A method for the ring-opening polymerization of lactones using indolyl rare earth metal complexes as catalysts

Abstract

The application relates to the field of metal organic chemistry, in particular to a method for catalyzing lactone ring-opening polymerization by using an indole-based rare earth metal complex. The method for catalyzing lactone ring-opening polymerization by using the indole-based rare earth metal complex comprises the following steps: mixing the indole-based rare earth metal complex, a lactone monomer and a solvent under an inert atmosphere, and performing a polymerization reaction. The method for catalyzing lactone ring-opening polymerization by using the indole-based rare earth metal complex provided by the application can solve the problems of long polymerization time, small molecular weight and low molecular weight distribution of the existing lactone ring-opening polymerization.

Description

Technical Field

[0001] This invention relates to the field of organometallic chemistry, and more particularly to a method for catalyzing the ring-opening polymerization of lactones using indole rare earth metal complexes. Background Technology

[0002] With increasing global attention to white pollution and a surge in demand for biomedical materials, environmentally friendly biodegradable polymer materials have become a research hotspot. Among them, polyester materials (such as polylactic acid (PLA), polycaprolactone (PCL), poly-β-butyrolactone (PBL), and polyvalerol (PVL)) have shown great potential in fields such as disposable packaging, drug delivery systems, and tissue engineering scaffolds due to their degradability, biocompatibility, and tunable physicochemical properties.

[0003] Indole ligands, by introducing different electron-donating or electron-withdrawing groups, can precisely control the charge distribution and steric hindrance of the metal center, thereby potentially achieving efficient control over the polymerization rate, molecular weight distribution, and stereoregularity. Indole rare earth complexes exhibit unique advantages in the field of catalysis, mainly due to the high coordination number and variable valence state of rare earth metal ions and the electron-rich characteristics of indole ligands. These complexes can efficiently catalyze various organic reactions through the Lewis acidity of rare earth ions and the synergistic effect of ligands. For example, Professor Wang Shaowu et al. reported that 2-indole rare earth metal complexes can efficiently catalyze the homopolymerization and copolymerization of valerate and lactide (Inorg. Chem. 2025, 64, 13684-13695. Polymer Bulletin, 2025, 38(10), 1525-1535). However, existing catalytic systems still have some shortcomings, mainly manifested in: long polymerization reaction time, low molecular weight of the obtained polymer, and wide molecular weight distribution, which limit their application in the efficient synthesis of high-performance polyester materials.

[0004] Therefore, developing a catalytic method that can achieve rapid ring-opening polymerization of lactones under mild conditions to obtain polymers with high molecular weight and narrow molecular weight distribution remains an urgent technical problem to be solved. Summary of the Invention

[0005] This invention provides a method for the ring-opening polymerization of lactones catalyzed by indole rare earth metal complexes, in order to solve the problems of excessively long ring-opening polymerization time, small molecular weight, and low molecular weight distribution of existing lactones.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: This invention provides a method for the ring-opening polymerization of lactones catalyzed by indole rare earth metal complexes, comprising the following steps: In an inert atmosphere, indole rare earth metal complexes, lactone monomers, and solvents are mixed and polymerized.

[0007] Preferably, the indole rare earth metal complex comprises at least one of the following complexes A1 to E2: Complex A1, Complex A2, Complex B1, Complex B2, Complex C1, Complex C2, Complex D1, Complex D2, Complex E1, Complex E2.

[0008] In this invention, the complexes A1 to E2 have all been disclosed in the prior art, such as (1) A1, A2, C1 and C2 in the paper "Huang Zeming. Synthesis, characterization and performance study of novel CNO and NCN tridentate rare earth metal complexes [D]. Anhui: Anhui Normal University, 2021."; (2) B1 and B2 in the paper "Chem. Sci. 2024, 15, 20315-20327"; (3) D1 and D2 in the paper "Wang Weigang. Synthesis, characterization and performance study of 1-(2-pyridyl)-3-(1-methylbenzimidazolyl)indole ligand binuclear rare earth metal hydrocarbon complexes [D]. Anhui: Anhui Normal University, 2023."; (4) E1 and E2 in the paper "Chem. Sci., 2025, 16, 11870-11887".

[0009] Preferably, the mixing further includes the addition of a co-catalyst, which includes benzyl alcohol.

[0010] Preferably, the molar ratio of the co-catalyst and the indole rare earth metal complex is 1:(1~2).

[0011] Preferably, the lactone monomer includes rac-lactide, β-butyrolactone, δ-valactone, or caprolactone.

[0012] Preferably, the solvent includes at least one of tetrahydrofuran, chlorobenzene, and toluene.

[0013] Preferably, the molar ratio of the lactone monomer to the indole rare earth metal complex is 50:1 to 2000:1.

[0014] In this invention, the amount of solvent used is not specifically limited, as long as it is sufficient to disperse the raw materials. In some embodiments, the ratio of the lactone monomer to the solvent is (500~20000) μmol: (0.5~165) mL.

[0015] Preferably, the polymerization reaction temperature is 0~80℃ and the polymerization reaction time is 1~1500min.

[0016] Preferably, after the polymerization reaction is completed, the reaction further includes: adding n-hexane to terminate the reaction, and then drying the resulting product to constant weight.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention provides various methods for the ring-opening polymerization of different lactones catalyzed by indole rare earth metal complexes, demonstrating efficient ring-opening polymerization for a wide range of lactones. The catalysts used in this invention are more diverse, exhibiting high efficiency not only in the homopolymerization of valproic acid and lactide, but also in the homopolymerization of caprolactone and β-butyrolactone. Furthermore, this invention provides, for the first time, a method for the ring-opening polymerization of lactones catalyzed by a 2-indole divalent ytterbium complex. Simultaneously, for the more difficult-to-ring-open β-butyrolactone, this invention can achieve polymerization of β-butyrolactone by adding the co-catalyst benzyl alcohol for different indole rare earth metal complexes. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments. The embodiments of this application are only examples, and all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Example 1 This embodiment provides a reaction for the ring-opening polymerization of β-butyrolactone catalyzed by rare earth metal complex A1, the steps of which are as follows: 10 μmol of rare earth metal complex A1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 163 μL of toluene was added as solvent, followed by 2000 μmol of β-butyrolactone monomer. The reaction was carried out at 0 °C for 24 h, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 82.6%, and the number-average molecular weight of the polymer was Mn = 18.5 × 10⁻⁶. 3 Molecular weight distribution =1.21.

[0020] Example 2 This embodiment provides a reaction for the ring-opening polymerization of β-butyrolactone catalyzed by rare earth metal complex A1, the steps of which are as follows: 10 μmol of rare earth metal complex A1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 122 μL of toluene was added as solvent, followed by 1500 μmol of β-butyrolactone monomer. The reaction was carried out at 0 °C for 24 h, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 88.0%, and the number-average molecular weight of the polymer was Mn = 14.1 × 10⁻⁶. 3 Molecular weight distribution =1.19.

[0021] Example 3 This embodiment provides a reaction for the ring-opening polymerization of β-butyrolactone catalyzed by rare earth metal complex A1, the steps of which are as follows: 10 μmol of rare earth metal complex A1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 82 μL of toluene was added as solvent, followed by 1000 μmol of β-butyrolactone monomer. The reaction was carried out at 0 °C for 24 h, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 91.7%, and the number-average molecular weight of the polymer was Mn = 12.2 × 10⁻⁶. 3 Molecular weight distribution =1.24.

[0022] Example 4 This embodiment provides a reaction for the ring-opening polymerization of β-butyrolactone catalyzed by rare earth metal complex A1, the steps of which are as follows: 10 μmol of rare earth metal complex A1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 41 μL of toluene was added as solvent, followed by 500 μmol of β-butyrolactone monomer. The reaction was carried out at 0 °C for 24 h, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 97.1%, and the polymer number-average molecular weight Mn = 8.0 × 10⁻⁶. 3 Molecular weight distribution =1.18.

[0023] Example 5 This embodiment provides a reaction for the ring-opening polymerization of β-butyrolactone catalyzed by rare earth metal complex A2, the steps of which are as follows: 10 μmol of rare earth metal complex A2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 163 μL of toluene was added as solvent, followed by 2000 μmol of β-butyrolactone monomer. The reaction was carried out at 0 °C for 24 h, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 82.6%, and the number-average molecular weight of the polymer was Mn = 17.4 × 10⁻⁶. 3 Molecular weight distribution =1.19.

[0024] Example 6 This embodiment provides a reaction for the ring-opening polymerization of β-butyrolactone catalyzed by rare earth metal complex A2, the steps of which are as follows: 10 μmol of rare earth metal complex A2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 122 μL of toluene was added as solvent, followed by 1500 μmol of β-butyrolactone monomer. The reaction was carried out at 0 °C for 24 h, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 86.9%, and the number-average molecular weight of the polymer was Mn = 16.5 × 10⁻⁶. 3 Molecular weight distribution =1.33.

[0025] Example 7 This embodiment provides a reaction for the ring-opening polymerization of β-butyrolactone catalyzed by rare earth metal complex A2, the steps of which are as follows: 10 μmol of rare earth metal complex A2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 82 μL of toluene was added as solvent, followed by 1000 μmol of β-butyrolactone monomer. The reaction was carried out at 0 °C for 24 h, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 87.7%, and the number-average molecular weight of the polymer was Mn = 13.1 × 10⁻⁶. 3 Molecular weight distribution =1.31.

[0026] Example 8 This embodiment provides a reaction for the ring-opening polymerization of β-butyrolactone catalyzed by rare earth metal complex A2, the steps of which are as follows: 10 μmol of rare earth metal complex A2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 41 μL of toluene was added as solvent, followed by 500 μmol of β-butyrolactone monomer. The reaction was carried out at 0 °C for 24 h, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 92.6%, and the number-average molecular weight of the polymer was Mn = 9.6 × 10⁻⁶. 3 Molecular weight distribution =1.28.

[0027] Examples 1-8 are summarized in Table 1 below.

[0028] Table 1

[0029] Example 9 This embodiment provides a reaction for the ring-opening polymerization of β-butyrolactone catalyzed by rare earth metal complex B1, the steps of which are as follows: 10 μmol of rare earth metal complex B1 was weighed in a glove box under an argon atmosphere and placed in a 25 mL reaction flask. 163 μL of toluene was added as a solvent, followed by 10 μmol of benzyl alcohol and 2000 μmol of β-butyrolactone monomer. The reaction was carried out at 25 °C for 24 h, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight, and the polymerization yield was 93.5%.

[0030] Example 10 This embodiment provides a reaction for the ring-opening polymerization of β-butyrolactone catalyzed by rare earth metal complex B1, the steps of which are as follows: 10 μmol of rare earth metal complex B1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 163 μL of toluene was added as a solvent, followed by 10 μmol of benzyl alcohol and 2000 μmol of β-butyrolactone monomer. The reaction was carried out at 0 °C for 24 h, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was greater than 99%, and the number-average molecular weight of the polymer was Mn = 13.1 × 10⁻⁶. 3 Molecular weight distribution =1.21.

[0031] Example 11 This embodiment provides a reaction for the ring-opening polymerization of β-butyrolactone catalyzed by rare earth metal complex B1, the steps of which are as follows: 10 μmol of rare earth metal complex B1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 122 μL of toluene was added as a solvent, followed by 10 μmol of benzyl alcohol and 1500 μmol of β-butyrolactone monomer. The reaction was carried out at 0 °C for 24 h, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was greater than 99%, and the number-average molecular weight of the polymer was Mn = 10.9 × 10⁻⁶. 3 Molecular weight distribution =1.19.

[0032] Example 12 This embodiment provides a reaction for the ring-opening polymerization of β-butyrolactone catalyzed by rare earth metal complex B1, the steps of which are as follows: 10 μmol of rare earth metal complex B1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 82 μL of toluene was added as a solvent, followed by 10 μmol of benzyl alcohol and 1000 μmol of β-butyrolactone monomer. The reaction was carried out at 0 °C for 24 h, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was greater than 99%, and the number-average molecular weight of the polymer was Mn = 8.6 × 10⁻⁶. 3 Molecular weight distribution =1.20.

[0033] Example 13 This embodiment provides a reaction for the ring-opening polymerization of β-butyrolactone catalyzed by rare earth metal complex B1, the steps of which are as follows: 10 μmol of rare earth metal complex B1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 41 μL of toluene was added as a solvent, followed by 10 μmol of benzyl alcohol and 500 μmol of β-butyrolactone monomer. The reaction was carried out at 0 °C for 24 h, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was greater than 99%, and the number-average molecular weight of the polymer was Mn = 5.2 × 10⁻⁶. 3 Molecular weight distribution =1.20.

[0034] Example 14 This embodiment provides a reaction for the ring-opening polymerization of β-butyrolactone catalyzed by rare earth metal complex B2, the steps of which are as follows: 10 μmol of rare earth metal complex B2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 163 μL of toluene was added as a solvent, followed by 10 μmol of benzyl alcohol and 2000 μmol of β-butyrolactone monomer. The reaction was carried out at 0 °C for 24 h, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was greater than 99%, and the number-average molecular weight of the polymer was Mn = 15.0 × 10⁻⁶. 3 Molecular weight distribution =1.24.

[0035] Example 15 This embodiment provides a reaction for the ring-opening polymerization of β-butyrolactone catalyzed by rare earth metal complex B2, the steps of which are as follows: 10 μmol of rare earth metal complex B2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 122 μL of toluene was added as a solvent, followed by 10 μmol of benzyl alcohol and 1500 μmol of β-butyrolactone monomer. The reaction was carried out at 0 °C for 24 h, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was greater than 99%, and the number-average molecular weight of the polymer was Mn = 13.6 × 10⁻⁶. 3 Molecular weight distribution =1.27.

[0036] Example 16 This embodiment provides a reaction for the ring-opening polymerization of β-butyrolactone catalyzed by rare earth metal complex B2, the steps of which are as follows: 10 μmol of rare earth metal complex B2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 82 μL of toluene was added as a solvent, followed by 10 μmol of benzyl alcohol and 1000 μmol of β-butyrolactone monomer. The reaction was carried out at 0 °C for 24 h, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was greater than 99%, and the number-average molecular weight of the polymer was Mn = 9.4 × 10⁻⁶. 3 Molecular weight distribution =1.24.

[0037] Example 17 This embodiment provides a reaction for the ring-opening polymerization of β-butyrolactone catalyzed by rare earth metal complex B2, the steps of which are as follows: 10 μmol of rare earth metal complex B2 was weighed into a 25 mL reaction flask in an argon-atmospheric glove box. 41 μL of toluene was added as a solvent, followed by 10 μmol of benzyl alcohol and 500 μmol of β-butyrolactone monomer. The reaction was carried out at 0 °C for 24 h, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was greater than 99%, and the number-average molecular weight of the polymer was Mn = 5.4 × 10⁻⁶. 3 Molecular weight distribution =1.23.

[0038] Examples 9-17 are summarized in Table 2 below.

[0039] Table 2

[0040] Example 18 This embodiment provides a reaction for the ring-opening polymerization of δ-valerol catalyzed by a rare earth metal complex C1, the steps of which are as follows: 10 μmol of rare earth metal complex C1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 0.5 mL of tetrahydrofuran was added as a solvent, followed by 1000 μmol of δ-valerolactone monomer. The reaction was carried out at 25 °C for 5 min, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 94.2%, and the number-average molecular weight of the polymer was Mn = 19.8 × 10⁻⁶. 3 Molecular weight distribution =1.64.

[0041] Example 19 This embodiment provides a reaction for the ring-opening polymerization of δ-valerol catalyzed by a rare earth metal complex C1, the steps of which are as follows: 10 μmol of rare earth metal complex C1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 0.5 mL of toluene was added as a solvent, followed by 1000 μmol of δ-valerolactone monomer. The reaction was carried out at 25 °C for 5 min, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 94.4%, and the number-average molecular weight of the polymer was Mn = 16.1 × 10⁻⁶. 3 Molecular weight distribution =1.56.

[0042] Example 20 This embodiment provides a reaction for the ring-opening polymerization of δ-valerol catalyzed by a rare earth metal complex C1, the steps of which are as follows: 10 μmol of rare earth metal complex C1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 0.5 mL of toluene was added as a solvent, followed by 1000 μmol of δ-valerolactone monomer. The reaction was carried out at 25 °C for 10 min, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 96.1%, and the polymer number-average molecular weight Mn = 20.7 × 10⁻⁶. 3 Molecular weight distribution =1.61.

[0043] Example 21 This embodiment provides a reaction for the ring-opening polymerization of δ-valerol catalyzed by a rare earth metal complex C1, the steps of which are as follows: 10 μmol of rare earth metal complex C1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 1 mL of toluene was added as a solvent, followed by 2000 μmol of δ-valerolactone monomer. The reaction was carried out at 25 °C for 10 min, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 95.7%, and the number-average molecular weight of the polymer was Mn = 31.4 × 10⁻⁶. 3 Molecular weight distribution =1.54.

[0044] Example 22 This embodiment provides a reaction for the ring-opening polymerization of δ-valerol catalyzed by a rare earth metal complex C1, the steps of which are as follows: 10 μmol of rare earth metal complex C1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 2.5 mL of toluene was added as solvent, followed by 5000 μmol of δ-valerolactone monomer. The reaction was carried out at 25 °C for 15 min, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 95.4%, and the number-average molecular weight of the polymer was Mn = 54.2 × 10⁻⁶. 3 Molecular weight distribution =1.50.

[0045] Example 23 This embodiment provides a rare earth metal complex C2-catalyzed ring-opening polymerization reaction of δ-valerolactone, the steps of which are as follows: 10 μmol of rare earth metal complex C2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 0.5 mL of toluene was added as a solvent, followed by 1000 μmol of δ-valerolactone monomer. The reaction was carried out at 25 °C for 10 min, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 94.9%, and the number-average molecular weight of the polymer was Mn = 22.6 × 10⁻⁶. 3 Molecular weight distribution =1.51.

[0046] Example 24 This embodiment provides a rare earth metal complex C2-catalyzed ring-opening polymerization reaction of δ-valerolactone, the steps of which are as follows: 10 μmol of rare earth metal complex C2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 1 mL of toluene was added as a solvent, followed by 2000 μmol of δ-valerolactone monomer. The reaction was carried out at 25 °C for 10 min, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 94.5%, and the number-average molecular weight of the polymer was Mn = 31.7 × 10⁻⁶. 3 Molecular weight distribution =1.58.

[0047] Example 25 This embodiment provides a rare earth metal complex C2-catalyzed ring-opening polymerization reaction of δ-valerolactone, the steps of which are as follows: 10 μmol of rare earth metal complex C2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 2.5 mL of toluene was added as solvent, followed by 5000 μmol of δ-valerolactone monomer. The reaction was carried out at 25 °C for 15 min, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 94.5%, and the number-average molecular weight of the polymer was Mn = 51.2 × 10⁻⁶. 3 Molecular weight distribution =1.64.

[0048] Example 26 This embodiment provides a reaction for the ring-opening polymerization of δ-valerol catalyzed by rare earth metal complex A2, the steps of which are as follows: 10 μmol of rare earth metal complex A2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 0.5 mL of tetrahydrofuran was added as a solvent, followed by 1000 μmol of δ-valerolactone monomer. The reaction was carried out at 25 °C for 1 min, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 92.4%, and the number-average molecular weight of the polymer was Mn = 15.3 × 10⁻⁶. 3 Molecular weight distribution =1.60.

[0049] Example 27 This embodiment provides a reaction for the ring-opening polymerization of δ-valerol catalyzed by rare earth metal complex A2, the steps of which are as follows: 10 μmol of rare earth metal complex A2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 0.5 mL of toluene was added as a solvent, followed by 1000 μmol of δ-valerolactone monomer. The reaction was carried out at 25 °C for 1 min, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 94.3%, and the polymer number-average molecular weight Mn = 21.6 × 10⁻⁶. 3 Molecular weight distribution =1.69.

[0050] Example 28 This embodiment provides a reaction for the ring-opening polymerization of δ-valerol catalyzed by rare earth metal complex A2, the steps of which are as follows: 10 μmol of rare earth metal complex A2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 0.5 mL of toluene was added as a solvent, followed by 1000 μmol of δ-valerolactone monomer. The reaction was carried out at 25 °C for 5 min, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 96.5%, and the number-average molecular weight of the polymer, Mn, was 13.1 × 10⁻⁶. 3 Molecular weight distribution =1.69.

[0051] Example 29 This embodiment provides a reaction for the ring-opening polymerization of δ-valerol catalyzed by rare earth metal complex A2, the steps of which are as follows: 10 μmol of rare earth metal complex A2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 1 mL of toluene was added as a solvent, followed by 2000 μmol of δ-valerolactone monomer. The reaction was carried out at 25 °C for 5 min, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 96.3%, and the polymer number-average molecular weight Mn = 28.8 × 10⁻⁶. 3 Molecular weight distribution =1.52.

[0052] Example 30 This embodiment provides a reaction for the ring-opening polymerization of δ-valerol catalyzed by rare earth metal complex A2, the steps of which are as follows: 10 μmol of rare earth metal complex A2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 2.5 mL of toluene was added as solvent, followed by 5000 μmol of δ-valerolactone monomer. The reaction was carried out at 25 °C for 10 min, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 96.0%, and the polymer number-average molecular weight Mn = 46.1 × 10⁻⁶. 3 Molecular weight distribution =1.45.

[0053] Example 31 This embodiment provides a reaction for the ring-opening polymerization of δ-valerol catalyzed by rare earth metal complex A1, the steps of which are as follows: 10 μmol of rare earth metal complex A1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 0.5 mL of toluene was added as a solvent, followed by 1000 μmol of δ-valerolactone monomer. The reaction was carried out at 25 °C for 5 min, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 96.1%, and the number-average molecular weight of the polymer was Mn = 16.5 × 10⁻⁶. 3 Molecular weight distribution =1.65.

[0054] Example 32 This embodiment provides a reaction for the ring-opening polymerization of δ-valerol catalyzed by rare earth metal complex A1, the steps of which are as follows: 10 μmol of rare earth metal complex A1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 1 mL of toluene was added as a solvent, followed by 2000 μmol of δ-valerolactone monomer. The reaction was carried out at 25 °C for 5 min, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 95.3%, the number-average molecular weight Mn was 22.8 × 10³, and the molecular weight distribution was [not specified]. =1.53.

[0055] Example 33 This embodiment provides a reaction for the ring-opening polymerization of δ-valerol catalyzed by rare earth metal complex A1, the steps of which are as follows: 10 μmol of rare earth metal complex A1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 2.5 mL of toluene was added as solvent, followed by 5000 μmol of δ-valerolactone monomer. The reaction was carried out at 25 °C for 10 min, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 95.1%, and the number-average molecular weight of the polymer, Mn, was 48.1 × 10⁻⁶.3 Molecular weight distribution =1.51.

[0056] Example 34 This embodiment provides a reaction for the ring-opening polymerization of δ-valerolactone catalyzed by rare earth metal complex B2, the steps of which are as follows: 10 μmol of rare earth metal complex B2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 0.5 mL of toluene was added as a solvent, followed by 1000 μmol of δ-valerolactone monomer. The reaction was carried out at 25 °C for 5 min, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 94.0%, and the polymer number-average molecular weight Mn = 14.8 × 10⁻⁶. 3 Molecular weight distribution =1.68.

[0057] Example 35 This embodiment provides a reaction for the ring-opening polymerization of δ-valerolactone catalyzed by rare earth metal complex B2, the steps of which are as follows: 10 μmol of rare earth metal complex B2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 1 mL of toluene was added as a solvent, followed by 2000 μmol of δ-valerolactone monomer. The reaction was carried out at 25 °C for 5 min, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 93.1%, and the polymer number-average molecular weight Mn = 23.7 × 10⁻⁶. 3 Molecular weight distribution =1.53.

[0058] Example 36 This embodiment provides a reaction for the ring-opening polymerization of δ-valerolactone catalyzed by rare earth metal complex B2, the steps of which are as follows: 10 μmol of rare earth metal complex B2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 2.5 mL of toluene was added as solvent, followed by 5000 μmol of δ-valerolactone monomer. The reaction was carried out at 25 °C for 10 min, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 92.9%, and the polymer number-average molecular weight Mn = 36.6 × 10⁻⁶. 3 Molecular weight distribution =1.38.

[0059] Example 37 This embodiment provides a reaction for the ring-opening polymerization of δ-valerol catalyzed by rare earth metal complex B1, the steps of which are as follows: 10 μmol of rare earth metal complex B1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 0.5 mL of toluene was added as a solvent, followed by 1000 μmol of δ-valerolactone monomer. The reaction was carried out at 25 °C for 5 min, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 95.6%, and the number-average molecular weight of the polymer, Mn, was 11.1 × 10⁻⁶. 3 Molecular weight distribution =1.82.

[0060] Example 38 This embodiment provides a reaction for the ring-opening polymerization of δ-valerol catalyzed by rare earth metal complex B1, the steps of which are as follows: 10 μmol of rare earth metal complex B1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 1 mL of toluene was added as a solvent, followed by 2000 μmol of δ-valerolactone monomer. The reaction was carried out at 25 °C for 5 min, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 95.5%, and the number-average molecular weight of the polymer, Mn, was 23.3 × 10⁻⁶. 3 Molecular weight distribution =1.53.

[0061] Example 39 This embodiment provides a reaction for the ring-opening polymerization of δ-valerol catalyzed by rare earth metal complex B1, the steps of which are as follows: 10 μmol of rare earth metal complex B1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 2.5 mL of toluene was added as a solvent, followed by 5000 μmol of δ-valerolactone monomer. The reaction was carried out at 25 °C for 10 min, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 94.9%, and the polymer number-average molecular weight Mn = 43.5 × 10⁻⁶. 3 Molecular weight distribution =1.56.

[0062] Examples 18-39 are summarized in Table 3 below.

[0063] Table 3

[0064] Example 40 This embodiment provides a reaction for the ring-opening polymerization of caprolactone catalyzed by a rare earth metal complex C1, the steps of which are as follows: 10 μmol of rare earth metal complex C1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 1.07 mL of toluene was added as a solvent, followed by 1000 μmol of caprolactone monomer. The reaction was carried out at 25 °C for 2 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 98.7%, and the number-average molecular weight of the polymer was Mn = 29.1 × 10⁻⁶. 3 Molecular weight distribution =1.8.

[0065] Example 41 This embodiment provides a reaction for the ring-opening polymerization of caprolactone catalyzed by a rare earth metal complex C1, the steps of which are as follows: 10 μmol of rare earth metal complex C1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 2.14 mL of toluene was added as solvent, followed by 2000 μmol of caprolactone monomer. The reaction was carried out at 25 °C for 2 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 98.1%, and the polymer number-average molecular weight Mn = 47.3 × 10⁻⁶. 3 Molecular weight distribution =1.8.

[0066] Example 42 This embodiment provides a reaction for the ring-opening polymerization of caprolactone catalyzed by a rare earth metal complex C1, the steps of which are as follows: 10 μmol of rare earth metal complex C1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 5.35 mL of toluene was added as solvent, followed by 5000 μmol of caprolactone monomer. The reaction was carried out at 25 °C for 2 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 90.7%, the number-average molecular weight Mn was 129.8 × 10³, and the molecular weight distribution was [not specified]. =2.0.

[0067] Example 43 This embodiment provides a rare earth metal complex C2-catalyzed reaction for the ring-opening polymerization of caprolactone, the steps of which are as follows: 10 μmol of rare earth metal complex C2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 1.07 mL of toluene was added as solvent, followed by 1000 μmol of caprolactone monomer. The reaction was carried out at 25 °C for 2 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 98.8%, and the polymer number-average molecular weight Mn = 26.7 × 10⁻⁶. 3 Molecular weight distribution =1.2.

[0068] Example 44 This embodiment provides a rare earth metal complex C2-catalyzed reaction for the ring-opening polymerization of caprolactone, the steps of which are as follows: 10 μmol of rare earth metal complex C2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 2.14 mL of toluene was added as solvent, followed by 2000 μmol of caprolactone monomer. The reaction was carried out at 25 °C for 2 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 98.3%, and the number-average molecular weight of the polymer, Mn, was 51.6 × 10⁻⁶. 3 Molecular weight distribution =1.7.

[0069] Example 45 This embodiment provides a rare earth metal complex C2-catalyzed reaction for the ring-opening polymerization of caprolactone, the steps of which are as follows: 10 μmol of rare earth metal complex C2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 5.35 mL of toluene was added as solvent, followed by 5000 μmol of caprolactone monomer. The reaction was carried out at 25 °C for 2 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 97.6%, and the number-average molecular weight of the polymer, Mn, was 131.3 × 10⁻⁶. 3 Molecular weight distribution =1.9.

[0070] Example 46 This embodiment provides a reaction for the ring-opening polymerization of caprolactone catalyzed by rare earth metal complex D1, the steps of which are as follows: 10 μmol of rare earth metal complex D1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 1.07 mL of toluene was added as a solvent, followed by 1000 μmol of caprolactone monomer. The reaction was carried out at 25 °C for 2 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was greater than 99%, and the number-average molecular weight of the polymer was Mn = 35.4 × 10⁻⁶. 3 Molecular weight distribution =1.5.

[0071] Example 47 This embodiment provides a reaction for the ring-opening polymerization of caprolactone catalyzed by rare earth metal complex D1, the steps of which are as follows: 10 μmol of rare earth metal complex D1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 2.14 mL of toluene was added as solvent, followed by 2000 μmol of caprolactone monomer. The reaction was carried out at 25 °C for 2 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was greater than 99%, and the polymer number-average molecular weight Mn = 48.9 × 10⁻⁶. 3 Molecular weight distribution =1.4.

[0072] Example 48 This embodiment provides a reaction for the ring-opening polymerization of caprolactone catalyzed by rare earth metal complex D1, the steps of which are as follows: 10 μmol of rare earth metal complex D1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 5.35 mL of toluene was added as solvent, followed by 5000 μmol of caprolactone monomer. The reaction was carried out at 25 °C for 2 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was greater than 99%, and the number-average molecular weight of the polymer, Mn, was 154.5 × 10⁻⁶. 3 Molecular weight distribution =2.1.

[0073] Example 49 This embodiment provides a reaction for the ring-opening polymerization of caprolactone catalyzed by rare earth metal complex D2, the steps of which are as follows: 10 μmol of rare earth metal complex D2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 1.07 mL of toluene was added as a solvent, followed by 1000 μmol of caprolactone monomer. The reaction was carried out at 25 °C for 2 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was greater than 99%, and the polymer number-average molecular weight Mn = 55.3 × 10⁻⁶. 3 Molecular weight distribution =1.5.

[0074] Example 50 This embodiment provides a reaction for the ring-opening polymerization of caprolactone catalyzed by rare earth metal complex D2, the steps of which are as follows: 10 μmol of rare earth metal complex D2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 2.14 mL of toluene was added as solvent, followed by 2000 μmol of caprolactone monomer. The reaction was carried out at 25 °C for 2 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was greater than 99%, and the number-average molecular weight of the polymer was Mn = 81.5 × 10⁻⁶. 3 Molecular weight distribution =1.6.

[0075] Example 51 This embodiment provides a reaction for the ring-opening polymerization of caprolactone catalyzed by rare earth metal complex D2, the steps of which are as follows: 10 μmol of rare earth metal complex D2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 5.35 mL of toluene was added as solvent, followed by 5000 μmol of caprolactone monomer. The reaction was carried out at 25 °C for 2 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was greater than 99%, and the number-average molecular weight of the polymer, Mn, was 145.4 × 10⁻⁶. 3 Molecular weight distribution =1.7.

[0076] Example 52 This embodiment provides a reaction for the ring-opening polymerization of caprolactone catalyzed by rare earth metal complex D2, the steps of which are as follows: 10 μmol of rare earth metal complex D2 was weighed into a 100 mL reaction flask in an argon-atmosphere glove box. 10.7 mL of toluene was added as a solvent, followed by 10000 μmol of caprolactone monomer. The reaction was carried out at 25 °C for 2 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 92.9%, and the polymer number-average molecular weight Mn = 205.6 × 10⁻⁶. 3 Molecular weight distribution =1.8.

[0077] Example 53 This embodiment provides a reaction for the ring-opening polymerization of caprolactone catalyzed by rare earth metal complex E1, the steps of which are as follows: 10 μmol of rare earth metal complex E1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 1.07 mL of toluene was added as a solvent, followed by 1000 μmol of caprolactone monomer. The reaction was carried out at 25 °C for 5 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was greater than 99%, and the number-average molecular weight of the polymer was Mn = 44.5 × 10⁻⁶. 3 Molecular weight distribution =1.5.

[0078] Example 54 This embodiment provides a reaction for the ring-opening polymerization of caprolactone catalyzed by rare earth metal complex E1, the steps of which are as follows: 10 μmol of rare earth metal complex E1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 2.14 mL of toluene was added as solvent, followed by 2000 μmol of caprolactone monomer. The reaction was carried out at 25 °C for 5 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was greater than 99%, and the number-average molecular weight of the polymer was Mn = 76.4 × 10⁻⁶. 3 Molecular weight distribution =1.6.

[0079] Example 55 This embodiment provides a reaction for the ring-opening polymerization of caprolactone catalyzed by rare earth metal complex E2, the steps of which are as follows: 10 μmol of rare earth metal complex E2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 1.07 mL of toluene was added as a solvent, followed by 1000 μmol of caprolactone monomer. The reaction was carried out at 25 °C for 5 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was greater than 99%, and the number-average molecular weight of the polymer was Mn = 55.6 × 10⁻⁶. 3 Molecular weight distribution =1.5.

[0080] Example 56 This embodiment provides a reaction for the ring-opening polymerization of caprolactone catalyzed by rare earth metal complex E2, the steps of which are as follows: 10 μmol of rare earth metal complex E2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 2.14 mL of toluene was added as solvent, followed by 2000 μmol of caprolactone monomer. The reaction was carried out at 25 °C for 5 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was greater than 99%, and the number-average molecular weight of the polymer was Mn = 81.7 × 10⁻⁶. 3 Molecular weight distribution =1.6.

[0081] Example 57 This embodiment provides a reaction for the ring-opening polymerization of caprolactone catalyzed by rare earth metal complex A1, the steps of which are as follows: 10 μmol of rare earth metal complex A1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 1.07 mL of toluene was added as a solvent, followed by 1000 μmol of caprolactone monomer. The reaction was carried out at 25 °C for 1 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was greater than 99%, and the number-average molecular weight of the polymer was Mn = 23.7 × 10⁻⁶. 3 Molecular weight distribution =1.5.

[0082] Example 58 This embodiment provides a reaction for the ring-opening polymerization of caprolactone catalyzed by rare earth metal complex A1, the steps of which are as follows: 10 μmol of rare earth metal complex A1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 2.14 mL of toluene was added as solvent, followed by 2000 μmol of caprolactone monomer. The reaction was carried out at 25 °C for 1 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was greater than 99%, and the number-average molecular weight of the polymer was Mn = 37.6 × 10⁻⁶. 3 Molecular weight distribution =1.8.

[0083] Example 59 This embodiment provides a reaction for the ring-opening polymerization of caprolactone catalyzed by rare earth metal complex A1, the steps of which are as follows: 10 μmol of rare earth metal complex A1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 5.35 mL of toluene was added as solvent, followed by 5000 μmol of caprolactone monomer. The reaction was carried out at 25 °C for 1 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was greater than 99%, and the polymer number-average molecular weight Mn = 80.7 × 10⁻⁶. 3 Molecular weight distribution =1.7.

[0084] Example 60 This embodiment provides a reaction for the ring-opening polymerization of caprolactone catalyzed by rare earth metal complex A2, the steps of which are as follows: 10 μmol of rare earth metal complex A2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 1.07 mL of toluene was added as a solvent, followed by 1000 μmol of caprolactone monomer. The reaction was carried out at 25 °C for 1 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was greater than 99%, and the polymer number-average molecular weight Mn = 25.4 × 10⁻⁶. 3 Molecular weight distribution =1.4.

[0085] Example 61 This embodiment provides a reaction for the ring-opening polymerization of caprolactone catalyzed by rare earth metal complex A2, the steps of which are as follows: 10 μmol of rare earth metal complex A2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 2.14 mL of toluene was added as solvent, followed by 2000 μmol of caprolactone monomer. The reaction was carried out at 25 °C for 1 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was greater than 99%, and the polymer number-average molecular weight Mn = 33.3 × 10⁻⁶. 3 Molecular weight distribution =1.4.

[0086] Example 62 This embodiment provides a reaction for the ring-opening polymerization of caprolactone catalyzed by rare earth metal complex A2, the steps of which are as follows: 10 μmol of rare earth metal complex A2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 5.35 mL of toluene was added as solvent, followed by 5000 μmol of caprolactone monomer. The reaction was carried out at 25 °C for 1 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was greater than 99%, and the number-average molecular weight of the polymer was Mn = 74.5 × 10⁻⁶. 3 Molecular weight distribution =1.6.

[0087] Example 63 This embodiment provides a reaction for the ring-opening polymerization of caprolactone catalyzed by rare earth metal complex A2, the steps of which are as follows: 10 μmol of rare earth metal complex A2 was weighed into a 100 mL reaction flask in an argon-atmosphere glove box. 10.7 mL of toluene was added as a solvent, followed by 10000 μmol of caprolactone monomer. The reaction was carried out at 25 °C for 1 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was greater than 99%, and the number-average molecular weight of the polymer, Mn, was 163.7 × 10⁻⁶. 3 Molecular weight distribution =1.7.

[0088] Example 64 This embodiment provides a reaction for the ring-opening polymerization of caprolactone catalyzed by rare earth metal complex B1, the steps of which are as follows: 10 μmol of rare earth metal complex B1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 1.07 mL of toluene was added as a solvent, followed by 1000 μmol of caprolactone monomer. The reaction was carried out at 25 °C for 1 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was greater than 99%, and the polymer number-average molecular weight Mn = 23.7 × 10⁻⁶. 3 Molecular weight distribution =1.4.

[0089] Example 65 This embodiment provides a reaction for the ring-opening polymerization of caprolactone catalyzed by rare earth metal complex B1, the steps of which are as follows: 10 μmol of rare earth metal complex B1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 2.14 mL of toluene was added as solvent, followed by 2000 μmol of caprolactone monomer. The reaction was carried out at 25 °C for 1 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was greater than 99%, and the number-average molecular weight of the polymer was Mn = 31.8 × 10⁻⁶. 3 Molecular weight distribution =1.3.

[0090] Example 66 This embodiment provides a reaction for the ring-opening polymerization of caprolactone catalyzed by rare earth metal complex B1, the steps of which are as follows: 10 μmol of rare earth metal complex B1 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 5.35 mL of toluene was added as solvent, followed by 5000 μmol of caprolactone monomer. The reaction was carried out at 25 °C for 1 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was greater than 99%, and the number-average molecular weight of the polymer was Mn = 79.3 × 10⁻⁶. 3 Molecular weight distribution =1.8.

[0091] Example 67 This embodiment provides a reaction for the ring-opening polymerization of caprolactone catalyzed by rare earth metal complex B2, the steps of which are as follows: 10 μmol of rare earth metal complex B2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 1.07 mL of toluene was added as a solvent, followed by 1000 μmol of caprolactone monomer. The reaction was carried out at 25 °C for 1 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was greater than 99%, and the number-average molecular weight of the polymer was Mn = 25.7 × 10⁻⁶. 3 Molecular weight distribution =1.4.

[0092] Example 68 This embodiment provides a reaction for the ring-opening polymerization of caprolactone catalyzed by rare earth metal complex B2, the steps of which are as follows: 10 μmol of rare earth metal complex B2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 2.14 mL of toluene was added as solvent, followed by 2000 μmol of caprolactone monomer. The reaction was carried out at 25 °C for 1 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was greater than 99%, and the number-average molecular weight of the polymer was Mn = 33.9 × 10⁻⁶. 3 Molecular weight distribution =1.4.

[0093] Example 69 This embodiment provides a reaction for the ring-opening polymerization of caprolactone catalyzed by rare earth metal complex B2, the steps of which are as follows: 10 μmol of rare earth metal complex B2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 5.35 mL of toluene was added as solvent, followed by 5000 μmol of caprolactone monomer. The reaction was carried out at 25 °C for 1 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was greater than 99%, and the number-average molecular weight of the polymer was Mn = 74.8 × 10⁻⁶. 3 Molecular weight distribution =1.6.

[0094] Examples 40-69 are summarized in Table 4 below.

[0095] Table 4

[0096] Example 70 This embodiment provides a reaction for the ring-opening polymerization of rac-lactide catalyzed by rare earth metal complex A2, and the steps are as follows: 10 μmol of rare earth metal complex A2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 1 mL of tetrahydrofuran was added as a solvent, followed by 1000 μmol of rac-lactide monomer. The reaction was carried out at 25 °C for 5 min, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 99.0%, and the number-average molecular weight of the polymer was Mn = 30.2 × 10⁻⁶. 3 Molecular weight distribution =1.32.

[0097] Example 71 This embodiment provides a reaction for the ring-opening polymerization of rac-lactide catalyzed by rare earth metal complex A2, and the steps are as follows: 10 μmol of rare earth metal complex A2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 2 mL of tetrahydrofuran was added as a solvent, followed by 2000 μmol of rac-lactide monomer. The reaction was carried out at 25 °C for 60 min, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 95.7%, and the number-average molecular weight of the polymer was Mn = 53.0 × 10⁻⁶. 3 Molecular weight distribution =1.56.

[0098] Example 72 This embodiment provides a reaction for the ring-opening polymerization of rac-lactide catalyzed by rare earth metal complex A2, and the steps are as follows: 10 μmol of rare earth metal complex A2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 5 mL of tetrahydrofuran was added as a solvent, followed by 5000 μmol of rac-lactide monomer. The reaction was carried out at 25 °C for 180 min, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 96.0%, and the number-average molecular weight of the polymer was Mn = 77.5 × 10⁻⁶. 3 Molecular weight distribution =1.65.

[0099] Example 73 This embodiment provides a reaction for the ring-opening polymerization of rac-lactide catalyzed by rare earth metal complex A2, and the steps are as follows: 10 μmol of rare earth metal complex A2 was weighed into a 100 mL reaction flask in an argon-atmosphere glove box. 10 mL of tetrahydrofuran was added as a solvent, followed by 10000 μmol of rac-lactide monomer. The reaction was carried out at 25 °C for 180 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 91.5%, and the number-average molecular weight of the polymer, Mn, was 121.0 × 10⁻⁶. 3 Molecular weight distribution =1.84.

[0100] Example 74 This embodiment provides a reaction for the ring-opening polymerization of rac-lactide catalyzed by rare earth metal complex D2, and the steps are as follows: 10 μmol of rare earth metal complex D2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 1 mL of tetrahydrofuran was added as a solvent, followed by 1000 μmol of rac-lactide monomer. The reaction was carried out at 25 °C for 60 min, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 98.0%, and the number-average molecular weight of the polymer was Mn = 33.6 × 10⁻⁶. 3 Molecular weight distribution =1.96.

[0101] Example 75 This embodiment provides a reaction for the ring-opening polymerization of rac-lactide catalyzed by rare earth metal complex D2, and the steps are as follows: 10 μmol of rare earth metal complex D2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 2 mL of tetrahydrofuran was added as a solvent, followed by 2000 μmol of rac-lactide monomer. The reaction was carried out at 25 °C for 60 min, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 96.5%, and the number-average molecular weight of the polymer, Mn, was 51.8 × 10⁻⁶. 3 Molecular weight distribution =1.81.

[0102] Example 76 This embodiment provides a reaction for the ring-opening polymerization of rac-lactide catalyzed by rare earth metal complex D2, and the steps are as follows: 10 μmol of rare earth metal complex D2 was weighed into a 25 mL reaction flask in an argon-atmosphere glove box. 5 mL of tetrahydrofuran was added as a solvent, followed by 5000 μmol of rac-lactide monomer. The reaction was carried out at 25 °C for 300 min, and then 5 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 99.0%, and the number-average molecular weight of the polymer was Mn = 75.5 × 10⁻⁶. 3 Molecular weight distribution =1.97.

[0103] Example 77 This embodiment provides a reaction for the ring-opening polymerization of rac-lactide catalyzed by rare earth metal complex D2, and the steps are as follows: 10 μmol of rare earth metal complex D2 was weighed into a 100 mL reaction flask in an argon-atmosphere glove box. 10 mL of tetrahydrofuran was added as a solvent, followed by 10000 μmol of rac-lactide monomer. The reaction was carried out at 25 °C for 300 min, and then 10 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 96.0%, and the number-average molecular weight of the polymer was Mn = 87.4 × 10⁻⁶. 3 Molecular weight distribution =2.42.

[0104] Example 78 This embodiment provides a reaction for the ring-opening polymerization of rac-lactide catalyzed by rare earth metal complex D2, and the steps are as follows: 10 μmol of rare earth metal complex D2 was weighed into a 100 mL reaction flask in an argon-atmosphere glove box. 20 mL of tetrahydrofuran was added as a solvent, followed by 20000 μmol of rac-lactide monomer. The reaction was carried out at 25 °C for 600 min, and then 15 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 91.3%, and the polymer number-average molecular weight Mn = 98.7 × 10⁻⁶. 3 Molecular weight distribution =2.63.

[0105] Example 79 This embodiment provides a reaction for the ring-opening polymerization of lactide catalyzed by the rare earth metal complex B2rac, and the steps are as follows: 10 μmol of rare earth metal complex B2 was weighed into a 100 mL reaction flask in an argon-atmosphere glove box. 20 mL of tetrahydrofuran was added as a solvent, followed by 1000 μmol of rac-lactide monomer. The reaction was carried out at 25 °C for 210 min, and then 15 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 91.7%, and the number-average molecular weight of the polymer, Mn, was 21.9 × 10⁻⁶. 3 Molecular weight distribution =1.55.

[0106] Example 80 This embodiment provides a reaction for the ring-opening polymerization of rac-lactide catalyzed by rare earth metal complex B2, and the steps are as follows: 10 μmol of rare earth metal complex B2 was weighed into a 100 mL reaction flask in an argon-atmosphere glove box. 20 mL of tetrahydrofuran was added as a solvent, followed by 5000 μmol of rac-lactide monomer. The reaction was carried out at 25 °C for 240 min, and then 15 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 94.0%, and the number-average molecular weight of the polymer, Mn, was 65.9 × 10⁻⁶. 3 Molecular weight distribution =1.56.

[0107] Example 81 This embodiment provides a reaction for the ring-opening polymerization of rac-lactide catalyzed by rare earth metal complex B2, and the steps are as follows: 10 μmol of rare earth metal complex B2 was weighed into a 100 mL reaction flask in an argon-atmosphere glove box. 20 mL of tetrahydrofuran was added as a solvent, followed by 10000 μmol of rac-lactide monomer. The reaction was carried out at 25 °C for 240 min, and then 15 mL of n-hexane was added to terminate the reaction. The solid powder was dried to constant weight. The polymerization yield was 92.2%, and the number-average molecular weight of the polymer, Mn, was 91.5 × 10⁻⁶. 3 Molecular weight distribution =1.67.

[0108] Examples 70-81 are summarized as shown in Table 5 below.

[0109] Table 5

[0110] Examples 1-81 show that the neutral indole rare earth metal complex of the present invention has high activity and high conversion rate for the ring-opening polymerization of rac-lactide, β-butyrolactone, δ-valerolactone and caprolactone under mild conditions, and can obtain polymers with high molecular weight and low molecular weight distribution.

[0111] Although preferred embodiments of the invention have been shown and described, it is conceivable that those skilled in the art can devise various modifications to the invention within the spirit and scope of the appended claims.

Claims

1. A method for ring-opening polymerization of lactones catalyzed by indole rare earth metal complexes, characterized in that, Includes the following steps: In an inert atmosphere, indole rare earth metal complexes, lactone monomers, and solvents are mixed and polymerized.

2. The method for ring-opening polymerization of lactones catalyzed by indole-based rare earth metal complexes according to claim 1, characterized in that, The indole rare earth metal complex includes at least one of the following complexes A1 to E2: Complex A1, Complex A2, Complex B1, Complex B2, Complex C1, Complex C2, Complex D1, Complex D2, Complex E1, Complex E2.

3. The method for ring-opening polymerization of lactones catalyzed by indole rare earth metal complexes according to claim 1, characterized in that, The mixing process also includes the addition of a co-catalyst; The co-catalyst includes benzyl alcohol.

4. The method for ring-opening polymerization of lactones catalyzed by indole rare earth metal complexes according to claim 1, characterized in that, The molar ratio of the co-catalyst to the indole rare earth metal complex is 1:(1~2).

5. The method for ring-opening polymerization of lactones catalyzed by indole rare earth metal complexes according to claim 1, characterized in that, The lactone monomers include rac-lactide, β-butyrolactone, δ-valerolactone, or caprolactone.

6. The method for ring-opening polymerization of lactones catalyzed by indole rare earth metal complexes according to claim 1, characterized in that, The solvent includes at least one of tetrahydrofuran, chlorobenzene, and toluene.

7. The method for ring-opening polymerization of lactones catalyzed by indole rare earth metal complexes according to claim 1, characterized in that, The molar ratio of the lactone monomer to the indole rare earth metal complex is 50:1 to 2000:

1.

8. The method for ring-opening polymerization of lactones catalyzed by indole rare earth metal complexes according to claim 1, characterized in that, The polymerization reaction is carried out at a temperature of 0~80℃ and for a time of 1~1500 min.

9. The method for ring-opening polymerization of lactones catalyzed by indole rare earth metal complexes according to claim 1, characterized in that, After the polymerization reaction is completed, the process further includes: adding n-hexane to terminate the reaction, and then drying the resulting product to constant weight.

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