A simple method for preparing high molecular weight modifiable copolyesters

Abstract

The present invention provides a novel method for preparing a high molecular weight modifiable copolyester by catalyzing the chemical selective ring-opening copolymerization of α-methylene-δ-valerolactone and ε-caprolactone or δ-valerolactone using an organic base / binary urea. The method provided by the present invention has the following advantages compared with the previously reported methods: 1) the preparation method of the modifiable copolyester is simpler, does not require cumbersome protection and deprotection processes, and the obtained copolyester can be functionalized and modified by click chemistry, thereby improving or regulating its physicochemical properties; 2) the catalytic system used has high catalytic activity and selectivity, and can achieve chemical selective controllable ring-opening copolymerization of α-methylene-δ-valerolactone and ε-caprolactone or δ-valerolactone under mild conditions, and the content of carbon-carbon double bonds in the prepared copolyester varies between 0.5 and 100 mol%; 3) the prepared copolyester has a high molecular weight; 4) the monomer conversion rate is high, the atom economy is good, and the monomer is nearly completely converted.

Description

Technical Field

[0001] The present invention relates to the fields of polymer materials and chemistry and chemical engineering. Specifically, the present invention relates to a method for preparing a bio-based copolyester containing modifiable functional groups. Technical Background

[0002] Aliphatic polyesters, due to their unique biodegradability, biocompatibility, and excellent mechanical properties, are the preferred alternative to non-degradable polymers and have garnered increasing attention over the past few decades. Currently available aliphatic polyesters, including poly(ε-caprolactone) (PCL), poly(δ-valerolactone) (PVL), poly(glycolic acid) (PGA), poly(lactide) (PLA), and random copolymers of lactic acid and glycolic acid (PLGA), are widely used as biomaterials for absorbable surgical sutures, tissue engineering scaffolds, and drug delivery vehicles. Despite their tremendous success, efforts continue to develop modifiable polyesters to meet the growing demand for material performance in various fields. Modifiable polyesters are polyester polymers containing modifiable groups in their backbone. By introducing different functional groups, drug release and degradation rates can be further regulated, and coupling sites for bioactive molecules such as drugs, peptides, and proteins can be provided. Polyester materials containing various modifiable groups, including halogen groups, hydroxyl groups, amino groups, carboxyl groups, and carbon-carbon double bonds, have been successfully prepared.

[0003] Currently, there are two methods for preparing modifiable copolyesters. One method is to directly introduce functional groups into the backbone of commercial polyesters, but this post-modification strategy has some problems, such as harsh reaction conditions, chain scission, and racemization. Another method for preparing modifiable aliphatic polyesters is to perform ring-opening polymerization (ROP) of lactones or lactides containing functional groups, or to copolymerize such functional monomers with commercial cyclic monomers. Most reports focus on the five-membered ring α-methylene-γ-butyrolactone (MBL). However, the low ring tension of pentacyclic lactones is thermodynamically unfavorable for ring-opening polymerization. The chemoselective ring-opening copolymerization of α-methylene-γ-butyrolactone (MBL) must be carried out at low temperatures (typically -40°C) (J.Am.Chem.Soc.2016,138,14326-14337; Macromolecules.2014,47,3614-3624; Macromolecules.2020,53,3380-3389; Macromolecules.2018,51,3582-3596; CCS Chem.2021,3,620-630). Furthermore, the chemoselective ring-opening copolymerization of MBL with other commercial cyclic lactones suffers from low monomer conversion, uncontrollable polymerization, and low molecular weight of the modifiable copolyesters, significantly hindering their application in materials. α-Methylene-δ-valerolactone (MVL) is an important bio-based six-membered ring lactone containing an exocyclic double bond. It can be easily synthesized in a one-pot two-step reaction of δ-valerolactone and ethyl formate. Modifiable polyesters containing carbon-carbon double bonds in the side chains prepared by the chemical selective ring-opening polymerization of α-methylene-δ-valerolactone can be post-modified on the side double bonds by a thiol-olefin click reaction to obtain polyesters containing desired groups or specific functions, showing great potential in the preparation of modifiable polyesters. Copolymerization is a simple and effective strategy to regulate the thermal and mechanical properties of polyesters. The properties of the copolymer can be regulated by changing the type and composition of the comonomers. At present, there is only one report on the copolymerization of α-methylene-δ-valerolactone with other cyclic lactones (Macromol.Chem.Phys.2014,215,426-430). This method uses stannous octoate as a catalyst and requires the polymerization reaction to be carried out at a high temperature (130°C). The prepared P(MVL-co-VL) copolyester has a very low molecular weight (M n ≤6.3kg / mol), and the carbon-carbon double bond content in the copolyester cannot be adjusted over a wide range, which limits the application range of the copolyester and results in higher economic costs. On the other hand, compared with α-methylene-γ-butyrolactone, α-methylene-δ-valerolactone can be ring-opening polymerized at room temperature to produce high molecular weight polyesters.

[0004] In view of this, the present invention provides a new method for preparing high molecular weight modifiable poly (α-methylene-δ-valerolactone-co-ε-caprolactone) (P(MVL-co-CL)) or poly (α-methylene-δ-valerolactone-co-δ-valerolactone) (P(MVL-co-VL)) by chemically selective ring-opening copolymerization of α-methylene-δ-valerolactone and ε-caprolactone or δ-valerolactone catalyzed by organic base / binary urea. Compared with previously reported methods, the method provided by the present invention has the following advantages: 1) the preparation method of the modifiable copolyester is simpler and does not require tedious protection and deprotection processes. The obtained copolyester can be functionalized and modified through click chemistry, thereby improving or regulating its physical and chemical properties; 2) the catalytic system used has high catalytic activity and selectivity, and can achieve chemically selective and controllable ring-opening polymerization of α-methylene-δ-valerolactone and ε-caprolactone or δ-valerolactone under mild conditions, and the content of carbon-carbon double bonds in the prepared copolyester varies between 0.5 and 100 mol%; 3) the prepared copolyester has a high molecular weight; 4) the monomer conversion rate is high, the atom economy is good, and the monomer conversion is close to complete. Summary of the Invention

[0005] The present invention aims to provide a method for preparing high molecular weight modifiable P(MVL-co-CL) or P(MVL-co-VL) by chemoselective ring-opening copolymerization of α-methylene-δ-valerolactone and ε-caprolactone or δ-valerolactone catalyzed by organic base / binary urea, comprising the following steps:

[0006] (1) Dissolve the initiator, organic base, and co-catalyst in an organic solvent and stir at 0-50°C for 10-30 minutes;

[0007] (2) After α-methylene-δ-valerolactone and ε-caprolactone or δ-valerolactone are mixed evenly, the mixture is added to the above mixed solution, and the reaction is carried out at 0-50°C for 0.1-24 hours. An acidic substance is added to terminate the reaction, and P(MVL-co-CL) or P(MVL-co-VL) is obtained after precipitation with methanol.

[0008] In the above preparation method, the chemical structures of P(MVL-co-CL) and P(MVL-co-VL) are shown in formula (I) and formula (II), respectively:

[0009]

[0010] It is characterized in that R1 is hydroxyl, alkoxy or arylalkoxy, specifically hydroxyl, methoxy, ethoxy, isopropoxy, tert-butoxy, benzyloxy, phenylethoxy, phenylpropoxy, diphenylmethoxy, 2,2-diphenylethoxy.

[0011] In the above preparation method, the co-catalyst is at least one of the diureas, wherein the diurea is a compound represented by formula (III), R2 and R4 are independently selected from alkyl or aryl groups, specifically methyl, ethyl, propyl, isopropyl, cyclohexyl, phenyl, 4-chlorophenyl, 4-methoxyphenyl, 4-trifluoromethylphenyl, 3,5-bis(trifluoromethyl)phenyl, 2,6-dimethylphenyl, 2,4-dimethoxyphenyl, 2,4,6-trimethoxyphenyl. R3 can be propylene, butylene, hexylene, or oxypentylene.

[0012]

[0013] According to an embodiment of the present invention, the co-catalyst has one of the following structures:

[0014]

[0015] In the above preparation method, the initiator in step (1) is an alcohol, specifically methanol, ethanol, isopropanol, tert-butanol, benzyl alcohol, phenylethyl alcohol, phenylpropyl alcohol, diphenylmethanol, 2,2-diphenylethanol, ethylene glycol, 1,4-phenyldimethanol, glycerol, and pentaerythritol; the organic base can be hexa[tris(dimethylamino)phosphazene]tripolyphosphazene ({[(NMe2)3P=N]2P=N}3), phosphazene ligand P4-tert-butyl ([(NMe2)3P=N]3P=NtBu, tert-Bu-P4), or phosphazene ligand P2-tert-butyl ([(NMe2)3P=N](NMe2)2P=NtBu, tert-Bu-P2); the molar ratio of the organic base to the initiator is 1 / 10 to 20 / 1; and the molar ratio of the organic base to the diurea is 1 / 1 to 1 / 20.

[0016] The organic solvent in the above preparation method can be toluene, tetrahydrofuran, dichloromethane, or acetonitrile.

[0017] In the above preparation method, the molar concentration of α-methylene-δ-valerolactone in the system in step (2) is 1 to 8 mol / L, and the molar concentration of ε-caprolactone or δ-valerolactone in the system is 1 to 8 mol / L; the total molar feed ratio of the initiator and α-methylene-δ-valerolactone to ε-caprolactone or δ-valerolactone is 1 / 200 to 1 / 3500; and the molar feed ratio of the α-methylene-δ-valerolactone to ε-caprolactone or δ-valerolactone is 1 / 199 to 199 / 1.

[0018] In the above preparation method, the acidic substance is acetic acid, benzoic acid, hydrochloric acid, sulfuric acid, or phosphoric acid, and the molar ratio of the acidic substance to the organic base is 1 / 1 to 10 / 1. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The poly (α-methylene-δ-valerolactone-co-ε-caprolactone) prepared in Example 1 1 H NMR spectrum.

[0020] Figure 2 The poly (α-methylene-δ-valerolactone-co-ε-caprolactone) prepared in Example 1 13 C NMR spectrum.

[0021] Figure 3 The GPC spectra of poly (α-methylene-δ-valerolactone-co-ε-caprolactone) prepared in Examples 1 to 4 are shown.

[0022] Figure 4 The poly (α-methylene-δ-valerolactone-co-δ-valerolactone) prepared in Example 5 1 H NMR spectrum.

[0023] Figure 5 The poly (α-methylene-δ-valerolactone-co-δ-valerolactone) prepared in Example 5 13 C NMR spectrum.

[0024] Figure 6 This is the GPC spectrum of poly (α-methylene-δ-valerolactone-co-δ-valerolactone) prepared in Examples 5 and 6.

[0025] Figure 7 The thiol product obtained by post-modification in Example 1 1 H NMR spectrum.

[0026] Figure 8 The sulfhydrylation product obtained by post-modification in Example 5 1 H NMR spectrum. DETAILED DESCRIPTION

[0027] The present invention is described in detail with reference to the following embodiments, but the present invention is not limited to these embodiments.

[0028] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0029] Comparative Example 1

[0030] Benzyl alcohol (0.05 mmol, 5.4 mg), phosphazene ligand P2-tert-butyl catalyst (0.05 mmol, 18.4 mg), and 1-(3,5-bis(trifluoromethyl)phenyl)-3-cyclohexylurea (0.10 mmol, 35.4 mg) were dissolved in 3.54 mL of toluene and stirred in an oil bath at 0°C for 10 min. α-methylene-δ-valerolactone (12.5 mmol, 1.33 mL) and ε-caprolactone (12.5 mmol, 1.40 mL) were then added to the reaction tube via syringe. The reaction was carried out at 0°C under nitrogen for 2 h and terminated by the addition of 1 mL of acetic acid. The reaction mixture was dissolved in 5 mL of chloroform and poured into 200 mL of methanol. The polymer was separated by centrifugation and precipitated. Nuclear magnetic resonance imaging confirmed that the polymer was a ring-opening polymerization product, namely, poly(α-methylene-δ-valerolactone-co-ε-caprolactone). GPC measured the number average molecular weight to be 12.1 kg / mol and the molecular weight distribution to be 1.68.

[0031]

[0032] Comparative Example 2

[0033] Benzyl alcohol (0.05 mmol, 5.4 mg), phosphazene ligand P2-tert-butyl catalyst (0.05 mmol, 18.4 mg), and 1,1'-(propane-1,3-diyl)bis(3-phenylurea) (0.10 mmol, 31.2 mg) were dissolved in 3.54 mL of toluene and stirred in an oil bath at 0°C for 10 min. α-methylene-δ-valerolactone (12.5 mmol, 1.33 mL) and ε-caprolactone (12.5 mmol, 1.40 mL) were then added to the reaction tube via syringe. The reaction was carried out at 0°C under nitrogen for 2 h and terminated by the addition of 1 mL of acetic acid. The reaction mixture was dissolved in 5 mL of chloroform and poured into 200 mL of methanol. The polymer was separated by centrifugation and precipitated to obtain a ring-opening polymerization product, poly(α-methylene-δ-valerolactone-co-ε-caprolactone), according to NMR analysis. GPC measured the number average molecular weight to be 14.7 kg / mol and the molecular weight distribution to be 1.87.

[0034]

[0035] Comparative Example 3

[0036] Benzyl alcohol (0.05 mmol, 5.4 mg), phosphazene ligand P2-tert-butyl catalyst (0.05 mmol, 18.4 mg), and 1,1'-(oxybis(ethane-2,1-diyl))bis(3,5-bis(trifluoromethyl)phenyl)urea (0.10 mmol, 58.6 mg) were dissolved in 3.54 mL of toluene and stirred in an oil bath at 0°C for 10 min. α-methylene-δ-valerolactone (12.5 mmol, 1.33 mL) and ε-caprolactone (12.5 mmol, 1.40 mL) were then added to the reaction tube via syringe. The reaction was carried out at 0°C under nitrogen for 2 h and terminated by the addition of 1 mL of acetic acid. The reaction mixture was dissolved in 5 mL of chloroform and poured into 200 mL of methanol. The polymer was separated by centrifugation and precipitated to obtain a ring-opening polymerization product, poly(α-methylene-δ-valerolactone-co-ε-caprolactone), according to NMR analysis. GPC measured the number average molecular weight to be 13.7 kg / mol and the molecular weight distribution to be 1.89.

[0037]

[0038] Comparative Example 4

[0039] Potassium methoxide (0.05 mmol, 3.5 mg) and 1,1'-(propane-1,3-diyl)bis(3-(3,5-bis(trifluoromethyl)phenyl)urea) (0.10 mmol, 58.4 mg) were dissolved in 3.54 mL of toluene and stirred in an oil bath at 0°C for 10 min. α-methylene-δ-valerolactone (12.5 mmol, 1.33 mL) and ε-caprolactone (12.5 mmol, 1.40 mL) were then added to the reaction tube via syringe. The reaction was carried out at 0°C under nitrogen for 1 h and terminated by the addition of 1 mL of acetic acid. The reaction mixture was dissolved in 10 mL of chloroform, but it was not completely soluble, and a double bond addition product was formed.

[0040]

[0041] Example 1

[0042] Benzyl alcohol (0.05 mmol, 5.4 mg), phosphazene ligand P2-tert-butyl catalyst (0.05 mmol, 18.4 mg), 1,1'-(propane-1,3-diyl)bis(3-(3,5-bis(trifluoromethyl)phenyl)urea (0.10 mmol, 58.4 mg) were dissolved in 3.54 mL of toluene and placed in an oil bath at 0 °C and stirred for 10 min. α-methylene-δ-valerolactone and (12.5 mmol, 1.33 mL) were added by syringe. 2.5 mmol, 1.40 mL) of ε-caprolactone was added to a reaction tube. The reaction was carried out at 0°C under nitrogen for 2 hours and terminated by the addition of 1 mL of acetic acid. The reaction mixture was dissolved in 10 mL of chloroform and poured into 200 mL of methanol. The polymer was precipitated by centrifugation. Nuclear magnetic resonance imaging confirmed that the polymer was a ring-opening polymerization product, namely poly(α-methylene-δ-valerolactone-co-ε-caprolactone). GPC analysis revealed a number average molecular weight of 55.9 kg / mol and a molecular weight distribution of 1.19. 1 H NMR spectrum Figure 1 As shown, 13 C NMR spectrum Figure 2 As shown in the GPC spectrum. Figure 3 shown.

[0043] By comparing Examples 1-4 with Example 1, it can be seen that the monourea reported in the literature (Macromolecules.2020, 53, 3380-3389; CN110804163A) cannot achieve controlled ring-opening polymerization of MVL and CL, and the prepared molecular weight is low and the molecular weight distribution is wide. It was also found that not all diureas (Angew.Chem.Int.Ed.2022, 61 (32), e202207105; CN114276524A) can achieve controlled ring-opening copolymerization of MVL and CL to prepare high molecular weight modifiable copolyesters. Moreover, when the organic phosphazene base is replaced with potassium methoxide, the polymerization becomes uncontrollable, and ring-opening polymerization and double bond addition occur simultaneously.

[0044]

[0045] Example 2

[0046] (0.05 mmol, 6.9 mg) of p-phenylenediol, (0.10 mmol, 63.4 mg) of phosphazene ligand P4-tert-butyl catalyst, (0.10 mmol, 44.8 mg) of 1,1'-(propane-1,3-diyl)bis(3-(4-(trifluoromethyl)phenyl)urea) were dissolved in 2.87 mL of acetonitrile and stirred in an oil bath at 25 °C for 15 min. (37.5 mmol, 3.99 mL) of α-methylene-δ-valerolactone and (12.5 mg) of acetonitrile were added by syringe. mol, 1.40 mL) ε-caprolactone was added to the reaction tube. The reaction was carried out at 25 ° C under nitrogen protection for 4 hours, and 2 mL of sulfuric acid was added to terminate the reaction. The reaction mixture was dissolved in 20 mL of chloroform, poured into 300 mL of methanol, and centrifuged to separate the precipitate to obtain a polymer. Nuclear magnetic resonance characterization showed that the polymer was a ring-opening polymerization product, namely poly (α-methylene-δ-valerolactone-co-ε-caprolactone). GPC measured the number average molecular weight to be 112.2 kg / mol and the molecular weight distribution to be 1.41. The GPC spectrum is shown below. Figure 3 shown.

[0047]

[0048] Example 3

[0049] (0.10 mmol, 9.2 mg) glycerol, (0.30 mmol, 359.4 mg) hexa[tris(dimethylamino)phosphazene]triphosphazene, (0.50 mmol, 224.2 mg) 1,1'-(propane-1,3-diyl)bis(3-(4-(trifluoromethyl)phenyl)urea) were dissolved in 33.62 mL of dichloromethane and stirred in an oil bath at 50 °C for 20 min. (50 mmol, 5.32 mL) α-methylene-δ-valerolactone and (10 0mmol, 11.2mL)ε-caprolactone was added to the reaction tube. The reaction was carried out at 50℃ under nitrogen protection for 6h, and 3mL of phosphoric acid was added to terminate the reaction. The reaction mixture was dissolved in 30mL of chloroform, poured into 300mL of methanol, and centrifuged to separate the precipitate to obtain a polymer. Nuclear magnetic resonance characterization showed that the polymer was a ring-opening polymerization product, namely poly(α-methylene-δ-valerolactone-co-ε-caprolactone). GPC measured the number average molecular weight to be 165.5kg / mol, and the molecular weight distribution was 1.45. The GPC spectrum is shown in the figure below. Figure 3 shown.

[0050]

[0051] Example 4

[0052] Ethylene glycol (0.10 mmol, 6.2 mg), phosphazene ligand P4-tert-butyl catalyst (0.40 mmol, 253.6 mg), and 1,1'-(propane-1,3-diyl)bis(3-(3,5-bis(trifluoromethyl)phenyl)urea) (0.60 mmol, 350.6 mg) were dissolved in 78.4 mL of toluene and stirred in an oil bath at 25°C for 30 min. α-methylene-δ-valerolactone (100.0 mmol, 10.64 mL) and ε-caprolactone (100.0 mmol, 11.20 mL) were then added to the reaction tube via syringe. The reaction was carried out at 25°C under nitrogen for 12 h and terminated by the addition of 5 mL of acetic acid. The reaction mixture was dissolved in 50 mL of chloroform and poured into 400 mL of methanol. The polymer was separated and precipitated by centrifugation. The polymer was characterized by nuclear magnetic resonance as a ring-opening polymerization product, namely poly (α-methylene-δ-valerolactone-co-ε-caprolactone). The number average molecular weight measured by GPC was 220.1 kg / mol and the molecular weight distribution was 1.39. The GPC spectrum is shown in FIG. Figure 3 shown.

[0053]

[0054] Example 5

[0055] Benzyl alcohol (0.05 mmol, 5.4 mg), phosphazene ligand P2-tert-butyl catalyst (0.10 mmol, 36.7 mg), and 1,1'-(propane-1,3-diyl)bis(3-(3,5-bis(trifluoromethyl)phenyl)urea) (0.20 mmol, 116.9 mg) were dissolved in 33.6 mL of tetrahydrofuran and stirred in an oil bath at 0°C for 20 min. α-methylene-δ-valerolactone (15.0 mmol, 1.60 mL) and δ-valerolactone (35.0 mmol, 3.17 mL) were then added to the reaction tube via syringe. The reaction was carried out at 0°C under nitrogen for 6 h, and then terminated by the addition of 3 mL of acetic acid. The reaction mixture was dissolved in 30 mL of chloroform, poured into 300 mL of methanol, and centrifuged to separate the precipitate to obtain a polymer. Nuclear magnetic resonance imaging showed that the polymer was a ring-opening polymerization product, namely poly(α-methylene-δ-valerolactone-co-δ-valerolactone). GPC measured a number average molecular weight of 162.1 kg / mol and a molecular weight distribution of 1.32. 1 H NMR spectrum Figure 4 As shown, 13 C NMR spectrum Figure 5 As shown in the GPC spectrum. Figure 6 shown.

[0056]

[0057] Example 6

[0058] (0.10 mmol, 6.0 mg) isopropanol, (0.30 mmol, 190.2 mg) phosphazene ligand P2-tert-butyl catalyst, (0.80 mmol, 358.7 mg) 1,1'-(propane-1,3-diyl)bis(3-(4-(trifluoromethyl)phenyl)urea) were dissolved in 78.4 mL toluene and stirred in an oil bath at 25 °C for 30 min. (100 mmol, 10.60 mL) α-methylene-δ-valerolactone and (100 mm Hg) were added by syringe. ol,9.05mL)δ-valerolactone was added to the reaction tube. The reaction was carried out at 25℃ under nitrogen protection for 10h, and 4mL hydrochloric acid was added to terminate the reaction. The reaction mixture was dissolved in 40mL chloroform, poured into 500mL methanol, and centrifuged to separate the precipitate to obtain a polymer. Nuclear magnetic resonance characterization showed that the polymer was a ring-opening polymerization product, namely poly(α-methylene-δ-valerolactone-co-δ-valerolactone). GPC measured the number average molecular weight to be 165.5kg / mol, and the molecular weight distribution was 1.45. The GPC spectrum is shown as follows Figure 6 shown.

[0059]

[0060] Example 7

[0061] 0.90 g of poly(α-methylene-δ-valerolactone-co-ε-caprolactone), benzyl mercaptan (12 mmol, 1.49 g), and triethylamine (0.1 mmol, 10.1 mg) were added to 0.4 mL of dimethyl sulfoxide. After 10 hours at 40°C, the mixture was washed with 50 mL of methanol and centrifuged to obtain a polymer. Nuclear magnetic resonance imaging confirmed that the polymer was a post-modified product, namely, thiol-substituted poly(α-methylene-δ-valerolactone-co-ε-caprolactone), with a conversion rate of 100%. 1 H NMR spectrum Figure 7 shown.

[0062] Example 8

[0063] 0.80 g of poly(α-methylene-δ-valerolactone-co-ε-δ-valerolactone), benzyl mercaptan (12 mmol, 1.49 g), and triethylamine (0.1 mmol, 10.1 mg) were added to 0.4 mL of dimethyl sulfoxide. After 10 hours at 40°C, the mixture was washed with 50 mL of methanol and centrifuged to obtain a polymer. Nuclear magnetic resonance imaging showed that the polymer was a post-modified product, namely, thiol-substituted poly(α-methylene-δ-valerolactone-co-δ-valerolactone), with a conversion rate of 100%. 1 H NMR spectrum Figure 8 shown.

Claims

1. A method for preparing high molecular weight modifiable poly (α-methylene-δ-valerolactone-co-ε-caprolactone) or poly (α-methylene-δ-valerolactone-co-δ-valerolactone) by chemically selective ring-opening copolymerization of α-methylene-δ-valerolactone and ε-caprolactone or δ-valerolactone, characterized in that: The steps include: (1) Dissolve the initiator, organic base, and co-catalyst in an organic solvent and stir at 0-50°C for 10-30 minutes; (2) α-methylene-δ-valerolactone and ε-caprolactone or δ-valerolactone are mixed uniformly, and then added to the above mixed solution, reacted at 0-50° C. for 0.1-24 h, and an acidic substance is added to terminate the reaction. After precipitation with methanol, poly(α-methylene-δ-valerolactone-co-ε-caprolactone) or poly(α-methylene-δ-valerolactone-co-δ-valerolactone) is obtained; The initiator is methanol, ethanol, isopropanol, tert-butyl alcohol, benzyl alcohol, phenylethyl alcohol, phenylpropyl alcohol, diphenylmethanol, 2,2-diphenylethanol, ethylene glycol, 1,4-phenyldimethanol, glycerol, pentaerythritol; the organic base is hexa[tris(dimethylamino)phosphazene]tripolyphosphazene ({[(NMe2)3P=N]2P=N}3), phosphazene ligand P4-tert-butyl ([(NMe2)3P=N]3P=NtBu, tert-Bu-P4), phosphazene ligand P2-tert-butyl ([(NMe2)3P=N](NMe2)2P=NtBu, tert-Bu-P2); the cocatalyst has one of the following structures:

2. The method according to claim 1, characterized in that The chemical structures of the poly(α-methylene-δ-valerolactone-co-ε-caprolactone) or poly(α-methylene-δ-valerolactone-co-δ-valerolactone) are shown in formula (I) and formula (II), respectively: It is characterized in that R1 is hydroxy, methoxy, ethoxy, isopropoxy, tert-butoxy, benzyloxy, phenylethoxy, phenylpropoxy, diphenylmethoxy or 2,2-diphenylethoxy; and the sum of n and m is a natural number greater than or equal to 200.

3. The method according to claim 1, wherein: The molar ratio of the organic base to the initiator is 1 / 10 to 20 / 1; the molar ratio of the organic base to the co-catalyst is 1 / 1 to 1 / 20; the total molar feed ratio of the initiator to α-methylene-δ-valerolactone and ε-caprolactone or δ-valerolactone is 1 / 200 to 1 / 3500; and the molar feed ratio of the α-methylene-δ-valerolactone to ε-caprolactone or δ-valerolactone is 1 / 199 to 199 / 1.

4. The method according to claim 1, wherein: The organic solvent is toluene, tetrahydrofuran, dichloromethane or acetonitrile; the molar concentration of the α-methylene-δ-valerolactone in the system is 1 to 8 mol / L; the molar concentration of the ε-caprolactone or δ-valerolactone in the system is 1 to 8 mol / L.

5. The method according to claim 1, wherein: The acidic substance is acetic acid, benzoic acid, hydrochloric acid, sulfuric acid, and phosphoric acid, and the molar ratio of the acidic substance to the organic base is 1 / 1 to 10 / 1.

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