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

Abstract

The invention provides a high-performance bio-based closed-loop recyclable thermoplastic elastomer (TPE) and a preparation method thereof, the prepared thermoplastic elastomer can be depolymerized and recycled to obtain a monomer and polymerized again, and a monomer-polymer-monomer closed cycle is realized. The method provided by the invention has the following beneficial effects: 1) the used raw materials are low in price and are biomass-sourced, the prepared block copolymer can be completely depolymerized and recycled in the presence of a catalyst to obtain a monomer, the monomer can be polymerized again, and the mechanical property of the obtained TPE is the same as that of the initial TPE; (2) the used catalytic system is high in catalytic activity and high in monomer conversion rate; and 3) the prepared TPE material is high in mechanical strength, good in rebound resilience and high in use temperature.

Description

Technical Field

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

[0002] Thermoplastic elastomer (TPE) is an important class of polymer materials. It has the reproducible processing properties of thermoplastics and the flexibility and high elasticity of traditional rubber materials. It is widely used in pressure-sensitive adhesives, automotive parts, medical devices and other fields. ABA-type triblock copolymers are important components of thermoplastic elastomers, in which block A is a hard segment, usually composed of a high glass transition temperature (T g ) or amorphous polymers with a higher melting point (T m ) is composed of a crystalline polymer, block B is a rubbery soft segment, and has a lower T g or T m Polymers. Soft and hard blocks are usually thermodynamically incompatible. When the copolymer has a suitable composition and molecular weight, microphase separation occurs between the soft and hard segments, and the hard segments are distributed as physical crosslinking points in the rubbery matrix formed by the soft segments, thereby giving the material strength and resilience. In addition to ABA-type triblock copolymers, copolymers of other topological structures can also be used as thermoplastic elastomer materials if they have a suitable composition and molecular weight, such as multi-block copolymers, star-shaped block copolymers, grafted copolymers, bottle-brush copolymers, and hyperbranched copolymers. Among them, multi-arm star-shaped block copolymers can disperse stress more evenly during stretching due to the presence of star cores, and show higher tensile strength and better elastic recovery than ABA-type triblock copolymers.

[0003] In 1965, Shell Chemical Company prepared polystyrene-based thermoplastic elastomers, which are good in quality, low in price and widely used. However, their raw materials come from non-renewable petroleum resources, and the main chain of these thermoplastic elastomers has a stable carbon-carbon structure and cannot be degraded in the natural environment. Their large-scale production and improper disposal after disposal will bring serious resource and environmental pollution problems. The best solution to environmental pollution and resource waste may be to develop chemically recyclable polymers with closed-loop cycles, which can be depolymerized into original monomers or converted into value-added chemicals after use. The use of safe and cheap bio-based cyclic lactone monomers to prepare recyclable thermoplastic elastomers has attracted increasing attention. β-Methyl-δ-valerolactone (βMδVL) is a β-substituted δ-valerolactone that can be fermented from glucose at a cost of only 15,000 yuan / ton; while p-dioxanone (PDO) is a commercial monomer that can also be synthesized from bio-derived diethylene glycol at a cost of 50,000 yuan / ton. By selecting a suitable catalyst system and realizing the sequential ring-opening polymerization of β-methyl-δ-valerolactone and p-dioxanone, a well-structured poly(p-dioxanone)-b-poly(β-methyl-δ-valerolactone)-b-poly(p-dioxanone) (PPDO-b-PβMδVL-b-PPDO) triblock copolymer can be prepared. By adjusting the composition and molecular weight of the triblock copolymer, a thermoplastic elastomer material with excellent mechanical properties and high resilience can be obtained.

[0004] Previous literature reported that δ-valerolactone (δVL) and α-alkyl-substituted valerolactone were used as raw materials to prepare a completely closed-loop recyclable triblock thermoplastic elastomer, which exhibited excellent mechanical properties and high resilience. However, since the melting point of poly(δ-valerolactone) is only 60°C, the maximum operating temperature of the thermoplastic elastomer is low and cannot adapt to high-temperature usage scenarios (Nat. Commun., 2024, 15, 7904). The current maximum operating temperature of closed-loop recyclable TPE materials is somewhat different from that of polystyrene elastomers and cannot meet application requirements. In addition, the fracture strength and elastic recovery rate of closed-loop recyclable TPE can be improved by multi-arm star block copolymers.

[0005] In view of this, the present invention provides a high-performance bio-based closed-loop recyclable thermoplastic elastomer and a preparation method thereof, that is, a method for realizing sequential ring-opening polymerization of β-methyl-δ-valerolactone and p-dioxanone to prepare a poly-p-dioxanone-b-poly(β-methyl-δ-valerolactone)-b-poly-p-dioxanone triblock copolymer or a star-shaped multi-arm block copolymer with a clear structure. The prepared 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 low in price and derived from biomass, and the prepared block copolymer can be completely depolymerized and recovered to obtain cyclic lactone monomers under the presence of a catalyst, and the monomers can be polymerized again, and the mechanical properties of the obtained TPE are the same as those of the initial one; 2) The catalytic system used has high catalytic activity and high monomer conversion rate, and the conversion rates of β-methyl-δ-valerolactone and p-dioxanone can reach more than 85%; 3) The prepared TPE material has high mechanical strength, good resilience, and high use temperature. Summary of the invention

[0006] The purpose of the present invention is to provide a high-performance bio-based closed-loop recyclable thermoplastic elastomer and a preparation method thereof.

[0007] 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).

[0008]

[0009] The feature is that m is a natural number greater than or equal to 200, n is a natural number greater than or equal to 100, and m≥n.

[0010] 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:

[0011] (1) Dissolve the initiator, organic base and urea in an organic solvent and stir at room temperature for 1 to 10 minutes;

[0012] (2) adding β-methyl-δ-valerolactone to the above mixed solution and reacting at -20 to 60° C. for 0.1 to 10 hours;

[0013] (3) adding p-dioxanone to the above reaction system, continuing the reaction at -20 to 60°C for 0.1 to 10 hours, and adding an acidic substance to terminate the reaction to obtain an ABA type triblock copolymer or (AB) x Star-shaped multi-arm block copolymers.

[0014] In the above preparation method, the urea may be one of the following structures:

[0015]

[0016]

[0017] The organic base has one of the following structures:

[0018]

[0019] In the above preparation method, the initiator is a polyol, specifically ethylene glycol, 1,2-propylene glycol, 1,2-butanediol, 1,4-butanediol, 1,4-cyclohexanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,2-benzenedimethanol, 1,3-benzenedimethanol, 1,4-benzenedimethanol, pentaerythritol, dipentaerythritol, trimethylolpropane; when a diol is used as an initiator, a poly(p-dioxanone)-b-poly(β-methyl-δ-valerolactone)-b-poly(p-dioxanone) 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;

[0020] The molar ratio of the organic base to the initiator is 0.1 / 1 to 20 / 1; the molar ratio of the organic base to urea is 1 / 1 to 1 / 10.

[0021] In the above preparation method, the organic solvent in step (1) is toluene, tetrahydrofuran, dichloromethane, chloroform, acetonitrile, or N,N-dimethylformamide.

[0022] In the above preparation method, the molar concentration of the β-methyl-δ-valerolactone in the system in step (2) is 4 to 9.1 mol / L; the molar ratio of the β-methyl-δ-valerolactone to the initiator is 200 / 1 to 3000 / 1.

[0023] In the above preparation method, the molar concentration of the p-dioxanone in the system in step (3) is 0.1 to 12.4 mol / L; the molar ratio of the p-dioxanone to β-methyl-δ-valerolactone is 1 / 1 to 1 / 20.

[0024] In the above preparation method, the acidic substance can be acetic acid, benzoic acid, hydrochloric acid, sulfuric acid, phosphoric acid, and the molar ratio of the acidic substance to the organic base is 1 / 1 to 10 / 1.

[0025] The present invention also provides a recycling method for the thermoplastic elastomer, comprising the following steps:

[0026] (1) mixing a thermoplastic elastomer with stannous octoate, heating at 100 to 200° C. for 2 to 10 hours, and distilling under reduced pressure to obtain a high-purity mixture of p-dioxanone and β-methyl-δ-valerolactone;

[0027] (2) The mixture is separated to obtain p-dioxanone and β-methyl-δ-valerolactone, which are then repolymerized to obtain an ABA type triblock copolymer or (AB) x Star-shaped multi-arm block copolymers. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The poly(p-dioxanone)-b-poly(β-methyl-δ-valerolactone)-b-poly(p-dioxanone) prepared in Example 1 is 1 H NMR spectrum.

[0029] Figure 2 The poly(p-dioxanone)-b-poly(β-methyl-δ-valerolactone)-b-poly(p-dioxanone) prepared in Example 1 is 13 C NMR spectrum.

[0030] Figure 3 The DSC spectra of polydioxanone-b-poly(β-methyl-δ-valerolactone)-b-polydioxanone prepared in Examples 1 to 3 at a scanning rate of 10° C. / min.

[0031] Figure 4 The poly(p-dioxanone)-b-poly(β-methyl-δ-valerolactone)-b-poly(p-dioxanone) and β-methyl-δ-valerolactone, p-dioxanone and the recycled β-methyl-δ-valerolactone and p-dioxanone prepared in Example 2 are 1 H NMR spectrum.

[0032] Figure 5 It is the uniaxial stretching spectra of polydioxanone-b-poly(β-methyl-δ-valerolactone)-b-polydioxanone prepared in Example 2 and polydioxanone-b-poly(β-methyl-δ-valerolactone)-b-polydioxanone prepared by repolymerizing the recycled monomers.

[0033] Figure 6 This is the DSC spectrum of polydioxanone-b-poly(β-methyl-δ-valerolactone)-b-polydioxanone prepared in Examples 4 to 6 at a scanning rate of 10°C / min.

[0034] Figure 7 This is a uniaxial stretching spectrum of polydioxanone-b-poly(β-methyl-δ-valerolactone)-b-polydioxanone prepared in Examples 1 to 3.

[0035] Figure 8 This is the uniaxial stretching spectrum of polydioxanone-b-poly(β-methyl-δ-valerolactone)-b-polydioxanone prepared in Examples 4 to 6.

[0036] Fig. 9 This is the DMA spectrum of polydioxanone-b-poly(β-methyl-δ-valerolactone)-b-polydioxanone prepared in Example 6.

[0037] Fig.10 This is the stretching cycle spectrum of the three-arm star-shaped block copolymer (PβMδVL-PPDO) 3 prepared in Example 7.

[0038] Fig.11 This is the DMA spectrum of the three-arm star-shaped block copolymer (PβMδVL-PPDO) 3 prepared in Example 7. DETAILED DESCRIPTION

[0039] The present invention is described in detail with reference to the following embodiments, but the present invention is not limited to these embodiments.

[0040] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0041] Comparative Example 1

[0042] (0.08 mmol, 8.3 μL) benzyl alcohol, (0.08 mmol, 12.0 μL) 1,8-diazabicyclo-7-undecene, (0.16 mmol, 77.5 mg) 1,3-bis(3,5-bis(trifluoromethyl)phenyl)urea Dissolve in 3.2mL tetrahydrofuran, stir at room temperature for 10min, add (56mmol, 6.1mL) β-methyl-δ-valerolactone to the reaction tube, and react for 4h under nitrogen protection at 30℃. Then (16mmol, 1.6g) p-dioxanone is dissolved in 1.3mL tetrahydrofuran and added to the above system, react for 30min under nitrogen protection at 25℃, and add 1mL dilute hydrochloric acid to terminate the reaction. The reaction mixture is dissolved in 20mL chloroform, poured into 150mL methanol, and centrifuged to precipitate to obtain a polymer. The polymer is characterized by nuclear magnetic resonance as a diblock copolymer, i.e., poly(β-methyl-δ-valerolactone)-b-poly(p-dioxanone). Compared with Example 1, the elongation at break is low, there is an obvious yield point, and it cannot be used as a thermoplastic elastomer.

[0043] Comparative Example 2

[0044] (0.08 mmol, 11.1 mg) 1,4-benzenedimethanol, (0.08 mmol, 12.0 μL) 1,8-diazabicyclo-7-undecene, (0.16 mmol, 77.5 mg) 1,3-bis(3,5-bis(trifluoromethyl)phenyl)urea Dissolve in 230 μL tetrahydrofuran, stir at room temperature for 10 min, add (4 mmol, 436 μL) β-methyl-δ-valerolactone to the reaction tube, and react for 4 h at 30 ° C under nitrogen protection. Then (8 mmol, 816 mg) p-dioxanone is dissolved in 689 μL tetrahydrofuran and added to the above system, react for 30 min under nitrogen protection at 25 ° C, and add 1 mL dilute hydrochloric acid to terminate the reaction. The reaction mixture is dissolved in 20 mL chloroform, poured into 150 mL methanol, and centrifuged to separate and precipitate to obtain a polymer. The polymer is characterized by nuclear magnetic resonance as a triblock copolymer, namely poly-p-dioxanone-b-poly (β-methyl-δ-valerolactone)-b-poly-p-dioxanone. Compared with Example 1, m=50, n=100, and the total degree of polymerization DP=150. m and n are not within the given range and cannot be used as a thermoplastic elastomer.

[0045] Example 1

[0046] (0.08 mmol, 11.1 mg) 1,4-benzenedimethanol, (0.08 mmol, 12.0 μL) 1,8-diazabicyclo-7-undecene, (0.16 mmol, 77.5 mg) 1,3-bis(3,5-bis(trifluoromethyl)phenyl)urea Dissolve in 3.2 mL of tetrahydrofuran, stir at room temperature for 10 min, add (56 mmol, 6.1 mL) of β-methyl-δ-valerolactone to the reaction tube, and react for 4 h at 30 ° C under nitrogen protection. Then dissolve (16 mmol, 1.6 g) of p-dioxanone in 1.3 mL of tetrahydrofuran and add it to the above system, react for 30 min at 25 ° C under nitrogen protection, and add 1 mL of dilute hydrochloric acid to terminate the reaction. The reaction mixture was dissolved in 20 mL of chloroform, poured into 150 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, namely poly-p-dioxanone-b-poly(β-methyl-δ-valerolactone)-b-poly-p-dioxanone, and its nuclear magnetic hydrogen spectrum was as follows Figure 1 As shown, the NMR carbon spectrum is Figure 2 As shown in the DSC spectrum Figure 3 As shown, the stretching spectrum is Figure 7As shown, the tensile mechanical properties test shows that the elongation at break of the polymer is 600%, and the tensile strength is about 5.2MPa. After stretching to 100% of the original length and cycling 10 times, the elastic recovery rate is about 91%, and the residual strain is about 7%. After use, the polymer can be completely recovered by vacuum distillation with stannous octoate as a catalyst to obtain the monomer, which is polymerized again to obtain a triblock copolymer with an elongation at break of 590% and a tensile strength of about 5.3MPa.

[0047] Example 2

[0048] (0.05mmol, 6.9mg) 1,4-benzenedimethanol, (0.05mmol, 7.5μL) 1,8-diazabicyclo-7-undecene, (0.15mmol, 52.2mg) 1-(3,5-bis(trifluoromethyl)phenyl)-3-phenylurea Dissolve in 480 μL toluene, stir at room temperature for 5 min, add (30 mmol, 3.3 mL) β-methyl-δ-valerolactone to the reaction tube, react at 25 ° C under nitrogen protection for 5 h, then dissolve (15 mmol, 1.5 g) p-dioxanone in 605 μL toluene and add to the above system, react at 25 ° C under nitrogen protection for 40 min, add 10 mg benzoic acid to terminate the reaction. The reaction mixture was dissolved in 15 mL chloroform, poured into 60 mL methanol, centrifuged and precipitated to obtain a polymer, and the polymer was characterized by nuclear magnetic resonance as a triblock copolymer, namely poly-p-dioxanone-b-(poly-β-methyl-δ-valerolactone)-b-poly-p-dioxanone, and the DSC spectrum was as follows Figure 3 As shown, the stretching spectrum is Figure 7 As shown, the tensile mechanical properties test shows that the elongation at break of the polymer is 1174%, and the tensile strength is about 15.8MPa. 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 6%. After use, the polymer can be completely recovered by vacuum distillation with stannous octoate as a catalyst to obtain the monomer, and the triblock copolymer is polymerized again under the same conditions, and its elongation at break is 1100%, and the tensile strength is about 15.3MPa. The recovered H NMR spectrum is as follows Figure 4 As shown in Figure 2, the tensile curve after cycling is Figure 6 shown.

[0049] Example 3

[0050] (0.1 mmol, 5.6 mL) ethylene glycol, (0.1 mmol, 1.5 μL) 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, (0.2 mmol, 56.1 mg) 1-phenyl-3-(4-(trifluoromethyl)phenyl)urea and 7.1 mL of dichloromethane were added to the reaction tube, stirred at room temperature for 10 min, (50 mmol, 5.5 mL) of β-methyl-δ-valerolactone was added to the reaction tube, and the reaction was carried out at 29°C under nitrogen protection for 6 h. Then (40 mmol, 4.1 g) of p-dioxanone was dissolved in 6.6 mL of dichloromethane and added to the above system, reacted at 40°C under nitrogen protection for 1 h, and 0.5 mL of dilute hydrochloric acid was added to terminate the reaction. The reaction mixture was dissolved in 30 mL of chloroform, poured into 240 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, namely poly-p-dioxanone-b-poly(β-methyl-δ-valerolactone)-b-poly-p-dioxanone, and the DSC spectrum was as shown in Figure 3 As shown, the stretching spectrum is Figure 7 As shown, the tensile mechanical properties test shows that the elongation at break of the polymer is 1297%, and the tensile strength is about 20.7MPa. After stretching to 100% of the original length and cycling 10 times, the elastic recovery rate is about 85%, and the residual strain is about 9%. After use, the polymer can be completely recovered by vacuum distillation with stannous octoate as a catalyst to obtain the monomer, which is polymerized again to obtain a triblock copolymer with an elongation at break of 1310% and a tensile strength of about 22.3MPa.

[0051] Example 4

[0052] (0.05 mmol, 2.8 mL) ethylene glycol, (0.05 mmol, 7.5 μL) 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, (0.20 mmol, 42.4 mg) 1,3-diphenylurea and 1.7 mL of chloroform were added to the reaction tube, stirred at room temperature for 10 min, (30 mmol, 3.3 mL) of β-methyl-δ-valerolactone was added to the reaction tube, and the reaction was carried out at 19°C under nitrogen protection for 3 h. Then (15 mmol, 1.5 g) of p-dioxanone was dissolved in 1.2 mL of chloroform and added to the above system, and the reaction was carried out at 40°C under nitrogen protection for 50 min, and 1 mL of dilute sulfuric acid was added to terminate the reaction. The reaction mixture was dissolved in 50 mL of chloroform, poured into 180 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, namely poly-p-dioxanone-b-poly(β-methyl-δ-valerolactone)-b-poly-p-dioxanone, and the DSC spectrum was as shown in Figure 6 As shown, the stretching spectrum is Figure 8As shown, the tensile mechanical properties test shows that the elongation at break of the polymer is 1100%, and the tensile strength is about 15.6MPa. 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 10%. After use, the polymer can be completely recovered by vacuum distillation with stannous octoate as a catalyst to obtain the monomer, which is polymerized again to obtain a triblock copolymer with an elongation at break of 1090% and a tensile strength of about 15.3MPa.

[0053] Example 5

[0054] (0.03 mmol, 1.7 mL) ethylene glycol, (0.03 mmol, 7.5 μL) phosphazene ligand P1-tert-butyl, (0.12 mmol, 33.7 mg) 1,3-bis(4-chlorophenyl)urea and 238 μL acetonitrile were added to the reaction tube, stirred at room temperature for 2 min, (15 mmol, 1.6 mL) β-methyl-δ-valerolactone was added to the reaction tube, and the reaction was carried out at 20 ° C under nitrogen protection for 2 h. Then (7.5 mmol, 765 mg) p-dioxanone was dissolved in 304 μL acetonitrile and added to the above system, and the reaction was carried out at 30 ° C under nitrogen protection for 45 min, and 10 drops of acetic acid were added to terminate the reaction. The reaction mixture was dissolved in 25 mL chloroform, poured into 150 mL 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-p-dioxanone-b-poly(β-methyl-δ-valerolactone)-b-poly-p-dioxanone, and the DSC spectrum was as follows Figure 6 As shown, the stretching spectrum is Figure 8 As shown, the tensile mechanical properties test shows that the elongation at break of the polymer is 1189%, and the tensile strength is about 10.3MPa. After stretching to 100% of the original length and cycling 10 times, the elastic recovery rate is about 89%, and the residual strain is about 7%. After use, the polymer can be completely recovered by vacuum distillation with stannous octoate as a catalyst to obtain the monomer, which is polymerized again to obtain a triblock copolymer with an elongation at break of 1239% and a tensile strength of about 11.3MPa.

[0055] Example 6

[0056] (0.4 mol, 5.5 g) 1,4-benzenedimethanol, (0.4 mol, 100 mL) phosphazene ligand P1-tert-butyl, (0.6 mol, 148.0 g) 1-(4-chlorophenyl)-3-phenylurea Dissolve in 2.5L tetrahydrofuran, stir at room temperature for 10min, add (160mol, 17.5L) β-methyl-δ-valerolactone to the reaction tube, and react for 3h at 25℃ under nitrogen protection. Then dissolve (80mol, 8160g) p-dioxanone in 3.2L tetrahydrofuran and add to the above system, react for 30min under nitrogen protection at 30℃, and add 200mL hydrochloric acid to terminate the reaction. Dissolve the reaction mixture in 85L chloroform, pour into 220L methanol, centrifuge and precipitate to obtain a polymer. The polymer is characterized by nuclear magnetic resonance as a triblock copolymer, namely poly(p-dioxanone)-b-poly(β-methyl-δ-valerolactone)-b-poly(p-dioxanone). The tensile mechanical properties test shows that the polymer has an elongation at break of 683%, a tensile strength of about 5.8MPa, and a DSC spectrum as shown in the figure. Figure 6 As shown, the stretching spectrum is Figure 8 As shown. After stretching to 100% of the original length and cycling 10 times, the elastic recovery rate was measured to be about 90% and the residual strain was about 7%. The DMA spectrum is shown in Fig. 9 As shown, the storage modulus is always higher than the loss modulus, and its maximum operating temperature is 72.5°C. After use, the polymer can be completely recovered by vacuum distillation with stannous octoate as a catalyst to obtain the monomer, which is polymerized again to obtain a triblock copolymer with an elongation at break of 657% and a tensile strength of about 5.9MPa.

[0057] Example 7

[0058] (0.5 mol, 67.1 g) trimethylolpropane, (0.5 mol, 75 mL) 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, (1.0 mol, 212.2 g) 1,3-diphenylurea Dissolve in 4.7L tetrahydrofuran, stir at room temperature for 10min, add (300mol, 32.8L) β-methyl-δ-valerolactone to the reaction tube, and react for 6h at 0℃ under nitrogen protection. Then (150mol, 15.3kg) p-dioxanone is dissolved in 6.1L tetrahydrofuran and added to the above system, react for 30min under nitrogen protection at 25℃, and add 100mL phosphoric acid to terminate the reaction. The reaction mixture is dissolved in 200L chloroform, poured into 300L methanol, and centrifuged to precipitate to obtain a polymer. The polymer is characterized by nuclear magnetic resonance as a triblock copolymer, i.e., a three-arm star-shaped block copolymer (PβMδVL-PPDO)3. The tensile mechanical properties test shows that the polymer has an elongation at break of 1054% and a tensile strength of about 21.2MPa. It is stretched to 100% of its original length and cycled 10 times. Its elastic recovery rate is about 93% and the residual strain is about 6%. Its tensile cycle spectrum is as follows Fig.10 DMA spectrum is shown as Fig.11As shown, the storage modulus is always higher than the loss modulus, and its maximum operating temperature is 81.3°C. After use, the polymer can be completely recovered by vacuum distillation with stannous octoate as a catalyst to obtain the monomer, which is polymerized again to obtain a three-arm star-shaped block copolymer with an elongation at break of 1160% and a tensile strength of about 22.3MPa.

Claims

1. ABA type triblock copolymer or (AB) x A star-shaped multi-arm block copolymer, wherein x≥2; characterized in that Segment A has a structure as shown in formula (I), and segment B has a structure as shown in formula (II): m is a natural number greater than or equal to 200, n is a natural number greater than or equal to 100, and m≥n.

2. The ABA type triblock copolymer according to claim 1 or (AB) x A method for preparing a star-shaped multi-arm block copolymer, characterized in that: The steps include: (1) Dissolve the initiator, organic base and urea in an organic solvent and stir at room temperature for 1 to 10 minutes; (2) adding β-methyl-δ-valerolactone to the above mixed solution and reacting at -20 to 60° C. for 0.1 to 10 hours; (3) Add p-dioxanone to the above reaction system, continue the reaction at -20 to 60°C for 0.1 to 10 hours, and then add an acidic substance to terminate the reaction.

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

4. The method according to claim 2, characterized in that: The initiator is a polyol selected from ethylene glycol, 1,2-propylene glycol, 1,2-butanediol, 1,4-butanediol, 1,4-cyclohexanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,2-benzenedimethanol, 1,3-benzenedimethanol, 1,4-benzenedimethanol, pentaerythritol, dipentaerythritol, and trimethylolpropane; the organic base is one of 1,8-diazabicyclo-7-undecene, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, and phosphazene ligand P1-tert-butyl; the organic solvent is toluene, tetrahydrofuran, dichloromethane, chloroform, acetonitrile, and N,N-dimethylformamide.

5. The method according to claim 2, characterized in that: The molar ratio of the organic base to the initiator is 0.1 / 1 to 20 / 1; the molar ratio of the organic base to urea is 1 / 1 to 1 / 10.

6. The method according to claim 2, characterized in that The molar concentration of the β-methyl-δ-valerolactone in the system is 4 to 9.1 mol / L; the molar ratio of the β-methyl-δ-valerolactone to the initiator is 200 / 1 to 3000 / 1.

7. The method according to claim 2, characterized in that: The molar concentration of p-dioxanone in the system is 0.1-12.4 mol / L; the acidic substance is acetic acid, benzoic acid, hydrochloric acid, sulfuric acid or phosphoric acid; and the molar ratio of the acidic substance to the base is 1 / 1-10 / 1.

8. The ABA type triblock copolymer according to claim 1 or (AB) x The circulation method of the star-shaped multi-arm block copolymer comprises the following steps: (1) mixing a thermoplastic elastomer with stannous octoate, heating at 100 to 200° C. for 2 to 10 hours, and distilling under reduced pressure to obtain a high-purity mixture of p-dioxanone and β-methyl-δ-valerolactone; (2) The mixture is separated to obtain p-dioxanone and β-methyl-δ-valerolactone, which are then repolymerized to obtain an ABA type triblock copolymer or (AB) x Star-shaped multi-arm block copolymers.

9. The ABA type triblock copolymer according to claim 1 or (AB) x Application of star-shaped multi-arm block copolymers in thermoplastic elastomers.

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