A method for the synthesis of lactones using polyionic liquids

Abstract

The application belongs to the technical field of polymer materials, and particularly relates to a method for synthesizing and preparing lactones by using polyionic liquids. In the method, a suitable polyionic liquid diluent is used, a molecular structure is designed, a preparation process is optimized, and a series of lactones are directly synthesized from dihydric alcohol and diacid by using an organic catalyst through a 'polycondensation-directional depolymerization' method. The application realizes metal residue-free, non-toxic raw material and strong corrosion waste-free lactones, and can be applied to the medical and food fields. The conversion from easily available dihydric alcohol and diacid to a series of lactone monomers breaks the limitation of only commercially available cyclic monomers such as propiolactone and caprolactone, expands the cyclic monomer system and polyester material categories, and has important significance for promoting the upgrading of green degradable polyester industry and widening the application scenarios of high-end functional materials.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a method for synthesizing lactones using polyionic liquids. Technical Background

[0002] Polyester materials are currently widely used in packaging, plastics, clothing and other fields. Among them, aliphatic polyesters occupy an important position due to their excellent biodegradability, bioabsorbability and biocompatibility, and have become a research hotspot in recent years. As a green polymer material with excellent biocompatibility, biodegradability and good processing performance, aliphatic polyesters are important materials to replace traditional petroleum-based non-degradable plastics and to be adapted to the fields of biomedicine and environmental protection new materials. There are three main technical routes for their industrial synthesis: (1) melt polycondensation of diols and diacids; (2) ring-opening polymerization of cyclic esters (ROP); (3) ring-opening copolymerization of cyclic anhydrides and cyclic ethers (ROCOP).

[0003] Ring-opening polymerization, with its mild reaction conditions, high controllability, and narrow molecular weight distribution of products, is the mainstream process for preparing high-performance recyclable polyester materials. Lactones are a class of functional monomers that can be used to prepare aliphatic polyesters through ring-opening polymerization. The resulting polymers possess excellent biocompatibility, biodegradability, and mechanical tunability, and are widely used in biomedicine, food packaging, and many other fields. However, the types of lactone monomers commonly used in industrial and laboratory applications are extremely limited. The mainstream types include only a few conventionally structured monomers such as lactide, glycolide, ε-caprolactone, and δ-valerolactone. This homogeneity in monomer molecular structure leads to severe performance homogenization in polyester materials obtained from existing commercial monomer polymerization. These materials suffer from defects such as uncontrollable degradation rates, difficulty in balancing flexibility and rigidity, and limited potential for functional modification. This significantly restricts the continuous iteration and upgrading of biodegradable polymer materials and the expansion of their application scenarios, making it difficult to meet the differentiated and multifunctional application needs of high-end fields.

[0004] One of the mainstream methods for preparing novel lactone monomers is the transesterification or dehydration condensation of bifunctional monomers (diols, hydroxy acids, diesters) to generate low-molecular-weight linear prepolymers. Then, under the action of a catalyst, the linear prepolymers undergo intramolecular back-biting transesterification, closing the ring to form cyclic monomers. Simultaneously, the cyclic monomers are continuously distilled off through high-temperature, high-vacuum processes. This process uses inexpensive raw materials, is environmentally friendly, involves no highly toxic reagents, and is adaptable to closed-loop production, and has been applied to the synthesis of various cyclic lactone monomers. However, this process also has some problems. For example, the linear oligomers obtained from the pre-condensation of raw materials have high viscosity, leading to poor melt flow and hindered molecular chain movement during high-temperature depolymerization. This severely inhibits the efficiency of intramolecular back-biting cyclization and easily causes problems such as localized overheating, material carbonization, and increased intermolecular cross-linking side reactions. Polyionic liquids are a class of high-molecular functional materials obtained by polymerizing ionic liquid monomers. They combine the advantages of ionic liquids, such as extremely low vapor pressure, high thermal stability, and designable structure, with the high-molecular properties of polymers. They can effectively reduce the melt viscosity of polyester prepolymers, improve the reaction mass and heat transfer effect, and avoid the pollution problem of small molecule solvent volatilization. Their greenness is significantly better than that of traditional organic solvents and small molecule ionic liquid systems, and they have potential application value in the field of cyclic lactone monomer preparation.

[0005] Meanwhile, this route is highly dependent on metal catalysts. During high-temperature depolymerization, metal components can embed into the oligomeric polyester molecular chains through transesterification. Some metal components may also enter the monomer product through co-distillation with crude lactones. In medical applications, this could trigger cytotoxicity and inflammatory responses, and in food packaging, it could pose a risk of heavy metal contamination. This does not align with the green development requirements of recyclable polymers: "metal-free throughout the entire process, with low environmental impact." In recent years, organic catalysis has made significant progress in small molecule synthesis and polymer polymerization. The absence of metal elements fundamentally avoids the problem of metal residues, resulting in high product purity, making it particularly suitable for biomedical and food contact materials where strict metal content requirements exist. Furthermore, the catalyst structure is easy to design and modify, allowing for the control of catalytic activity and selectivity to meet the needs of different reaction systems.

[0006] Therefore, developing a universal, efficient, and scalable synthesis process that applies suitable polyionic liquids to the development of novel lactones, while using organic catalysts to convert some inexpensive and readily available raw materials into a series of diversified lactone monomers, not only avoids the problem of metal residues, but also expands the cyclic monomer system and polyester material categories. This is of great significance for promoting the upgrading of the green and biodegradable polyester industry and broadening the application scenarios of high-end functional materials. Summary of the Invention

[0007] The problem this invention aims to solve is a large-scale method for directly synthesizing lactones from diols and diacids. It provides a lactone synthesis method that uses diols and diacids as raw materials, and through different combinations, can synthesize a series of lactones, filling a gap in the variety of cyclic monomer systems.

[0008] To solve the above-mentioned technical problems, the technical solution adopted in this invention is to prepare lactones through a process design of "condensation-directional depolymerization".

[0009] This invention provides a class of lactones, as shown in formula (I):

[0010]

[0011] Where n is 1-14 and m is 3-14.

[0012] The specific preparation method of the lactone of formula (I) prepared by the present invention is as follows: a diol and a diacid undergo a polycondensation reaction under the action of a catalyst to obtain a polyester, a diluent is added to depolymerize, and then recrystallization is carried out to obtain the product.

[0013] The reaction equation is as follows:

[0014]

[0015] Where n is 1-14, m is 3-14, and x is the degree of polymerization.

[0016] The polycondensation reaction is preferably carried out under bulk conditions:

[0017] The molar ratio of the diol to the diacid is 1.0-2.0:1, preferably 1.4:1.

[0018] The catalyst may be 1,3-dimethylurea, 1,1,3,3-tetramethylurea, 1,3-diphenylurea, trichlorodiphenylurea, 1-(4-methoxyphenyl)-3-phenylurea, 1,3-diphenylurea, 1-(4-chlorophenyl)-3-phenylurea, 1-(4-trifluoromethylphenyl)-3-phenylurea, 1,3-bis(3,5-bistrifluoromethylphenyl)urea, 1,3-bis(4-trifluoromethylphenyl)urea, N,N'-dicyclohexylurea, N,N'-diisopropylurea, 1-(2-pyridyl)-3-phenylurea, 1,3-bis(2,6-diisopropylphenyl)urea, 1,3-bis(4-nitrophenyl)urea, 1,3-bis(4-methoxyphenyl)urea, 1-adamantyl-3-phenylurea, 1,3-Di(tert-butyl)urea, chiral α-amino acid-derived urea, 1,3-bis(3,5-dimethylphenyl)urea, 1,3-dimethylthiourea, 1,3-diphenylthiourea, 1,3-bis(3,5-bistrifluoromethylphenyl)thiourea, 1-(3,5-bistrifluoromethylphenyl)-3-phenylthiourea, 1,3-dicyclohexylthiourea, 1,3-diisopropylthiourea, 1-(4-nitrophenyl)-3-phenylthiourea, 1-(4-methoxyphenyl)-3-phenylthiourea, 1-(2-pyridyl)-3-phenylthiourea, 1,3-bis(2,6-diisopropylphenyl)thiourea, 1-adamantyl-3-phenylthiourea, 1,3-bis(4-trifluoromethylphenyl)thiourea, 1,3-bis(3-chlorophenyl)thiourea, 1,3-Bis(4-bromophenyl)thiourea, 1,3-bis(4-iodophenyl)thiourea, N,N'-bis(2-hydroxyethyl)thiourea, 1-(4-carboxyphenyl)-3-phenylthiourea, chiral binatol-derived thiourea, 1,3-bis(2-naphthyl)thiourea, 1,3-bis(4-dimethylaminophenyl)thiourea, 1,8-diazabicycloundec-7-ene, 1,5-diazabicyclonon-5-ene, 1,4-diazabicyclooctane, 7-methyl-1,5,7-triazabicyclodec-5-ene, 1,5,7-triazabicyclodec-5-ene, N,N'-dimethylbenzylamidinium, N,N'-dicyclohexylmethylamidinium, benzylamidinium, p-nitrobenzylamidinium, p-methoxybenzylamidinium, 1,8-bis(dimethylamino)naphthalene, tetramethylguanidine Related amidine derivatives, 2-phenyl-1,3-dimethylimidazoline amidine, 1,3-di(tert-butyl)imidazoline-2-imine, bicyclic amidine, triazabicyclodecene derivatives, polystyrene-supported diazabicycloundecene, silica gel-supported triazabicyclodecene, polyethylene glycol-supported diazabicycloundecene, chiral bicyclic amidine tetramethylguanidine, 1,5,7-triazabicyclodec-5-ene, 7-methyltriazabicyclodecene, 1,1,3,3-tetramethylguanidine, 1,2,3-triphenylguanidine, N,N'-dicyclohexyl-N”-phenylguanidine, 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, guanidinoacetic acid, arginine derivatives, biguanide compounds, polyhexamethylene biguanide, 1,3-bis(4-trifluoromethylphenyl)guanidine, 1...3-Bis(4-methoxyphenyl)guanidine, chiral guanidine salts, bifunctional thiourea-guanidine catalysts, polystyrene-supported tetramethylguanidine, silica-supported triazabicyclodecene, 1,3-bis(2,6-diisopropylphenyl)guanidine, N-methyl-N'-phenyl-N'”-cyclohexylguanidine, tert-butylphosphazene base P1, tert-butylphosphazene base P2, tert-butylphosphazene base P4, tert-butyliminodiethylaminodimethylperhydrodiazaphosphazenecyclohexane, cyanotris(dimethylamino)phosphazene base, phosphazene base P1 and urea binary system, phosphazene base P2 and urea binary system, phosphazene base P4 and urea binary system, phosphazene base P4 and thiourea binary system. The following are possible binary systems: tert-butyliminodiethylaminodimethylperhydrodiazaphosphacyclohexane and urea; tert-butyliminodiethylaminodimethylperhydrodiazaphosphacyclohexane and thiourea; cyanotris(dimethylamino)phosphazene base and urea; cyanotris(dimethylamino)phosphazene base and thiourea; phosphazene base P2 and chiral urea; cyanotris(dimethylamino)phosphazene base and chiral urea; tert-butyliminodiethylaminodimethylperhydrodiazaphosphacyclohexane and chiral thiourea; and polystyrene supported on tert-butyliminodiethylaminodimethylperhydrodiazaphosphacyclohexane.

[0019] The total amount of catalyst added is 1-20% of the total mass of the raw materials, preferably 2%.

[0020] The polycondensation reaction temperature is 60-340 °C, preferably 180-230 °C.

[0021] The polycondensation reaction is characterized in that the reaction is carried out under a vacuum of 0.001 MPa to 0.1 MPa, preferably 0.098 MPa.

[0022] The polycondensation reaction time is 3-12 h, preferably 4-6 h.

[0023] The depolymerization reaction temperature is 200-300 °C, preferably 270 °C.

[0024] The depolymerization reaction is characterized in that the reaction occurs at a temperature of 1 × 10⁻⁶. -3 MPa to 1×10 -7 The test is performed under a vacuum of MPa, preferably 1×10 MPa. -6 MPa.

[0025] The depolymerization reaction time is 8-24 h, preferably 12 h.

[0026] The diluent may be poly(1-vinyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide), poly(1-vinyl-3-ethylimidazolium bis(trifluoromethanesulfonyl)imide), poly(1-vinyl-3-propylimidazolium bis(trifluoromethanesulfonyl)imide), poly(1-vinyl-3-butylimidazolium bis(trifluoromethanesulfonyl)imide), poly(1-vinyl-3-pentylimidazolium bis(trifluoromethanesulfonyl)imide), poly(1-vinyl-3-hexylimidazolium bis(trifluoromethanesulfonyl)imide), poly(1-vinyl-3-heptylimidazolium bis(trifluoromethanesulfonyl)imide), poly(1-vinyl-3-octylimidazolium bis(trifluoromethanesulfonyl)imide), poly(1-vinyl-3-nonylimidazolium bis(trifluoromethanesulfonyl)imide), poly(1-vinyl-3-dec ... Poly(1-vinyl-3-butylimidazolium bis(fluorosulfonyl)imidazolium), poly(1-vinyl-3-butylimidazolium trifluoromethanesulfonate), poly(1-vinyl-3-butylimidazolium hexafluorophosphate), poly(1-allyl-3-methylimidazolium bis(fluoromethanesulfonyl)imidazolium), poly(1-allyl-3-butylimidazolium bis(fluoromethanesulfonyl)imidazolium), poly(1-hydroxyethyl-3-vinylimidazolium bis(fluoromethanesulfonyl)imidazolium), poly(1-carboxymethyl-3-vinylimidazolium bis(fluoromethanesulfonyl)imidazolium), poly(1-vinyl-2,3-dimethylimidazolium bis(fluoromethanesulfonyl)imidazolium), poly(1-vinyl-2-methyl-3-butylimidazolium bis(fluoromethanesulfonyl)imidazolium), poly(1- Vinyl-3-benzylimidazolium bis(trifluoromethanesulfonyl)imide salt, poly(1-vinyl-3-(2-methoxyethyl)imidazolium bis(trifluoromethanesulfonyl)imide salt), poly(1-vinyl-3-(3-hydroxypropyl)imidazolium bis(trifluoromethanesulfonyl)imide salt), poly(1-vinyl-3-butylimidazolium bis(perfluoroethanesulfonyl)imide salt), poly(1-vinyl-3-butylimidazolium bis(trifluoromethoxysulfonyl)imide salt), poly(1-vinyl-3-butylimidazolium p-toluenesulfonate), poly(1-vinyl-3-butylimidazolium dodecyl sulfate), poly(1-vinyl-3-butylimidazolium tetrafluoroborate), poly(1-vinyl-3-isopropylimidazolium bis(trifluoromethanesulfonyl)imide salt), poly(1-vinyl-3-isobutylimidazolium tetrafluoroborate), poly(1-vinyl-3-isopropylimidazolium bis(trifluoromethanesulfonyl)imide salt), poly(1-vinyl-3-isobutylimidazolium tetrafluoroborate), poly(1-vinyl-3-isobutylimidazolium tetrafluoromethanesulfonyl)imide salt, ... Imidazole bis(trifluoromethanesulfonyl)imide salt), poly(1-vinyl-3-sec-butylimide bis(trifluoromethanesulfonyl)imide salt), poly(1-vinyl-3-tert-butylimide bis(trifluoromethanesulfonyl)imide salt), poly(1-vinyl-3-(2-cyanoethyl)imide bis(trifluoromethanesulfonyl)imide salt), poly(1-vinyl-3-(3-aminopropyl)imide bis(trifluoromethanesulfonyl)imide salt), poly(1-vinyl-3-(4-hydroxybutyl)imide bis(trifluoromethanesulfonyl)imide salt), poly(1-vinyl-3-(2-chloroethyl)imide bis(trifluoromethanesulfonyl)imide salt), poly(1-vinyl-3-(2-bromoethyl)imide bis(trifluoromethanesulfonyl)imide salt), poly(1-vinyl-3-(2-iodoethyl)imide bis(trifluoromethanesulfonyl)imide salt), poly(1-vinyl-3-(2-iodoethyl)imide bis(trifluoromethanesulfonyl)imide salt),Poly(1-vinyl-3-(2-phenylethyl)imidazolium bis(trifluoromethanesulfonyl)imide), poly(1-vinyl-3-(3-phenylpropyl)imidazolium bis(trifluoromethanesulfonyl)imide), poly(1-vinyl-3-(4-phenylbutyl)imidazolium bis(trifluoromethanesulfonyl)imide), poly(N-vinyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide), poly(N-vinyl-N-ethylpyrrolidine bis(trifluoromethanesulfonyl)imide), poly(N-vinyl-N-propylpyrrolidine bis(trifluoromethanesulfonyl)imide), poly(N-vinyl-N-butylpyrrolidine bis(trifluoromethanesulfonyl)imide), poly(N-vinyl-N-pentylpyrrolidine bis(trifluoromethanesulfonyl)imide), poly(N-vinyl-N-hexylpyrrolidine bis(trifluoromethanesulfonyl)imide), poly (N-vinyl-N-methylpyrrolidine bis(fluorosulfonyl)imide), poly(N-vinyl-N-butylpyrrolidine bis(fluorosulfonyl)imide), poly(1-vinyl-1-methylpiperidine bis(fluorosulfonyl)imide), poly(1-vinyl-1-ethylpiperidine bis(fluorosulfonyl)imide), poly(1-vinyl-1-propylpiperidine bis(fluorosulfonyl)imide), poly(1-vinyl-1-butylpiperidine bis(fluorosulfonyl)imide), poly(1-vinyl-1-methylpiperidine bis(fluorosulfonyl)imide), poly(1-vinyl-1-butylpiperidine bis(fluorosulfonyl)imide), poly(1-vinyl-1-methylpiperidine trifluoromethanesulfonate), poly(1-vinyl-1-butylpiperidine trifluoromethanesulfonate), poly(N-vinyl-N-methyl ... Alkenyl-N-methylpyrrolidine trifluoromethanesulfonate, poly(N-vinyl-N-butylpyrrolidine trifluoromethanesulfonate), poly(1-vinyl-1-methylpiperidine hexafluorophosphate), poly(1-vinyl-1-butylpiperidine hexafluorophosphate), poly(trimethylvinylammonium bis(trifluoromethanesulfonyl)imide), poly(triethylvinylammonium bis(trifluoromethanesulfonyl)imide), poly(tripropylvinylammonium bis(trifluoromethanesulfonyl)imide), poly(tributylvinylammonium bis(trifluoromethanesulfonyl)imide), poly(tributylmethylvinylammonium bis(trifluoromethanesulfonyl)imide), poly(trimethylvinylphosphonium bis(trifluoromethanesulfonyl)imide), poly(triethylvinylphosphonium bis(trifluoromethanesulfonyl)imide), poly(tripropylvinylphosphonium bis(trifluoromethanesulfonyl)imide), poly(tributyl... Vinylphosphonium bis(trifluoromethanesulfonyl)imide salt, poly(tributylmethylvinylphosphonium bis(trifluoromethanesulfonyl)imide salt), poly(tetravinylammonium bis(trifluoromethanesulfonyl)imide salt, poly(tetravinylphosphonium bis(trifluoromethanesulfonyl)imide salt), poly(trimethylvinylammonium bis(fluorosulfonyl)imide salt), poly(trimethylvinylammonium trifluoromethanesulfonate), poly(tributylvinylphosphonium trifluoromethanesulfonate), poly(trimethylvinylammonium hexafluorophosphate), poly(tributylvinylphosphonium hexafluorophosphate), poly(tris(2-methoxyethyl)vinylammonium bis(trifluoromethanesulfonyl)imide salt), poly(tris(2-hydroxyethyl)vinylammonium bis(trifluoromethanesulfonyl)imide salt), poly(1-vinylpyridine bis(trifluoromethanesulfonyl)imide salt),Poly(1-vinyl-2-methylpyridine bis(trifluoromethanesulfonyl)imide), Poly(1-vinyl-3-methylpyridine bis(trifluoromethanesulfonyl)imide), Poly(1-vinyl-4-methylpyridine bis(trifluoromethanesulfonyl)imide), Poly(1-vinyl-4-butylpyridine bis(trifluoromethanesulfonyl)imide), Poly(1-vinyl-1,2,3-triazole bis(trifluoromethanesulfonyl)imide), Poly(1-vinyl-1,2,4-triazole bis(trifluoromethanesulfonyl)imide), Poly(1-vinyl-3-methyl-1,2,3-triazole bis(trifluoromethanesulfonyl)imide), Poly(1-vinyl-4-methyl-1,2,4-triazole bis(trifluoromethanesulfonyl)imide), Poly(4-vinylmorpholine bis(trifluoromethanesulfonyl)imide The following are all of the following: (salt), poly(4-vinyl-2-methylmorpholine bis(fluorosulfonyl)imide), poly(1-vinylpyridine bis(fluorosulfonyl)imide), poly(1-vinyl-4-methylpyridine bis(fluorosulfonyl)imide), poly(1-vinyl-1,2,3-triazole bis(fluorosulfonyl)imide), poly(4-vinylmorpholine bis(fluorosulfonyl)imide), poly(1-vinylpyridine trifluoromethanesulfonate), poly(1-vinyl-4-methylpyridine trifluoromethanesulfonate), poly(1-vinyl-1,2,3-triazole trifluoromethanesulfonate), poly(4-vinylmorpholine trifluoromethanesulfonate), poly(1-vinyl-3-(2-hydroxyethyl)pyridine bis(fluoromethanesulfonyl)imide).

[0027] Beneficial effects

[0028] (1) Lactones with the structure of formula (I) have not been reported before. They are bio-based, green, and environmentally friendly products with the dual benefits of saving petroleum resources and protecting the environment. They are of great significance to promoting the sustainable development of the polyester industry.

[0029] (2) The raw materials used in this invention are biologically derived diols and dicarboxylic acids, which have the advantages of being inexpensive, readily available, green and non-toxic. A cyclic lactone with the structure of formula (I) can be obtained through simple polycondensation and depolymerization reactions, and can be produced on a large scale using existing chemical equipment.

[0030] (3) The depolymerization reaction rate is fast and there are few by-products. The catalyst has no highly toxic raw materials or highly corrosive waste. Attached Figure Description

[0031] The embodiments of the present invention will be described in detail with reference to the accompanying drawings, wherein...

[0032] Figure 1 Example 1 (I) of implementation: lactone E34 1 H NMR image

[0033] Figure 2 Example 2 (I) of implementation: lactone E45 1 H NMR image

[0034] Figure 3 Example 3 (I) of implementation: lactone E54 1 H NMR image

[0035] Figure 4 Example 4 (I) of implementation: lactone E56 1 H NMR image

[0036] Figure 5 Example 5 (I) of implementation: lactone E59 1 H NMR image

[0037] Figure 6 Example 6 (I) of implementation: lactone E84 1 H NMR image Detailed Implementation

[0038] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and materials described are as follows:

[0039] Unless otherwise specified, all items are available through commercial channels.

[0040] The 1H NMR spectra involved in the examples were measured using a Bruker Ascend TM-400 NMR spectrometer, and the deuterated reagent used was deuterated chloroform (CDCl3).

[0041] Example 1

[0042] (I) Preparation of lactone E34: 80 g of 1,3-propanediol (37.94 g, 0.498 mol, 1.4 eq) and succinic acid (42.06 g, 0.356 mol, 1 eq) were added to a 250 mL round-bottom flask. The mixture was heated and stirred, and the vacuum was adjusted to 0.098 MPa. The mixture was dehydrated at 120 °C for 2 h. Then, 1,3,3-tetramethylurea (1.6 g, 2 wt%) was added, and the temperature was gradually increased from 180 °C to 220 °C. The reaction was carried out for 4 h to obtain a condensation product. Poly(1-vinyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt) (30 g) was added, and the mixture was distilled under reduced pressure at 270 °C for 12 h to obtain a crude product. The crude product was then recrystallized from ethanol to obtain lactone E34.

[0043] Example 2

[0044] (I) Preparation of lactone E45: 80 g of 1,4-butanediol (39.07 g, 0.433 mol, 1.4 eq) and glutaric acid (40.92 g, 0.309 mol, 1 eq) were added to a 250 mL round-bottom flask. The mixture was heated and stirred, and the vacuum was adjusted to 0.098 MPa. The mixture was dehydrated at 120 °C for 2 h. Then, 1,3-dimethylthiourea (1.6 g, 2 wt%) was added, and the temperature was gradually increased from 180 °C to 230 °C. The reaction was carried out for 4 h to obtain a condensation product. Poly(1-vinyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt) (30 g) was added, and the mixture was distilled under reduced pressure at 270 °C for 12 h to obtain a crude product. The crude product was then recrystallized from ethanol to obtain lactone E45.

[0045] Example 3

[0046] (I) Preparation of lactone E54: 80 g of 1,5-pentanediol (44.2 g, 0.424 mol, 1.4 eq) and succinic acid (35.79 g, 0.303 mol, 1 eq) were added to a 250 mL round-bottom flask. The mixture was heated and stirred, and the vacuum was adjusted to 0.098 MPa. The mixture was dehydrated at 120 °C for 2 h. N,N'-dimethylbenzylamidinium (1.6 g, 2 wt%) was added, and the temperature was gradually increased from 180 °C to 250 °C. The reaction was carried out for 4 h to obtain a condensation product. Poly(1-vinyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt) (30 g) was added, and the mixture was distilled under reduced pressure at 270 °C for 12 h to obtain a crude product. The crude product was then recrystallized from ethanol to obtain lactone E54.

[0047] Example 4

[0048] (I) Preparation of lactone E56: 80 g of 1,5-pentanediol (39.95 g, 0.383 mol, 1.4 eq) and adipic acid (40.04 g, 0.274 mol, 1 eq) were added to a 250 mL round-bottom flask. The mixture was heated and stirred, and the vacuum was adjusted to 0.098 MPa. The mixture was dehydrated at 120 °C for 2 h. N,N'-dicyclohexylformamidinium (1.6 g, 2 wt%) was added, and the temperature was gradually increased from 180 °C to 250 °C. The reaction was carried out for 4 h to obtain the condensation product. Poly(1-vinyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt) (30 g) was added, and the mixture was distilled under reduced pressure at 270 °C for 12 h to obtain the crude product. The crude product was then recrystallized from ethanol to obtain lactone E56.

[0049] Example 5

[0050] (I) Preparation of lactone E59: 80 g of 1,5-pentanediol (34.92 g, 0.335 mol, 1.4 eq) and azelaic acid (45.07 g, 0.239 mol, 1 eq) were added to a 250 mL round-bottom flask. The mixture was heated and stirred, and the vacuum was adjusted to 0.098 MPa. The mixture was dehydrated at 120 °C for 2 h. 1,2,3-triphenylguanidine (1.6 g, 2 wt%) was added, and the temperature was gradually increased from 180 °C to 250 °C. The reaction was carried out for 4 h to obtain the condensation product. Poly(1-vinyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt) (30 g) was added, and the mixture was distilled under reduced pressure at 270 °C for 12 h to obtain the crude product. The crude product was then recrystallized from ethanol to obtain lactone E59.

[0051] Example 6

[0052] (I) Preparation of lactone E84: 80 g of 1,8-octanediol (50.73 g, 0.346 mol, 1.4 eq) and succinic acid (29.26 g, 0.247 mol, 1 eq) were added to a 250 mL round-bottom flask. The mixture was heated and stirred, and the vacuum was adjusted to 0.098 MPa. The mixture was dehydrated at 120 °C for 2 h. Then, tert-butylphosphazene base P2 (1.6 g, 2 wt%) was added, and the temperature was gradually increased from 180 °C to 250 °C. The reaction was carried out for 4 h to obtain a polycondensation product. Poly(1-vinyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt) (30 g) was added, and the mixture was distilled under reduced pressure at 270 °C for 12 h to obtain a crude product. The crude product was then recrystallized from ethanol to obtain lactone E84.

Claims

1. A method for synthesizing lactones using polyionic liquids: lactones are prepared through a process design of "condensation-directional depolymerization".

2. A lactone, characterized in that... It has a structure as shown in equation (I): Where n is 1-14 and m is 3-14.

3. The specific preparation method of the lactone according to formula (I) in claim 2 is as follows: a diol and a diacid undergo a polycondensation reaction under the action of a catalyst to obtain a polyester, a diluent is added for depolymerization, and then recrystallization is carried out to obtain the product. The reaction equation is as follows: in, n is 1-14, m is 3-14, and x is the degree of polymerization.

4. The molar ratio of the diol to the diacid as described in claim 3 is 1.2-1.6:1, preferably 1.4:

1.

5. The catalyst as described in claim 3 may be 1,3-dimethylurea, 1,1,3,3-tetramethylurea, 1,3-diphenylurea, trichlorodiphenylurea, 1-(4-methoxyphenyl)-3-phenylurea, 1,3-diphenylurea, 1-(4-chlorophenyl)-3-phenylurea, 1-(4-trifluoromethylphenyl)-3-phenylurea, 1,3-bis(3,5-bistrifluoromethylphenyl)urea, 1,3-bis(4-trifluoromethylphenyl)urea, N,N'-dicyclohexylurea, N,N'-diisopropylurea, 1-(2-pyridyl)-3-phenylurea, 1,3-bis(2,6-diisopropylphenyl)urea, 1,3-bis(4-nitrophenyl)urea, 1,3-bis(4-methoxyphenyl)urea, 1-adamantyl- 3-Phenylacetium urea, 1,3-Di(tert-butyl)urea, chiral α-amino acid-derived urea, 1,3-bis(3,5-dimethylphenyl)urea, 1,3-dimethylthiourea, 1,3-diphenylthiourea, 1,3-bis(3,5-bistrifluoromethylphenyl)thiourea, 1-(3,5-bistrifluoromethylphenyl)-3-phenylthiourea, 1,3-dicyclohexylthiourea, 1,3-diisopropylthiourea, 1-(4-nitrophenyl)-3-phenylthiourea, 1-(4-methoxyphenyl)-3-phenylthiourea, 1-(2-pyridyl)-3-phenylthiourea, 1,3-bis(2,6-diisopropylphenyl)thiourea, 1-adamantyl-3-phenylthiourea, 1,3-bis(4-trifluoromethylphenyl)thiourea, 1,3-bis(3-chlorophenyl) Thiourea, 1,3-bis(4-bromophenyl)thiourea, 1,3-bis(4-iodophenyl)thiourea, N,N'-bis(2-hydroxyethyl)thiourea, 1-(4-carboxyphenyl)-3-phenylthiourea, chiral binatol-derived thiourea, 1,3-bis(2-naphthyl)thiourea, 1,3-bis(4-dimethylaminophenyl)thiourea, 1,8-diazabicycloundec-7- Alkene, 1,5-diazabicyclonon-5-ene, 1,4-diazabicyclooctane, 7-methyl-1,5,7-triazabicyclodec-5-ene, 1,5,7-triazabicyclodec-5-ene, N,N'-dimethylbenzylamidinium, N,N'-dicyclohexylformamidinium, benzylamidinium, p-nitrobenzylamidinium, p-methoxybenzylamidinium, 1,8-bis(dimethylamino)naphthalene, tetramethyl... Amidine derivatives related to guanidine, 2-phenyl-1,3-dimethylimidazolinemidine, 1,3-di(tert-butyl)imidazoline-2-imine, bicyclic amidine, triazabicyclodecene derivatives, polystyrene-supported diazabicycloundecene, silica-supported triazabicyclodecene, polyethylene glycol-supported diazabicycloundecene, chiral bicyclic amidine tetramethylguanidine, 1,5,7-triazabicyclodec-5-ene, 7-methyltriazabicyclodecene, 1,1,3,3-tetramethylguanidine, 1,2,3-triphenylguanidine, N,N'-dicyclohexyl-N”-phenylguanidine, 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, guanidinoacetic acid, arginine derivatives, biguanide compounds, polyhexamethylene biguanide, 1,3-bis(4-trifluoromethylphenyl)guanidine, 1...3-Bis(4-methoxyphenyl)guanidine, chiral guanidine salts, bifunctional thiourea-guanidine catalysts, polystyrene-supported tetramethylguanidine, silica-supported triazabicyclodecene, 1,3-bis(2,6-diisopropylphenyl)guanidine, N-methyl-N'-phenyl-N'”-cyclohexylguanidine, tert-butylphosphazene base P1, tert-butylphosphazene base P2, tert-butylphosphazene base P4, tert-butyliminodiethylaminodimethylperhydrodiazaphosphazenecyclohexane, cyanotris(dimethylamino)phosphazene base, phosphazene base P1 and urea binary system, phosphazene base P2 and urea binary system, phosphazene base P4 and urea binary system, phosphazene base P4 and thiourea binary system. The following are possible binary systems: tert-butyliminodiethylaminodimethylperhydrodiazaphosphacyclohexane and urea; tert-butyliminodiethylaminodimethylperhydrodiazaphosphacyclohexane and thiourea; cyanotris(dimethylamino)phosphazene base and urea; cyanotris(dimethylamino)phosphazene base and thiourea; phosphazene base P2 and chiral urea; cyanotris(dimethylamino)phosphazene base and chiral urea; tert-butyliminodiethylaminodimethylperhydrodiazaphosphacyclohexane and chiral thiourea; and polystyrene supported on tert-butyliminodiethylaminodimethylperhydrodiazaphosphacyclohexane.

6. The total amount of catalyst added as described in claim 3 is 1-20% of the total mass of the raw materials, preferably 2%.

7. The polycondensation reaction temperature as described in claim 3 is 60-340 °C, preferably 180-230 °C. The reaction is carried out under a vacuum of 0.001 MPa to 0.1 MPa, preferably 0.098 MPa. The reaction time is 3-12 h, preferably 4-6 h.

8. The depolymerization reaction temperature as described in claim 3 is 200-300 °C, preferably 270 °C. The reaction is carried out at 1 × 10⁻⁶ °C. -3 MPa to 1×10 -7 The test is performed under a vacuum of MPa, preferably 1×10 MPa. -6 MPa. The reaction time is 8-24 h, preferably 12 h.

9. The diluent as described in claim 3 may be poly(1-vinyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide), poly(1-vinyl-3-ethylimidazolium bis(trifluoromethanesulfonyl)imide), poly(1-vinyl-3-propylimidazolium bis(trifluoromethanesulfonyl)imide), poly(1-vinyl-3-butylimidazolium bis(trifluoromethanesulfonyl)imide), poly(1-vinyl-3-pentylimidazolium bis(trifluoromethanesulfonyl)imide), poly(1-vinyl-3-hexylimidazolium bis(trifluoromethanesulfonyl)imide), poly(1-vinyl-3-heptylimidazolium bis(trifluoromethanesulfonyl)imide), poly(1-vinyl-3-octylimidazolium bis(trifluoromethanesulfonyl)imide), poly(1-vinyl-3-nonylimidazolium bis(trifluoromethanesulfonyl)imide), poly(1-vinyl-3-ethyl ... Alkenyl-3-decylimidazolium bis(trifluoromethanesulfonyl)imide salt), poly(1-vinyl-3-butylimidazolium bis(fluorosulfonyl)imide salt), poly(1-vinyl-3-butylimidazolium trifluoromethanesulfonate), poly(1-vinyl-3-butylimidazolium hexafluorophosphate), poly(1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt), poly(1-allyl-3-butylimidazolium bis(trifluoromethanesulfonyl)imide salt), poly(1-hydroxyethyl-3-vinylimidazolium bis(trifluoromethanesulfonyl)imide salt), poly(1-carboxymethyl-3-vinylimidazolium bis(trifluoromethanesulfonyl)imide salt), poly(1-vinyl-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide salt), poly(1-vinyl-2-methyl-3-butylimidazolium bis(trifluoromethanesulfonyl)imide salt), poly(1-vinyl-2-methyl-3-butylimidazolium bis(trifluoromethanesulfonyl)imide salt), Poly(1-vinyl-3-benzylimidazolium bis(trifluoromethanesulfonylimide), poly(1-vinyl-3-(2-methoxyethyl)imidazolium bis(trifluoromethanesulfonylimide), poly(1-vinyl-3-(3-hydroxypropyl)imidazolium bis(trifluoromethanesulfonylimide), poly(1-vinyl-3-butylimidazolium bis(perfluoroethanesulfonyl)imide), poly(1-vinyl-3-butylimidazolium bis(trifluoromethoxysulfonyl)imide), poly(1-vinyl-3-butylimidazolium p-toluenesulfonate), poly(1-vinyl-3-butylimidazolium dodecyl sulfate), poly(1-vinyl-3-butylimidazolium tetrafluoroborate), poly(1-vinyl-3-isopropylimidazolium bis(trifluoromethanesulfonylimide), poly(1-vinyl-3-isopropylimidazolium bis(trifluoromethanesulfonylimide)), poly(1-vinyl-3-isopropylimidazolium p-toluenesulfonate) Butylimidazolium bis(trifluoromethanesulfonyl)imide salt), poly(1-vinyl-3-sec-butylimidazolium bis(trifluoromethanesulfonyl)imide salt), poly(1-vinyl-3-tert-butylimidazolium bis(trifluoromethanesulfonyl)imide salt), poly(1-vinyl-3-(2-cyanoethyl)imidazolium bis(trifluoromethanesulfonyl)imide salt), poly(1-vinyl-3-(3-aminopropyl)imidazolium bis(trifluoromethanesulfonyl)imide salt), poly(1-vinyl-3-(4-hydroxybutyl)imidazolium bis(trifluoromethanesulfonyl)imide salt), poly(1-vinyl-3-(2-chloroethyl)imidazolium bis(trifluoromethanesulfonyl)imide salt), poly(1-vinyl-3-(2-bromoethyl)imidazolium bis(trifluoromethanesulfonyl)imide salt), poly(1-vinyl-3-(2-iodoethyl)imidazolium bis(trifluoromethanesulfonyl)imide salt), poly(1-vinyl-3-(2-iodoethyl)imidazolium bis(trifluoromethanesulfonyl)imide salt),Poly(1-vinyl-3-(2-phenylethyl)imidazolium bis(trifluoromethanesulfonyl)imide), poly(1-vinyl-3-(3-phenylpropyl)imidazolium bis(trifluoromethanesulfonyl)imide), poly(1-vinyl-3-(4-phenylbutyl)imidazolium bis(trifluoromethanesulfonyl)imide), poly(N-vinyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide), poly(N-vinyl-N-ethylpyrrolidine bis(trifluoromethanesulfonyl)imide), poly(N-vinyl-N-propylpyrrolidine bis(trifluoromethanesulfonyl)imide), poly(N-vinyl-N-butylpyrrolidine bis(trifluoromethanesulfonyl)imide), poly(N-vinyl-N-pentylpyrrolidine bis(trifluoromethanesulfonyl)imide), poly(N-vinyl-N-hexylpyrrolidine bis(trifluoromethanesulfonyl)imide), poly (N-vinyl-N-methylpyrrolidine bis(fluorosulfonyl)imide), poly(N-vinyl-N-butylpyrrolidine bis(fluorosulfonyl)imide), poly(1-vinyl-1-methylpiperidine bis(fluorosulfonyl)imide), poly(1-vinyl-1-ethylpiperidine bis(fluorosulfonyl)imide), poly(1-vinyl-1-propylpiperidine bis(fluorosulfonyl)imide), poly(1-vinyl-1-butylpiperidine bis(fluorosulfonyl)imide), poly(1-vinyl-1-methylpiperidine bis(fluorosulfonyl)imide), poly(1-vinyl-1-butylpiperidine bis(fluorosulfonyl)imide), poly(1-vinyl-1-methylpiperidine trifluoromethanesulfonate), poly(1-vinyl-1-butylpiperidine trifluoromethanesulfonate), poly(N-vinyl-N-methyl ... Alkenyl-N-methylpyrrolidine trifluoromethanesulfonate, poly(N-vinyl-N-butylpyrrolidine trifluoromethanesulfonate), poly(1-vinyl-1-methylpiperidine hexafluorophosphate), poly(1-vinyl-1-butylpiperidine hexafluorophosphate), poly(trimethylvinylammonium bis(trifluoromethanesulfonyl)imide), poly(triethylvinylammonium bis(trifluoromethanesulfonyl)imide), poly(tripropylvinylammonium bis(trifluoromethanesulfonyl)imide), poly(tributylvinylammonium bis(trifluoromethanesulfonyl)imide), poly(tributylmethylvinylammonium bis(trifluoromethanesulfonyl)imide), poly(trimethylvinylphosphonium bis(trifluoromethanesulfonyl)imide), poly(triethylvinylphosphonium bis(trifluoromethanesulfonyl)imide), poly(tripropylvinylphosphonium bis(trifluoromethanesulfonyl)imide), poly(tributyl... Vinylphosphonium bis(trifluoromethanesulfonyl)imide salt, poly(tributylmethylvinylphosphonium bis(trifluoromethanesulfonyl)imide salt), poly(tetravinylammonium bis(trifluoromethanesulfonyl)imide salt, poly(tetravinylphosphonium bis(trifluoromethanesulfonyl)imide salt), poly(trimethylvinylammonium bis(fluorosulfonyl)imide salt), poly(trimethylvinylammonium trifluoromethanesulfonate), poly(tributylvinylphosphonium trifluoromethanesulfonate), poly(trimethylvinylammonium hexafluorophosphate), poly(tributylvinylphosphonium hexafluorophosphate), poly(tris(2-methoxyethyl)vinylammonium bis(trifluoromethanesulfonyl)imide salt), poly(tris(2-hydroxyethyl)vinylammonium bis(trifluoromethanesulfonyl)imide salt), poly(1-vinylpyridine bis(trifluoromethanesulfonyl)imide salt),Poly(1-vinyl-2-methylpyridine bis(trifluoromethanesulfonyl)imide), Poly(1-vinyl-3-methylpyridine bis(trifluoromethanesulfonyl)imide), Poly(1-vinyl-4-methylpyridine bis(trifluoromethanesulfonyl)imide), Poly(1-vinyl-4-butylpyridine bis(trifluoromethanesulfonyl)imide), Poly(1-vinyl-1,2,3-triazole bis(trifluoromethanesulfonyl)imide), Poly(1-vinyl-1,2,4-triazole bis(trifluoromethanesulfonyl)imide), Poly(1-vinyl-3-methyl-1,2,3-triazole bis(trifluoromethanesulfonyl)imide), Poly(1-vinyl-4-methyl-1,2,4-triazole bis(trifluoromethanesulfonyl)imide), Poly(4-vinylmorpholine bis(trifluoromethanesulfonyl)imide), Poly(4-vinyl-2-methyl-3 ... The poly(1-vinylpyridine bis(fluorosulfonyl)imide), poly(1-vinyl-4-methylpyridine bis(fluorosulfonyl)imide), poly(1-vinyl-1,2,3-triazole bis(fluorosulfonyl)imide), poly(4-vinylmorpholine bis(fluorosulfonyl)imide), poly(1-vinylpyridine trifluoromethanesulfonate), poly(1-vinyl-4-methylpyridine trifluoromethanesulfonate), poly(1-vinyl-1,2,3-triazole trifluoromethanesulfonate), poly(4-vinylmorpholine trifluoromethanesulfonate), poly(1-vinyl-3-(2-hydroxyethyl)pyridine bis(fluoromethanesulfonyl)imide), preferably poly(1-vinyl-3-methylimidazolium bis(fluoromethanesulfonyl)imide).

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