Poly delta-thiopivalactone and methods of its preparation and depolymerization

Abstract

The application belongs to the field of polymer synthesis, and discloses a kind of poly delta-thiopentolide and its preparation and depolymerization method.A kind of compound as shown in formula is disclosed.The application also discloses the preparation method of the high molecular compound.The number average molecular weight of poly delta-thiopentolide prepared by the preparation method of the application is significantly improved, and the mechanical property is significantly improved.The application also discloses the degradation method of the high molecular compound.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of polymer synthesis, and relates to polydelta-valerolactone and a preparation and depolymerization method thereof. BACKGROUND

[0002] Plastics are a class of synthetic polymer materials that are ubiquitous and are used in almost all commercial and industrial fields. Since the 1950s, the growth rate of plastic production has exceeded that of any other category of man-made materials, and it is predicted that the future growth of petrochemical products, including plastics, will account for half of the global oil demand by 2050. Chemically recyclable polymers, as a new type of material, can be depolymerized into polymer precursors after use, avoiding polymer pollution and providing raw materials for polymer production, effectively improving the problem of "white pollution" of plastics. Delta-valerolactone is a commercial reagent that can form chemically recyclable polymers through ring-opening polymerization, and the formed polyester also has biodegradability, so polydelta-valerolactone is a very valuable green polymer material. However, the use temperature of this type of polymer is lower than 56℃, and the heat resistance is poor (the melting point of polydelta-valerolactone is 56℃). Therefore, increasing the melting point of this type of polymer is a difficulty in this field.

[0003] Changing the C-O single bond in delta-valerolactone to a C-S single bond forms polydelta-valerolactone with a melting point of 123℃, significantly improving the heat resistance of the polymer. At the same time, the main chain of the polymer has a thioester functional group, ensuring the degradability of the polymer. However, due to the poor orbital overlap between the 3P orbital of the sulfur atom and the 2P orbital of the oxygen atom, it is relatively difficult for the lone pair electrons of the single bond sulfur atom in the thioester bond to delocalize to the carbonyl carbon connected to it. Therefore, the thioester is more electrophilic and more susceptible to nucleophilic attack, and the thiolactone has poor stability. Thioester exchange reactions are common during synthesis, and it is very challenging to synthesize high molecular weight polydelta-valerolactone. Currently, polydelta-valerolactone can be prepared in three ways: 1) ring-opening polymerization of delta-thiovalerolactone; 2) ring-opening polymerization of delta-valerolactone; 3) self-polymerization of 4-pentene thio acid, as follows:

[0004] Ring-opening polymerization of delta-thiovalerolactone: delta-thiovalerolactone has a renewable green source and low cost, and can be obtained in high yield by directly thioating using commercial delta-valerolactone as raw material, and can be synthesized on a large scale in industry. However, delta-thiovalerolactone has high thermodynamic stability and is difficult to polymerize, and there is only one reported example of ring-opening polymerization of delta-thiovalerolactone (ACSMacro Lett. 2024, 13, 1411). The polydelta-valerolactone obtained in this document has a low molecular weight (number average molecular weight M n :1.3~14.3kg / mol), poor mechanical properties, and no application value.

[0005] δ-pentathiolactone ring-opening polymerization: Compared with δ-thiovalerolactone, δ-pentathiolactone is difficult to synthesize, raw materials are expensive, and the yield is low. The ring-opening polymerization of δ-pentathiolactone is also very difficult. Currently, there are only two documents reporting the preparation of poly-δ-pentathiolactone by ring-opening polymerization of δ-pentathiolactone. Overberger's group (J. Am. Chem. Soc. 1968, 90, 3533) obtained poly-δ-pentathiolactone with low molecular weight (number average molecular weight M n ~1.0 kg / mol) by anionic polymerization, and Gutekunst obtained poly-δ-pentathiolactone with low molecular weight (number average molecular weight M n ~14.3 kg / mol) (ACS Macro Lett. 2022, 11, 895) by using organic bases and alkyl mercaptans. The mechanical properties are poor, and there is no application value.

[0006] 4-pentenylthio acid self-polymerization: The self-polymerization process of 4-pentenylthio acid is uncontrollable, and the monomer synthesis is very difficult. The poly-δ-pentathiolactone obtained has low molecular weight (number average molecular weight M n ~1.0 kg / mol).

[0007] Therefore, the number average molecular weight of the poly-δ-pentathiolactone reported so far is less than 14.3 kg / mol, and the mechanical properties are poor, and there is no application value. It is still a technical blank to develop high molecular weight poly-δ-pentathiolactone with excellent mechanical properties. SUMMARY

[0008] The technical problem to be solved by the present application is to overcome the defects of low molecular weight and poor mechanical properties of existing poly-δ-pentathiolactone (PTVL), and to provide a poly-δ-pentathiolactone and a preparation method thereof. The number average molecular weight of the poly-δ-pentathiolactone prepared by the preparation method of the present application is significantly improved, and the mechanical properties are good.

[0009] The technical scheme of the present application is as follows:

[0010] A poly-δ-pentathiolactone, as shown in formula (I), has the following structure:

[0011] ;

[0012] Wherein, n is greater than or equal to 138.

[0013] According to the common sense of polymer chemistry, the structure in each "()" in the compound as shown in formula (I) represents a structural unit; and n is the degree of polymerization, which is also the number average degree of polymerization or average degree of polymerization.

[0014] The n is preferably 138-10000, more preferably 250-5000, such as 250, 600, 1000, 2000 or 5000.

[0015] The number average molecular weight of the compound of formula (I) is preferably greater than or equal to 16.0 kg / mol, more preferably 29.0-580 kg / mol, such as 29.0 kg / mol, 99.9 kg / mol, 101 kg / mol, 195 kg / mol, 249 kg / mol or 580 kg / mol.

[0016] The molecular weight distribution of the compound of formula (I) is 1.0-3.0, preferably 1.0-2.5, such as 1.0, 1.1, 1.2, 1.5, 2.0, 2.5 or 3.0.

[0017] The present application also provides a preparation method of the poly-δ-valerolactone of formula (I), comprising the following steps: polymerizing the compound of formula (II) in an organic solvent in the presence of a main catalyst and an alkyl mercaptan initiator at 80-120°C.

[0018] .

[0019] The main catalyst is one or a mixture of two or more of amidine organic base, guanidine organic base, N-heterocyclic carbene organic base, N-heterocyclic olefin organic base, preferably amidine organic base.

[0020] In the preparation method of the compound of formula (I), the organic solvent can be a conventional organic solvent in the art, preferably one or a mixture of two or more of hydrocarbon solvent, halogenated aromatic hydrocarbon solvent, more preferably aromatic hydrocarbon solvent and / or halogenated aromatic hydrocarbon solvent, more preferably toluene and / or o-dichlorobenzene. When the organic solvent is aromatic hydrocarbon solvent, the aromatic hydrocarbon solvent is one or a mixture of two or more of toluene, benzene, xylene, preferably toluene; when the organic solvent is halogenated aromatic hydrocarbon solvent, the halogenated aromatic hydrocarbon solvent is one or a mixture of two or more of o-dichlorobenzene, o-difluorobenzene, o-dibromobenzene, chlorobenzene, fluorobenzene, bromobenzene, mesitylene, preferably o-dichlorobenzene.

[0021] In the preparation method of the compound of formula (I), the amidine organic base is a conventional amidine organic base in the art, preferably 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU, formula III), the structure of which is as follows:

[0022] .

[0023] In the preparation method of the compound of formula (I), the guanidine organic base is a guanidine organic base commonly used in the art, preferably 1,5,7-triazido bicyclo(4.4.0)decane-5-ene (TBD, formula IV) and / or 7-methyl-1,5,7-triazido bicyclo[4.4.0]decane-5-ene (MTBD, formula V), the structures of which are shown below:

[0024] , .

[0025] In the preparation method of the compound of formula (I), the carbene organic base is a compound of formula (VI), the structure of which is shown below:

[0026] .

[0027] wherein R 1 and R 2 are independently hydrogen, a hydrocarbon group of 1-20 carbon atoms or an aromatic group of 6-20 carbon atoms, which are the same or different; R 3 and R 4 are independently a hydrocarbon group of 1-20 carbon atoms or an aromatic group of 6-20 carbon atoms, which are the same or different.

[0028] In the preparation method of the compound of formula (I), the N-heterocyclic carbene ene organic base is a compound of formula (VII), the structure of which is shown below:

[0029] .

[0030] wherein R 6 and R 7 are independently hydrogen, a hydrocarbon group of 1-20 carbon atoms or an aromatic group of 6-20 carbon atoms, which are the same or different; R 5 and R 8 are independently a hydrocarbon group of 1-20 carbon atoms or an aromatic group of 6-30 carbon atoms; R 9 and R 10 are independently hydrogen, methyl or ethyl;

[0031] In the preparation method of the compound of formula (I), the alkyl mercaptan initiator is one or more of R 11 SH, HSR 12 SH, R 13 (SH)3 and R 14 (SH)4, R 11 , R 12 , R 13 and R 14 are hydrocarbon groups of 1-20 carbon atoms.

[0032] The molar ratio of the compound of formula (II) to the main catalyst in the preparation method of the compound of formula (I) is 100:1-10000:1.

[0033] The molar ratio of the initiator to the main catalyst in the preparation method of the compound of formula (I) is 1:1-100:1.

[0034] The polymerization time in the preparation method of the compound of formula (I) is 5-1440 minutes.

[0035] The present application realizes the preparation of high molecular weight polymers of formula (I) from compounds of formula (II) by using a strong nucleophilic alkyl mercaptan reagent as an initiator. The nucleophilicity of this reagent is significantly better than that of the aryl mercaptan, aryl alcohol and thioacetic acid reagents reported in the literature. Strong nucleophilic reagents make the polymerization reaction easier to proceed, avoid ester exchange between polymer chains, and are conducive to the improvement of polymerization degree.

[0036] On the basis of not violating the common sense of the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain each preferred example of the present application.

[0037] The reagents and raw materials used in the present application are commercially available.

[0038] The polydelta-valerolactone provided by the present application is a strong and tough semi-crystalline material, and its melting temperature is 123℃, which is similar to that of commercial low-density polyethylene. The mechanical properties are comparable to those of commercial low-density polyethylene, and it can be rapidly and controllably degraded into delta-valerolactone under specific conditions. Therefore, the delta-valerolactone provided by the present application is a potential green alternative to low-density polyethylene.

[0039] The present application also provides a depolymerization method of the aforementioned delta-valerolactone, which comprises: mixing the delta-valerolactone with an acidic catalyst, and obtaining a lactone monomer of formula (VIII) under atmospheric pressure distillation or reduced pressure distillation at 100-350℃ (for example, 100℃, 150℃, 200℃, 250℃, 300℃, 350℃).

[0040]

[0041] Further, the acidic catalyst includes one or a combination of two or more of zinc chloride, ferrous chloride, ferric chloride, zinc acetate, stannous octoate, and phosphomolybdic acid.

[0042] Further, the acidic catalyst is 0.1-50% (e.g., 0.1%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%) of the weight of the δ-valerolactone.

[0043] Advantages of the present application: The preparation method of the present application effectively reduces the side reactions in the polymerization process, so that the monomer can be converted into poly-δ-valerolactone with high conversion rate. Compared with the method reported in the literature, high molecular weight poly-δ-valerolactone that cannot be synthesized in the literature is obtained, and the increase in molecular weight can significantly improve the mechanical properties of the polymer. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 is the nuclear magnetic resonance of the polymerization monomer δ-valerolactone of formula (II).

[0045] Figure 2 is the mechanical property test diagram of the poly-δ-valerolactone of the present application Comparative Example 1 and Example 7.

[0046] Figure 3 is the nuclear magnetic resonance diagram of the poly-δ-valerolactone of the present application Example 4.

[0047] Figure 4 is the rheological test result of poly-δ-valerolactone, the entanglement molecular weight of the polymer is 16 kg / mol, and the polymer molecular weight exceeds 16 kg / mol to exhibit good mechanical properties. DETAILED DESCRIPTION

[0048] The specific embodiments of the present application are further illustrated below in combination with the drawings and technical solutions.

[0049] Example 1

[0050] The compound of formula (II) described in the present application is a self-made product, and the initial raw material is commercial δ-valerolactone, which is prepared by one-step reaction. The preparation method is not particularly limited, and is preferably prepared according to the method described in the following literature (Bioorg. Chem. 2021, 108, 104650-104656.):

[0051] In a 500 mL three necked flask, 22.2 g of phosphorus pentasulfide and 54.2 g of hexamethyldisiloxane were added, stirred in 200 mL of acetonitrile, then 20.0 g of δ-valerolactone was added, stirred at reflux for 4 h. After the reaction was completed, when the reaction temperature dropped to room temperature, 200 mL of saturated potassium carbonate solution was added and stirred for 30 min, then the liquid was separated, the aqueous phase was extracted with acetonitrile three times, then the organic phases were combined. Dried with anhydrous sodium sulfate, filtered, rotary evaporated, then column chromatography was performed with petroleum ether / ethyl ether gradient elution (30:1~1:1) to collect the product. Then the monomer was added to calcium hydride and dried for 3 days, then distilled at 100 mTorr, 75 °C under reduced pressure, then stored in a glove box for use.

[0052] The δ-thiovalerolactone monomer obtained in the present application was a light yellow liquid, and the mass of the obtained δ-thiovalerolactone monomer was 20.9 g, and the calculated yield was 90%.

[0053] The δ-thiovalerolactone monomer obtained in the present application was subjected to nuclear magnetic resonance (NMR) characterization, 1 The H NMR spectrum is shown in Figure 1 , which is consistent with the literature report. It is proved that the δ-thiovalerolactone monomer prepared in the present application has the structure of formula (II).

[0054]

[0055] Example 2

[0056] At 80 °C, in a pre-dried 10 mL serum bottle. First, 2.0 g (8.61 mmol) of monomer δ-thiovalerolactone was weighed and dissolved in N,N-dimethylformamide to form a 5 mol / L solution, and then 2.17 mg (0.0344 mmol) of ethanethiol and 5.24 mg (0.0344 mmol) of catalyst DBU were added to the monomer δ-thiovalerolactone N,N-dimethylformamide solution. After 3 h, 5 mL of trifluoroacetic acid / CDCl3 (10 mg / mL) was added to immediately quench the polymerization reaction, and then 1 HNMR was used for analysis to obtain the conversion rate of the monomer. Then, the quenched mixture was precipitated into cold methanol, filtered, washed with cold methanol three times to remove any unreacted monomer, and dried in a vacuum drying oven at room temperature overnight to a constant weight. 1.52 g of light yellow solid was obtained, the average molecular weight of the polymer was 16.5 kg / mol, the molecular weight distribution was 2.03, and the DSC test showed that the melting point of the polymer was 123 °C.

[0057] Example 3

[0058] In a pre-dried 10 mL serum bottle at 100 °C. First, 1.0 g (8.61 mmol) of monomer δ- thiovalerolactone was weighed, and then 3.49 mg (0.0172 mmol) of initiator n-dodecanethiol and 2.62 mg (0.0172 mmol) of catalyst DBU were dissolved in 0.07 mL of toluene, which was added to the monomer δ-thiovalerolactone after being mixed well. After a period of time, 5 mL of benzoic acid / CDCl3(10 mg / mL) was added to immediately quench the polymerization reaction, and then the mixture was analyzed by H-NMR to obtain the conversion of monomer. Then, the quenched mixture was precipitated into cold methanol, filtered, washed with cold methanol three times to remove any unreacted monomer, and dried in a vacuum oven at room temperature overnight to a constant weight. 0.96 g of light yellow solid was obtained, and the average molecular weight of the polymer was determined by gel chromatography to be 17.1 kg / mol, with a molecular weight distribution of 1.71, and DSC testing showed that the melting point of the polymer was 123 °C. 1 H-NMR to obtain the conversion of monomer. Then, the quenched mixture was precipitated into cold methanol, filtered, washed with cold methanol three times to remove any unreacted monomer, and dried in a vacuum oven at room temperature overnight to a constant weight. 0.96 g of light yellow solid was obtained, and the average molecular weight of the polymer was determined by gel chromatography to be 17.1 kg / mol, with a molecular weight distribution of 1.71, and DSC testing showed that the melting point of the polymer was 123 °C.

[0059] Example 4

[0060] In a pre-dried 10 mL serum bottle at 100 °C. First, 1.0 g (8.61 mmol) of monomer δ- thiovalerolactone was weighed, and then 3.49 mg (0.0172 mmol) of initiator n-dodecanethiol and 2.62 mg (0.0172 mmol) of catalyst DBU were dissolved in 0.07 mL of toluene, which was added to the monomer δ-thiovalerolactone after being mixed well. After a period of time, 5 mL of benzoic acid / CDCl3(10 mg / mL) was added to immediately quench the polymerization reaction, and then the mixture was analyzed by H-NMR to obtain the conversion of monomer. Then, the quenched mixture was precipitated into cold methanol, filtered, washed with cold methanol three times to remove any unreacted monomer, and dried in a vacuum oven at room temperature overnight to a constant weight. 0.96 g of light yellow solid was obtained, and the average molecular weight of the polymer was determined by gel chromatography to be 17.1 kg / mol, with a molecular weight distribution of 1.71, and DSC testing showed that the melting point of the polymer was 123 °C. 1 H-NMR to obtain the conversion of monomer. Then, the quenched mixture was precipitated into cold methanol, filtered, washed with cold methanol three times to remove any unreacted monomer, and dried in a vacuum oven at room temperature overnight to a constant weight. 0.96 g of light yellow solid was obtained, and the average molecular weight of the polymer was determined by gel chromatography to be 17.1 kg / mol, with a molecular weight distribution of 1.71, and DSC testing showed that the melting point of the polymer was 123 °C.

[0061] Example 5

[0062] In a pre-dried 10 mL serum bottle at 100 °C. First, 1.0 g (8.61 mmol) of monomer δ- thiovalerolactone was weighed, and then 3.49 mg (0.0172 mmol) of initiator n-dodecanethiol and 2.62 mg (0.0172 mmol) of catalyst DBU were dissolved in 0.07 mL of toluene, which was added to the monomer δ-thiovalerolactone after being mixed well. After a period of time, 5 mL of benzoic acid / CDCl3(10 mg / mL) was added to immediately quench the polymerization reaction, and then the mixture was analyzed by H-NMR to obtain the conversion of monomer. Then, the quenched mixture was precipitated into cold methanol, filtered, washed with cold methanol three times to remove any unreacted monomer, and dried in a vacuum oven at room temperature overnight to a constant weight. 0.96 g of light yellow solid was obtained, and the average molecular weight of the polymer was determined by gel chromatography to be 17.1 kg / mol, with a molecular weight distribution of 1.71, and DSC testing showed that the melting point of the polymer was 123 °C.1 H NMR analysis was performed to obtain the conversion of monomer. Then, the quenched mixture was precipitated into cold methanol, filtered, washed with cold methanol three times to remove any unreacted monomer, and dried in a vacuum oven at room temperature overnight to a constant weight. 1.30 g of light yellow solid was obtained, the average molecular weight of the polymer was determined by gel permeation chromatography to be 92.1 kg / mol, the molecular weight distribution was 2.35, and the DSC test showed that the melting point of the polymer was 123 °C.

[0063] Example 6

[0064] In a pre-dried 10 mL serum bottle at 100 °C. First, 1 g (8.61 mmol) of monomer δ- thiovalerolactone was weighed, and then 0.27 mg (0.0043 mmol) of initiator n-dodecanethiol and 3.27 mg (0.043 mmol) of catalyst DBU were dissolved in 0.07 mL of toluene, which was then added to the monomer δ-thiovalerolactone. After a period of time, 5 mL of benzoic acid / CDCl3 (10 mg / mL) was added to immediately quench the polymerization reaction, and then the mixture was precipitated into cold methanol, filtered, washed with cold methanol three times to remove any unreacted monomer, and dried in a vacuum oven at room temperature overnight to a constant weight. 0.58 g of light yellow solid was obtained, the average molecular weight of the polymer was determined by gel permeation chromatography to be 54.4 kg / mol, the molecular weight distribution was 2.35, and the DSC test showed that the melting point of the polymer was 123 °C. 1 H NMR analysis was performed to obtain the conversion of monomer. Then, the quenched mixture was precipitated into cold methanol, filtered, washed with cold methanol three times to remove any unreacted monomer, and dried in a vacuum oven at room temperature overnight to a constant weight. 1.30 g of light yellow solid was obtained, the average molecular weight of the polymer was determined by gel permeation chromatography to be 92.1 kg / mol, the molecular weight distribution was 2.35, and the DSC test showed that the melting point of the polymer was 123 °C.

[0065] Example 7

[0066] In a pre-dried 10 mL serum bottle at 100 °C. First, 2.0 g (17.2 mmol) of monomer δ- thiovalerolactone was weighed, and then 3.48 mg (0.0172 mmol) of initiator n-dodecanethiol and 2.62 mg (0.0172 mmol) of catalyst DBU were dissolved in 0.07 mL of toluene, which was then added to the monomer δ-thiovalerolactone. After a period of time, 5 mL of benzoic acid / CDCl3 (10 mg / mL) was added to immediately quench the polymerization reaction, and then the mixture was precipitated into cold methanol, filtered, washed with cold methanol three times to remove any unreacted monomer, and dried in a vacuum oven at room temperature overnight to a constant weight. 1.60 g of light yellow solid was obtained, the average molecular weight of the polymer was determined by gel permeation chromatography to be 31.4 kg / mol, the molecular weight distribution was 1.51, and the DSC test showed that the melting point of the polymer was 123 °C. 1 H NMR analysis was performed to obtain the conversion of monomer. Then, the quenched mixture was precipitated into cold methanol, filtered, washed with cold methanol three times to remove any unreacted monomer, and dried in a vacuum oven at room temperature overnight to a constant weight. 1.30 g of light yellow solid was obtained, the average molecular weight of the polymer was determined by gel permeation chromatography to be 92.1 kg / mol, the molecular weight distribution was 2.35, and the DSC test showed that the melting point of the polymer was 123 °C.

[0067] Figure 3 The mechanical property test diagram of the polymer formed in Example 7 of the present invention is shown.

[0068] Example 8

[0069] 1.0 g of poly(δ-thiovalactone) obtained in Example 7 was added to a round-bottom flask, along with 10 mg of phosphomolybdic acid. The mixture was heated under vacuum of 0.07 torr at 160°C to obtain 0.97 g of δ-thiovalactone. NMR spectroscopy determined the purity to be greater than 99%. Figure 4 The following is a comparison of the NMR spectra of δ-thiovalactone recovered by chemical recycling and the synthesized δ-thiovalactone monomer in Example 7 of the present invention.

[0070] Comparative Example 1

[0071] This comparative example is the highest molecular weight polyδ-thiovalactone reported so far, reference: Stellmach KA; Paul MKK; Xu M.; Su YL; Fu L.; Toland AR; Tran H.; Chen L.; Ramprasad R.; Gutekunst WR ACS Macro Lett, 2022, 11, 895–901.

[0072] The polymerization of δ-thiovalactone was repeated under the conditions described in the literature (catalyst: DBU, molar ratio of DBU to δ-thiovalactone: 200:1, THF as solvent, monomer concentration: 5 mol / L, polymerization temperature: 20°C, reaction time: hours). The polymerization results were consistent with those in the literature (monomer conversion = 46%, M...). n =14.3 kg / mol, melting point 123℃) similar to: M n =14.4 kg / mol, monomer conversion rate = 45%, melting point 123℃). Tensile property tests show ( Figure 2 The polymer has a tensile strength of 4.0 MPa and an elongation at break of 1.9%, which is far lower than that of commercially available low-density polyethylene (elongation at break 200%, breaking stress 10 MPa, reference Nat. Chem. 2022, 14, 294), and has no practical value.

[0073] The mechanical properties of the polyδ-thiovalerate prepared in Example 7 were tested: tensile mechanical test (e.g.) Figure 4The experiment shows that the poly-δ-valerolactone with a number average molecular weight of 31.4 kg / mol has an elongation at break of 480% and a stress at break of 18.7 MPa; this shows that the poly-δ-valerolactone provided by the application is a strong and tough polymer material, and the mechanical tensile test indexes are all better than those of low-density polyethylene (elongation at break 200%, stress at break 10 MPa, document Nat. Chem. 2022, 14, 294), and more obviously better than the mechanical properties of the δ-valerolactone with the highest molecular weight reported at present.

[0074] High Polymer Chemistry indicates that a polymer will only show good mechanical properties after the molecular weight of the polymer reaches the critical entanglement molecular weight, and the entanglement molecular weight can be obtained by calculation through the Likhtman-Mcleish theory in Polymer Physics. Therefore, we measured the entanglement molecular weight of the polymer through oscillatory shear rheology experiment. We measured the relationship between the dynamic storage modulus (G'), loss modulus (G'') and complex viscosity (η * ) of poly-δ-valerolactone at different temperatures and the frequency of the rheometer, and used the theoretical principles of Williams-Landel-Ferry and automatically fitted by data analysis software TRIOS (TA Instruments, USA) to superimpose time-temperature-amplitude at 127°C to obtain Figure 4 . Using the model disclosed by McIlroy ((https: / / www.stevenabbott.co.uk / practical-rheology / L-M_Mc.php)), the data can be imported to deduce that the entanglement molecular weight of poly-δ-valerolactone is 16 kg / mol. That is, the molecular weight of the polymer reaches 16 kg / mol or more, and the polymer shows obvious chain entanglement, thereby obtaining poly-δ-valerolactone with practical mechanical properties.

[0075] Comparative Example 2

[0076] This comparative example is the reported polymerization of δ-thiovalerolactone using DBU and aryl mercaptan, document: ACSM Macro Lett. 2024, 13, 1411.

[0077] The polymerization of δ-thiovalerolactone was repeated according to the conditions of the document (the catalyst is DBU, the molar ratio of DBU and benzyl mercaptan is 1:1, the molar ratio of δ-thiovalerolactone and DBU is 100:1, N,N-dimethylformamide is used as the solvent, the monomer concentration is 5 moles / liter, the polymerization temperature is 80°C, and the reaction time is 3 hours), and the polymerization results are similar to those of the document (monomer conversion = 95%, M n = 3.3 kg / mol). M n = 3.4 kg / mol, monomer conversion = 95%).

[0078] Comparative Example 3

[0079] This comparative example is based on Comparative Example 2, further increasing the molar ratio of δ-valerolactone and DBU to 250:1 (catalyst is DBU, the molar ratio of DBU and benzyl mercaptan is 1:1, N,N-dimethylformamide as solvent, monomer concentration 5 mole / liter, polymerization temperature 80°C, reaction time 3 hours), and other conditions remain unchanged, the molecular weight of the polymer obtained by polymerization is almost unchanged, still 3.3 kg / mol, monomer conversion = 50%.

[0080] Comparative Example 3 of the present application Example 2 and the polymerization conditions compared, except for the initiator (Example 2 using alkyl mercaptan, the comparison using aryl mercaptan), the other conditions are exactly the same, Example 2 obtained molecular weight of 16.5 kg / mol of poly-δ-valerolactone, while the comparison only get molecular weight of 3.3 kg / mol of polymer. Thus, the alkyl mercaptan initiator in the present application is an important factor in the production of high molecular weight poly-δ-valerolactone.

Claims

1. A polydelta-thiopentalone characterized in that, The structure of the polydelta-valerolactone is shown as formula (I): ； Wherein, n is greater than or equal to 138; The preparation method of the polydelta-valerolactone is as follows: The compound shown as formula (II) is subjected to polymerization reaction in an organic solvent at 80-120℃ in the presence of a main catalyst and an alkyl mercaptan initiator; ； The main catalyst is one or a mixture of two or more of amidine organic base, guanidine organic base, N-heterocyclic carbene organic base, and N-heterocyclic olefin organic base; The alkyl mercaptan initiator is R 11 SH, HSR 12 SH, R 13 (SH)3, R 14 (SH)4, or a combination of two or more thereof, R 11 , R 12 , R 13 , and R 14 is a hydrocarbon group of 1 to 20 carbon atoms, the four being the same or different; The molar ratio of the compound shown as formula (II) to the main catalyst is 100:1-10000:1; the molar ratio of the alkyl mercaptan initiator to the main catalyst is 1:1-100:1; and the polymerization reaction time is 5-1440 minutes.

2. The polydelta-valerolactone according to claim 1, characterized in that, The n is 138-10000; The number average molecular weight of the polydelta-valerolactone is greater than or equal to 16.0 kg / mol; The molecular weight distribution of the polydelta-valerolactone is 1.0-3.

0.

3. The polydelta-thiopivalactone according to claim 1, characterized in that, The organic solvent is one or a mixture of two or more of hydrocarbon solvent and halogenated aromatic hydrocarbon solvent.

4. The depolymerization process of poly-δ-thiolvalerolactone as claimed in claim 1, wherein, The polydelta-valerolactone is mixed with an acidic catalyst, and subjected to normal pressure distillation or reduced pressure distillation at 100-350℃ to obtain a lactone monomer shown as formula (VIII): ； The acidic catalyst includes one or a combination of two or more of zinc chloride, ferrous chloride, ferric chloride, zinc acetate, stannous octoate, and phosphomolybdic acid.

5. The depolymerization method of claim 4, wherein, The acidic catalyst accounts for 0.1-50% of the weight of the polydelta-valerolactone.

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