A recyclable high molecular weight polysalicylate green material

Abstract

A kind of recyclable high molecular weight polysalicylate green material belongs to the field of material synthesis. With six-membered ring internal anhydride ester monomer (R-SAOCAs) prepared from salicylic acid and its derivatives as raw material, Lewis base and thiourea (urea) are used to catalyze the fast controllable ring-opening polymerization of the monomer at room temperature in inert gas atmosphere and in suitable polymerization solvent, to prepare polysalicylate polymer material with number average molecular weight of more than 100,000 and molecular weight distribution within 1.30, and with accurate structure. The new type of polysalicylate polymer material has a high glass transition temperature comparable to polystyrene, and can be used as a substitute product of petroleum-based chemicals. At the same time, the polyester structure of the main chain endows the material with good degradation performance, and the material can be recycled and regenerated into salicylic acid small molecules under suitable conditions. The development of the new type of high molecular weight polysalicylate material provides a new window for the sustainable development of green materials.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of green high-molecular polyester material synthesis, and particularly relates to Lewis base and thiourea (urea) catalyzing ring-opening polymerization of salicylic acid anhydride ester monomers in a suitable organic solvent to prepare recyclable high-molecular-weight polysalicylic acid material. BACKGROUND

[0002] Polysalicylic acid (PSA) is an important polymer material. Its backbone structure is salicylic acid, which is an aromatic β-hydroxy acid and has good anti-inflammatory and analgesic, malaria treatment and other pharmacological activities [1] . In addition, salicylic acid with different substituents, such as 5-chlorosalicylic acid (5-Cl-SA), is the pharmacologically active part of the prodrug Meseclazone and Seclazone for relieving pain [2] . 4-trifluoromethylsalicylic acid (4-CF3-SA) is a platelet anti-aggregation agent [3] . 4-trifluoromethylsalicylic acid can inhibit the activities of platelet cyclooxygenase and c-AMP phosphodiesterase [4] . Polysalicylic acid ester material has good biocompatibility and degradability, and is a green material with wide application prospect.

[0003]

[0004] In addition, the ester group on the PSA polymer backbone is directly connected to the benzene ring, which is similar to the backbone structure of polystyrene (PS) [5] , polyethylene terephthalate (PET) [6-7] (Formula I). PSA prepared by ring-opening polymerization can be used as a polymer with high T g g to process into valuable products,

[0005] At present, there are still many difficulties in the preparation of polysalicylic acid material: the raw material is limited to only salicylic acid; the obtained material is mostly copolymer, and it is difficult to obtain high-molecular-weight polysalicylic acid ester material. For example, in 2018, Serpell team prepared polysalicylic acid ester by condensation polymerization based on the method of White and Socha. First, under the protection of nitrogen, acetic anhydride and salicylic acid were heated to reflux at a temperature of 150-200℃ for 6-24 hours, and then the temperature was increased to 250-300℃, and the acetic acid by-product was removed under vacuum. After cooling, a linear polymer with a repeating unit of salicylic acid was obtained (M n = 688, ). However, the experimental conditions of this method are harsh, and the prepared polysalicylic acid has only about 10 repeating units, which greatly limits the application of this method [8]Until 2021, Professor Yang Jing's research group of Beijing University of Chemical Technology successfully obtained M n = 14.1 kg·mol -1 , homopolymer PSA material. However, due to the polymerization-induced self-assembly of PSA in THF solvent, it is difficult to further increase the molecular weight of the polymer [9] .

[0006] In summary, the current application of ring-opening polymerization synthesis of polysalicylate materials is only focused on one raw material of salicylic acid, and the obtained polymer material has a molecular weight of less than 14.1 kg·mol -1 material, and it is difficult to prepare high molecular weight PSA material due to the limitation of catalyst and reaction solvent.

[0007] The present application successfully prepared a variety of different substituted salicylic acid anhydride ester monomers (R-SAOCA) by using triphosgene method, which greatly expanded the types of salicylic acid polymer materials and the performance and application of salicylic acid materials; through the research on the performance of Lewis base (LB) and thiourea or urea (TU or U) catalyst, a method for preparing high molecular weight polysalicylate material under the catalytic system condition of R-SAOCA ring-opening polymerization was successfully established. The prepared new high molecular weight polysalicylic acid material has good thermal physical properties and can quickly degrade into salicylic acid small molecules (R-SA) under suitable conditions, and the obtained salicylic acid small molecules (R-SA) can be further prepared (can refer to the prior art) into salicylic acid anhydride ester monomers (R-SAOCA), thereby forming a kind of recyclable high molecular weight polysalicylate green material.

[0008] Reference:

[0009] [1]. J. G. Mahdi, A. J. Mahdi, A. J. Mahdi and I. D. Bowen Cell Prolif. 2006, 39, 147-155.

[0010] [2]. Sofia, R. Pharmacology 1978, 16, 148-152.

[0011] [3]. Bayon, Y.; Alonso, A.; Crespo, M. Br. J. Pharmacol. 1999, 126, 1359-1366.

[0012] [4]. Lee, J.; Lee, H.; Andrade, J. Prog. Polym. Sci. 1995, 20, 1043-1079.

[0013] [5] Liang X M, Jiang H C, Fang J L, et al.; Chemical Engineering Communications, 2018: 1-12.

[0014] [6] KIM H J, REDDI Y, CRAMER C J, et al. ACS Macro Lett., 2020, 9(1): 96-102.

[0015] [7] WHITE D M, SOCHA L A. Method for preparing polysalicylates: Application: US, 1988-1570104855483. 19880218.

[0016] [8] KRICHELDORF H R, LOMADZE N, SCHWARZ G. J. Macromol. Sci., Part A Pure Appl. Chem., 2009, 46(4): 346-352.[9] Han S, Yao S, Meng W, et al.; Polymer Chemistry, 2021, 12. 6465-6471. SUMMARY

[0017] The present application provides a method for synthesizing high molecular weight polysalicylate materials of more than 100,000. The material is prepared by ring-opening polymerization of internal anhydride ester monomers of salicylic acid derivatives catalyzed by a suitable Lewis base (LB) and thiourea or urea (TU or U) in a suitable solvent condition; the LB and TU (U) catalytic system used is the key to prepare high molecular weight polymers, which solves the limitation of simple organic base catalytic activity and difficulty in preparing high molecular weight polymers; at the same time, the catalytic system has good monomer applicability and wide range, and can catalyze the ring-opening polymerization of a variety of R-SAOCA monomers to prepare a series of salicylic acid polyester materials. The prepared material has good degradation performance and can be quickly degraded into salicylic acid under molecules under suitable conditions, thereby realizing the recycling of the material.

[0018] Provided is a method for preparing high molecular weight polysalicylate materials with different side chain groups and recycling the materials into small molecule raw materials by degradation, which is catalyzed by a Lewis base (LB) and thiourea or urea (TU or U) system (hereinafter abbreviated as LB, TU(U)), comprising the following steps:

[0019] a) The polymerization reaction is carried out at room temperature in an inert gas atmosphere, the Lewis base (LB) and thiourea or urea (TU or U) catalyst and the initiator ROH or R2NH are added to the reaction bottle in proportion, a suitable reaction solvent is added, and after sufficient stirring, the salicylic acid end anhydride ester monomer (R-SAOCA) is added for polymerization reaction. After monitoring the completion of monomer conversion, the polymerization reaction solution is precipitated in a precipitant, centrifuged and dried to obtain the polymerization product, i.e. the polysalicylic acid material.

[0020]

[0021] The salicylic acid end anhydride ester monomer (R-SAOCA) with different substituents includes but is not limited to SAOCA, 5-MeSAOCA, 4-MeSAOCA, 3-MeSAOCA, 5-MeOSAOCA, 4-MeOSAOCA, 5-ClSAOCA, 5-BrSAOCA, 4-FSAOCA, 4-CF3SAOCA, 5-NH2OSAOCA, 4-NH2SAOCA, 5-NO2SAOCA, NapSAOCA, 3,5- t BuSAOCA, etc.

[0022] The salicylic acid end anhydride ester monomer (R-SAOCA) is preferably SAOCA, 5-MeSAOCA, 4-MeSAOCA, 3-MeSAOCA, 4-FSAOCA, 4-CF3SAOCA.

[0023] The structure of the LB catalyst is shown in formula (III), including 8 different structures of carbene, phosphazene, tertiary amine, imine, etc. The LB is preferably NHC-1 or BEMP.

[0024] The structure of TU(U) in the catalyst is shown in formula (III), including 12 different substituents of thiourea or urea. The TU(U) is preferably TU-3 / 4.

[0025] In the catalyst, the proportion of LB and TU or U is LB:TU(U) molar ratio = 0.5:0.5-0.5:5, preferably LB:TU(U) molar ratio = 0.5:3.

[0026]

[0027] The anhydrous solvent for the polymerization reaction is an anhydrous solvent selected from one or more of tetrahydrofuran (THF), dioxane (Dio), dichloromethane (DCM), trichloromethane (TCM), toluene (TOL), N,N-dimethylformamide (DMF), acetonitrile (MeCN), and the like. Preferably, the anhydrous solvent is tetrahydrofuran (THF) or a mixture of THF / DMF.

[0028] The initiator is selected from initiators containing hydroxyl or amine groups, including monohydroxy initiators: benzyl alcohol, n-hexanol, ethanol, phenol, polyethylene glycol monomethyl ether, and the like; polyhydroxy initiators: pentaerythritol, p-xylenediol; carboxylic acid initiators: benzoic acid, formic acid, and the like; and primary amine initiators: n-hexylamine, benzylamine, adamantylamine, and the like. Preferably, the initiator is benzyl alcohol.

[0029] The catalyst corresponds to 50-1300 moles of monomer per mole of LB.

[0030] The ratio of initiator to monomer can be any ratio as desired, such as a molar ratio of 1:50-1300.

[0031] The specific reaction process is shown below:

[0032]

[0033] n is 50-1300.

[0034] In the polymerization reaction, the monomer is SAOCA, the initiator is preferably benzyl alcohol, TU(U) is preferably TU-3, LB is preferably NHC-1, the ratio of LB to TU is preferably LB:TU=0.5:3, the reaction solvent is preferably THF, and the ratio of initiator to monomer is 1:50-600.

[0035] In the polymerization reaction, the monomer is SAOCA, the initiator is preferably benzyl alcohol, TU(U) is preferably TU-3, LB is preferably BEMP, the ratio of LB to TU is preferably LB:TU=0.5:3, the reaction solvent is preferably a THF / DMF mixed solvent, and the ratio of initiator to monomer is 1:700-1300.

[0036] In the polymerization reaction, the monomer is 5-MeSAOCA, the initiator is preferably benzyl alcohol or n-hexanol, n-hexylamine, phenol, benzoic acid, TU(U) is preferably TU-3, LB is preferably NHC-1, the ratio of LB to TU is preferably LB:TU=0.5:3, the reaction solvent is preferably THF, and the ratio of initiator to monomer is 1:50-200.

[0037] In the polymerization reaction, the monomer is 5-MeSAOCA, the initiator is preferably TU-3; the LB is preferably BEMP; the ratio of LB and TU is preferably LB: TU = 0.5:3; the reaction solvent is preferably THF; the ratio of initiator to monomer is 1:200-600.

[0038] In the polymerization reaction, the monomer is 4-MeSAOCA, the initiator is preferably benzyl alcohol; TU(U) is preferably TU-3; the LB is preferably NHC-1; the ratio of LB and TU is preferably LB: TU = 0.5:3; the reaction solvent is preferably a THF / DMF mixed solvent; the ratio of initiator to monomer is 1:50-200.

[0039] In the polymerization reaction, the monomer is 3-MeSAOCA, the initiator is preferably benzyl alcohol; TU(U) is preferably TU-4; the LB is preferably NHC-1; the ratio of LB and TU is preferably LB: TU = 0.5:3; the reaction solvent is preferably a THF / DMF mixed solvent; the ratio of initiator to monomer is 1:50-300.

[0040] In the polymerization reaction, the monomer is 4-FSAOCA, the initiator is preferably benzyl alcohol; TU(U) is preferably TU-4; the LB is preferably NHC-1; the ratio of LB and TU is preferably LB: TU = 0.5:3; the reaction solvent is preferably DMF; the ratio of initiator to monomer is 1:50-200.

[0041] In the polymerization reaction, the monomer is 4-CF3SAOCA, the initiator is preferably benzyl alcohol; TU(U) is preferably TU-4; the LB is preferably BEMP; the ratio of LB and TU is preferably LB: TU = 0.5:3; the reaction solvent is preferably THF; the ratio of initiator to monomer is 1:50-300.

[0042] The catalysts, initiators and organic solvents used above are directly purchased from reagent companies without purification, are cheap and easy to obtain, and are simple to operate. When the proportion of the catalysts used is LB:TU=0.5:3, the obtained polymer structure and controllability of the molecular weight are optimal and consistent with the expected theoretical value. When the molar ratio of the feeding of one of LB or TU alone is changed, the controllability of the polymerization reaction is reduced to a certain extent, and the reaction efficiency is also affected. Therefore, LB:TU=0.5:3 is the most optimal in terms of controllability and reaction efficiency. The use of benzyl alcohol as an initiator has a similar benzene ring structure to the polymer main chain and does not cause great interference to the performance of the polymer material. At the same time, the methylene group of benzyl alcohol can be used as a characteristic signal for polymer characterization. The polymerization reaction solvent is preferably THF and DMF with strong solubility, or a mixed solvent of the two, which is beneficial to the preparation of high molecular weight polymers. Due to the influence of different substituents on the activity and steric hindrance of the monomers, different solvents, different catalyst systems NHC-1 or BEMP, TU-3 or TU-4 are selected for the polymerization of monomers with different substituents to achieve the best polymerization effect. Details are shown in the examples below.

[0043] b) The high molecular weight polysalicylic acid material prepared in the application is degraded by heating under the conditions of a solvent and a catalyst to obtain a salicylic acid small molecule (R-SA). The obtained salicylic acid small molecule (R-SA) can be further prepared (which can be referred to in the prior art) into a salicylic acid endocyclic anhydride ester monomer (R-SAOCA), thereby forming a recyclable high molecular weight polysalicylic acid ester green material. One of the degradation process steps is shown in formula IV:

[0044]

[0045] The specific reaction process is as follows:

[0046] The polymer degradation experiment is carried out in an oil bath. A certain amount of polysalicylic acid ester material is weighed, dissolved in a high-boiling solvent, and transferred to a thick-walled glass reaction tube, and a catalyst is added. After the above reaction tube is sealed, it is placed in a 120℃ oil bath for reaction. The degradation condition is monitored every 2h. After the material is completely degraded, the reaction solvent is dried by rotary evaporation, and the degradation product is recovered by vacuum distillation (vacuum degree: 45Pa; 95-100℃ fraction is collected).

[0047] In reaction formula IV, the catalysts include but are not limited to Lewis bases TBD, DBU, BEMP, and inorganic bases NaOH, KOH, etc. The reaction temperature is 50℃-180℃, the reaction solvent is preferably DMF, TOL, TCE, etc., and the reaction time is 2-8h. Among them, the catalyst is preferably TBD; the reaction temperature is preferably 120℃; and the reaction solvent is preferably DMF.

[0048] The method of the present application makes the polymer material structure accurate, the preparation process is fast and controllable ring-opening polymerization, the obtained material is a structure accurate polysalicylate high molecular material with controllable number average molecular weight and the molecular weight distribution is within 1.30. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 The nuclear magnetic (A) and mass spectrum (B / C) characterization graphs of the product obtained by ring-opening polymerization of 5-MeSAOCA with n = 50, benzyl alcohol as an initiator, and TU-3 / NHC-1 = 0.5:3 catalysis of TU-3 / NHC-1 = 0.5:3;

[0050] Figure 2 The nuclear magnetic (A) and mass spectrum (B / C) characterization graphs of the product obtained by ring-opening polymerization of 5-MeSAOCA with n = 50, benzyl alcohol as an initiator, and TU-3 / NHC-1 = 0.5:3 catalysis of TU-3 / NHC-1 = 0.5:3;

[0051] Figure 3 The nuclear magnetic (A) and mass spectrum (B / C) characterization graphs of the product obtained by ring-opening polymerization of 5-MeSAOCA with n = 50, benzyl alcohol as an initiator, and TU-3 / NHC-1 = 0.5:3 catalysis of TU-3 / NHC-1 = 0.5:3;

[0052] Figure 4 The nuclear magnetic (A) and mass spectrum (B / C) characterization graphs of the product obtained by ring-opening polymerization of 5-MeSAOCA with n = 50, benzyl alcohol as an initiator, and TU-3 / NHC-1 = 0.5:3 catalysis of TU-3 / NHC-1 = 0.5:3;

[0053] Figure 5 The nuclear magnetic (A) and mass spectrum (B / C) characterization graphs of the product obtained by ring-opening polymerization of 5-MeSAOCA with n = 50, benzyl alcohol as an initiator, and TU-3 / NHC-1 = 0.5:3 catalysis of TU-3 / NHC-1 = 0.5:3;

[0054] Figure 6 The nuclear magnetic (A) and mass spectrum (B / C) characterization graphs of the product obtained by ring-opening polymerization of 5-MeSAOCA with n = 50, benzyl alcohol as an initiator, and TU-3 / NHC-1 = 0.5:3 catalysis of TU-3 / NHC-1 = 0.5:3;

[0055] Figure 7 The nuclear magnetic (A) and mass spectrum (B / C) characterization graphs of the product obtained by ring-opening polymerization of 5-MeSAOCA with n = 50, benzyl alcohol as an initiator, and TU-3 / NHC-1 = 0.5:3 catalysis of TU-3 / NHC-1 = 0.5:3;

[0056] Figure 8 The nuclear magnetic (A) and mass spectrum (B / C) characterization graphs of the product obtained by ring-opening polymerization of 5-MeSAOCA with n = 50, benzyl alcohol as an initiator, and TU-3 / NHC-1 = 0.5:3 catalysis of TU-3 / NHC-1 = 0.5:3;

[0057] Figure 9 The nuclear magnetic (A) and mass spectrum (B / C) characterization graphs of the product obtained by ring-opening polymerization of 5-MeSAOCA with n = 50, benzyl alcohol as an initiator, and TU-3 / NHC-1 = 0.5:3 catalysis of TU-3 / NHC-1 = 0.5:3;

[0058] Figure 10 PSA (Example 1, attached Figure 2 , PSA degradation products and salicylic acid raw material nuclear magnetic hydrogen spectrum. DETAILED DESCRIPTION

[0059] The application is further illustrated by the following examples, but the application is not limited to the following examples. In the following examples, all the substance ratios are molar ratios, LB: TU = 0.5:3, and the precipitator is ethyl ether, n-hexane, and methanol (the volume ratio of the three is preferably 1 / 2 / 1).

[0060] Example 1

[0061] The polymerization reaction was carried out in a glove box under a nitrogen atmosphere at room temperature. NHC-1 and TU-3 and initiator benzyl alcohol were added to a 25ml Schlenk tube. Then, anhydrous THF solution was added. After stirring for 10min, 200 equivalents of SAOCA monomer were added. After 30min, the monomer conversion rate reached more than 95%. The reaction solution was precipitated three times in a precipitator and dried to obtain a white polymer sample. Gel permeation chromatography (GPC) results showed that the molecular weight M n = 25.40KDa, and the molecular weight distribution

[0062] Example 2

[0063] The polymerization reaction was carried out in a glove box under a nitrogen atmosphere at room temperature. NHC-1 and TU-3 and initiator benzyl alcohol were added to a 25ml Schlenk tube. Then, anhydrous THF solution was added. After stirring for 10min, 300 equivalents of SAOCA monomer were added. After 90min, the monomer conversion rate reached more than 95%. The reaction solution was precipitated three times in a precipitator and dried to obtain a white polymer sample. Gel permeation chromatography (GPC) results showed that the molecular weight M n = 33.97KDa, and the molecular weight distribution

[0064] Example 3

[0065] The polymerization reaction was carried out in a glove box under a nitrogen atmosphere at room temperature. NHC-1 and TU-3 and initiator benzyl alcohol were added to a 25ml Schlenk tube. Then, anhydrous THF solution was added. After stirring for 10min, 400 equivalents of SAOCA monomer were added. After 80min, the monomer conversion rate reached more than 95%. The reaction solution was precipitated three times in a precipitator and dried to obtain a white polymer sample. Gel permeation chromatography (GPC) results showed that the molecular weight M n = 51.75KDa, and the molecular weight distribution

[0066] Example 4

[0067] The polymerization reaction was carried out in a glove box under a nitrogen atmosphere at room temperature. NHC-1, TU-3, and the initiator benzyl alcohol were added to a 25 mL Schlenk tube; then anhydrous THF solution was added, and the mixture was stirred for 10 min. 500 equivalents of SAOCA monomer were then added. After 100 min, the monomer conversion reached over 95%. The reaction solution was precipitated three times in a precipitant and dried to obtain a white polymer sample. Gel permeation chromatography (GPC) results showed that the molecular weight M of the obtained polymer was... n =52.17 kDa, molecular weight distribution

[0068] Example 5

[0069] The polymerization reaction was carried out in a glove box under a nitrogen atmosphere at room temperature. BEMP, TU-3, and the initiator benzyl alcohol were added to a 25 mL Schlenk tube; then an anhydrous THF / DMF mixture of 8 / 1 was added. After mixing and stirring for 10 min, 600 equivalents of SAOCA monomer were added. After 210 min, the monomer conversion reached over 95%. The reaction solution was precipitated three times in a precipitant and dried to obtain a white polymer sample. Gel permeation chromatography (GPC) results showed that the molecular weight M of the obtained polymer was... n =71.86 kDa, molecular weight distribution

[0070] Example 6

[0071] The polymerization reaction was carried out in a glove box under a nitrogen atmosphere at room temperature. BEMP, TU-3, and the initiator benzyl alcohol were added to a 25 ml Schlenk tube; then an anhydrous THF / DMF mixture of 8 / 1 was added. After mixing and stirring for 10 min, 800 equivalents of SAOCA monomer were added. After 140 min, the monomer conversion reached over 95%. The reaction solution was precipitated three times in a precipitant and dried to obtain a white polymer sample. Gel permeation chromatography (GPC) results showed that the molecular weight M of the obtained polymer was... n =107.60 kDa, molecular weight distribution

[0072] Example 7

[0073] The polymerization reaction was carried out in a glove box under a nitrogen atmosphere at room temperature. BEMP, TU-3, and the initiator benzyl alcohol were added to a 25 ml Schlenk tube; then an anhydrous THF / DMF (8 / 1) mixture was added, and after stirring for 10 min, 1200 equivalents of SAOCA monomer were added. After 210 min, the monomer conversion reached over 95%. The reaction solution was precipitated three times in a precipitant and dried to obtain a white polymer sample. Gel permeation chromatography (GPC) results showed that the molecular weight M of the obtained polymer was... n= 152.15 KDa, molecular weight distribution

[0074] Example 8

[0075] The polymerization reaction was carried out in a glove box under nitrogen atmosphere at room temperature. NHC-1 and TU-3 and amine initiator: n-hexylamine were added into a 25ml Schlenk tube. After stirring for 10min, 50 equivalents of 5-MeSAOCA monomer were added. After 10min, the monomer conversion reached more than 95%. The reaction solution was precipitated in precipitator three times and dried to get white polymer sample. The gel permeation chromatography (GPC) results showed that the molecular weight of the polymer obtained was M n = 6.72 KDa, molecular weight distribution

[0076] Example 9

[0077] The polymerization reaction was carried out in a glove box under nitrogen atmosphere at room temperature. NHC-1 and TU-3 and amine initiator: n-hexylamine were added into a 25ml Schlenk tube. After stirring for 10min, 50 equivalents of 5-MeSAOCA monomer were added. After 10min, the monomer conversion reached more than 95%. The reaction solution was precipitated in precipitator three times and dried to get white polymer sample. The gel permeation chromatography (GPC) results showed that the molecular weight of the polymer obtained was M n = 7.59 KDa, molecular weight distribution

[0078] Example 10

[0079] The polymerization reaction was carried out in a glove box under nitrogen atmosphere at room temperature. NHC-1 and TU-3 and polyol initiator: pentaerythritol were added into a 25ml Schlenk tube. After stirring for 10min, 50 equivalents of 5-MeSAOCA monomer were added. After 60min, the monomer conversion reached more than 95%. The reaction solution was precipitated in precipitator three times and dried to get white polymer sample. The gel permeation chromatography (GPC) results showed that the molecular weight of the polymer obtained was M n = 5.52 KDa, molecular weight distribution

[0080] Example 11

[0081] The polymerization was carried out in a glove box under nitrogen atmosphere at room temperature. NHC-1 and TU-3 and carboxylic acid initiator, benzoic acid, were added into a 25ml Schlenk tube. Anhydrous THF was added, and after 10min stirring, 50 equivalents of 5-MeSAOCA monomer were added. After 25min, the monomer conversion reached more than 95%, and the reaction solution was precipitated three times in precipitator and dried to obtain white polymer sample. Gel permeation chromatography (GPC) results showed that the molecular weight of the obtained polymer was M n = 8.27KDa, and the molecular weight distribution

[0082] Example 12

[0083] The polymerization was carried out in a glove box under nitrogen atmosphere at room temperature. NHC-1 and TU-3 and long-chain monohydroxyl initiator, mPEG-OH 2000 , were added into a 25ml Schlenk tube. Anhydrous THF was added, and after 10min stirring, 50 equivalents of 5-MeSAOCA monomer were added. After 30min, the monomer conversion reached more than 95%, and the reaction solution was precipitated three times in precipitator and dried to obtain white polymer sample. Gel permeation chromatography (GPC) results showed that the molecular weight of the obtained polymer was M n = 10.50KDa, and the molecular weight distribution

[0084] Example 13

[0085] The polymerization was carried out in a glove box under nitrogen atmosphere at room temperature. BEMP and TU-3 and initiator, benzyl alcohol, were added into a 25ml Schlenk tube. Anhydrous THF was added, and after 50min stirring, 200 equivalents of 5-MeSAOCA monomer were added. After 60min, the monomer conversion reached more than 95%, and the reaction solution was precipitated three times in precipitator and dried to obtain white polymer sample. Gel permeation chromatography (GPC) results showed that the molecular weight of the obtained polymer was M n = 20.88KDa, and the molecular weight distribution

[0086] Example 14

[0087] The polymerization was carried out in a glove box under nitrogen atmosphere at room temperature. BEMP and TU-3 and initiator, benzyl alcohol, were added into a 25ml Schlenk tube. Anhydrous THF was added, and after 10min stirring, 300 equivalents of 5-MeSAOCA monomer were added. After 70min, the monomer conversion reached more than 95%, and the reaction solution was precipitated three times in precipitator and dried to obtain white polymer sample. Gel permeation chromatography (GPC) results showed that the molecular weight of the obtained polymer was M n = 39.20KDa, and the molecular weight distribution

[0088] Example 15

[0089] The polymerization reaction was carried out in a glove box under a nitrogen atmosphere at room temperature. BMMP, TU-3, and the initiator benzyl alcohol were added to a 25 ml Schlenk tube; then anhydrous THF / DMF (8 / 1) mixed solvent was added, and the mixture was stirred for 10 min. 500 equivalents of 5-MeSAOCA monomer were added, and after 150 min, the monomer conversion reached over 95%. The reaction solution was precipitated three times in a precipitant and dried to obtain a white polymer sample. Gel permeation chromatography (GPC) results showed that the molecular weight M of the obtained polymer was... n = 66.34 kDa, molecular weight distribution

[0090] Example 16

[0091] The polymerization reaction was carried out in a glove box under a nitrogen atmosphere at room temperature. BEMP, TU-3, and the initiator benzyl alcohol were added to a 25 ml Schlenk tube; then anhydrous THF / DMF (8 / 1) mixed solvent was added, and the mixture was stirred for 10 min. 600 equivalents of 5-MeSAOCA monomer were added, and after 180 min, the monomer conversion reached over 95%. The reaction solution was precipitated three times in a precipitant and dried to obtain a white polymer sample. Gel permeation chromatography (GPC) results showed that the molecular weight M of the obtained polymer was... n = 87.04 kDa, molecular weight distribution

[0092] Example 17

[0093] The polymerization reaction was carried out in a glove box under a nitrogen atmosphere at room temperature. NHC-1, TU-3, and 1 equivalent of benzyl alcohol were added to a 25 ml Schlenk tube; then anhydrous THF solution was added, and the mixture was stirred for 10 min. Afterward, 50 equivalents of 4-MeSAOCA monomer were added. After 20 min, the monomer conversion reached over 95%. The reaction solution was precipitated three times in a precipitant and dried to obtain a white polymer sample. Gel permeation chromatography (GPC) results showed that the molecular weight M of the obtained polymer was... n =7.33 kDa, molecular weight distribution

[0094] Example 18

[0095] The polymerization was carried out in a glove box under nitrogen atmosphere at room temperature. NHC-1 and TU-3 and initiator benzyl alcohol were added into a 25ml Schlenk tube. Then anhydrous THF / DMF=4 / 1 mixed solvent was added. After stirring for 10min, 150 equivalents of 4-MeSAOCA monomer were added. After 80min, the monomer conversion reached more than 95%. The reaction solution was precipitated in precipitator for three times and dried to get white polymer sample. The gel permeation chromatography (GPC) results showed that the molecular weight of the obtained polymer was M n = 19.76 KDa, and the molecular weight distribution

[0096] Example 19

[0097] The polymerization was carried out in a glove box under nitrogen atmosphere at room temperature. NHC-1 and TU-4 and initiator benzyl alcohol were added into a 25ml Schlenk tube. Then anhydrous THF solution was added. After stirring for 10min, 50 equivalents of 3-MeSAOCA monomer were added. After 30min, the monomer conversion reached more than 95%. The reaction solution was precipitated in precipitator for three times and dried to get white polymer sample. The gel permeation chromatography (GPC) results showed that the molecular weight of the obtained polymer was M n = 6.28 KDa, and the molecular weight distribution

[0098] Example 20

[0099] The polymerization was carried out in a glove box under nitrogen atmosphere at room temperature. BEMP and TU-4 and initiator benzyl alcohol were added into a 25ml Schlenk tube. Then anhydrous THF / DMF=4 / 1 mixed solvent was added. After stirring for 10min, 300 equivalents of 3-MeSAOCA monomer were added. After 230min, the monomer conversion reached more than 95%. The reaction solution was precipitated in precipitator for three times and dried to get white polymer sample. The gel permeation chromatography (GPC) results showed that the molecular weight of the obtained polymer was M n = 45.01 KDa, and the molecular weight distribution

[0100] Example 21

[0101] The polymerization was carried out in a glove box under nitrogen atmosphere at room temperature. NHC-1 and TU-4 and initiator benzyl alcohol were added into a 25ml Schlenk tube. Then anhydrous THF solution was added. After stirring for 10min, 50 equivalents of 4-CF3SAOCA monomer were added. After 5min, the monomer conversion reached more than 95%. The reaction solution was precipitated in precipitator for three times and dried to get white polymer sample. The gel permeation chromatography (GPC) results showed that the molecular weight of the obtained polymer was M n = 8.35 KDa, and the molecular weight distribution

[0102] Example 22

[0103] The polymerization was carried out in a glove box under nitrogen atmosphere at room temperature. NHC-1 and TU-4 and initiator benzyl alcohol were added into a 25ml Schlenk tube. After 10min stirring, 200 equivalents of 4-CF3SAOCA monomer was added. After 20min, the monomer conversion reached more than 95%. The reaction solution was precipitated in precipitator for three times and dried to get white polymer sample. The gel permeation chromatography (GPC) result showed that the molecular weight of the polymer was M n = 34.50KDa, and the molecular weight distribution

[0104] Example 23

[0105] The polymerization was carried out in a glove box under nitrogen atmosphere at room temperature. NHC-1 and TU-4 and initiator benzyl alcohol were added into a 25ml Schlenk tube. After 10min stirring, 50 equivalents of 4-CF3SAOCA monomer was added. After 5min, the monomer conversion reached more than 95%. The reaction solution was precipitated in precipitator for three times and dried to get white polymer sample. The gel permeation chromatography (GPC) result showed that the molecular weight of the polymer was M n = 7.83KDa, and the molecular weight distribution

[0106] Example 24

[0107] The polymerization was carried out in a glove box under nitrogen atmosphere at room temperature. NHC-1 and TU-4 and 1 equivalent of initiator benzyl alcohol were added into a 25ml Schlenk tube. After 10min stirring, 200 equivalents of 4-CF3SAOCA monomer was added. After 20min, the monomer conversion reached more than 95%. The reaction solution was precipitated in precipitator for three times and dried to get white polymer sample. The gel permeation chromatography (GPC) result showed that the molecular weight of the polymer was M n = 25.51KDa, and the molecular weight distribution

[0108] Example 25

[0109] The degradation experiment of the polymer was carried out in an oil bath at 120°C. A certain amount of the polysalicylate material obtained in Example 1 (structure as shown in the attached figure) was weighed and added into a 20ml Schlenk tube. After 10min stirring, 1 equivalent of 4-CF3SAOCA monomer was added. After 20min, the monomer conversion reached more than 95%. The reaction solution was precipitated in precipitator for three times and dried to get white polymer sample. The gel permeation chromatography (GPC) result showed that the molecular weight of the polymer was M Figure 2The material was dissolved in DMF solvent (5 mg / ml) and transferred to a thick-walled glass reaction tube, 1% mol of TBD catalyst was added. The reaction tube was sealed and placed in an oil bath at 120°C. The degradation was monitored by sampling every 2 h. After complete degradation of the material, the reaction solvent was evaporated and the degradation product was recovered by means of distillation under reduced pressure (vacuum: 45 Pa; collection of the fraction at 95-100°C).

Claims

1. A method for preparing a recyclable high molecular weight polysalicylic acid ester-based green material, characterized in that, Includes the following steps: The polymerization reaction is carried out in an inert gas atmosphere at room temperature. Lewis base LB, thiourea TU or urea U catalyst, and initiators containing hydroxyl or amine groups or carboxylic acid initiators are added to the reaction flask in proportion. A suitable reaction solvent is added, and after thorough stirring, salicylic acid anhydride ester monomer R-SAOCA is added to carry out the polymerization reaction. After monitoring the completion of monomer conversion, the polymerization reaction solution is precipitated in a precipitant, centrifuged and dried to obtain the polymerization product - polysalicylic acid ester material. The structure of the LB catalyst is shown below. ; The TU or U structure in the catalyst is shown below, and is selected from thiourea or urea with different substituents; ； Hydroxyl initiators are selected from: benzyl alcohol, n-hexanol, ethanol, phenol, polyethylene glycol monomethyl ether, pentaerythritol, and terephthalic acid; carboxylic acid initiators are selected from: benzoic acid and formic acid; and amine initiators are selected from: n-hexylamine, benzylamine, and adamantaneamine. R-SAOCA is selected from one of the following: 。 2. The method according to claim 1, characterized in that, The salicylic acid anhydride ester monomer R-SAOCA is selected from SAOCA, 5-MeSAOCA, 4-MeSAOCA, 3-MeSAOCA, 4-FSAOCA, and 4-CF3SAOCA.

3. The method according to claim 1, characterized in that, LB is either NHC-1 or BEMP.

4. The method according to claim 1, characterized in that, In the catalyst, the ratio of LB to TU / U is LB:TU / U molar ratio = 0.5:0.5 to 0.5:5, and each mole of LB in the catalyst corresponds to 50-1300 moles of monomer.

5. The method according to claim 4, characterized in that, LB:TU / U molar ratio = 0.5:

3.

6. The method according to claim 1, characterized in that, In the polymerization reaction, the monomer is SAOCA, the initiator is benzyl alcohol; TU is TU-3; LB is NHC-1; the molar ratio of LB to TU is LB:TU = 0.5:3; the reaction solvent is THF; the molar ratio of initiator to monomer is 1:50-600. In the polymerization reaction, the monomer is SAOCA, the initiator is benzyl alcohol; TU is TU-3; LB is BEMP; the molar ratio of LB to TU is LB:TU = 0.5:3; the reaction solvent is a THF / DMF mixed solvent; the molar ratio of initiator to monomer is 1:700-1300. In the polymerization reaction, the monomer is 5-MeSAOCA, the initiator is benzyl alcohol or n-hexanol, n-hexylamine, phenol, benzoic acid; TU is TU-3; LB is NHC-1; the molar ratio of LB to TU is LB:TU = 0.5:3; the reaction solvent is THF; the molar ratio of initiator to monomer is 1:50-200. In the polymerization reaction, the monomer is 4-MeSAOCA, the initiator is benzyl alcohol; TU is TU-3; LB is NHC-1; the molar ratio of LB to TU is LB:TU = 0.5:3; the reaction solvent is a THF / DMF mixed solvent; the molar ratio of initiator to monomer is 1:50-200. In the polymerization reaction, the monomer is 3-MeSAOCA, the initiator is benzyl alcohol; TU is TU-4; LB is NHC-1; the molar ratio of LB to TU is LB:TU = 0.5:3; the reaction solvent is a THF / DMF mixed solvent; the molar ratio of initiator to monomer is 1:50-300. In the polymerization reaction, the monomer is 4-FSAOCA, the initiator is benzyl alcohol; TU is TU-4; LB is NHC-1; the molar ratio of LB to TU is LB:TU = 0.5:3; the reaction solvent is DMF; the molar ratio of initiator to monomer is 1:50-200. In the polymerization reaction, the monomer is 4-CF3SAOCA, the initiator is benzyl alcohol; TU is TU-4; LB is BEMP; the molar ratio of LB to TU is LB:TU = 0.5:3; the reaction solvent is THF; the molar ratio of initiator to monomer is 1:50-300.

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