Novel bio-based closed-loop recyclable thermoplastic elastomer and preparation method thereof

Abstract

The invention provides a novel closed-loop recyclable thermoplastic elastomer (TPE) and a preparation method thereof. The method provided by the invention has the following beneficial effects: 1) the used raw materials are non-toxic and harmless and are biomass-sourced, and the prepared triblock copolymer or star-shaped multi-arm block copolymer can be completely degraded under natural conditions; 2) the prepared TPE can be completely depolymerized and recycled to obtain a monomer under a mild condition, and the TPE with the same property as the original material can be obtained by re-polymerizing the monomer, so that closed circulation is realized; (3) the used catalytic system is high in catalytic activity and high in monomer conversion rate; and 4) the prepared TPE material has good mechanical properties.

Description

Technical Field

[0001] The present invention relates to the fields of polymer materials and chemical engineering, and in particular to a novel bio-based closed-loop recyclable thermoplastic elastomer and a preparation method thereof. Background Art

[0002] Thermoplastic elastomers (TPEs) combine the elasticity of cross-linked rubbers with the thermal processing capabilities of thermoplastics. TPEs have been widely used in coatings, automotive parts, footwear, medical devices, and pressure-sensitive adhesives. The most widely used commercial TPEs are styrenic block copolymers, such as polystyrene-b-polybutadiene-b-polystyrene (SBS) and polystyrene-b-polyisoprene-b-polystyrene (SIS). Despite their low cost and good performance, these styrenic TPEs have the major disadvantage of being derived from limited fossil resources. In addition, due to their stable carbon-carbon backbone structure, these materials are not naturally degradable at the end of their service life, which can lead to environmental pollution. With increasing concerns about the depletion of limited petroleum resources and the environmental impact of mass production and improper disposal of petroleum-based polymers, the development of sustainable, biomass-derived TPEs has great application prospects.

[0003] Preparation of ABA triblock copolymers or (AB) by ring-opening polymerization (ROP) of cyclic lactones and lactide xStar-shaped multi-arm block copolymers have become a research hotspot for the development of new biodegradable TPEs (Accounts of Chemical Research 2014, 47(8), 2390-2396; Accounts of Chemical Research 2017, 50(7), 1762-1773). For example, Hillmyer and his team developed a series of biodegradable aliphatic polyester TPEs, in which polylactic acid (PLA) is usually used as the hard segment (Biomacromolecules 2007, 8(11), 3634-3640; Biomacromolecules 2009, 10(10), 2904-2911; Macromolecules 2011, 44(1), 87-94). Although the above TPEs can be reused multiple times through physical recycling, chain breakage and oxidation during thermal reprocessing may lead to performance degradation, causing the material to eventually enter the "end of life" stage. Therefore, achieving chemical recycling of TPEs at this stage can not only recover the value of the materials, but also prevent them from entering the environment in the form of waste after degradation. The development of closed-loop recyclable polymers has become the research frontier of next-generation polymers. Such polymers can recover the original monomers through controllable depolymerization at the end of their service life, thereby establishing a closed-loop life cycle and theoretically achieving unlimited chemical recycling. Current research mainly focuses on the preparation of closed-loop recyclable homopolymers by designing new monomers, while research on chemically recyclable TPEs is relatively small. For example, our research group reported the chemical recycling of TPEs based on polylactic acid-b-poly(δ-caprolactone)-b-polylactic acid, which can recover δ-caprolactone and ethyl acetate with high yield and high purity (Angewandte Chemie International Edition. 2022, 61(16), e202201407). Recently, a method based on PδVL-b-Pα R Preparation and chemical recovery of TPE of VL-b-PδVL, and successful recovery of δ-valerolactone (δVL) and α-alkyl-substituted δ-valerolactone (α RVL)(Nature Communications 2024, 15(1), 7904). Despite the above examples, there is still an urgent need to further explore high-performance chemically recyclable TPEs, especially those TPE materials that can be mass-produced using low-cost, readily available monomers. β-Methyl-δ-valerolactone is a biorenewable six-membered ring lactone monomer that can be efficiently synthesized through glucose fermentation or from the intermediate fermentation product 3-methyl-1,5-pentanediol by dehydrogenation reaction. The estimated cost is less than $2 per kilogram, making it very suitable for bulk applications. Poly(β-methyl-δ-valerolactone) has a low glass transition temperature and is rubbery at room temperature, and can be used as a soft segment of thermoplastic elastomers. Hillmyer et al. reported the synthesis of a triblock copolymer of polylactic acid-b-poly(β-methyl-δ-valerolactone)-b-polylactic acid. The obtained triblock copolymer exhibited the properties of a thermoplastic elastomer and had high mechanical strength and elongation at break (Proceedings of the National Academy of Sciences of the United States of America, 2014, 111(23), 8357). δ-Valerolactone is an important lactone compound that can be biosynthesized by microbial fermentation technology. δ-Valerolactone is generated by biotransformation of substrates (such as valeric acid) by engineered bacteria or natural microorganisms, which has the advantages of being environmentally friendly and renewable. Since δ-valerolactone has good reactivity and biodegradability, it is widely used in polymer synthesis, especially in the preparation of degradable polyester materials such as poly(δ-valerolactone). Poly(δ-valerolactone) is a semi-crystalline polyester that can be used as a hard segment of a thermoplastic elastomer. By selecting a suitable catalyst system, the sequential ring-opening polymerization of β-methyl-δ-valerolactone and δ-valerolactone can be achieved to prepare a well-structured poly(δ-valerolactone)-b-poly(β-methyl-δ-valerolactone)-b-poly(δ-valerolactone) triblock copolymer or (poly(β-methyl-δ-valerolactone)-b-poly(δ-valerolactone)) x Star-shaped multi-arm block copolymers. By adjusting the composition and ratio of the block copolymers, it is expected that thermoplastic elastomer materials with excellent properties can be obtained. By selecting a suitable catalyst and depolymerization temperature, the block copolymer can be depolymerized and recovered to obtain the original monomer, which can be separated or directly used to prepare TPE with equivalent performance to the original TPE, thereby establishing a closed-loop life cycle. However, in recent literature reports, attempts to prepare TPE materials using sequential ring-opening polymerization of β-methyl-δ-valerolactone and δ-valerolactone failed because the ratio of the added β-methyl-δ-valerolactone to δ-valerolactone was not appropriate, and the resulting polymer had no mechanical properties.

[0004] In view of this, the present invention provides a method for preparing a triblock copolymer of poly(δ-valerolactone)-b-poly(β-methyl-δ-valerolactone)-b-poly(δ-valerolactone) or (poly(β-methyl-δ-valerolactone)-b-poly(δ-valerolactone)) with a clear structure by using a base or base / urea binary catalyst system to achieve sequential ring-opening polymerization of β-methyl-δ-valerolactone and δ-valerolactone. x The method of preparing a star-shaped multi-arm block copolymer. The obtained poly(δ-valerolactone)-b-poly(β-methyl-δ-valerolactone)-b-poly(δ-valerolactone) triblock copolymer or (poly(β-methyl-δ-valerolactone)-b-poly(δ-valerolactone)) x The star-shaped multi-arm block copolymer has the properties of a thermoplastic elastomer. The method provided by the present invention has the following advantages: 1) The raw materials used are non-toxic and harmless and are derived from biomass, and the prepared triblock copolymer or star-shaped multi-arm block copolymer can be completely degraded under natural conditions; 2) The prepared TPE can be completely depolymerized and recovered to obtain monomers under mild conditions, and the monomers can be repolymerized to obtain TPE with the same properties as the original material, realizing a closed cycle of the thermoplastic elastomer; 3) The catalytic system used has high catalytic activity, and can realize the ring-opening polymerization of β-methyl-δ-valerolactone and δ-valerolactone under the same conditions, while achieving a high conversion rate, the conversion rate of β-methyl-δ-valerolactone>85%, and the conversion rate of δ-valerolactone>95%; 4) The prepared poly(δ-valerolactone)-b-poly(β-methyl-δ-valerolactone)-b-poly(δ-valerolactone) triblock copolymer or (poly(β-methyl-δ-valerolactone)-b-poly(δ-valerolactone)) x Star-shaped multi-arm block copolymers have good mechanical properties. Summary of the invention

[0005] The purpose of the present invention is to provide a novel bio-based closed-loop recyclable thermoplastic elastomer and a preparation method thereof.

[0006] The thermoplastic elastomer provided by the present invention has an ABA type triblock copolymer structure or (AB) x A star-shaped multi-arm block copolymer structure, wherein x≥2; the segment A has a structure as shown in formula (I), and the segment B has a structure as shown in formula (II):

[0007]

[0008] The feature is that 1 / 2<n / m<5 / 2, wherein m is a natural number greater than or equal to 300, and n is a natural number greater than or equal to 150.

[0009] The present invention also provides the above-mentioned ABA type triblock copolymer or (AB) x The preparation method of the star-shaped multi-arm block copolymer comprises the following steps:

[0010] (1) Dissolve the initiator and catalyst in an organic solvent and stir at room temperature for 1 to 10 minutes;

[0011] (2) adding β-methyl-δ-valerolactone to the above mixed solution and reacting at -20 to 60° C. for 0.1 to 8 hours;

[0012] (3) Add δ-valerolactone to the above reaction system, continue the reaction at -20 to 60°C for 0.1 to 8 hours, and purify to obtain an ABA type triblock copolymer or (AB) x Star-shaped multi-arm block copolymers.

[0013] In the above preparation method, the initiator is a diol or a polyol containing two or more hydroxyl groups. The diol can be specifically ethylene glycol, 1,2-propylene glycol, 1,2-butylene glycol, 1,4-butylene glycol, 1,4-cyclohexanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,2-benzenedimethanol, 1,3-benzenedimethanol, 1,4-benzenedimethanol; the polyol containing two or more hydroxyl groups can be specifically trimethylolpropane, pentaerythritol and dipentaerythritol. When a diol is used as an initiator, an ABA type triblock copolymer is prepared. When a polyol containing two or more hydroxyl groups is used as an initiator, (AB) x Star-shaped multi-arm block copolymers.

[0014] In the above-mentioned preparation method, the catalyst is an alkali or an alkali / urea binary catalyst;

[0015] The base can be an alkali metal, an alkali metal compound, or an organic base catalyst, specifically sodium, potassium, potassium hydride, sodium hydride, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1,8-diazabicycloundec-7-ene, N-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, hexa[tris(dimethylamino)phosphazene]triphosphazene ({[(NMe 2 ) 3 P = N] 2 P = N} 3 ), phosphazene ligand P4-tert-butyl ([(NMe 2 ) 3 P = N] 3 P=NtBu,tert-Bu-P 4 ), phosphazene ligand P 2 -tert-butyl ([(NMe 2 ) 3 P=N](NMe 2 ) 2 P=NtBu,tert-Bu-P 2 ); the urea has one of the structures shown in formula (III) or formula (IV), R1 and R 2 are independently selected from alkyl or aryl, 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, R 3 It can be ethylene, propylene, butylene, hexylene, or oxypentylene.

[0016]

[0017] According to an embodiment of the present invention, the urea has one of the following structures:

[0018]

[0019] The molar ratio of the catalyst to the initiator is 0.1 / 1 to 10 / 1; the molar ratio of the base to urea is 1 / 1 to 1 / 10.

[0020] In the above preparation method, the organic solvent in step (1) can be toluene, tetrahydrofuran, dichloromethane, acetonitrile, or N,N-dimethylformamide.

[0021] In the above preparation method, the molar concentration of the β-methyl-δ-valerolactone in the system in step (2) is 4 to 9 mol / L; the molar ratio of the β-methyl-δ-valerolactone to the initiator is 200 / 1 to 3000 / 1.

[0022] In the above preparation method, the molar concentration of the δ-valerolactone in the system is 0.1 to 11 mol / L; the molar ratio of the β-methyl-δ-valerolactone to δ-valerolactone is 10 / 1 to 1 / 20.

[0023] The present invention also provides a recycling method for the thermoplastic elastomer: stannous octoate and a thermoplastic elastomer are mixed, heated at 100 to 200° C. for 1 to 10 hours, and recovered by reduced pressure distillation to obtain a mixture of β-methyl-δ-valerolactone and δ-valerolactone; the mixed monomer can be utilized by two methods: the first method is to separate the mixed monomer and then re-prepare the block polymer by sequential ring-opening polymerization; the second method is to directly utilize the mixed monomer for random copolymerization and then add δ-valerolactone to prepare the block copolymer. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The poly(δ-valerolactone)-b-poly(β-methyl-δ-valerolactone)-b-poly(δ-valerolactone) prepared in Example 1 1 H NMR spectrum.

[0025] Figure 2 The poly(δ-valerolactone)-b-poly(β-methyl-δ-valerolactone)-b-poly(δ-valerolactone) prepared in Example 1 13 C NMR spectrum.

[0026] Figure 3 It is the uniaxial stretching spectrum of poly(δ-valerolactone)-b-poly(β-methyl-δ-valerolactone)-b-poly(δ-valerolactone) prepared in Examples 1 to 3.

[0027] Figure 4 This is the GPC spectrum of the poly(δ-valerolactone)-b-poly(β-methyl-δ-valerolactone)-b-poly(δ-valerolactone) prepared in Examples 3 to 5.

[0028] Figure 5 This is the uniaxial stretching spectrum of poly(δ-valerolactone)-b-poly(β-methyl-δ-valerolactone)-b-poly(δ-valerolactone) prepared in Examples 3 to 5.

[0029] Figure 6 This is the stretching cycle spectrum of poly(δ-valerolactone)-b-poly(β-methyl-δ-valerolactone)-b-poly(δ-valerolactone) prepared in Example 6.

[0030] Figure 7 This is the uniaxial stretching spectrum of poly(δ-valerolactone)-b-poly(β-methyl-δ-valerolactone)-b-poly(δ-valerolactone) prepared in Example 7 and Example 8.

[0031] Figure 8 (poly(β-methyl-δ-valerolactone)-b-poly(δ-valerolactone)) obtained in Example 9 3 Three-arm block copolymer 1 H NMR spectrum.

[0032] Fig. 9 ((poly(β-methyl-δ-valerolactone)-b-poly(δ-valerolactone)) obtained in Example 10 4 Stretching cycle spectrum of the four-arm block copolymer. DETAILED DESCRIPTION

[0033] The present invention is described in detail with reference to the following embodiments, but the present invention is not limited to these embodiments.

[0034] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0035] Comparative Example 1

[0036] (0.05mmol, 6.9mg) 1,4-benzenedimethanol, (0.05mmol, 18.4mg) phosphazene ligand P 2 -tert-butyl catalyst, (0.05mmol, 29.2mg) 1,1'-(propylene)bis(3-(3,5-bis(trifluoromethyl)phenyl)urea) was dissolved in 0.91mL tetrahydrofuran and stirred at room temperature for 10min. (10mmol, 1.09mL) β-methyl-δ-valerolactone was added to the reaction tube and the reaction was carried out at 25℃ under nitrogen protection for 20min. Then (10mmol, 0.87mL) δ-valerolactone was mixed with 1.13mL tetrahydrofuran and added to the above system. The reaction was carried out at 25℃ under nitrogen protection for 10min and 1mL acetic acid was added to terminate the reaction. The reaction mixture was dissolved in 10 mL of dichloromethane, poured into 100 mL of methanol, and centrifuged to separate and precipitate to obtain a polymer. The polymer was characterized by nuclear magnetic resonance as a triblock copolymer, i.e., poly(δ-valerolactone)-b-poly(β-methyl-δ-valerolactone)-b-poly(δ-valerolactone), m=200, n=200, n / m=1. The molecular weight measured by GPC was 36.9 kg / mol, the molecular weight distribution was 1.38, the m value was small, the molecular weight of the polymer was low, and there was no mechanical property.

[0037] Comparative Example 2

[0038] (0.05mmol, 6.9mg) 1,4-benzenedimethanol, (0.05mmol, 18.4mg) phosphazene ligand P 2 -tert-butyl catalyst, (0.05mmol, 29.2mg) 1,1'-(propylene)bis(3-(3,5-bis(trifluoromethyl)phenyl)urea) was dissolved in 2.72mL tetrahydrofuran and stirred at room temperature for 10min. (30mmol, 3.28mL) β-methyl-δ-valerolactone was added to the reaction tube and the reaction was carried out at 25℃ under nitrogen protection for 20min. Then (10mmol, 0.87mL) δ-valerolactone was mixed with 1.13mL tetrahydrofuran and added to the above system. The reaction was carried out at 25℃ under nitrogen protection for 10min and 1mL acetic acid was added to terminate the reaction. The reaction mixture was dissolved in 10 mL of dichloromethane, poured into 100 mL of methanol, and centrifuged to separate and precipitate to obtain a polymer. The polymer was characterized by nuclear magnetic resonance as a triblock copolymer, i.e., poly(δ-valerolactone)-b-poly(β-methyl-δ-valerolactone)-b-poly(δ-valerolactone), m=600, n=200, n / m=1 / 3. The number average molecular weight measured by GPC was 88.2 kg / mol, the molecular weight distribution was 1.35, the ratio of the added β-methyl-δ-valerolactone to δ-valerolactone was not appropriate, the hard segment content was low, n / m=1 / 2, and the obtained polymer was a transparent viscous state with no mechanical properties.

[0039] Example 1

[0040] (0.05mmol, 6.9mg) 1,4-benzenedimethanol, (0.05mmol, 6.9mg) 1,5,7-triazabicyclo[4.4.0]dec-5-ene catalyst, dissolved in 1.36mL tetrahydrofuran, stirred at room temperature for 10min, (15mmol, 1.64mL) β-methyl-δ-valerolactone was added to the reaction tube, and the reaction was carried out at 25℃ under nitrogen protection for 30min. Then (30mmol, 2.6mL) δ-valerolactone was mixed with 3.4mL tetrahydrofuran and added to the above system, reacted at 25℃ under nitrogen protection for 2h, and 1mL acetic acid was added to terminate the reaction. The reaction mixture was dissolved in 10 mL of dichloromethane, poured into 100 mL of methanol, and centrifuged to separate the precipitate to obtain a polymer. The polymer was characterized by NMR to be a triblock copolymer, i.e., poly(δ-valerolactone)-b-poly(β-methyl-δ-valerolactone)-b-poly(δ-valerolactone), m=300, n=600, n / m=2, 1 H NMR spectrum Figure 1 As shown, 13 C NMR spectrum Figure 2 As shown. GPC measured the number average molecular weight to be 102.5 kg / mol, and the molecular weight distribution was 1.15. The tensile mechanical properties test showed that the polymer elongation at break was 2007%, and the tensile strength was about 48.2 MPa. The tensile spectrum was as shown Figure 3 After being stretched to 100% of its original length and cycled 10 times, its elastic recovery rate was measured to be about 96% and the residual strain was about 3%.

[0041] Example 2

[0042] (0.05mmol, 6.9mg) 1,4-benzenedimethanol, (0.05mmol, 6.9mg) 1,5,7-triazabicyclo[4.4.0]dec-5-ene catalyst, dissolved in 1.36mL tetrahydrofuran, stirred at room temperature for 10min, (15mmol, 1.64mL) β-methyl-δ-valerolactone was added to the reaction tube, and the reaction was carried out at 25℃ under nitrogen protection for 30min. Then (22.5mmol, 1.96mL) δ-valerolactone was mixed with 2.54mL tetrahydrofuran, and added to the above system, reacted at 25℃ under nitrogen protection for 1h, and 1mL acetic acid was added to terminate the reaction. The reaction mixture was dissolved in 10 mL of dichloromethane, poured into 100 mL of methanol, and centrifuged to separate the precipitate to obtain a polymer. The NMR characterization of the polymer was a triblock copolymer, i.e., poly(δ-valerolactone)-b-poly(β-methyl-δ-valerolactone)-b-poly(δ-valerolactone), m=300, n=450, n / m=3 / 2. The number average molecular weight measured by GPC was 92.4 kg / mol, and the molecular weight distribution was 1.12. The tensile mechanical properties test showed that the polymer had an elongation at break of 1986%, a tensile strength of about 39.4 MPa, and a tensile spectrum as shown in FIG. Figure 3 After being stretched to 100% of its original length and cycled 10 times, its elastic recovery rate was measured to be about 96% and the residual strain was about 4%.

[0043] Example 3

[0044] (0.05mmol, 6.9mg) 1,4-benzenedimethanol, (0.05mmol, 6.9mg) 1,5,7-triazabicyclo[4.4.0]dec-5-ene catalyst, dissolved in 1.36mL tetrahydrofuran, stirred at room temperature for 10min, (15mmol, 1.64mL) β-methyl-δ-valerolactone was added to the reaction tube, and the reaction was carried out at 25℃ under nitrogen protection for 30min. Then (15mmol, 1.3mL) δ-valerolactone was mixed with 1.7mL tetrahydrofuran and added to the above system, reacted at 25℃ under nitrogen protection for 1h, and 1mL acetic acid was added to terminate the reaction. The reaction mixture was dissolved in 10 mL of dichloromethane, poured into 100 mL of methanol, and centrifuged to separate the precipitate to obtain a polymer. The polymer was characterized by NMR to be a triblock copolymer, i.e., poly(δ-valerolactone)-b-poly(β-methyl-δ-valerolactone)-b-poly(δ-valerolactone), m=300, n=300, n / m=1. The number average molecular weight measured by GPC was 85.0 kg / mol, the molecular weight distribution was 1.10, and the GPC spectrum was as follows: Figure 4 As shown. The tensile mechanical properties test shows that the polymer elongation at break is 1667%, the tensile strength is about 10.8MPa, and the tensile spectrum is shown Figure 3 After being stretched to 100% of its original length and cycled 10 times, its elastic recovery rate was measured to be about 92% and the residual strain was about 6%.

[0045] Example 4

[0046] (0.05mmol, 6.9mg) 1,4-benzenedimethanol, (0.05mmol, 6.9mg) 1,5,7-triazabicyclo[4.4.0]dec-5-ene catalyst, dissolved in 1.81mL tetrahydrofuran, stirred at room temperature for 10min, (20mmol, 2.19mL) β-methyl-δ-valerolactone was added to the reaction tube, and the reaction was carried out at 25℃ under nitrogen protection for 45min. Then (20mmol, 1.74mL) δ-valerolactone was mixed with 2.26mL tetrahydrofuran and added to the above system, reacted at 25℃ under nitrogen protection for 1.5h, and 1mL acetic acid was added to terminate the reaction. The reaction mixture was dissolved in 10 mL of dichloromethane, poured into 100 mL of methanol, and centrifuged to separate the precipitate to obtain a polymer. The polymer was characterized by NMR to be a triblock copolymer, i.e., poly(δ-valerolactone)-b-poly(β-methyl-δ-valerolactone)-b-poly(δ-valerolactone), m=400, n=400, n / m=1. The number average molecular weight measured by GPC was 103.3 kg / mol, and the molecular weight distribution was 1.11. The GPC spectrum was as follows: Figure 4 As shown. The tensile mechanical properties test shows that the polymer elongation at break is 2044%, the tensile strength is about 15.4MPa, and the tensile spectrum is shown as Figure 5 After being stretched to 100% of its original length and cycled 10 times, its elastic recovery rate was measured to be about 94% and the residual strain was about 5%.

[0047] Example 5

[0048] (0.05mmol, 6.9mg) 1,4-benzenedimethanol, (0.05mmol, 6.9mg) 1,5,7-triazabicyclo[4.4.0]dec-5-ene catalyst, dissolved in 2.27mL tetrahydrofuran, stirred at room temperature for 10min, (25mmol, 2.73mL) β-methyl-δ-valerolactone was added to the reaction tube, and the reaction was carried out at 25℃ under nitrogen protection for 1h. Then (25mmol, 2.18mL) δ-valerolactone was mixed with 2.82mL tetrahydrofuran and added to the above system, reacted at 25℃ under nitrogen protection for 2h, and 1mL acetic acid was added to terminate the reaction. The reaction mixture was dissolved in 10 mL of dichloromethane, poured into 100 mL of methanol, and centrifuged to separate the precipitate to obtain a polymer. The polymer was characterized by NMR to be a triblock copolymer, i.e., poly(δ-valerolactone)-b-poly(β-methyl-δ-valerolactone)-b-poly(δ-valerolactone), m=500, n=500, n / m=1. The number average molecular weight measured by GPC was 118.1 kg / mol, the molecular weight distribution was 1.10, and the GPC spectrum was as follows: Figure 4As shown. The tensile mechanical properties test shows that the polymer elongation at break is 2136%, the tensile strength is about 23.7MPa, and the tensile spectrum is shown as Figure 5 After being stretched to 100% of its original length and cycled 10 times, its elastic recovery rate was measured to be about 95% and the residual strain was about 4%.

[0049] Example 6

[0050] (0.05 mmol, 2.8 μL) ethylene glycol, (0.05 mmol, 18.4 mg) phosphazene ligand P 2 -tert-butyl catalyst, (0.05mmol, 34.8mg) 1-(3,5-bis(trifluoromethyl)phenyl)-3-phenylurea was dissolved in 0.86mL tetrahydrofuran, stirred at room temperature for 10min, (15mmol, 1.64mL) β-methyl-δ-valerolactone was added to the reaction tube, and the reaction was carried out at 25℃ under nitrogen protection for 20min. Then (15mmol, 1.3mL) δ-valerolactone was mixed with 1.2mL tetrahydrofuran and added to the above system, and the reaction was carried out at 25℃ under nitrogen protection for 10min, and 1mL acetic acid was added to terminate the reaction. The reaction mixture was dissolved in 10mL dichloromethane, poured into 100mL methanol, and centrifuged to separate and precipitate to obtain a polymer. The polymer was characterized by nuclear magnetic resonance as a triblock copolymer, namely poly(δ-valerolactone)-b-poly(β-methyl-δ-valerolactone)-b-poly(δ-valerolactone), m=300, n=300, n / m=1. The number average molecular weight measured by GPC is 52.9 kg / mol, and the molecular weight distribution is 1.75. The tensile mechanical properties test shows that the polymer elongation at break is 1208%, and the tensile strength is about 5.1 MPa. After stretching to 100% of the original length and cycling 10 times, the elastic recovery rate is about 84%, and the residual strain is about 10%. The tensile cycle spectrum is shown in Figure 6 shown.

[0051] Example 7

[0052] (0.05mmol, 3.7μL) 1,2-propylene glycol, (0.05mmol, 31.7mg) phosphazene ligand P4-tert-butyl catalyst, (0.05mmol, 30.7mg) 1,1'-(oxybis(ethylene))bis(3-(3,5-bis(trifluoromethyl)phenyl)urea) were dissolved in 1.81mL tetrahydrofuran and stirred at room temperature for 20min. (20mmol, 2.19mL) β-methyl-δ-valerolactone was added to the reaction tube and the reaction was carried out at 25℃ under nitrogen protection for 30min. Then (20mmol, 1.73mL) δ-valerolactone was mixed with 2.27mL tetrahydrofuran and added to the above system. The reaction was carried out at 25℃ under nitrogen protection for 10min and 1mL acetic acid was added to terminate the reaction. The reaction mixture was dissolved in 10 mL of dichloromethane, poured into 100 mL of methanol, and centrifuged to separate the precipitate to obtain a polymer. The polymer was characterized by NMR as a triblock copolymer, i.e., poly(δ-valerolactone)-b-poly(β-methyl-δ-valerolactone)-b-poly(δ-valerolactone), m=400, n=400, n / m=1. The number average molecular weight measured by GPC was 66.8 kg / mol, and the molecular weight distribution was 1.78. The tensile mechanical properties test showed that the elongation at break of the polymer was 1134%, the tensile strength was about 14.7 MPa, and the tensile spectrum was as follows Figure 7 After being stretched to 100% of its original length and cycled 10 times, its elastic recovery rate was measured to be about 87% and the residual strain was about 9%.

[0053] Example 8

[0054] (0.05mmol, 3.7μL) 1,4-butanediol, (0.05mmol, 59.9mg) hexa[tris(dimethylamino)phosphazene]triphosphazene, (0.05mmol, 22.4mg) 1,1'-(propane-1,3-diyl)bis(3-(3,5-bis(trifluoromethyl)phenyl)urea were dissolved in 2.27mL tetrahydrofuran and stirred at room temperature for 30min. (25mmol, 2.73mL) β-methyl-δ-valerolactone was added to the reaction tube and the reaction was carried out at 25℃ under nitrogen protection for 40min. Then (25mmol, 2.17mL) δ-valerolactone was mixed with 2.83mL tetrahydrofuran. Mix and add the above system, react under nitrogen protection at 25°C for 10 minutes, and add 1 mL of acetic acid to terminate the reaction. The reaction mixture was dissolved in 10 mL of dichloromethane, poured into 100 mL of methanol, and centrifuged to separate the precipitate to obtain a polymer. The NMR characterization of the polymer was a triblock copolymer, i.e., poly(δ-valerolactone)-b-poly(β-methyl-δ-valerolactone)-b-poly(δ-valerolactone), m=500, n=500, n / m=1. GPC measured the number average molecular weight to be 80.5 kg / mol, and the molecular weight distribution was 1.81. The tensile mechanical properties test showed that the polymer had an elongation at break of 1145%, a tensile strength of approximately 21 MPa, and a tensile spectrum as shown below. Figure 7 After being stretched to 100% of its original length and cycled 10 times, its elastic recovery rate was measured to be about 92% and the residual strain was about 6%.

[0055] Example 9

[0056] (0.05mmol, 6.8mg) trimethylolpropane, (0.05mmol, 6.9mg) 1,5,7-triazabicyclo[4.4.0]dec-5-ene catalyst, dissolved in 2.72mL tetrahydrofuran, stirred at room temperature for 10min, (30mmol, 3.28mL) β-methyl-δ-valerolactone was added to the reaction tube, and the reaction was carried out at 25℃ under nitrogen protection for 30min. Then (30mmol, 2.6mL) δ-valerolactone was mixed with 3.4mL tetrahydrofuran and added to the above system, and the reaction was carried out at 25℃ under nitrogen protection for 1h, and 1mL acetic acid was added to terminate the reaction. The reaction mixture was dissolved in 10mL dichloromethane, poured into 100mL methanol, and centrifuged to separate and precipitate to obtain a polymer. The polymer was characterized by nuclear magnetic resonance as a three-arm star block copolymer, namely (poly(β-methyl-δ-valerolactone)-b-poly(δ-valerolactone)) 3 , m=600, n=600, n / m=1, 1 H NMR spectrum Figure 8As shown. The number average molecular weight measured by GPC is 126.9kg / mol, and the molecular weight distribution is 1.21. The tensile mechanical properties test shows that the polymer elongation at break is 1988%, and the tensile strength is about 26.8MPa. After stretching to 100% of the original length and cycling 10 times, the elastic recovery rate is about 92%, and the residual strain is about 4%.

[0057] Example 10

[0058] (0.05mmol, 6.8mg) pentaerythritol, (0.05mmol, 6.9mg) 1,5,7-triazabicyclo[4.4.0]dec-5-ene catalyst, dissolved in 2.72mL tetrahydrofuran, stirred at room temperature for 10min, (30mmol, 3.28mL) β-methyl-δ-valerolactone was added to the reaction tube, and the reaction was carried out at 25℃ under nitrogen protection for 30min. Then (30mmol, 2.6mL) δ-valerolactone was mixed with 3.4mL tetrahydrofuran and added to the above system, and the reaction was carried out at 25℃ under nitrogen protection for 1h, and 1mL acetic acid was added to terminate the reaction. The reaction mixture was dissolved in 10mL dichloromethane, poured into 100mL methanol, and centrifuged to separate and precipitate to obtain a polymer. The polymer was characterized by nuclear magnetic resonance as a four-arm star block copolymer, namely (poly(β-methyl-δ-valerolactone)-b-poly(δ-valerolactone)) 4 , m=600, n=600, n / m=1. The number average molecular weight measured by GPC is 130.1kg / mol, and the molecular weight distribution is 1.20. The tensile mechanical properties test shows that the polymer elongation at break is 1763%, and the tensile strength is about 23.5MPa. After stretching to 100% of the original length and cycling 10 times, the elastic recovery rate is about 93%, and the residual strain is about 5%. The tensile cycle spectrum is shown in the figure below. Fig. 9 shown.

Claims

1. A novel bio-based closed-loop recyclable thermoplastic elastomer, characterized in that: Having an ABA type triblock copolymer structure or (AB) x A star-shaped multi-arm block copolymer structure, wherein x≥2; the segment A has a structure as shown in formula (I), and the segment B has a structure as shown in formula (II): Among them, 1 / 2<n / m<5 / 2, m is a natural number greater than or equal to 300, and n is a natural number greater than or equal to 150.

2. The method for preparing a thermoplastic elastomer according to claim 1, comprising the following steps: (1) Dissolve the initiator and catalyst in an organic solvent and stir at room temperature for 1 to 10 minutes; (2) adding β-methyl-δ-valerolactone to the mixed solution and reacting at -20 to 60° C. for 0.1 to 8 hours; (3) adding δ-valerolactone to the above reaction system, continuing the reaction at -20 to 60° C. for 0.1 to 8 hours, and obtaining a thermoplastic elastomer after purification; It is characterized in that The catalyst is an alkali or alkali / urea binary catalyst.

3. The method according to claim 2, characterized in that: The initiator is a diol or a polyol containing two or more hydroxyl groups; the diol is selected from ethylene glycol, 1,2-propylene glycol, 1,2-butylene glycol, 1,4-butylene glycol, 1,4-cyclohexanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,2-benzenedimethanol, 1,3-benzenedimethanol, 1,4-benzenedimethanol; the polyol containing two or more hydroxyl groups is selected from trimethylolpropane, pentaerythritol and dipentaerythritol.

4. The method according to claim 2, characterized in that: The base is an alkali metal, an alkali metal compound or an organic base; the alkali metal is selected from sodium or potassium; the alkali metal compound is selected from potassium hydride or sodium hydride; the organic base is selected from 1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1,8-diazabicycloundec-7-ene, N-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, 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).

5. The method according to claim 2, characterized in that: The urea has one of the structures shown in formula (III) or formula (IV): R1 and R2 are independently selected from 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 is one of ethylene, propylene, butylene, hexylene, and oxypentylene.

6. The method according to claim 2, characterized in that The urea has one of the following structures:

7. The method according to claim 2, characterized in that: The molar ratio of the catalyst to the initiator is 0.1 / 1 to 10 / 1; the molar ratio of the base to the urea is 1 / 1 to 1 / 10; the organic solvent in step (1) is toluene, tetrahydrofuran, dichloromethane, acetonitrile or N,N-dimethylformamide; the molar concentration of β-methyl-δ-valerolactone in the system in step (2) is 4 to 9 mol / L; the molar ratio of β-methyl-δ-valerolactone to the initiator is 200 / 1 to 3000 / 1; the molar concentration of δ-valerolactone in the system in step (3) is 0.1 to 11 mol / L; the molar ratio of β-methyl-δ-valerolactone to δ-valerolactone is 10 / 1 to 1 / 20.

8. The method for recycling thermoplastic elastomer according to claim 1, characterized in that: Stannous octoate and a thermoplastic elastomer are mixed, heated at 100 to 200° C. for 1 to 10 hours, and recovered by reduced pressure distillation to obtain a mixture of β-methyl-δ-valerolactone and δ-valerolactone; the mixed monomer can be utilized in two ways: the first method is to separate the mixed monomer and then re-prepare the thermoplastic elastomer through sequential ring-opening polymerization; the second method is to directly utilize the mixed monomer for random copolymerization and then add δ-valerolactone to prepare the thermoplastic elastomer.

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