Method for preparing multifunctional CO2-based copolymer through ester exchange

Abstract

The invention discloses a method for preparing a multifunctional CO2-based copolymer through a transesterification method. According to the invention, alpha-ethylidene-delta-vinyl-delta-valerolactone is inserted into polyester or polycarbonate by using a binary catalytic system consisting of a main catalyst strong base and a cocatalyst urea or thiourea, so that the multifunctional polyester or polycarbonate copolymer is obtained. The method provided by the invention has the following beneficial effects: 1) EVP is derived from butadiene and CO2 and has good atom economy; 2) the ester exchange system has relatively high reaction activity and selectivity and can be efficiently inserted into a polymer main chain under a mild condition, and meanwhile, the catalyst has good tolerance to the environment and can react in the air; and 3) the polymer substrate is wide in application range, the commercial polymer can be directly utilized for ester exchange modification, and the application field is further expanded.

Description

Technical Field

[0001] The present invention relates to the fields of polymer materials and chemistry and chemical engineering, and in particular to a method for preparing a multifunctional CO2-based copolymer through ester exchange. Background Art

[0002] Aliphatic polyesters or polycarbonates are important polymer materials, widely used in healthcare, packaging, and other fields due to their excellent biodegradability and compatibility. However, the characteristics of these common polymer chain structures make it difficult to modify them through functionalization to enhance their performance. To impart specialized properties to polyester materials, reactive functional groups can be introduced into the polymer chain through copolymerization with other monomers.

[0003] Carbon dioxide (CO2) is abundant, non-toxic, and inexpensive, making it one of the most attractive C1 renewable resources. Converting CO2 with inexpensive petrochemical raw materials, olefins, into high-value-added polymers has significant economic benefits and important practical significance. Among them, α-ethylidene-δ-vinyl-δ-valerolactone (EVP), synthesized by the polymerization of CO2 and 1,3-butadiene, is a multi-double-bond substituted δ-valerolactone. Multifunctional aliphatic biodegradable polyesters can be prepared through ring-opening polymerization and further functionalized through post-modification. However, due to the inherent low ring tension and highly reactive double bonds of EVP, the ring-opening polymerization process faces two major challenges: first, insufficient thermodynamic driving force leading to difficulty in ring opening, and second, the reactive double bonds are prone to side reactions. In response to this scientific problem, the latest research has made an important breakthrough: in 2024, the literature reported that the selective ring-opening polymerization of EVP at low temperature was achieved for the first time using an alkali / urea catalytic system (Nat. Commun. 2024, 15, 8698; CN202410430657.5), and a linear unsaturated polyester material with EVP as a monomer was prepared. Based on this research, the copolymerization strategy is an effective way to regulate EVP polymerization - by introducing a second monomer, not only can the ring-opening energy barrier be reduced, but the sequence structure of the copolymer can also be precisely controlled. Research in 2025 further confirmed that EVP and caprolactone can be gradient copolymerized at room temperature to obtain copolyesters with adjustable EVP insertion rate (0-60 mol%) and thermal properties (Macromolecules 2025, 58, 3497-3508; CN202410430725.8).

[0004] The ester exchange strategy is both cost-effective and has industrial potential - it utilizes commercially available polyesters and practical melt modification technology, and its operation is similar to the traditional ester exchange process used for polymer blending and compatibilization, introduction of new functional units and construction of polymer networks. Based on this, the present invention proposes a method for preparing copolymers containing two double bond functional groups in the side chain by selective ring-opening copolymerization of EVP and other polymers through ester exchange reaction. The method of the present invention has the following advantages: 1) EVP is derived from butadiene and CO2, and has good atom economy; 2) The ester exchange system has high reactivity and selectivity, and can achieve efficient insertion into the polymer backbone under mild conditions. At the same time, the catalyst has good tolerance to the environment and can react in air; 3) The polymer substrate has a wide range of applications, and commercial polymers can be directly used for ester exchange modification, further expanding its application field. Summary of the Invention

[0005] The object of the present invention is to provide a CO2-based copolymer having two modifiable functional groups in its side chain and a preparation method thereof, comprising the following steps:

[0006] (1) Dissolve the catalyst and polymer in an organic solvent and stir for 2 minutes;

[0007] (2) adding EVP monomer to the above mixed solution and reacting at a certain temperature for a period of time;

[0008] (3) Add an acidic substance to terminate the reaction, add the reaction mixture into methanol for sedimentation, centrifuge, and dry to obtain a copolymer.

[0009] In the above preparation method, the chemical structure of the CO2-based copolymer is shown in formula (I), (II), and (III):

[0010]

[0011] The feature is that x is a natural number greater than or equal to 1, and n and m are natural numbers greater than or equal to 5.

[0012] According to an embodiment of the present invention, the CO2-based copolymer has a structure shown in Formula (IV-IX):

[0013]

[0014] The feature is that n and m are natural numbers greater than or equal to 5.

[0015] In the above preparation method, the catalyst in step (1) includes a main catalyst and a co-catalyst, wherein the main catalyst can be an alkali metal compound (such as potassium hydride, sodium hydride, potassium methoxide, sodium methoxide) or an organic base catalyst (including DBU, TBD, hexachlorocyclotriphosphazene base CTPB, tert-butyl substituted phosphazene ligands t-BuP4 and t-BuP2); the co-catalyst is urea or thiourea.

[0016] In the above preparation method, the urea or thiourea has one of the following structures:

[0017]

[0018] In the above preparation method, the molar ratio of the main catalyst to the co-catalyst is 1 / 0.2 to 1 / 8; the mass ratio of the EVP to the polymer is 1 / 9 to 9 / 1; and the amount of the catalyst used is 0.1% to 10% of the total mass of the EVP and the polymer.

[0019] In the above preparation method, the polymer is polyester or polycarbonate, specifically one of polyβ-butyrolactone, polyγ-butyrolactone, polyvalerolactone, polycaprolactone, polylactic acid, and polytrimethylene carbonate.

[0020] In the above preparation method, the organic solvent in step (1) is selected from at least one of toluene, tetrahydrofuran, dichloromethane, and chloroform; the certain temperature in step (2) is -20 to 90°C; the reaction time is 0.5 to 24 hours; and the acidic substance in step (3) is at least one of acetic acid, benzoic acid, or hydrochloric acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The copolymer Poly (TMC-co-EVP) obtained in Example 1 1 HNMR spectrum.

[0022] Figure 2 The copolymer Poly (TMC-co-EVP) obtained in Example 1 13 C NMR spectrum.

[0023] Figure 3 This is the GPC chart of the copolymer Poly(TMC-co-EVP) obtained in Example 2.

[0024] Figure 4 This is the two-dimensional NMR DOSY spectrum of the copolymer Poly(TMC-co-EVP) obtained in Example 1.

[0025] Figure 5 This is the MALDI-TOF of the copolymer Poly(TMC-co-EVP) obtained in Example 1.

[0026] Figure 6 The copolymer Poly(LA-co-EVP) obtained in Example 9 1 HNMR spectrum.

[0027] Figure 7 The copolymer Poly(LA-co-EVP) obtained in Example 9 13 C NMR spectrum.

[0028] Figure 8 This is the GPC chart of the copolymer Poly(LA-co-EVP) obtained in Example 10. DETAILED DESCRIPTION

[0029] The present invention is described in detail with reference to the following embodiments, but the present invention is not limited to these embodiments.

[0030] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0031] Example 1

[0032] 102mg of polytrimethylene carbonate was dissolved in 0.37mL of tetrahydrofuran and stirred at room temperature for 30min. (0.02mmol, 24mg) CTPB and (0.02mmol, 12mg) 3,5-bis(trifluoromethylphenyl)diurea were added to the reaction tube and stirred for 10min. (1mmol, 0.13mL) α-ethylene-δ-vinyl-δ-valerolactone was added to the reaction tube with a syringe. The reaction was carried out under nitrogen protection for 4h, and 2 drops of acetic acid were added to terminate the reaction. The reaction mixture was poured into 10mL of methanol and centrifuged and precipitated to obtain the copolymer Poly(TMC-co-EVP). GPC measured the number average molecular weight to be 6.2kg / mol, and the molecular weight distribution was 1.39. 1 H NMR spectrum Figure 1 As shown, 13 C NMR spectrum Figure 2 As shown, the DOSY spectrum is as follows Figure 4 As shown, the MALDI-TOF spectrum is as follows Figure 5 shown.

[0033] Example 2

[0034] 102 mg of polytrimethylene carbonate was dissolved in 0.37 mL of tetrahydrofuran and stirred at 50 ° C for 30 minutes. (0.02 mmol, 24 mg) CTPB and (0.02 mmol, 12 mg) 3,5-bis(trifluoromethyl)phenyl diurea were added to the reaction tube and stirred for 10 minutes. (1 mmol, 0.13 mL) α-ethylene-δ-vinyl-δ-valerolactone was added to the reaction tube with a syringe. The reaction was carried out under nitrogen protection for 8 hours, and 2 drops of acetic acid were added to terminate the reaction. The reaction mixture was poured into 10 mL of methanol and centrifuged to precipitate to obtain the copolymer Poly (TMC-co-EVP). GPC measured the number average molecular weight to be 4.6 kg / mol, the molecular weight distribution to be 1.89, and the GPC spectrum was as shown below. Figure 3 shown.

[0035] Example 3.

[0036] 102 mg of polytrimethylene carbonate was dissolved in 0.37 mL of tetrahydrofuran and stirred at 50°C for 30 minutes. (0.02 mmol, 24 mg) of CTPB and (0.04 mmol, 14 mg) of 1-cyclohexyl-3-(3,5-bis(trifluoromethyl)phenyl)urea were added to a reaction tube and stirred for 10 minutes. (1 mmol, 0.13 mL) of α-ethylidene-δ-vinyl-δ-valerolactone was added to the reaction tube via syringe. The reaction was allowed to proceed under nitrogen for 8 hours and terminated by the addition of 2 drops of acetic acid. The reaction mixture was poured into 10 mL of methanol and centrifuged to precipitate the copolymer. GPC analysis revealed a number average molecular weight of 5.2 kg / mol and a molecular weight distribution of 1.56.

[0037] Example 4.

[0038] 102 mg of polytrimethylene carbonate was dissolved in 0.37 mL of tetrahydrofuran and stirred at room temperature for 30 minutes. (0.02 mmol, 24 mg) of CTPB and (0.04 mmol, 14 mg) of 1-phenyl-3-(3,5-bis(trifluoromethyl)phenyl)urea were added to a reaction tube and stirred for 10 minutes. (1 mmol, 0.13 mL) of α-ethylidene-δ-vinyl-δ-valerolactone was added to the reaction tube via syringe. The reaction was allowed to proceed under nitrogen for 5 hours and terminated by adding 2 drops of acetic acid. The reaction mixture was poured into 10 mL of methanol and centrifuged to precipitate the copolymer. GPC analysis revealed a number average molecular weight of 8.4 kg / mol and a molecular weight distribution of 1.43.

[0039] Example 5

[0040] 102 mg of polytrimethylene carbonate was dissolved in 0.37 mL of tetrahydrofuran and stirred at -10°C for 30 minutes. (0.02 mmol, 12.7 mg) of the phosphazene ligand P4-tert-butyl catalyst t-BuP4 and (0.02 mmol, 12 mg) of 3,5-bis(trifluoromethylphenyl)diurea were added to the reaction tube and stirred for 10 minutes. (1 mmol, 0.13 mL) of α-ethylidene-δ-vinyl-δ-valerolactone was added to the reaction tube via syringe. The reaction was allowed to proceed under nitrogen for 4 hours and terminated by the addition of 2 drops of acetic acid. The reaction mixture was poured into 10 mL of methanol and centrifuged to precipitate the copolymer. GPC analysis revealed a number average molecular weight of 6.2 kg / mol and a molecular weight distribution of 1.33.

[0041] Example 6

[0042] 102 mg of polytrimethylene carbonate was dissolved in 0.87 mL of tetrahydrofuran and stirred at -20°C for 30 minutes. (0.02 mmol, 8 mg) of the phosphazene ligand P2-tert-butyl catalyst t-BuP2 and (0.02 mmol, 12 mg) of 3,5-bis(trifluoromethylphenyl)diurea were added to the reaction tube and stirred for 10 minutes. (1 mmol, 0.13 mL) of α-ethylidene-δ-vinyl-δ-valerolactone was added to the reaction tube via syringe. The reaction was allowed to proceed under nitrogen for 4 hours and terminated by the addition of 2 drops of acetic acid. The reaction mixture was poured into 10 mL of methanol and centrifuged to precipitate the copolymer. GPC analysis revealed a number average molecular weight of 5.7 kg / mol and a molecular weight distribution of 1.47.

[0043] Example 7

[0044] 144 mg of polylactic acid was dissolved in 0.37 mL of tetrahydrofuran and stirred at 40 ° C for 30 min. (0.10 mmol, 119.8 mg) of CTPB and (0.20 mmol, 57.3 mg) of 1-cyclohexyl-3-(4-trifluoromethylphenyl) urea were added to the reaction tube and stirred for 10 min. (1 mmol, 0.13 mL) of α-ethylidene-δ-vinyl-δ-valerolactone was added to the reaction tube with a syringe. The reaction was carried out under nitrogen protection for 6 hours, and 2 drops of acetic acid were added to terminate the reaction. The reaction mixture was poured into 10 mL of methanol and centrifuged and precipitated to obtain the copolymer Poly (LA-co-EVP). GPC measured the number average molecular weight to be 17.6 kg / mol, and the molecular weight distribution was 1.19. 1 HNMR spectrum Figure 6 As shown, 13 C NMR spectrum Figure 7 As shown, the GPC spectrum is as follows Figure 8 shown.

[0045] Example 8

[0046] 144 mg of polylactic acid was dissolved in 0.37 mL of tetrahydrofuran and stirred at 25°C for 30 min. (0.02 mmol, 1.4 mg) of potassium methoxide and (0.04 mmol, 24 mg) of 3,5-bis(trifluoromethylphenyl)diurea were added to the reaction tube and stirred for 10 min. (1 mmol, 0.13 mL) of α-ethylidene-δ-vinyl-δ-valerolactone was added to the reaction tube using a syringe. The reaction was carried out under nitrogen for 6 h and terminated by adding 2 drops of acetic acid. The reaction mixture was poured into 10 mL of methanol and centrifuged to precipitate the copolymer Poly(LA-co-EVP). GPC measured the number average molecular weight to be 14.8 kg / mol and the molecular weight distribution to be 1.24.

[0047] Example 9

[0048] 144 mg of polylactic acid was dissolved in 0.37 mL of tetrahydrofuran and stirred at -30°C for 30 min. (0.02 mmol, 1.4 mg) of potassium methoxide and (0.04 mmol, 24 mg) of 3,5-bis(trifluoromethylphenyl)diurea were added to the reaction tube and stirred for 10 min. (1 mmol, 0.13 mL) of α-ethylidene-δ-vinyl-δ-valerolactone was added to the reaction tube using a syringe. The reaction was carried out under nitrogen for 8 h and terminated by adding 2 drops of acetic acid. The reaction mixture was poured into 10 mL of methanol and centrifuged to precipitate to obtain the copolymer Poly(LA-co-EVP). GPC measured the number average molecular weight to be 15.1 kg / mol and the molecular weight distribution to be 1.17.

[0049] Example 10

[0050] 144 mg of polylactic acid was dissolved in 0.37 mL of tetrahydrofuran and stirred at 25°C for 30 minutes. (0.02 mmol, 24 mg) of CTPB and (0.04 mmol, 14 mg) of 1-phenyl-3-(3,5-bis(trifluoromethyl)phenyl)urea were added to a reaction tube and stirred for 10 minutes. (1 mmol, 0.13 mL) of α-ethylidene-δ-vinyl-δ-valerolactone was added to the reaction tube via syringe. The reaction was carried out under nitrogen for 2 hours and terminated by adding 2 drops of acetic acid. The reaction mixture was poured into 10 mL of methanol and centrifuged to precipitate the copolymer Poly(LA-co-EVP). GPC analysis revealed a number average molecular weight of 9.7 kg / mol and a molecular weight distribution of 1.01.

[0051] Example 11

[0052] 144 mg of polylactic acid was dissolved in 0.37 mL of tetrahydrofuran and stirred at 25°C for 30 minutes. (0.02 mmol, 24 mg) of CTPB and (0.04 mmol, 19.36 mg) of 1-(3,5-bis(trifluoromethyl)phenyl)-3-(3,5-bis(trifluoromethyl)phenyl)urea were added to a reaction tube and stirred for 10 minutes. (1 mmol, 0.13 mL) of α-ethylidene-δ-vinyl-δ-valerolactone was added to the reaction tube via syringe. The reaction was carried out under nitrogen for 4 hours and terminated by adding 2 drops of acetic acid. The reaction mixture was poured into 10 mL of methanol and centrifuged to precipitate the copolymer, Poly(LA-co-EVP). GPC analysis revealed a number average molecular weight of 10.9 kg / mol and a molecular weight distribution of 1.23.

[0053] Example 12

[0054] 114 mg of polycaprolactone was dissolved in 0.37 mL of tetrahydrofuran and stirred at 25°C for 30 min. (0.02 mmol, 24 mg) of CTPB and (0.04 mmol, 19.36 mg) of 1-(3,5-bis(trifluoromethyl)phenyl)-3-(3,5-bis(trifluoromethyl)phenyl)urea were added to a reaction tube and stirred for 10 min. (1 mmol, 0.13 mL) of α-ethylidene-δ-vinyl-δ-valerolactone was added to the reaction tube via syringe. The reaction was carried out under nitrogen for 2 h and terminated by adding 2 drops of acetic acid. The reaction mixture was poured into 10 mL of methanol and centrifuged to precipitate the copolymer, Poly(CL-co-EVP). GPC analysis revealed a number average molecular weight of 12.7 kg / mol and a molecular weight distribution of 1.14.

[0055] Example 13

[0056] 102 mg of polyvalerolactone was dissolved in 0.37 mL of tetrahydrofuran and stirred at -30°C for 30 min. (0.02 mmol, 24 mg) of CTPB and (0.04 mmol, 24 mg) of 3,5-bis(trifluoromethylphenyl)diurea were added to a reaction tube and stirred for 10 min. (1 mmol, 0.13 mL) of α-ethylidene-δ-vinyl-δ-valerolactone was added to the reaction tube via syringe. The reaction was carried out under nitrogen for 4 h and terminated by adding 2 drops of acetic acid. The reaction mixture was poured into 10 mL of methanol and centrifuged to precipitate the copolymer Poly(VL-co-EVP). GPC analysis revealed a number average molecular weight of 5.1 kg / mol and a molecular weight distribution of 1.42.

[0057] Example 14

[0058] 86 mg of polybutyrolactone was dissolved in 0.37 mL of tetrahydrofuran and stirred at -30°C for 30 min. (0.02 mmol, 24 mg) of CTPB and (0.04 mmol, 24 mg) of 3,5-bis(trifluoromethylphenyl)diurea were added to a reaction tube and stirred for 10 min. (1 mmol, 0.13 mL) of α-ethylene-δ-vinyl-δ-valerolactone was added to the reaction tube via syringe. The reaction was carried out under nitrogen for 4 h and terminated by adding 2 drops of acetic acid. The reaction mixture was poured into 10 mL of methanol and centrifuged to precipitate the copolymer Poly(BL-co-EVP). GPC analysis revealed a number average molecular weight of 5.3 kg / mol and a molecular weight distribution of 1.37.

Claims

1. A CO2-based copolymer having two modifiable functional groups in its side chain is prepared by an ester exchange method and a preparation method thereof, characterized in that: The steps include: (1) Dissolve the catalyst and polymer in an organic solvent and stir for 2 minutes; (2) adding EVP monomer to the above mixed solution and reacting at a temperature of -20 to 90°C for 0.5 to 24 hours; (3) adding an acidic substance to terminate the reaction, adding the reaction mixture to methanol for sedimentation, centrifuging, and drying to obtain a copolymer; The chemical structure of the CO2-based copolymer is shown in formula (I), (II), and (III): x is a natural number greater than or equal to 1, and n and m are natural numbers greater than or equal to 5.

2. The CO2-based copolymer according to claim 1, characterized in that The CO2-based copolymer structural formula is one of the following: n and m are natural numbers greater than or equal to 5.

3. The preparation method according to claim 1, characterized in that The catalyst in step (1) includes a main catalyst and a co-catalyst, wherein the main catalyst can be an alkali metal compound (such as potassium hydride, sodium hydride, potassium methoxide, sodium methoxide) or an organic base catalyst (including DBU, TBD, hexachlorocyclotriphosphazene base CTPB, tert-butyl substituted phosphazene ligands t-BuP4 and t-BuP2); the co-catalyst is urea or thiourea.

4. The promoter according to claim 3, characterized in that The structural formula of the urea or thiourea is one of the following:

5. The catalyst according to claim 3, characterized in that The dosage of the catalyst is 0.1%-10% of the total mass of EVP and polymer, and the molar ratio of the main catalyst to the co-catalyst is 1 / 0.2-1 / 8.

6. The preparation method according to claim 1, characterized in that The polymer is polyester or polycarbonate, specifically one of polyβ-butyrolactone, polyγ-butyrolactone, polyvalerolactone, polycaprolactone, polylactic acid, and polytrimethylene carbonate; the organic solvent is selected from at least one of toluene, tetrahydrofuran, dichloromethane, and chloroform; and the acidic substance is at least one of acetic acid, benzoic acid, or hydrochloric acid.

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