Method for synthesizing xylosyl seven-membered cyclic lactone monomer and polyester

Abstract

The invention discloses a method for synthesizing a xylosyl seven-membered cyclic lactone monomer and polyester, which is characterized in that 1, 2-O-isopropylidene-alpha-furan xylose is used as a reaction raw material, and a novel furan xylosyl thiaseven-membered cyclic lactone monomer is efficiently synthesized through a simple four-step method (bromination reaction, nucleophilic substitution reaction, hydrolysis reaction and molecular lactonization reaction). The ring-opening polymerization reaction of the monomer under the mild condition is realized, the monomer conversion rate in the room temperature reaction can reach 95%, and the high molecular weight (21.2 kg mol <-1 >) and narrow distribution (Dlt; 1.2) of the polymer.

Description

Technical Field

[0001] The present invention discloses a method for synthesizing xylose-based seven-membered cyclic lactone monomers and polyesters, which is a new method for synthesizing novel seven-membered cyclic lactone monomers and polymerizing to prepare polyesters using the bio-based platform molecule furan xylose as a raw material, and relates to technical fields such as organic synthesis, degradable polymers, functional polymers, pharmaceutical chemistry, and 3D printing materials. Background Art

[0002] With the increasing urgency of global demand for environmental protection and sustainable development, the pollution problems caused by traditional petroleum-based polymer materials are becoming increasingly severe. Against this background, the development of bio-based polymer materials that can be completely degraded and have renewable raw materials has become one of the key paths to solve the plastic pollution problem. Xylose and its derivatives (such as furanose) as hydrolysis products of hemicellulose have significant advantages of wide sources, low cost, renewable, and environmentally friendly. The annual global production of xylose from agricultural waste reaches tens of millions of tons, and its efficient utilization can simultaneously reduce production costs and reduce straw burning pollution. The synergistic effect of multiple hydroxyl groups and rigid furan rings in its molecule provides unique sites and conformational stability for chemical modification. In recent years, great progress has been made in the design and synthesis of new polymerization monomers and functional polymers around xylose-based platform molecules. In 2020, the Antoine Buchard research group synthesized a new type of stereopure xylose-based oxetane monomer (Formula 1, I) by sulfonylation reaction and intramolecular nucleophilic cyclization reaction using furanose as the raw material. Further, this type of monomer can be obtained optically pure isotactic polyether through ring-opening polymerization reaction. Among them, stereocomplexes can be formed between glycosyl polyethers with opposite chirality, and this complex has better thermal properties than single-chiral polymers, providing new ideas for improving material properties (Angew. Chem. Int. Ed. 2021, 60, 4524-4528). In 2021, the Wooley research group and the Darensbourg research group at Texas A&M University in the United States prepared xylose-based six-membered cyclic carbonate monomers by the cycloaddition reaction of this oxetane monomer with CO2 and realized the ring-opening polymerization process to prepare the corresponding polycarbonate polymer materials (Polym. Chem., 2021, 12, 5271–5278). In the same year, the Antoine Buchard research group further synthesized bifunctional diene monomers by one-step acylation reaction and prepared the corresponding polyester materials using the second-generation Grubbs-catalyzed acyclic diene metathesis polymerization process (Formula 1, II). This type of polymer combines the rigid cyclic structure of carbohydrates and the flexible structure of unsaturated aliphatic chains, showing excellent toughness and barrier properties (ACS Appl. Polym. Mater. 2021, 3, 5870-5881). In recent years, our research group has synthesized alkynoate and six-membered cyclic thio-carbonate monomers (Formula 1, III, and IV) using 1,2-O-isopropylidene-D / L-furanose as the raw material. Among them, the alkynoate monomer can carry out "hydroxy-alkyne" click polymerization reaction under the catalysis of the organic base 1,4-diazabicyclo[2.2.2]octane, and a number-average molecular weight as high as 21.6×10 3Bio - based polyalkylene ether ester materials with g / mol (European Polymer Journal. 2024, 211, 112997). It is worth noting that the design concept of introducing rigid structures and stereochemical characteristics into the polymer chain significantly improves the thermal stability of the material (T d，5％ up to 340 °C) and the glass transition temperature (T g up to 143 °C). The six - membered cyclic thio - carbonate monomer can initiate the ring - opening polymerization process under mild conditions (room temperature) through a bifunctional organic catalyst and alkali metal alkoxide. The resulting sulfur - containing polycarbonate exhibits excellent thermal stability and outstanding optical properties (J Polym Sci. 2023, 61, 2133–2138.). In addition, in 2022, the research group of Jeremy S. Luterbacher prepared a bifunctional carboxylic acid ester monomer (Formula 4, V) at the kilogram scale using xylose as a raw material through an acetalization reaction. The bio - based polyesters obtained by the polycondensation reaction of this monomer with a series of different diols can be degraded in water and chemically recycled. At the same time, their fused - ring structure endows them with characteristics such as a high glass transition temperature, strong and tough mechanical properties, high barrier properties, and processability (Nature Chemistry, 2022, 14, 976–984). Further, in 2024, this research group developed a catalyst - free melt polymerization process to achieve the direct melt polycondensation reaction of bifunctional carboxylic acid ester monomers with various aliphatic diamines. The properties of the prepared amorphous polyamides can be comparable to those of petrochemical - based semi - aromatic alternatives (Nat. Sustain., 2024, 7, 640–651). Based on cheap and readily available xylose - based biomass raw materials, constructing new monomers through molecular design and developing efficient and controllable polymerization systems have become the forefront research directions in the field of polymer science. This research paradigm not only conforms to the global trend of green chemistry and sustainable development, but also opens up an innovative path for the creation of high - performance bio - based polyester materials by combining the natural advantages of biomass resources with the precise regulation of synthetic chemistry, showing great potential to promote the low - carbon transformation of the materials field.

[0003] The design, synthesis, and polymerization reaction of xylose - based monomers have been reported as shown in Formula 1 below:

[0004] SUMMARY OF THE INVENTION

[0005] Based on the above research status, the present invention uses readily available and inexpensive 1,2-O-isopropylidene-α-xylopyranose as a reaction raw material, and efficiently synthesizes novel xylopyranosyl thiaheptalactone monomers through a simple four-step method (bromination reaction, nucleophilic substitution reaction, hydrolysis reaction, and intramolecular esterification reaction), and realizes the ring-opening polymerization reaction of such monomers under mild conditions. On the one hand, a rigid fused-ring structure is introduced into the polymer chain to enhance the stereoregularity of the polymer and improve the thermodynamic properties of the polymer. The thermodynamic properties indicate that the prepared bio-based polyester polymers have thermodynamic properties no inferior to those of traditional polycaprolactone. On the other hand, the introduction of sulfur atoms enriches the post-modifiability of the polyester material. By selectively oxidizing the thioether groups in the polymer backbone to sulfone groups, the glass transition temperature of the polymer is increased from a maximum of 94 °C to a maximum of 154 °C, greatly broadening the application scope of such polymer materials.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for synthesizing xylopyranosyl heptalactone monomers, which synthesizes three xylopyranosyl heptalactone monomers with definite stereoconfigurations through the selective bromination reaction of the primary alcohol group in the 1,2-O-isopropylidene-α-xylopyranose substrate, the nucleophilic substitution reaction of the bromide with methyl thioglycolate, the saponification reaction, and the intramolecular cyclization reaction.

[0008] The structural formulas of the three monomers are as follows:

[0009]

[0010] The reaction formulas are as follows:

[0011]

[0012] The specific steps are as follows:

[0013] First, triphenylphosphine, carbon tetrabromide, and pyridine are successively added to 1,2-O-isopropylidene-α-xylopyranose, and the reaction is carried out in a solvent at 30-60 °C to obtain xylopyranose with the primary alcohol group substituted by bromine. After the xylopyranose with the primary alcohol group substituted by bromine is purified by column chromatography, anhydrous potassium carbonate and methyl thioglycolate are successively added, and the mixture is heated to reflux in a solvent for 12-24 hours. After the reaction is completed, the product is purified by column chromatography, then an excessive amount of sodium hydroxide is added, and the reaction is carried out at room temperature in a solvent for 10-24 hours. After the reaction is completed, the pH of the reaction solution is adjusted to neutral and then extracted to obtain a crude product. The crude product is added with 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride under anhydrous and anaerobic conditions, and then 4-dimethylaminopyridine is added as a catalyst, and the reaction is carried out at room temperature in a solvent for 6-24 hours. After the reaction is completed, the xylopyranosyl heptalactone monomer is obtained by column chromatography.

[0014] Among them, the molar ratios of triphenylphosphine, carbon tetrabromide, pyridine to 1,2 - O - isopropylidene - α - xylopyranose are respectively (1 - 2):1, (1 - 2):1, (1 - 5):1.

[0015] The molar ratios of anhydrous potassium carbonate, methyl thioglycolate to 1,2 - O - isopropylidene - α - xylopyranose are respectively (1 - 2):1, (1 - 2):1.

[0016] The molar ratios of 1 - (3 - dimethylaminopropyl) - 3 - ethylcarbodiimide hydrochloride, 4 - dimethylaminopyridine to 1,2 - O - isopropylidene - α - xylopyranose are respectively (1 - 2):1, (0.05 - 0.1):1.

[0017] The solvent described above is one or a mixture of two or more of dichloromethane, acetone, methanol, acetonitrile, and tetrahydrofuran.

[0018] A method for synthesizing xylose - based seven - membered cyclic polyester uses an organic catalyst or a metal catalyst, and an initiator to initiate the ring - opening polymerization of the above - mentioned xylose - based seven - membered cyclic lactone monomer to obtain a synthesized xylose - based seven - membered cyclic polyester, which is a new type of bio - based polyester material.

[0019] The reaction formula is as follows:

[0020]

[0021] The specific steps are as follows:

[0022] Under anhydrous and anaerobic conditions, a solvent is added to dissolve the seven - membered cyclic monomer, and then an initiator and a catalyst are added, and the reaction is carried out at 10 - 120 °C for 2 - 24 hours. After the reaction is completed, a quenching reagent is used to quench the polymerization reaction, and then a poor solvent for recrystallization is added to the polymerization reaction solution to produce a white precipitate. Centrifuge and vacuum - dry to constant weight to obtain the synthesized xylose - based seven - membered cyclic polyester.

[0023] The molar ratios of the initiator, catalyst to the xylose - based seven - membered cyclic lactone monomer are respectively (0.001% - 20%):1, (0.001% - 20%):1.

[0024] The organic catalyst described above is one or a mixture of two or more of 1,5,7 - triazabicyclo[4.4.0]dec - 5 - ene, 1,8 - diazabicyclo[5.4.0]undec - 7 - ene, 1,5 - diazabicyclo[4.3.0]non - 5 - ene, 7 - methyl - 1,5,7 - triazabicyclo[4.4.0]dec - 5 - ene, and tetramethylguanidine.

[0025] The metal catalyst described above is one or a mixture of two of β - diimine zinc catalyst and stannous octoate.

[0026] The initiator is one or a mixture of two of benzyl alcohol, 4-methylbenzyl alcohol, and polyether polyol.

[0027] The solvent is one or a mixture of two or more of dichloromethane, tetrahydrofuran, toluene, dioxane, and mesitylene.

[0028] The quenching reagent is hydrochloric acid or toluenesulfonic acid.

[0029] The poor solvent is one or a mixture of two or more of ether, methanol, ethanol, and toluene.

[0030] Advantages of the present invention:

[0031] Using bio-based furan xylose as a raw material, a novel seven-membered cyclic lactone monomer DM, LM, DM-2S was efficiently designed and synthesized through four steps of reaction. This seven-membered cyclic lactone monomer can, under the catalysis of a catalyst, undergo an efficient polymerization reaction for the initiator in a solvent. The monomer conversion rate in the room-temperature reaction can reach 95%, obtaining a polymer with a high molecular weight (21.2 kg mol -1 ), and a narrow distribution (D < 1.2). By controlling the reaction ratio of the monomer and the initiator, polyesters with different molecular weights can be obtained, achieving precise control of the polymerization reaction. P(DM), P(LM), and P(DM-2S) all have good thermal stability. With the introduction of chiral methyl groups on the seven-membered ring, the thermal weight loss temperature of P(DM-2S) is significantly increased (T d,5％ = 317 °C), and the glass transition temperature is increased by 20 °C (T m = 94.4 °C). Selective oxidation of sulfur atoms on the polymer backbone is carried out to achieve the conversion of thioether to sulfone. After oxidation, the thermodynamic properties of the polymer are significantly improved. Description of the Drawings

[0032] Figure 1 is the structural formula of the monomer and the single crystal analysis image (DM CDCC number: 2407919; LM CDCC number: 2407920).

[0033] Figure 2 are the TGA and DSC curves of the polymer.

[0034] Figure 3 is the DSC diagram of P(DM)-SO2 obtained by reacting different ratios of P(DM) and m-chloroperoxybenzoic acid.

[0035] Figure 4 are the TGA and DSC analysis diagrams of P(DM)-SO2 and P(LM)-SO2. Detailed Embodiments

[0036] The following further describes the detailed embodiments of the present invention in combination with the drawings and technical solutions.

[0037] 1. Preparation of monomer (taking D-lactone monomer DM as an example)

[0038] Add D-xylose (1 equiv), triphenylphosphine (1 - 2 equiv) and tetrahydrofuran or dichloromethane into a round-bottom flask in sequence. After complete dissolution, add carbon tetrabromide (1 - 3 equiv) and pyridine (1 - 5 equiv) into the solution, and react in an oil bath at 25 - 60 °C for 1 - 6 h. After the reaction is completed, filter, rotary evaporate the filtrate, and obtain white solid D-bromoxylose through column chromatography (yield 79%).

[0039] D-bromoxylose: 1 H NMR (500 MHz, Chloroform-d) δ 5.9 (d, J = 3.6 Hz, 1H), 4.5 (d, J = 3.6 Hz, 1H), 4.4 (m, 1H), 4.3 (m, 1H), 3.6–3.5 (m, 2H), 2.0 (d, J = 5.4 Hz, 1H), 1.5 (s, 3H), 1.3 (s, 3H). HRMS (ESI, m / z): calcd for C8H 13 BrO4: [M + Cl] - 288.9664, found: 288.9669.

[0040]

[0041] Add D-bromoxylose (1 equiv) and anhydrous potassium carbonate (1 - 2 equiv) into a round-bottom flask, and add acetone or tetrahydrofuran to dissolve it. After mixing evenly, add methyl thioglycolate (1 - 2 equiv) into the reaction system, and reflux for 10 - 24 h. After the reaction is completed, filter, and rotary evaporate the filtrate to obtain intermediate 1, with a yield > 99%.

[0042] 1: 1 H NMR (400 MHz, CDCl3) δ 5.8 (d, J = 3.7 Hz, 1H), 4.4 (d, J = 3.7 Hz, 1H), 4.2 (m, 2H), 3.6 (s, 3H), 3.4 (d, J = 5.3 Hz, 1H), 3.3 (m, 2H), 2.8 (m, 2H), 1.3 (d, J = 3.6 Hz, 6H).

[0043] Add 1 (1.0 equiv.) and sodium hydroxide (1 - 20 equiv.) to a single-necked flask. Place it in an ice-water bath and dissolve it in methanol or ethanol. React at room temperature for 6 - 24 h. After the reaction is completed, add acetic acid to adjust the reaction solution to weakly acidic. Extract with dichloromethane, dry over anhydrous sodium sulfate, and rotary evaporate the filtrate to obtain intermediate 2. Under an argon atmosphere, add 2 (1.0 equiv.), dichloromethane (10 - 20 mL), 4-dimethylaminopyridine (DMAP) (0.01 - 0.1 equiv.) and EDC (1 - 3 equiv.) to a three-necked flask respectively. React at room temperature overnight. After the reaction is completed, extract with water 3 times to remove the salts in the solution, dry over anhydrous sodium sulfate, filter and concentrate. Column chromatography gives white solid DM (yield 66%).

[0044] DM: 1 H NMR (600 MHz, CDCl3) δ 6.0 (d, J = 3.7 Hz, 1H), 4.7 (m, 2H), 4.60 (s,

[0045] 1H), 3.7 - 3.4 (m, 2H), 3.0–2.7 (m, 2H), 1.5 (s, 3H), 1.3 (s, 3H); 13 C NMR (101 MHz, CDCl3) δ 166.3, 112.6, 105.4, 83.5, 82.6, 79.8, 29.7, 28.6, 27.0, 26.5. FTIR (neat) 2989, 1751, 1376, 1247, 1218, 1077, 1021 cm -1 . HRMS (ESI, m / z): calcd for C 10 H 14 O5S: [M+Na] + 269.0454, found: 269.0454.

[0046] The synthesis method of LM refers to that of DM, using L-xylose as the starting material. Yield: 70%

[0047] LM: 1 H NMR (600 MHz, CDCl3) δ 6.0 (d, J = 3.7 Hz, 1H), 4.8 (m, 2H), 4.6

[0048] (m, 3.0 Hz, 1H), 3.6 (m, 2H), 3.0–2.7 (m, 2H), 1.5 (s, 3H), 1.3 (s, 3H); 1313C NMR (101 MHz, CDCl3) δ 166.3, 112.6, 105.4, 83.5, 82.6, 79.8, 29.7, 28.5, 27.0, 26.5. FTIR (neat) 2991, 1751, 1450, 1375, 1258, 1163, 1076, 1024 cm -1 . HRMS (ESI, m / z): calcd for C 10 H 14 O5S: [M+Na] + 269.0454, found: 269.0435.

[0049] The synthesis method of DM-2S monomer refers to that of DM, using methyl 2-mercaptopropionate as the raw material. Yield: 30%

[0050] DM-2S: 1 1H NMR (400 MHz, CDCl3) δ 6.0 (d, J = 3.7 Hz, 1H), 5.1 (d, J = 2.9

[0051] Hz, 1H), 4.7 (d, J = 3.7 Hz, 1H), 4.5 (m, 1H), 4.1 (m, J = 7.3 Hz, 1H), 3.1–2.8 (m, 2H), 1.6 (d, J = 7.2 Hz, 3H), 1.5 (s, 3H), 1.3 (s, 3H); 13 13C NMR (101 MHz, CDCl3) δ 170.6, 112.5, 106.1, 83.2, 82.2, 79.5, 43.5, 30.6, 27.0, 26.4, 18.2. FTIR (neat) 2986, 2935, 1735, 1376, 1216, 1084, 1020 cm -1 . HRMS (ESI, m / z): calcd for C 11 H 16 O5S: [M+Na] + 283.0610, found: 283.0615.

[0052] 2. Ring-opening polymerization of xylosyl heptalactone monomer

[0053] First, conduct ring-opening polymerization experiments on monomer DM, and explore the effects of different catalysts and different solvents on the polymerization reaction by the method of controlling variables. Fix the molar ratio of feed as M / C / I = 100:1:1, the monomer concentration as 0.5 mol / L, and the reaction time as 12 hours. Determine the reaction conversion rate by NMR characterization of samples taken at intervals of 3 h. Quench the reaction after reaching the maximum conversion rate and record the time.

[0054] It can be seen from Experiments 1 - 3 that using 1,5,7 - triazabicyclo[4.4.0]dec - 5 - ene (TBD) as the catalyst for the polymerization reaction can obtain polymers with medium molecular weight and a relatively wide molecular weight distribution. When dichloromethane is used as the polymerization solvent, DM is completely converted within 12 h, while the monomer conversion rate is relatively low in tetrahydrofuran and toluene. Using tetrahydrofuran as the polymerization reaction solvent can obtain a polymer with a narrower molecular weight distribution than when using dichloromethane as the solvent. The monomer DM has poor solubility in toluene, and the reaction temperature needs to be increased to completely dissolve the monomer in the solution, while the reaction can be carried out at room temperature when using dichloromethane and tetrahydrofuran as solvents. When using 1,5,7 - triazabicyclo[4.4.0]dec - 5 - ene (DBU) as the catalyst for the polymerization reaction, the monomer conversion rate is low, and a polymer with medium molecular weight and a relatively narrow molecular weight distribution is obtained (Experiments 4 - 6). It can be seen from Experiments 7 - 8 that using BDI - Zn as the catalyst can obtain polymers with high molecular weight and narrow molecular weight distribution, among which the molecular weight distribution is the narrowest when using tetrahydrofuran as the solvent, and the polymer chains are well - controlled. Finally, using stannous octoate (Sn(Oct)2) as the catalyst for the polymerization reaction, the conversion rate after 12 h of reaction is only 31%, and the catalytic effect is not good (Experiment 10).

[0055] It can be seen from Experiments 1 - 10 that under the conditions of using BDI - Zn as the catalyst for the polymerization reaction and tetrahydrofuran as the solvent, a polymer with high conversion rate, high molecular weight, and narrow distribution can be obtained at room temperature. Therefore, these conditions are used as the optimal reaction conditions for subsequent reactions.

[0056] Table 1 Ring - opening polymerization reaction of monomer DM 1

[0057]

[0058] (1) Polymerization conditions: [M]0 = 1 M. (2) The monomer conversion rate is calculated from the ratio of the relevant peak areas on the 1H NMR spectrum. (3) The polymer is dissolved in chromatographically pure THF and measured by a gel permeation chromatograph. Test temperature: 25 °C, flow rate: 1.0 mL / min, standard sample: polystyrene. (4) Polymerization monomer: LM; (5) Polymerization monomer: DM - 2S.

[0059] Example 1

[0060] Taking the polymerization experiment No. 1 as an example, first prepare a 0.01 M solution of TBD and 4-MeBnOH in the glove box: Weigh 14 mg of TBD and 12.2 mg of 4-MeBnOH solids into a 10 mL serum bottle, and add 10 mL of DCM to dissolve them. Weigh 123 mg of monomer DM into a dried 3.0 mL polymerization vial in the glove box, and use a 1 mL syringe to add 0.5 mL of 0.01 M 4-MeBnOH and DBU solution to the polymerization vial, and react at room temperature. Take samples every 3 h to measure the conversion rate. After 12 h, add 1 drop of 0.1 M benzoic acid solution to quench the polymerization reaction, 1 The conversion rate measured by 1H NMR is 99%. Take the polymerization vial out of the glove box, transfer the reaction solution to a small test tube, add 10 mL of anhydrous methanol, and white precipitate is produced. Centrifuge and vacuum dry to constant weight.

[0061] Example 2

[0062] Taking the polymerization experiment No. 4 as an example, first prepare a 0.01 M solution of DBU and 4-MeBnOH in the glove box: Weigh 15.2 mg of DBU and 12.2 mg of 4-MeBnOH solids into a 10 mL serum bottle, and add 10 mL of DCM to dissolve them. Weigh 123 mg of monomer DM into a dried 3.0 mL polymerization vial in the glove box, and use a 1 mL syringe to add 0.5 mL of 0.01 M 4-MeBnOH and DBU solution to the polymerization vial, and react at room temperature. Take samples every 3 h to measure the conversion rate. After 12 h, add 1 drop of 0.1 M benzoic acid solution to quench the polymerization reaction, 1 The conversion rate measured by 1H NMR is 86%. Take the polymerization vial out of the glove box, transfer the reaction solution to a small test tube, add 10 mL of anhydrous methanol, and white precipitate is produced. Centrifuge and vacuum dry to constant weight.

[0063] Example 3

[0064] Taking the polymerization experiment No. 8 as an example, first prepare a 0.01 M solution of BDI-Zn and 4-MeBnOH in the glove box: Weigh 59 mg of BDI-Zn and 12.2 mg of 4-MeBnOH solids into a 10 mL serum bottle, and add 10 mL of THF to dissolve them. Weigh 123 mg of monomer DM into a dried 3.0 mL polymerization vial in the glove box, and use a 1 mL syringe to add 0.5 mL of 0.01 M 4-MeBnOH and BDI-Zn solution to the polymerization vial, and react at room temperature. Take samples every 3 h to measure the conversion rate. After 12 h, add 1 drop of 0.1 M benzoic acid solution to quench the polymerization reaction, 1 The conversion rate measured by 1H NMR is 92%. Take the polymerization vial out of the glove box, transfer the reaction solution to a small test tube, add 10 mL of anhydrous methanol, and white precipitate is produced. Centrifuge and vacuum dry to constant weight.

[0065] Example 4

[0066] Taking the 11th polymerization experiment as an example, a 0.01 M solution of BDI-Zn and 4-MeBnOH was first prepared in a glove box: 59 mg of BDI-Zn and 12.2 mg of 4-MeBnOH solids were weighed into a 10 mL serum bottle, and 10 mL of THF was added to dissolve them. 123 mg of monomer LM was weighed into a dried 3.0 mL polymerization vial in the glove box, and 0.5 mL of 0.01 M 4-MeBnOH and BDI-Zn solution was added to the polymerization vial with a 1 mL syringe, and the reaction was carried out at room temperature. Samples were taken every 3 h to measure the conversion rate. After 12 h, 1 drop of 0.1 M benzoic acid solution was added to quench the polymerization reaction, 1 The conversion rate measured by 1H NMR was 93%. The polymerization vial was taken out of the glove box, the reaction solution was transferred to a small test tube, 10 mL of anhydrous methanol was added, and a white precipitate was produced. Centrifuged and vacuum dried to constant weight.

[0067] Example 5

[0068] Taking the 12th polymerization experiment as an example, a 0.01 M solution of BDI-Zn and 4-MeBnOH was first prepared in a glove box: 59 mg of BDI-Zn and 12.2 mg of 4-MeBnOH solids were weighed into a 10 mL serum bottle, and 10 mL of THF was added to dissolve them. 130 mg of monomer DM-2S was weighed into a dried 3.0 mL polymerization vial in the glove box, and 0.5 mL of 0.01 M 4-MeBnOH and BDI-Zn solution was added to the polymerization vial with a 1 mL syringe, and the reaction was carried out at room temperature. Samples were taken every 3 h to measure the conversion rate. After 12 h, 1 drop of 0.1 M benzoic acid solution was added to quench the polymerization reaction, 1 The conversion rate measured by 1H NMR was 95%. The polymerization vial was taken out of the glove box, the reaction solution was transferred to a small test tube, 10 mL of anhydrous methanol was added, and a white precipitate was produced. Centrifuged and vacuum dried to constant weight.

[0069] By the characterization and assignment of the 1H NMR and 13C NMR spectra of the polymer, as well as the comparison with the 1H NMR spectrum of the monomer, the correctness of the polymer structure was determined. The similarity between the polymer and monomer spectra also proved the accuracy of the polymer structural units.

[0070] P(DM): 1 1H NMR (600 MHz, CDCl3) δ 5.9 (d, J = 3.8 Hz, 1H), 5.2 (d, J = 2.9 Hz,

[0071] 1H NMR (600 MHz, CDCl3) δ 5.9 (d, J = 3.8 Hz, 1H), 5.2 (d, J = 2.9 Hz, 1H), 4.6 (d, J = 3.8 Hz, 1H), 4.5 - 4.4 (m, 1H), 3.4 (d, J = 15.2 Hz, 1H), 3.3 (d, J = 15.0 Hz, 1H), 2.9 (m, 1H), 2.8 (m, 1H), 1.5 (s, 3H), 1.3 (s, 3H). 13 13C NMR (101 MHz, CDCl3) δ 169.5, 112.4, 104.8, 83.2, 79.4, 34.1, 30.6, 26.8, 26.4.

[0072] P(LM): 1 1H NMR (600 MHz, CDCl3) δ 5.9 (d, J = 3.8 Hz, 1H), 5.2 (d, J = 2.9 Hz,

[0073] 1H), 4.6 (d, J = 3.8 Hz, 1H), 4.5 (m, 1H), 3.4 (d, J = 15.1 Hz, 1H), 3.3 (d, J = 15.2 Hz, 1H), 2.9 (m, 1H), 2.8 (m, 1H), 1.5 (s, 3H), 1.3 (s, 3H). 13 13C NMR (101 MHz, CDCl3) δ 169.5, 112.4, 104.9, 83.2, 79.4, 53.5, 34.2, 30.6, 26.8, 26.4.

[0074] P(DM - 2S): 1 1H NMR (400 MHz, CDCl3) δ 5.9 (m, J = 4.2 Hz, 1H), 5.2 (d, J = 3.3

[0075] Hz, 1H), 4.6 - 4.5 (m, 1H), 4.46 - 4.40 (m, 1H), 3.6 - 3.4 (m, 1H), 3.0 (m, 1H), 2.9 (m, 1H), 2.8 (m, 1H), 1.5 (s, 3H), 1.4 (m, 3H), 1.3 (d, J = 2.1 Hz, 3H). 13 13C NMR (151 MHz, DMSO - d6) δ 171.5, 111.3, 104.3, 82.5, 78.2, 76.5, 40.6, 28.3, 26.3, 26.0.

[0076] 3. Characterization of the Thermodynamic Properties of Polyester

[0077] To study the properties of the polymer, the present invention characterized the synthesized monomers and the corresponding polymers of their derivatives in terms of thermogravimetric temperature and glass transition temperature to study their stability.

[0078] The high-temperature resistance property of the polymer can be seen from the thermal decomposition temperature, thereby determining the application scope of the polymer. In the present invention, thermogravimetric analysis tests were respectively carried out on polymers P(DM), P(LM), and P(DM-2S) with a molecular weight of about 15.0 KDa. During the monitoring of the polymer mass, the temperature at which the polymer mass loss is 5% is taken as the thermal decomposition temperature T of the polymer. d , and the Ts of P(DM), P(LM), and P(DM-2S) were measured. d They were 294 °C, 297 °C, and 317 °C respectively. From Figure 2 in (a), it can be seen that the thermal decomposition temperatures of P(DM) and P(LM) with opposite steric structures are similar, both around 295 °C, indicating that substances with the same structure have roughly the same thermal properties. P(M4) has only one more chiral carbon on the polymer side chain than P(DM), and the thermal decomposition temperature of P(DM-2S) is 23 °C higher than that of P(DM), indicating that the thermal stability of the corresponding polymer can be improved by changing the chiral structure of the monomer.

[0079] In the present invention, differential scanning calorimetry tests (DSC) were respectively carried out on polymers P(DM), P(LM), and P(DM-2S) with a molecular weight of about 15.0 KDa to obtain their glass transition temperatures respectively. Figure 2 From (b) in

[0080] 4. Post-modification of the polymer

[0081]

[0082] In the present invention, by adjusting the reaction molar ratio of polymer P(DM) and m-chloroperoxybenzoic acid, different degrees of oxidation reactions were carried out on the thioether groups in the polymer backbone to obtain the corresponding polymer P(DM)-SO2s. The differential scanning calorimetry analysis results show (see Figure 3)。P(DM): When the molar ratio of m-chloroperbenzoic acid is 1:0.5, the glass transition temperature of the oxidized P(DM)-SO2 increases to 98.6 °C. When the molar ratio of P(DM):m-chloroperbenzoic acid is increased to 1:1, the glass transition temperature of the resulting polymer increases to 131.5 °C. When m-chloroperbenzoic acid participates in the reaction in a 2-fold molar amount, the sulfide groups on the polymer chain are completely converted to sulfone groups, resulting in the transformation of the polymer from an amorphous state to a semi-crystalline state. Along with the enhancement of stereoregularity, the crystallization temperature reaches 179.2 °C and the crystallization enthalpy is -16.60 J / mol. The thermogravimetric analysis results show that the thermal stability of the oxidized P(DM)-SO2 and P(LM)-SO2 is slightly lower than that of the polymers before oxidation ( Figure 4 as shown in (a) therein), but their thermal properties are effectively improved. From Figure 4 it can be seen from (b) therein that the oxidized P(DM)-SO2 and P(LM)-SO2 are both semi-crystalline materials. The melting peak temperature appears around 174 - 179 °C during the first heating. Although there is no melting peak during the second heating, the glass transition temperature remains at 145 - 157 °C, showing excellent thermal properties.

[0083] Example 6

[0084] Weigh 123 mg of P(DM) into three 10 mL reaction flasks respectively, and add 1 mL of dichloromethane to dissolve. Weigh 9.5 mg, 19.0 mg, and 38.0 mg of m-chloroperbenzoic acid, and add them to the three reaction flasks at 0 °C respectively, and react at room temperature for 1 h. After the reaction is completed, add 8 mL of anhydrous methanol to produce a white precipitate. Centrifuge and vacuum dry to constant weight to obtain the P(DM)-SO2 polymer.

[0085] Example 7

[0086] Weigh 123 mg of P(LM) into three 10 mL reaction flasks respectively, and add 1 mL of dichloromethane to dissolve. Weigh 9.5 mg, 19.0 mg, and 38.0 mg of m-chloroperbenzoic acid, and add them to the three reaction flasks at 0 °C respectively, and react at room temperature for 1 h. After the reaction is completed, add 8 mL of anhydrous methanol to produce a white precipitate. Centrifuge and vacuum dry to constant weight to obtain the P(LM)-SO2 polymer.

Claims

1. A method for synthesizing a xylosyl seven-membered cyclic lactone monomer, characterized in that: Three xylofuranose seven-membered cyclic lactone monomers with clear stereoconfiguration were synthesized through the selective bromination reaction of the primary alcohol group in 1,2-O-isopropylidene-α-xylofuranose substrate, the nucleophilic substitution reaction between the brominated product and methyl thioglycolate, the saponification reaction and the intramolecular cyclization reaction. The structural formulas of the three monomers are as follows:

2. The method for synthesizing a xylosyl seven-membered cyclic lactone monomer according to claim 1, characterized in that: The specific steps are as follows: First, triphenylphosphine, carbon tetrabromide and pyridine are added to 1,2-O-isopropylidene-α-xylofuranose in sequence, and the reaction is carried out in a solvent at 30-60°C to obtain xylofuranose in which the primary alcohol is substituted with bromine; after the xylofuranose in which the primary alcohol is substituted with bromine is purified by column chromatography, anhydrous potassium carbonate and methyl thioglycolate are added in sequence, and the mixture is heated to reflux in a solvent for 12-24 hours; after the reaction is completed, the product is purified by column chromatography, and then an excess of sodium hydroxide is added, and the mixture is reacted at room temperature in a solvent for 10-24 hours. After the reaction is completed, the pH of the reaction solution is adjusted to neutral and then extracted to obtain a crude product; 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride is added to the crude product under anhydrous and oxygen-free conditions, and then 4-dimethylaminopyridine is added as a catalyst, and the mixture is reacted at room temperature in a solvent for 6-24 hours. After the reaction is completed, a xylosyl seven-membered cyclic lactone monomer is obtained by column chromatography.

3. A method for synthesizing a xylosyl seven-membered cyclic lactone monomer according to claim 2, characterized in that: in, The molar ratios of triphenylphosphine, carbon tetrabromide, pyridine and 1,2-O-isopropylidene-α-xylofuranose are (1-2):1, (1-2):1, (1-5):1, respectively; The molar ratios of anhydrous potassium carbonate, methyl thioglycolate and 1,2-O-isopropylidene-α-xylofuranose are (1-2):1 and (1-2):1, respectively; The molar ratios of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 4-dimethylaminopyridine and 1,2-O-isopropylidene-α-xylofuranose are (1-2):1 and (0.05-0.1):1, respectively.

4. The method for synthesizing a xylosyl seven-membered cyclic lactone monomer according to claim 2, characterized in that: The solvent is one of dichloromethane, acetone, methanol, acetonitrile and tetrahydrofuran, or a mixture of two or more thereof.

5. A method for synthesizing a xylosyl seven-membered cyclic polyester, comprising: using a xylosyl seven-membered cyclic lactone monomer prepared by any one of the methods of claims 1 to 4, characterized in that: An organic catalyst or a metal catalyst and an initiator are used to initiate the ring-opening polymerization of the xylosyl seven-membered cyclic lactone monomer to obtain a synthetic xylosyl seven-membered cyclic polyester.

6. A method for synthesizing a xylosyl seven-membered cyclic polyester according to claim 5, characterized in that: The specific steps are as follows: The method comprises the following steps: adding a solvent to the seven-membered cyclic monomer under anhydrous and oxygen-free conditions to dissolve the monomer, then adding an initiator and a catalyst, and reacting the monomer at 10-120° C. for 2-24 hours; using a quenching reagent to quench the polymerization reaction after the reaction is completed, and then adding a poor solvent used for recrystallization to the polymerization reaction solution to generate a white precipitate; centrifuging the mixture, and vacuum drying the mixture to a constant weight to obtain a synthetic xylose-based seven-membered cyclic polyester.

7. A method for synthesizing a xylosyl seven-membered cyclic polyester according to claim 6, characterized in that: The molar ratios of the initiator, the catalyst and the xylose seven-membered cyclic lactone monomer are (0.001%-20%):1 and (0.001%-20%):1 respectively.

8. The method for synthesizing a xylosyl seven-membered cyclic polyester according to claim 6, characterized in that: The organic catalyst is one or a mixture of two or more of 1,5,7-triazidobicyclo[4.4.0]dec-5-ene, 1,8-diazabicyclo[5.4.0]undec-7-ene, 1,5-diazabicyclo[4.3.0]non-5-ene, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene and tetramethylguanidine; The metal catalyst is one of β-diimine zinc catalyst and stannous octoate, or a mixture of the two; The initiator is one of benzyl alcohol, 4-methylbenzyl alcohol and polyether polyol or a mixture of two of them.

9. The method for synthesizing a xylosyl seven-membered cyclic polyester according to claim 6, characterized in that: The solvent is one of dichloromethane, tetrahydrofuran, toluene, dioxane and trimethylbenzene or a mixture of two or more thereof.

10. The method for synthesizing a xylosyl seven-membered cyclic polyester according to claim 6, characterized in that: The quenching reagent is hydrochloric acid or toluenesulfonic acid; the poor solvent is one or a mixture of two or more of ether, methanol, ethanol and toluene.

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