPa of carbon dioxide is introduced into the high-pressure reactor to obtain a reaction mixture;

[0132] (3) React the reaction mixture described in step (2) at room temperature for 7.2 hours. After the reaction is completed, slowly release the carbon dioxide in the reactor and quench the reaction to obtain crude product A.

[0133] (4) Purify the crude product A obtained in step (3) to obtain a polyamino acid-polyester-polycarbonate triblock copolymer. Take a small amount of the crude product A obtained in step (3) for... 1 1H NMR analysis revealed that the remaining crude product A was first diluted with dichloromethane and then precipitated in frozen methanol. The polymer product obtained by precipitation was dried overnight in a vacuum oven to synthesize a polyamino acid-polyester-polycarbonate triblock copolymer.

[0134] Example 8

[0135] A type of -[NH-CO] 12 -[COO] 20 -[OCO] 10A triblock copolymer, wherein the polyamino acid block has 12 repeating units; the polyester block has 20 repeating units; and the polycarbonate block has 10 repeating units. The number-average molecular weight of this block copolymer was determined to be 7600 by gel permeation chromatography, and the molecular weight distribution index was 1.28. The catalyst switching frequency was calculated to be 6.2 h⁻¹ by proton nuclear magnetic resonance spectroscopy. -1 T was measured by differential scanning calorimetry. g1 -20℃, T g2 At 50℃, the structure of this block copolymer is shown below (where n = 12, m = 20, z = 10):

[0136]

[0137] The synthesis steps of this block copolymer are as follows:

[0138] (1) Add benzyl alcohol, diethylene glycol anhydride, N-carboxylate anhydride (Formula VI), n-butyl glycidyl ether and triethylborane sequentially into the high-pressure reactor in a molar ratio of 1:20:12:300:2; use an oil pump to evacuate and fill with argon gas to ensure that oxygen and water vapor in the high-pressure reactor are completely removed; mix thoroughly in the reactor for 3 hours to completely dissolve the N-carboxylate anhydride.

[0139] (2) After adding 1 equivalent of phosphazene ligand P2-tert-butyl to the high-pressure reactor described in step (1), 1 MPa of carbon dioxide is introduced into the high-pressure reactor to obtain a reaction mixture;

[0140] (3) React the reaction mixture described in step (2) at room temperature for 10 hours. After the reaction is completed, slowly release the carbon dioxide in the reactor and quench the reaction to obtain crude product A.

[0141] (4) Purify the crude product A obtained in step (3) to obtain a polyamino acid-polyester-polycarbonate triblock copolymer. Take a small amount of the crude product A obtained in step (3) for... 1 1H NMR analysis revealed that the remaining crude product A was first diluted with dichloromethane and then precipitated in frozen methanol. The polymer product obtained by precipitation was dried overnight in a vacuum oven to synthesize a polyamino acid-polyester-polycarbonate triblock copolymer.

[0142] Example 9

[0143] A type of -[NH-CO] 12 -[COO] 20 -[OCO] 10A triblock copolymer, wherein the polyamino acid block has 12 repeating units; the polyester block has 20 repeating units; and the polycarbonate block has 10 repeating units. The number-average molecular weight of this block copolymer was determined to be 8600 by gel permeation chromatography, and the molecular weight distribution index was 1.32. The catalyst switching frequency was calculated to be 7.2 h⁻¹ by proton nuclear magnetic resonance spectroscopy. -1 T was measured by differential scanning calorimetry. g1 At 2℃, T g2 At 60℃, the structure of this block copolymer is shown below (where n = 12, m = 20, z = 10):

[0144]

[0145] The synthesis steps of this block copolymer are as follows:

[0146] (1) Add benzyl alcohol, tetrahydrophthalic anhydride, N-carboxylate anhydride (formula VII), tert-butyl glycidyl ether and tris(pentafluorophenyl)borane sequentially to the high-pressure reactor in a molar ratio of 1:20:12:300:2; use an oil pump to evacuate and fill with argon gas to ensure that oxygen and water vapor in the high-pressure reactor are completely removed; mix thoroughly in the reactor for 3 hours to completely dissolve the N-carboxylate anhydride.

[0147] (2) After adding 1 equivalent of phosphazene ligand P2-tert-butyl to the high-pressure reactor described in step (1), 1 MPa of carbon dioxide is introduced into the high-pressure reactor to obtain a reaction mixture;

[0148] (3) React the reaction mixture described in step (2) at room temperature for 8.5 hours. After the reaction is completed, slowly release the carbon dioxide in the reactor and quench the reaction to obtain crude product A.

[0149] (4) Purify the crude product A obtained in step (3) to obtain a polyamino acid-polyester-polycarbonate triblock copolymer. Take a small amount of the crude product A obtained in step (3) for... 1 1H NMR analysis revealed that the remaining crude product A was first diluted with dichloromethane and then precipitated in frozen methanol. The polymer product obtained by precipitation was dried overnight in a vacuum oven to synthesize a polyamino acid-polyester-polycarbonate triblock copolymer.

[0150] Comparative Example 1

[0151] A type of -[NH-CO]4-[COO] 20 -[OCO] 10A triblock copolymer, wherein the polyamino acid block has 4 repeating units (less than 5); the polyester block has 20 repeating units; and the polycarbonate block has 10 repeating units. The number-average molecular weight of this block copolymer was determined to be 6100 and the molecular weight distribution index was 1.22 by gel permeation chromatography. Since the polyamino acid block did not exhibit secondary conformation, the catalyst switching frequency was calculated to be 3.3 h⁻¹ by 1H NMR spectroscopy. -1 Compared to Example 1, the catalytic efficiency decreased by 78%, as measured by differential scanning calorimetry (T). g1 The temperature is 15℃, T g2 At a temperature of 65℃, the structure of this block copolymer is shown below (where n = 4, m = 20, z = 10):

[0152]

[0153] The synthesis steps of this block copolymer are as follows:

[0154] (1) Add benzyl alcohol, phthalic anhydride, N-carboxylate anhydride (Formula I), propylene oxide and triethylborane sequentially into the high-pressure reactor in a molar ratio of 1:20:4:300:2; use an oil pump to evacuate and fill with argon gas to ensure that oxygen and water vapor in the high-pressure reactor are completely removed; mix thoroughly in the reactor for 1 hour to completely dissolve the N-carboxylate anhydride.

[0155] (2) After adding 1 equivalent of 1,8-diazabicyclo(5.4.0)undec-7-ene to the high-pressure reactor described in step (1), carbon dioxide at 3 MPa is introduced into the high-pressure reactor to obtain a reaction mixture;

[0156] (3) React the reaction mixture described in step (2) at room temperature for 18 hours. After the reaction is completed, slowly release the carbon dioxide in the reactor and quench the reaction to obtain crude product A.

[0157] (4) Purify the crude product A obtained in step (3) to obtain a polyamino acid-polyester-polycarbonate triblock copolymer. Take a small amount of the crude product A obtained in step (3) for... 1 1H NMR analysis revealed that the remaining crude product A was first diluted with dichloromethane and then precipitated in frozen methanol. The polymer product obtained by precipitation was dried overnight in a vacuum oven to synthesize a polyamino acid-polyester-polycarbonate triblock copolymer.

[0158] Comparative Example 2

[0159] A type of -[NH-CO] 31 -[COO] 20 -[OCO] 10A triblock copolymer, wherein the polyamino acid block has 31 repeating units (greater than 30); the polyester block has 20 repeating units; and the polycarbonate block has 10 repeating units. The number-average relative molecular mass of this block copolymer was determined to be 12000 and the molecular weight distribution index to be 1.30 by gel permeation chromatography. Since the polyamino acid block precipitates from the epoxy compound, the catalyst switching frequency was calculated to be 2.5 h⁻¹ by 1H NMR spectroscopy. -1 Compared to Example 1, the catalytic efficiency decreased by 83%, as measured by differential scanning calorimetry (T). g1 The temperature is 15℃, T g2 At 65℃, the structure of this block copolymer is shown below (where n = 31, m = 20, z = 10):

[0160]

[0161] The synthesis steps of this block copolymer are as follows:

[0162] (1) Add benzyl alcohol, phthalic anhydride, N-carboxylate anhydride (Formula I), propylene oxide and triethylborane sequentially into the high-pressure reactor in a molar ratio of 1:20:31:300:2; use an oil pump to evacuate and fill with argon gas to ensure that oxygen and water vapor in the high-pressure reactor are completely removed; mix thoroughly in the reactor for 1 hour to completely dissolve the N-carboxylate anhydride.

[0163] (2) After adding 1 equivalent of 1,8-diazabicyclo(5.4.0)undec-7-ene to the high-pressure reactor described in step (1), carbon dioxide at 3 MPa is introduced into the high-pressure reactor to obtain a reaction mixture;

[0164] (3) React the reaction mixture described in step (2) at room temperature for 24 hours. After the reaction is completed, slowly release the carbon dioxide in the reactor and quench the reaction to obtain crude product A.

[0165] (4) Purify the crude product A obtained in step (3) to obtain a polyamino acid-polyester-polycarbonate triblock copolymer. Take a small amount of the crude product A obtained in step (3) for... 1 1H NMR analysis revealed that the remaining crude product A was first diluted with dichloromethane and then precipitated in frozen methanol. The polymer product obtained by precipitation was dried overnight in a vacuum oven to synthesize a polyamino acid-polyester-polycarbonate triblock copolymer.

[0166] Comparative Example 3

[0167] A homopolymer, [NH-CO]8-, wherein the polyamino acid block has 8 repeating units and only one type of block, is a homopolymer rather than a polyamino acid-polyester-polycarbonate triblock copolymer, and the polymerization time exceeds 2 days. Gel permeation chromatography determined the number-average relative molecular mass of this homopolymer to be 1900 and the molecular weight distribution index to be 3.85. Differential scanning calorimetry determined that it has only one glass transition temperature, T0. g At 75℃, the structure of this block copolymer is shown below (where n = 8):

[0168]

[0169] The synthesis steps of this homopolymer are as follows:

[0170] (1) Add phthalic anhydride, N-carboxylate anhydride (Formula I), propylene oxide and hexamethyldisilazane sequentially to the high-pressure reactor in a molar ratio of 20:8:300:1; use an oil pump to evacuate and fill with argon gas to ensure that oxygen and water vapor in the high-pressure reactor are completely removed; mix thoroughly in the reactor for 1 hour to completely dissolve the N-carboxylate anhydride.

[0171] (2) Carbon dioxide at 2 MPa is introduced into the high-pressure reactor to obtain a reaction mixture;

[0172] (3) React the reaction mixture described in step (2) at room temperature for 50 hours. After the reaction is completed, slowly release the carbon dioxide in the reactor and quench the reaction to obtain crude product A.

[0173] (4) Purify the crude product A obtained in step (3) to obtain a polyamino acid homopolymer. Take a small amount of the crude product A obtained in step (3) for... 1 1H NMR analysis showed that the remaining crude product A was first diluted with dichloromethane and then precipitated in frozen methanol. The polymer product obtained by precipitation was dried overnight in a vacuum oven, and only polyamino acid homopolymers were synthesized.

[0174] Figure 5 The image shows the gel permeation chromatogram of the polyamino acid homopolymer synthesized in Comparative Example 3 in the mobile phase of tetrahydrofuran. Because polyamino acids have poor solubility in tetrahydrofuran, the curve in its gel permeation chromatogram does not show a single peak distribution and the distribution is very broad, with a molecular weight distribution index of 3.85.

[0175] Comparative Example 4

[0176] A quaternary random copolymer, wherein the polyamino acid blocks have 10 repeating units; the polyester and polycarbonate are randomly distributed, and the product is a random copolymer rather than a block copolymer. The number-average molecular weight of this random copolymer was determined to be 7500 and the molecular weight distribution index to be 1.25 by gel permeation chromatography. The catalyst switching frequency was calculated to be 13.2 h⁻¹ by proton nuclear magnetic resonance spectroscopy. -1 Only one glass transition temperature, T, was measured using a differential scanning calorimeter. g The temperature is 58℃, and the structure of this block copolymer is shown below:

[0177]

[0178] The synthesis steps of this random copolymer are as follows:

[0179] (1) Add benzyl alcohol, phthalic anhydride, N-carboxylate anhydride (Formula I), propylene oxide and triethylborane sequentially into the high-pressure reactor in a molar ratio of 1:20:10:300:2; use an oil pump to evacuate and fill with argon gas to ensure that oxygen and water vapor in the high-pressure reactor are completely removed; mix thoroughly in the reactor for 1 hour to completely dissolve the N-carboxylate anhydride.

[0180] (2) 1 equivalent of phosphazene ligand P4-tert-butyl (pK in acetonitrile) a (Value 42.7, greater than 35) After adding to the high-pressure reactor described in step (1), 3MPa carbon dioxide is introduced into the high-pressure reactor to obtain the reaction mixture;

[0181] (3) React the reaction mixture described in step (2) at room temperature for 4.5 hours. After the reaction is completed, slowly release the carbon dioxide in the reactor and quench the reaction to obtain crude product A.

[0182] (4) Purify the crude product A obtained in step (3) to obtain a polyamino acid-polyester-polycarbonate triblock copolymer. Take a small amount of the crude product A obtained in step (3) for... 1 1H NMR analysis revealed that the remaining crude product A was first diluted with dichloromethane and then precipitated in frozen methanol. The polymer product obtained by precipitation was dried overnight in a vacuum oven, thus synthesizing a polyamino acid-polyester-polycarbonate quaternary random copolymer.

[0183] The above embodiments are merely examples. For instance, the protective atmosphere may be nitrogen or other inert gases in addition to argon.

[0184] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A polyamino acid-polyester-polycarbonate triblock copolymer, characterized in that, It is synthesized in one step using a mixture of N-carboxylic anhydride, epoxy compound, cyclic anhydride and carbon dioxide as raw materials, under the action of catalyst and initiator; Wherein, the polyamino acid is the ring-opening polymerization product of the N-carboxyl ring anhydride, and the number of repeating units n of the polyamino acid block is 5~30; the polyester is the ring-opening copolymer of the epoxy compound and the cyclic anhydride; and the polycarbonate is the ring-opening copolymer of the carbon dioxide and the epoxy compound. The catalyst comprises a main catalyst and a co-catalyst. The main catalyst is an organic Lewis acid catalyst, and the co-catalyst is a sterically hindered organic Lewis basic catalyst. The co-catalyst in acetonitrile has a p K a The value is greater than 24 and less than 35.

2. The polyamino acid-polyester-polycarbonate triblock copolymer as described in claim 1, characterized in that, The general structural formula of the polyamino acid-polyester-polycarbonate triblock copolymer is shown below: Polyamino acid polyester polycarbonate Wherein, R1 is one of the following structural formulas: R2 is one of the following structural formulas: R3 is one of the following structural formulas: R4 is one of the following structural formulas: Furthermore, m = 20~50, z = 10~30.

3. The polyamino acid-polyester-polycarbonate triblock copolymer as described in claim 1, characterized in that, The polyamino acid-polyester-polycarbonate triblock copolymer has two glass transition temperatures, one of which is -20 ℃ to 20 ℃ and the other is 50 ℃ to 70 ℃.

4. The method for synthesizing the polyamino acid-polyester-polycarbonate triblock copolymer according to any one of claims 1-3, characterized in that, Includes the following steps: (1) Under a protective atmosphere and under oxygen-free and anhydrous conditions, the three monomers, namely N-carboxyl intracyclic anhydride, cyclic anhydride and epoxy compound, are first thoroughly mixed with the initiator and the main catalyst in the reactor for 1 to 4 hours. (2) After adding the co-catalyst to the reactor of step (1), carbon dioxide is introduced into the reactor to obtain a reaction mixture; (3) React the reaction mixture from step (2) at room temperature for 4 to 10 hours. After the reaction is complete, release the carbon dioxide in the reactor and quench the reaction to obtain crude product A. (4) Purify the crude product A obtained in step (3) to obtain polyamino acid-polyester-polycarbonate triblock copolymer.

5. The synthesis method as described in claim 4, characterized in that, The molar ratio of the N-carboxylic acid anhydride to the initiator in step (1) is 5~30:

1.

6. The synthesis method as described in claim 4, characterized in that, The N-carboxyl ring anhydride has a structure as shown in formula (I): Formula (1) Wherein, R1 is one of the following structural formulas: R2 is one of the following structural formulas: 。 7. The synthesis method as described in claim 6, characterized in that, The N-carboxyl ring anhydride has the structure shown in any one of formulas (I) to (VIII): (AND) (II) (III) (IV) (V) (VI) (VII) (VIII)。 8. The synthesis method as described in claim 4, characterized in that, The main catalyst is one or more selected from triethylborane, tributylborane, triphenylborane, and tris(pentafluorophenyl)borane; The cocatalyst is one or more of the following: phosphazene ligand P1-tert-butyl, phosphazene ligand P2-tert-butyl, 7-methyl-1,5,7-triazabicyclo(4.4.0)dec-5-ene, 1,5,7-triazidobicyclo(4.4.0)dec-5-ene, and 1,8-diazabicyclo(5.4.0)undec-7-ene.

9. The synthesis method as described in claim 4, characterized in that, The epoxy compound is one or more selected from ethylene oxide, propylene oxide, 1,2-epoxybutane, n-butyl glycidyl ether, and tert-butyl glycidyl ether. The cyclic anhydride is one or more of phthalic anhydride, norbornene anhydride, tetrahydrophthalic anhydride, succinic anhydride, glutaric anhydride, and diethylene glycol anhydride; The initiator is a terminal hydroxyl or carboxyl compound.

10. The synthesis method according to claim 9, characterized in that, The initiator is one or more of benzyl alcohol and benzoic acid.

11. The synthesis method according to claim 4, characterized in that, The molar ratio of the cyclic anhydride to the initiator is 20-50:1; the molar ratio of the epoxy compound to the initiator is 300-500:

1.

12. The synthesis method according to claim 4, characterized in that, The molar ratio of the main catalyst to the co-catalyst is 1:1 to 5:1; In step (2), the pressure of carbon dioxide is 1~4 MPa.

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