A [2.1.1] bridged lactone monomer and recyclable polyester and method of making the same

Abstract

The application discloses a [2.1.1] bridged lactone monomer and a recyclable polyester and a preparation method thereof. A recyclable polyester with a four-membered ring in a main chain shown in formula (II) is generated by ring-opening polymerization of a [2.1.1] bridged lactone monomer shown in formula (I) and a metal catalyst in an organic solvent. By ring-opening copolymerization of the monomer shown in formula (I) and other lactone monomers, a recyclable random copolymer or block copolymer can also be prepared. The polyester compound prepared by the application has the characteristics of high molecular weight and narrow dispersity, and has excellent thermal performance, mechanical performance, hydrolysis stability and chemical degradability, and is a polyester material with high polymerization activity, high recyclability and high performance, and is expected to become a substitute for current non-degradable commercial plastics, such as low-density polyethylene and polystyrene.

Description

Technical Field

[0001] This invention relates to the fields of monomer synthesis and polymer synthesis technology, specifically to [2.1.1] bridged ring lactone monomers and their synthesis methods, methods for preparing polyesters with four-membered rings in the main chain by ring-opening (co)polymerization, and methods for efficiently degrading polymers into monomers. Background Technology

[0002] Polymer materials are the most widely used man-made materials in the world, widely applied in human society and production due to their low cost, light weight, corrosion resistance, high strength, transparency, and low toxicity. Plastics are the most typical representative of polymer materials. Statistics show that in 2020, plastic production was approximately 367 million tons, and it is projected to reach approximately 1.1 billion tons by 2050. However, traditional plastic products, prioritizing high performance and durability, are very difficult to degrade after use, often ending up in incineration, landfills, or oceans. This linear "production-use-waste" model causes serious environmental pollution, ecological damage, and resource waste, posing a significant challenge to a sustainable green materials economy. Developing recyclable polymers can effectively alleviate this dilemma. The "monomer-polymer-monomer" cycle allows polymer materials to be selectively recycled after use, yielding monomers for repolymerization or reuse.

[0003] Polyesters are a class of polymer materials with good biocompatibility and biodegradability, and are potential alternatives to traditional, difficult-to-degrade, all-carbon-chain polymers. Utilizing inexpensive bulk chemicals as raw materials to synthesize highly polymerizable monomers and then using efficient catalysts to prepare recyclable polyesters with excellent material properties through ring-opening polymerization is currently a research hotspot in the field of sustainable polymer materials. However, most reported recyclable polyesters still suffer from problems such as complex monomer synthesis, polymer properties that cannot compare with commercial plastics (such as polyolefins), and low recycling efficiency. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of complex synthesis of recyclable polyester monomers, limited polymer performance that is difficult to match commercial plastics (such as polyolefins), and low recycling efficiency. This invention provides a [2.1.1] bridged-ring lactone monomer and a polyester with a four-membered ring in its main chain, as well as a method for preparing the same. The monomer designed in this invention is prepared from inexpensive bulk chemicals via a simple synthetic route. It has high polymerization activity and, through ring-opening (co)polymerization, yields a polyester material with high molecular weight, narrow dispersion, excellent thermodynamic properties, and high recycling efficiency.

[0005] The present invention achieves the above-mentioned technical objectives through the following technical solutions.

[0006] In a first aspect of the invention, a [2.1.1] bridged ring lactone monomer is provided, the general structural formula of which is shown in formula (Ⅰ):

[0007]

[0008] In formula (I), R is hydrogen, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group; the substituent in R is selected from alkyl, alkoxy, halogen, etc. The aryl group is preferably a C6-C12 aryl group, such as phenyl, naphthyl, biphenyl, alkyl-substituted phenyl, alkoxy-substituted phenyl, halophenyl, etc.; the alkyl group is preferably a C1-C12 straight-chain or branched alkyl group, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, trifluoromethyl, etc.; the alkoxy group is preferably a C1-C12 alkoxy group, such as methoxy, ethoxy, propoxy, etc.; the halogen includes fluorine, chlorine, bromine, and iodine.

[0009] R includes, but is not limited to, the following structures:

[0010]

[0011] Where n is an integer greater than or equal to 0; X represents a halogen, selected from F, Cl, Br, and I.

[0012] In a second aspect of the invention, a method for synthesizing the bridged ring lactone monomer described above [2.1.1] is provided, comprising the following steps:

[0013] 1. When R is an alkyl group, the general reaction formula is as follows:

[0014]

[0015] (1a) Dissolve methyl 3-carbonyl-cyclobutane carboxylate in an organic solvent, add a reducing agent under an ice bath, stir and react for a period of time (e.g., 30-60 min), quench, extract, wash, dry, and evaporate the solvent to obtain methyl 3-hydroxy-cyclobutane carboxylate.

[0016] (1b) Under ice bath conditions, slowly add an organic solution of methyl 3-hydroxy-cyclobutane carboxylate to a non-nucleophilic strong base solution, stir, restore to room temperature and then stir for a period of time (e.g., 30-90 min), then add alkyl iodide dropwise and stir overnight; quench with acid solution, extract, wash, and evaporate solvent to obtain intermediate a;

[0017] (1c) Mix intermediate a with a strong base solution and stir to react for a period of time (e.g., 2-3 h). After the reaction is completed, add an acid solution to quench the reaction, extract, wash, dry, and evaporate the solvent to obtain intermediate b.

[0018] (1d) Dissolve intermediate b in an organic solvent, add condensing agent and HOBt (1-hydroxybenzotriazole), stir and react for a period of time (e.g., 20-60 min), extract, wash, and dry to obtain the target monomer alkyl-substituted [2.1.1] bridged ring lactone.

[0019] In step (1a) above, the organic solvent may be selected from one or more of methanol, ethanol, N,N-dimethylformamide, and tetrahydrofuran; the reducing agent may be selected from one or more of sodium borohydride, methyl magnesium bromide, phenyl magnesium bromide, and benzyl magnesium bromide.

[0020] In step (1b) above, the alkyl group in the alkyl iodide is preferably one of C1-C12 alkyl, C1-C12 alkoxy, or haloalkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, trifluoromethyl, methoxy, ethoxy, propoxy, etc.; the organic solvent can be selected from one or more of tetrahydrofuran, diethyl ether, and n-hexane; the strong base in the non-nucleophilic strong base solution can be one of diisopropylaminolithium or bis(trimethylsilylaminolithium); the acid solution can be one of 1-5M hydrochloric acid or sulfuric acid solution.

[0021] In step (1c) above, the strong alkaline solution can be one of sodium hydroxide, lithium hydroxide, or potassium hydroxide solution; the acid solution can be one of 1-5M hydrochloric acid or sulfuric acid solution.

[0022] In step (1d) above, the organic solvent may be selected from one or more of dichloromethane, chloroform, tetrahydrofuran, diethyl ether, toluene, and ethyl acetate; the condensing agent may be one of EDCI (1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride), DCC (1,3-dicyclohexylcarbodiimide), and DIC (N,N-diisopropylcarbodiimide).

[0023] 2. When R is an aryl group, the general reaction formula is as follows:

[0024]

[0025] (2a) Dissolve triphosphorus in an organic solvent, place in an ice bath, slowly add a mixed organic solution of ethanol and nucleophile to it, react for a period of time under ice bath conditions (e.g., 30-60 min), raise to room temperature and react for a period of time (e.g., 2-3 h), then wash with water, dry, remove solvent, and obtain ethyl chloroformate.

[0026] (2b) Under ice bath conditions, add an organic solution of arylacetic acid and epichlorohydrin to the Grignard reagent, stir, and react at room temperature for a period of time (e.g., 40-60 min). Then add more Grignard reagent and heat at 50-60 °C for a longer time (e.g., 14-16 h). After the reaction is completed, add an acid solution to quench, extract, wash, dry, evaporate the solvent, add a poor solvent to crystallize, and obtain intermediate c.

[0027] (2c) Dissolve intermediate c in an organic solvent, add an acid-binding agent, place in an ice bath, add ethyl chloroformate, react for a period of time (e.g., 30-60 min), restore to room temperature, and react for a longer time (e.g., 20-24 h); extract, wash, dry, and evaporate the solvent to obtain the target monomer aryl-substituted [2.1.1] bridged ring lactone.

[0028] In step (2a) above, the organic solvent may be selected from one or more of dichloromethane, chloroform, tetrahydrofuran, diethyl ether, and toluene; the nucleophile may be selected from one of triethylamine, pyridine, N,N-diisopropylethylamine, and dimethylformamide.

[0029] In step (2b) above, the aryl group in the arylacetic acid can be one of phenyl, naphthyl, biphenyl, alkyl-substituted phenyl, alkoxy-substituted phenyl, or halophenyl. The alkyl group in the alkyl-substituted phenyl is preferably a C1-C12 alkyl group, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, trifluoromethyl, etc. The alkoxy group in the alkoxy-substituted phenyl is preferably a C1-C12 alkoxy group, such as methoxy, ethoxy, propoxy, etc. The halogen in the halophenyl is preferably fluorine, chlorine, bromine, or iodine.

[0030] The organic solvent mentioned in step (2b) may be selected from one or more of dichloromethane, tetrahydrofuran, toluene, and ethyl acetate.

[0031] The Grignard reagent mentioned in step (2b) can be selected from one of isopropyl magnesium chloride, methyl magnesium chloride, and phenyl magnesium chloride; when the reaction requires the addition of a Grignard reagent, it must be carried out under the protection of an inert gas (such as nitrogen, argon, etc.). The acid solution is one of 1-5M hydrochloric acid or sulfuric acid solution.

[0032] In step (2c) above, the acid-binding agent can be one of triethylamine, n-butylamine, diethylmethylamine, and pyridine; the organic solvent can be selected from one or more of dichloromethane, chloroform, tetrahydrofuran, diethyl ether, and toluene.

[0033] In a third aspect of the invention, a polyester with a four-membered ring main chain prepared from the bridged cyclic lactone monomer described above [2.1.1] is provided, the general structural formula of which is shown in formula (II):

[0034]

[0035] Where n is the degree of polymerization, with a value ranging from 37 to 9600; R is hydrogen, substituted or unsubstituted alkyl, or substituted or unsubstituted aryl. As mentioned above, R can be selected from the following structures:

[0036]

[0037] The polyester shown in formula (II) provided by the present invention has a number-average molecular weight greater than or equal to 6.6 kg / mol, preferably 6.6 to 531 kg / mol, and a molecular weight distribution of 1.0 to 2.0, preferably 1.02 to 1.86.

[0038] In a fourth aspect of the present invention, a method for synthesizing the polyester represented by formula (II) above is provided, the specific steps of which are as follows:

[0039] The bridged ring lactone monomer compound shown in formula (Ⅰ) [2.1.1] was subjected to ring-opening polymerization in an organic solvent in the presence of a metal catalyst to obtain the polyester shown in formula (Ⅱ).

[0040] In the above technical solution, the metal catalyst can be one of the following structural compounds:

[0041]

[0042] In some cases, an initiator needs to be added. The initiator is mainly an alcohol compound, preferably one of benzyl alcohol, isopropanol, and 2,2-diphenylethanol.

[0043] The organic solvent may be one or a combination of dichloromethane, chloroform, toluene, and tetrahydrofuran.

[0044] In the ring-opening polymerization reaction, the molar concentration of the compound shown in formula (I) in the organic solvent is preferably 1.0 to 2.6 mol / L; the molar ratio of the compound shown in formula (I) to the metal catalyst is 50:1 to 2500:1; and the molar ratio of the metal catalyst to the initiator is 1:1 to 1:3.

[0045] The above ring-opening polymerization reaction was carried out under an inert gas atmosphere; the reaction temperature was room temperature (20-30℃); and the reaction time was 1 min to 35 h.

[0046] In a fifth aspect of the present invention, a method for preparing polyesters with different linear or cyclic topologies is provided, the specific steps of which are as follows:

[0047] The compound shown in formula (Ⅰ) was subjected to ring-opening polymerization in an organic solvent in the presence of a catalyst to obtain polyesters with different topologies as shown in formula (Ⅱ);

[0048] The catalyst used to prepare linear polymers is one of Y1, Zn1, La1+ initiator, and Y2+ initiator; the catalyst used to prepare cyclic polymers is La1, Y2+, ... t One of the options in BuOK;

[0049] The initiator is an alcohol compound, preferably one of benzyl alcohol, isopropanol, or 2,2-diphenylethanol.

[0050] In a sixth aspect of the present invention, a method for recovering monomers from a polymer under catalytic conditions is provided, the specific operation of which is as follows:

[0051]

[0052] In solution degradation and recycling, the polymer shown in formula (II) is prepared into a solution with a catalyst and heated to achieve the conversion of the polymer into monomers; wherein the catalyst used is Sn(Oct)2, ZnCl2, YCl3, LaCl3, TBD, DMAP, t The solvent used is one of BuOK, Y1, Y2, Zn1, La1 and Y(CH2SiMe3)3(THF)2, and is toluene, xylene and 1,2-dichlorobenzene.

[0053] In the bulk molten state recovery process, the polymer shown in formula (II) is mixed with a catalyst and heated to achieve the conversion of the polymer into monomers; wherein the catalysts used are Sn(Oct)2, ZnCl2, YCl3, LaCl3, TBD (1,5,7-triazabicyclo[4.4.0]dec-5-ene), DMAP (4-dimethylaminopyridine), t Any one of BuOK, Y1, Y2, Zn1, La1, and Y(CH2SiMe3)3(THF)2.

[0054] The present invention also investigated the thermal properties, mechanical properties, and hydrolysis resistance of the polyester compound shown in formula (II).

[0055] The polyester compound of formula (II) prepared by this invention has an initial decomposition temperature of 372-380℃, a glass transition temperature of 19-110℃, and a melting point of 92-241℃, and has excellent thermal properties and crystallinity.

[0056] The polyester shown in formula (II) has a tensile strength of 25.3 to 30.6 MPa, an elongation at break of 4.9 to 500%, and a Young's modulus of 446 to 1560 MPa, exhibiting excellent mechanical properties.

[0057] The polyester shown in formula (II) is used to prepare a polymer film by solvent evaporation. When placed in acidic, alkaline and neutral aqueous solutions, the film shows no significant mass change after 60 days, exhibiting excellent hydrolysis resistance.

[0058] In a seventh aspect of the invention, a recyclable polyester is provided [2.1.1] prepared by ring-opening copolymerization of a bridged-ring lactone monomer with other lactone monomers, which is one or more of random copolymers and block copolymers, and has the general structural formula shown in formula (Ⅲ):

[0059]

[0060] Where n and m are the degrees of polymerization, both greater than or equal to 10; x is an integer greater than or equal to 1; and the main components of the other lactone monomers are one or more of γ-butyrolactone, δ-valerolactone, ε-caprolactone, δ-caprolactone, and 7-heptyllactone; R 1 R is one or more of hydrogen, C1-C12 alkyl, C1-C12 alkoxy, halogen, and C6-C12 aryl; R is hydrogen, substituted or unsubstituted alkyl, or substituted or unsubstituted aryl; as mentioned above, R can be selected from the following structures:

[0061]

[0062] In an eighth aspect of the present invention, a method for synthesizing the above-mentioned copolymer is provided, the specific steps of which are as follows:

[0063]

[0064] One-pot feeding: The compound shown in formula (I) is mixed with a second lactone monomer, and then a metal catalyst and an initiator are added. The ring-opening copolymerization reaction is carried out in an organic solvent to obtain the random copolymer or block copolymer shown in formula (III).

[0065] Sequential feeding: A lactone monomer is first mixed with a metal catalyst and an initiator in an organic solvent to generate a first homopolymer, and then a second lactone monomer is added to the system to generate a second polymer, resulting in a block copolymer as shown in formula (Ⅲ).

[0066] In the above synthesis method, the metal catalyst can be one of the following structural compounds:

[0067]

[0068] The initiator is an alcohol compound, preferably one of benzyl alcohol, isopropanol, 2,2-diphenylethanol, 1,4-terephthalic acid, 1,4-butanediol, and 1,6-hexanediol;

[0069] The organic solvent is one or more of dichloromethane, chloroform, toluene, and tetrahydrofuran;

[0070] The polymerization reaction is carried out in an inert gas atmosphere; the reaction temperature is room temperature (20-30℃).

[0071] In summary, this invention utilizes inexpensive bulk chemicals as raw materials to design and synthesize a [2.1.1] bridged-ring lactone monomer. This monomer exhibits significant ring strain and can be efficiently ring-opened polymerized at room temperature to obtain polyesters with a main chain containing four-membered rings. The number average molecular weight ranges from 6.6 to 531 kg / mol, with a maximum of 531 kg / mol, and the molecular weight distribution is mostly less than 1.2. Compared with existing recyclable polyester materials, the advantages of this invention are specifically reflected in:

[0072] 1) The monomer synthesis steps are simple, the raw materials are inexpensive and readily available, and monomers with different substituents can be easily prepared, making them suitable for large-scale production;

[0073] 2) The monomer exhibits high polymerization activity, enabling rapid ring-opening polymerization at room temperature to obtain the target polymer, with a number-average molecular weight as high as 531.

[0074] kg / mol, with molecular weight distribution mostly less than 1.2, and the polymerization process is highly controllable;

[0075] 3) The polyester compound in this invention has high thermal stability, with an initial decomposition temperature as high as 380°C;

[0076] 4) The thermal properties of the polyester compounds in this invention can be adjusted according to the side chain substituents, and all of them have excellent thermal properties and crystallization properties, with a glass transition temperature of up to 110°C and a melting point of up to 241°C.

[0077] 5) The mechanical properties of the polyester compound in this invention can be adjusted according to the side chain substituents, with a maximum tensile strength of 30.6 MPa, a maximum elongation at break of 500%, and a maximum Young's modulus of 1.56 GPa;

[0078] 6) The polyester compound in this invention has excellent hydrolysis resistance properties, and there is no significant change in mass after soaking in acidic, alkaline and neutral aqueous solutions for 60 days;

[0079] 7) The polyester compound in this invention has excellent degradation and recycling properties. After being mixed with a catalyst (and solvent) and heated, the monomer can be efficiently recovered.

[0080] 8) The polyester compounds in this invention are comparable to commercial plastics such as low-density polyethylene and polystyrene in terms of thermal and mechanical properties, and can be efficiently degraded and recycled under certain conditions, making them potential alternatives to low-density polyethylene and polystyrene.

[0081] 9) The bridged ring lactone in [2.1.1] of this invention can be copolymerized with other lactone monomers through ring opening, which facilitates the preparation of random copolymers and block copolymers, and develops recyclable polyester materials with more diverse properties. Attached Figure Description

[0082] Figure 1 The 1H NMR spectrum of the [2.1.1] bridged ring lactone Bu-BL monomer prepared in Example 1 ( 1 H NMR).

[0083] Figure 2 The carbon NMR spectrum of the [2.1.1] bridged ring lactone Bu-BL monomer prepared in Example 1 ( 13 (C NMR).

[0084] Figure 3 The 1H NMR spectrum of the [2.1.1] bridged ring lactone Ph-BL monomer prepared in Example 2 ( 1 H NMR).

[0085] Figure 4 The carbon NMR spectrum of the [2.1.1] bridged ring lactone Ph-BL monomer prepared in Example 2 ( 13 (C NMR).

[0086] Figure 5 The 1H NMR spectrum of the polyester P(Bu-BL) prepared in Example 3 is shown below. 1 H NMR).

[0087] Figure 6 The carbon NMR spectrum of the polyester P(Bu-BL) prepared in Example 3 is shown below. 13 (C NMR).

[0088] Figure 7 The 1H NMR spectrum of the polyester P (Ph-BL) prepared in Example 4 is shown below. 1 H NMR).

[0089] Figure 8 The carbon NMR spectrum of the polyester P (Ph-BL) prepared in Example 4 is shown below. 13 (C NMR).

[0090] Figure 9 The image shows the GPC spectrum of polyester P(Bu-BL) prepared in Example 3.

[0091] Figure 10 The image shows the GPC spectrum of polyester P (Ph-BL) prepared in Example 4.

[0092] Figure 11The TGA spectrum of polyester P(Bu-BL) prepared in Example 3 is shown.

[0093] Figure 12 The image shows the DSC spectrum of the polyester P(Bu-BL) prepared in Example 3.

[0094] Figure 13 The TGA spectrum of polyester P (Ph-BL) prepared in Example 4 is shown.

[0095] Figure 14 The image shows the DSC spectrum of the polyester P (Ph-BL) prepared in Example 4.

[0096] Figure 15 The XRD patterns are those of polyester P (Bu-BL) prepared in Example 3 and polyester P (Ph-BL) prepared in Example 4.

[0097] Figure 16 Stress-strain diagrams of polyester P (Bu-BL) prepared in Example 3 and polyester P (Ph-BL) prepared in Example 4.

[0098] Figure 17 The DMA spectrum of polyester P(Bu-BL) prepared in Example 3 is shown.

[0099] Figure 18 The DMA spectrum of polyester P (Ph-BL) prepared in Example 4 is shown.

[0100] Figure 19 The graph shows the change in the hydrolysis mass of polyester P(Bu-BL) prepared in Example 3.

[0101] Figure 20 The graph shows the change in the mass of polyester P (Ph-BL) prepared in Example 4 after hydrolysis.

[0102] Figure 21 The image shows a comparison of the proton NMR spectra of the polyester P (Ph-BL) prepared in Example 5 after degradation and recovery.

[0103] Figure 22 The image shows a comparison of the proton NMR spectra of the polyester P(Bu-BL) prepared in Example 6 after degradation and recovery.

[0104] Figure 23 The 1H NMR spectrum of the triblock copolymer P(Ph-BL)-b-PCL-bP(Ph-BL) prepared in Example 7 ( 1 H NMR).

[0105] Figure 24 The carbon NMR spectrum of the triblock copolymer P(Ph-BL)-b-PCL-bP(Ph-BL) prepared in Example 7 (13 (C NMR). Detailed Implementation

[0106] The present invention will be further illustrated by way of embodiments below, but the present invention is not limited to the scope of the embodiments described herein.

[0107] Example 1

[0108] The specific steps are as follows:

[0109]

[0110] 50 g (0.390 mol, 1.0 equivalent) of methyl 3-carbonyl-cyclobutane carboxylate was added to a 2 L round-bottom flask and dissolved in 600 mL of methanol. Sodium borohydride (8.86 g, 0.234 mol, 0.6 equivalent) was added in portions under ice bath conditions, and the mixture was stirred for 30 min. The solution was quenched to neutral with saturated ammonium chloride solution, and the methanol was evaporated to dryness. The aqueous phase was extracted three times with dichloromethane, and the organic phase was washed once with saturated brine. The mixture was dried over anhydrous sodium sulfate, and the solvent was evaporated to dryness, yielding 40.5 g of the product (80% yield), which was used directly in the next reaction. 1 H NMR (400MHz, CDCl3) δ4.19(m,1H),3.69(s,3H),2.64-2.55(m,3H),2.23-2.13(m,2H).

[0111]

[0112] Under nitrogen protection and an ice bath, a tetrahydrofuran / n-hexane solution of lithium diisopropylaminocarbon (2M, 254 mL, 0.507 mol, 2.2 equivalents) was added to a 1 L three-necked flask. Methyl 3-hydroxy-cyclobutanecarboxylate (30 g, 0.231 mol, 1.0 equivalents) prepared in the previous step was dissolved in 290 mL of tetrahydrofuran and slowly added to the flask. The mixture was stirred for 10 min, allowed to return to room temperature, and stirred for 1 h. Then, 1-iodobutane was slowly added and stirred overnight. The mixture was quenched with 2M HCl solution, the tetrahydrofuran was evaporated to dryness, extracted three times with ethyl acetate, washed once with water, washed once with saturated brine, dried, and the solvent was evaporated to dryness. Column chromatography was used to separate the product, yielding 22.6 g (53%). 1 H NMR(400MHz, CDCl3)δ4.27(qu,J=6.8Hz,1H),3.69(s,3H),2.38-2.27(m,4H),1.6 9-1.65(m,2H),1.28(qu,J=7.2Hz,2H),1.19-1.13(m,2H),0.88(t,J=7.2Hz,3H).

[0113]

[0114] Add the product prepared in the previous step (22.4 g, 0.121 mol, 1.0 equivalent) and 0.5 M NaOH solution (24 mL, 0.012 mol, 0.1 equivalent) to a 200 mL round-bottom flask, stir, and then add 5 M NaOH solution (24 mL, 0.121 mol, 0.1 equivalent) under ice bath conditions. Stir for 30 min, allow to return to room temperature, and stir for 2.5 h. Add 430 mL of concentrated hydrochloric acid to acidity under ice bath conditions. Extract the aqueous phase three times with diethyl ether, dry, and evaporate the solvent to obtain 19.7 g of product (94% yield), which can be used directly in the next reaction. 1 H NMR (400MHz, CDCl3) δ4.30(qu,J=6.8Hz,1H),2.37(m,4H),1.72-1.68(m,2H),1.31(qu,J=7.2Hz,2H),1.27-1.22(m,2H),0.90(t,J=7.2Hz,3H).

[0115]

[0116] Under nitrogen protection, the product from the previous step (22.7 g, 0.132 mol, 1.0 equivalent) was added to a 500 mL three-necked flask and dissolved in 230 mL of anhydrous dichloromethane. EDCI (27.8 g, 0.145 mol, 1.1 equivalent), HOBt (19.6 g, 0.145 mol, 1.1 equivalent), and anhydrous triethylamine (20.2 mL, 0.145 mol, 1.1 equivalent) were then added, and the mixture was stirred at room temperature for 30 min. The mixture was quenched with saturated brine, and the organic phase was separated. The aqueous phase was extracted three times with dichloromethane, and the organic phase was washed twice with water and once with saturated brine. The mixture was dried, the solvent was evaporated, and the mixture was separated by column chromatography to obtain 13.2 g of the target product [2.1.1] bridged ring lactone Bu-BL monomer, with a yield of 65%. 1 H NMR (400MHz, CDCl3) δ4.84 (s, 1H), 2.44-2.38 (m, 2H), 2.33-2.27 (m, 2H), 1.73-1.69 (m, 2H), 1.38-1.33 (m, 4H), 0.91 (t, J = 7.2Hz, 3H). 13 C NMR (101MHz, CDCl3) δ179.1,75.8,55.1,50.9,27.6,26.9,22.9,13.9.HRMS-ESI: calculated m / z 154.0994; found m / z155.1067[M+H + ]. 1 H NMR and 13 C NMR spectrum as follows Figure 1 and 2As shown.

[0117] Example 2

[0118] The specific steps are as follows:

[0119]

[0120] Triphosgene (25 g, 0.084 mol, 0.34 equivalence) was added to a 1 L round-bottom flask and dissolved in 70 mL of dichloromethane. Ethanol (11.4 g, 0.248 mol, 1.0 equivalence) and triethylamine (34.4 mL, 0.248 mol, 1.0 equivalence) were dissolved in 140 mL of dichloromethane and slowly added to the flask. The reaction was allowed to proceed for 1 h, then brought to room temperature and allowed to proceed for another 2 h. The mixture was washed three times with water, dried, and the solvent was removed by distillation under normal pressure to obtain 18.8 g of product, with a yield of 70%. 1 H NMR (400MHz, CDCl3): δ4.38 (q, J=7.2Hz, 2H), 1.39 (t, J=7.2Hz, 3H).

[0121]

[0122] Under nitrogen protection and in an ice bath, a tetrahydrofuran solution of isopropyl magnesium chloride (2M, 194 mL, 0.388 mol, 2.2 equivalents) was added to a 1 L three-necked flask. Phenylacetic acid (24 g, 0.176 mol, 1.0 equivalent) was dissolved in 100 mL of tetrahydrofuran and slowly added to the flask. Epichlorohydrin (30.3 g, 0.317 mol, 1.8 equivalents) was then added, and the mixture was stirred for 5 min. The mixture was then allowed to return to room temperature and stirred for 45 min. More tetrahydrofuran solution of isopropyl magnesium chloride (2M, 176 mL, 0.353 mol, 2.0 equivalents) was added, and the reaction was heated at 60 °C for 14 h. The reaction was quenched by slowly adding dilute hydrochloric acid solution in an ice bath. The tetrahydrofuran was removed by rotary evaporation, and the mixture was extracted three times with ethyl acetate. The organic phase was washed with water and saturated brine, dried, and the solvent was evaporated. Toluene was added, and crystals precipitated at low temperature. The product was obtained by filtration, yielding 20.3 g (60% yield). 1 H NMR (400MHz, DMSO-d6): δ12.23(br,1H),7.39-7.22(m,5H),3.85(qu,J=7.2Hz,1H),3.34(s,1H),2.77-2.72(m,2H),2.50(m,2H).

[0123]

[0124] Under nitrogen protection, the product from the previous step (20 g, 0.104 mol, 1.0 equivalent) was added to a 2 L three-necked flask and dissolved in 440 mL of anhydrous tetrahydrofuran. Then, anhydrous triethylamine (16 mL, 0.114 mol, 1.1 equivalent) was added and stirred at room temperature to dissolve. Under ice bath conditions, ethyl chloroformate (11.3 g, 0.104 mol, 1.0 equivalent) was added and stirred for 1 h. The mixture was then brought back to room temperature and stirred for 20 h. The solvent was evaporated, dissolved in a small amount of water, extracted with ethyl acetate, dried, and the solvent was evaporated again. Column chromatography analysis was performed to obtain 16.6 g of the target product [2.1.1] bridged ring lactone Ph-BL monomer, with a yield of 92%. 1 H NMR (400MHz, CDCl3) δ7.42-7.30(m,5H),4.97(s,1H),2.88(m,2H),2.71(m,2H). 13 C NMR (101MHz, CDCl3) δ176.9,134.2,128.6,128.0,126.9,75.2,57.5,52.6.HRMS-ESI: calculated m / z 174.0681; found m / z 175.0753[M+H + ]. 1 HNMR and 13 CNMR spectrum as follows Figure 3 and Figure 4 As shown.

[0125] Example 3

[0126] The specific steps are as follows:

[0127]

[0128] In an argon-atmospheric glove box, 10 mg of Zn1 catalyst and 1135 μL of toluene were added to a 5 mL reaction flask to prepare a catalyst solution for later use. In another 5 mL reaction flask, 100 mg of [2.1.1] bridged ring lactone monomer and 470 μL of toluene were added. 80 μL of the catalyst solution was then added to the monomer solution being stirred. At this point, the monomer / catalyst molar ratio was 500 / 1, the monomer concentration was 1.0 mol / L, and the polymerization temperature was room temperature. Samples were taken during the polymerization process and analyzed using 1H NMR spectroscopy (1H NMR spectroscopy). 1 The monomer conversion rate was monitored by ¹H NMR. After the polymerization reaction was completed, the reaction was quenched with a chloroform solution of benzoic acid (10 mg / mL), poured into ice-cold methanol to allow the polymer to settle, and washed with ice-cold methanol several times. The polymer was then dried in a vacuum oven at 60°C until its weight no longer changed.

[0129] The present invention performed 1H NMR spectroscopy on the obtained reaction solution, and the results showed that the monomer conversion rate was >99%; the dried polymer was further analyzed by NMR to confirm that it was a polyester P(Bu-BL) with a four-membered ring main chain. 1 H NMR and 13 CNMR spectrum as follows Figure 5 and Figure 6 As shown.

[0130] This invention employs gel permeation chromatography (GPC) to analyze the molecular weight of polymers, using chloroform as the mobile phase at a flow rate of 1 mL / min. A standard curve is constructed using polystyrene as a standard. The results show that the number-average molecular weight is M. n =109 kg / mol, dispersity D = 1.06, GPC curve as shown Figure 9 As shown.

[0131] In this invention, matrix-assisted laser desorption / ionization time-of-flight mass spectrometry (MALDI-TOF MS) was used to analyze the end groups of the polymer in this embodiment. Based on the fitting curve of the mass-to-charge ratio of the molecular ion peak and the repeating unit, it can be concluded that the polymer is a linear polymer with isopropoxy / hydrogen end groups.

[0132] Example 4

[0133] The specific steps are as follows:

[0134]

[0135] In an argon-atmospheric glove box, 10 mg of Y1 catalyst and 1540 μL of toluene were added to a 5 mL reaction flask to prepare a catalyst solution for later use. In another 5 mL reaction flask, 120 mg of [2.1.1] bridged ring lactone monomer and 544 μL of toluene were added. 54 μL of the catalyst solution was then added to the monomer solution being stirred. At this point, the monomer / catalyst molar ratio was 500 / 1, the monomer concentration was 1.0 mol / L, and the polymerization temperature was room temperature. Samples were taken during the polymerization process and analyzed using 1H NMR spectroscopy (1H NMR spectroscopy). 1 The monomer conversion rate was monitored by ¹H NMR. After the polymerization reaction was completed, the reaction was quenched with a chloroform solution of benzoic acid (10 mg / mL), poured into ice-cold methanol to allow the polymer to settle, and washed with ice-cold methanol several times. The polymer was then dried in a vacuum oven at 60°C until its weight no longer changed.

[0136] The present invention performed 1H NMR spectroscopy on the obtained reaction solution, and the results showed that the monomer conversion rate was 95%. NMR spectroscopy of the dried polymer confirmed it to be a polyester P (Ph-BL) with a four-membered ring main chain. 1 H NMR and 13 CNMR spectrum as follows Figure 7 and Figure 8 As shown.

[0137] This invention uses GPC to analyze the molecular weight of polymers, with chloroform as the mobile phase at a flow rate of 1 mL / min, and polystyrene as the standard to create a standard curve. The results show that the number-average molecular weight is M. n =486 kg / mol, dispersity GPC curve as shown Figure 10 As shown.

[0138] The present invention uses MALDI-TOF MS to analyze the end groups of the polymer in this embodiment. According to the fitting curve of the mass-to-charge ratio of the molecular ion peak and the repeating unit, the polymer is a linear polymer with Me3SiCH2 / H end groups.

[0139] Performance testing:

[0140] This invention employs thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) to determine the thermal decomposition temperature, glass transition temperature, melting point, and crystallization temperature of polymers P(Bu-BL) and P(Ph-BL) in Examples 3 and 4. Figure 11 and Figure 12 As shown, the initial decomposition temperature T of P(Bu-BL) is... d,5％ =380℃, glass transition temperature T g =21℃ (second heating), melting point T m =99℃ (first temperature rise); while if Figure 13 and Figure 14 As shown, the initial decomposition temperature T of P(Ph-BL) is... d,5％ =376℃, glass transition temperature T g =109℃ (second heating), melting point T m =241℃ (second heating). The results show that both polymers have high thermal stability and crystallinity. The initial decomposition temperature is higher than that of any other recyclable polyester reported in the literature, giving the polymers a processing window of more than 100℃ and excellent processing performance. At the same time, the thermal properties of the polymers can be easily adjusted by changing the side chain substituents.

[0141] This invention uses X-ray diffraction (XRD) to verify the crystallinity of polymers and calculate the degree of crystallinity, such as... Figure 15 As shown, the crystallinity of polymer P(Bu-BL) in Example 3 is 35%, and the crystallinity of polymer P(Ph-BL) in Example 4 is 42%.

[0142] This invention tested the mechanical properties of the polymers in Examples 3 and 4. Using the same polymerization steps, but changing the monomer / catalyst ratio, P(Bu-BL) with a molecular weight of 309 kg / mol and P(Ph-BL) with a molecular weight of 410 kg / mol were obtained, respectively. Polymer films were prepared from both by solvent evaporation, and then cut into dog-bone shaped strips for uniaxial tensile testing. Their stress-strain curves are shown below. Figure 16 As shown, the yield stress σ of P(Bu-BL) B =16.4MPa, tensile strength σ B =25.3MPa, elongation at break ε B =500%, Young's modulus E=446MPa, it is a strong and tough material, and its thermodynamic properties are comparable to those of commercial plastic low-density polyethylene (LDPE). m ~110℃, E~300MPa, σ y ~8.0MPa,σ B ~20MPa,ε B The tensile strength of P(Ph-BL) is comparable to, or even superior to, low-density polyethylene (LDPE); while the tensile strength σ of P(Ph-BL) is... B With a strength of 30.6 MPa, an elongation at break of 4.9%, and a Young's modulus of 1.56 GPa, it is a hard and brittle material. Its thermodynamic properties are similar to those of commercial plastic polystyrene (T...). g ~100℃, T m ~240℃, σ B ~42MPa,ε B The content is approximately 5%, and the thermal conductivity is approximately 3.6 GPa. Therefore, P(Bu-BL) and P(Ph-BL) show promise as potential alternatives to non-degradable commercial plastics such as low-density polyethylene and polystyrene.

[0143] This invention employs dynamic mechanical analysis (DMA) to further characterize the mechanical properties of the polymer, such as... Figure 17 As shown, at 25℃, the storage modulus of P(Bu-BL) is 1.31 GPa, and the loss modulus is 147 MPa. The value of T is obtained from the vertex value of tanδ. g It is 135℃; while if Figure 18 As shown, the storage modulus of P(Ph-BL) is 2.63 GPa, the loss modulus is 84 MPa, and T g It is 42℃. Above T g Afterwards, the energy storage modulus of both decreased by an order of magnitude, but remained above 100MPa, maintaining good elasticity.

[0144] The present invention tested the hydrolysis resistance of the polymers in Examples 3 and 4 by immersing the polymer films in acidic, alkaline, and neutral aqueous solutions, respectively. Figure 19 and Figure 20As shown, after 60 days, there was no significant change in quality, demonstrating excellent resistance to hydrolysis and suitability for various humid outdoor environments.

[0145] The rigid four-membered ring structure on the main chain endows the polymer with excellent thermal properties, mechanical properties and hydrolysis resistance, while the ester bonds present at the same time make the polymer biodegradable and the monomer can be recycled.

[0146] Example 5

[0147]

[0148] The specific steps are as follows:

[0149] Solution degradation and recovery: In a glove box, 10.8 mg Y1 and 20 mg polymer P (Ph-BL) were added to a 10 mL Schlenk tube, followed by 2.9 mL toluene (0.1 M). After sealing, the glove box was removed and heated at 130 °C for 29 h. Only 31% of the polymer was degraded into monomers.

[0150] Bulk melt degradation and recovery: In a glove box, add 1.13 mg Y(CH2SiMe3)3(THF)2 (2 mol%) and 20 mg polymer P (Ph-BL) to a 10 mL Schlenk tube. After sealing, remove the glove box and heat at 250 °C for 19 h. The polymer is efficiently degraded into monomers with a conversion rate >98%. See [link to relevant documentation]. Figure 21 .

[0151] Example 6

[0152]

[0153] The specific steps are as follows:

[0154] Bulk melt degradation and recovery: In a glove box, 1.61 mg La1 (2 mol%) and 20 mg polymer P (Bu-BL) were added to a 10 mL Schlenk tube. After sealing, the glove box was removed, and the mixture was heated to 260 °C for 8 hours. The polymer was efficiently degraded into monomers with a conversion rate >98%. (See [link to relevant documentation]). Figure 22 .

[0155] Example 7

[0156]

[0157] The specific steps are as follows:

[0158] One-pot preparation of triblock copolymers: In an argon-atmospheric glove box, 8 mg of Y2 catalyst and 1111 μL of toluene were added to a 5 mL reaction flask to prepare a catalyst solution for later use. In another 5 mL reaction flask, 8 mg of 1,4-butanediol and 800 μL of toluene were added. 44 μL of the 1,4-butanediol toluene solution was added to the Y2 catalyst solution, and the mixture was stirred for 10 min to allow in-situ alcoholysis. In a third 5 mL reaction flask, 60 mg of the [2.1.1]-bridged lactone monomer Ph-BL and 39 mg of ε-caprolactone were added, dissolved in 288 μL of toluene. 400 μL of the catalyst and initiator mixture was added to the stirred monomer solution. At this point, the molar ratio of Ph-BL / ε-caprolactone / catalyst / initiator was 200 / 200 / 2 / 1, and the polymer temperature was room temperature. Samples were taken during polymerization and analyzed using 1H NMR spectroscopy (NMR). 1 The monomer conversion rate was monitored by ¹H NMR. After the polymerization reaction was completed, the reaction was quenched with a chloroform solution of benzoic acid (10 mg / mL), poured into ice-cold methanol to allow the polymer to settle, and washed with ice-cold methanol several times. The polymer was then dried in a vacuum oven at 60°C until its weight no longer changed.

[0159] The reaction solution obtained in this invention was analyzed by proton NMR spectroscopy, and the results showed that the Ph-BL conversion rate was 87% and the ε-caprolactone conversion rate was 97%. NMR analysis of the dried polymer confirmed it to be a P(Ph-BL)-b-PCL-bP(Ph-BL) triblock copolymer. 1 H NMR and 13 C NMR spectrum as follows Figure 23 and Figure 24 As shown.

[0160] This invention uses GPC to analyze the molecular weight of polymers, with chloroform as the mobile phase at a flow rate of 1 mL / min, and polystyrene as the standard to create a standard curve. The results show that the number-average molecular weight is M. n =60.7 kg / mol, dispersity D = 1.25.

[0161] The above description is only a partial embodiment of the present invention and is not intended to limit the present invention. Any modifications or substitutions made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A [2.1.1]-bridged ring lactone monomer, the general structural formula of which is shown in Formula I: In Formula I, R is a substituted or unsubstituted C2-C12 alkyl group, and the substituents in R are C1-C12 alkyl groups, C1-C12 alkoxy groups, and / or halogens.

2. The bridged ring lactone monomer as described in claim 1, characterized in that, R is selected from the following structures: Where n is an integer greater than or equal to 0.

3. The method for preparing the bridged ring lactone monomer as described in claim 1 [2.1.1], comprising: 1a) Methyl 3-carbonyl-cyclobutane carboxylate was dissolved in an organic solvent, a reducing agent was added under ice bath, the mixture was stirred, the reaction was quenched, extracted, washed, dried, and the solvent was evaporated to obtain methyl 3-hydroxy-cyclobutane carboxylate. 1b) Under ice bath conditions, an organic solution of methyl 3-hydroxy-cyclobutane carboxylate was slowly added to a non-nucleophilic strong base solution, stirred, and brought to room temperature. The mixture was then stirred for a period of time, followed by the dropwise addition of alkyl iodide and stirring overnight. The mixture was then quenched with an acid solution, extracted, washed, and the solvent was evaporated to obtain intermediate a. 1c) Intermediate a is mixed with a strong base solution and stirred to react. After the reaction is complete, an acid solution is added to quench the reaction, followed by extraction, washing, drying, and rotary evaporation to obtain intermediate b. 1d) Dissolve intermediate b in an organic solvent, add condensing agent and HOBt, stir to react, extract, wash, and dry to obtain the target monomer alkyl-substituted [2.1.1] bridged ring lactone; Wherein, R is a substituted or unsubstituted C2-C12 alkyl group, and the substituents in R are C1-C12 alkyl groups, C1-C12 alkoxy groups, and / or halogens.

4. The method for preparing the [2.1.1] bridged ring lactone monomer as described in claim 3, characterized in that, The organic solvent in step 1a) is selected from one or more of methanol, ethanol, N,N-dimethylformamide, and tetrahydrofuran; the reducing agent is sodium borohydride; the organic solvent in step 1b) is selected from one or more of tetrahydrofuran, diethyl ether, and n-hexane; the strong base in the non-nucleophilic strong base solution is one of diisopropylaminolithium and bis(trimethylsilylaminolithium); the acid solution is one of 1-5M hydrochloric acid and sulfuric acid; the strong base solution in step 1c) is selected from one of sodium hydroxide, lithium hydroxide, and potassium hydroxide; the acid solution is one of 1-5M hydrochloric acid and sulfuric acid; the organic solvent in step 1d) is selected from one or more of dichloromethane, chloroform, tetrahydrofuran, diethyl ether, toluene, and ethyl acetate; the condensing agent is one of EDCI (1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride), DCC (1,3-dicyclohexylcarbodiimide), and DIC (N,N-diisopropylcarbodiimide).

5. A polyester whose main chain contains a four-membered ring, the general structural formula of which is shown in Formula II: In Formula II, n is the degree of polymerization; R is a substituted or unsubstituted C1-C12 alkyl group or a substituted or unsubstituted C6-C12 aryl group. The substituents in R are C1-C12 alkyl, C1-C12 alkoxy, and / or halogens, wherein the substituted or unsubstituted C1-C12 alkyl groups do not include methyl groups.

6. The polyester as claimed in claim 5, characterized in that, R is selected from the following structures: Where n is an integer greater than or equal to 0; X represents a halogen, selected from F, Cl, Br, and I.

7. The method for preparing the polyester according to claim 5, wherein the bridged ring lactone monomer shown in Formula I [2.1.1] is subjected to ring-opening polymerization in an organic solvent in the presence of a metal catalyst to obtain the polyester shown in Formula II; in, n represents the degree of polymerization; R represents hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C6-C12 aryl; the substituents in R are C1-C12 alkyl, C1-C12 alkoxy and / or halogen; The metal catalyst is selected from one of the following compounds:

8. The preparation method according to claim 7, characterized in that, The polyester shown in Formula II is a linear polymer. Under the catalysis of metal catalyst Y1 or Zn1, or under the co-catalysis of metal catalyst La1 or Y2 and an initiator, the bridged ring lactone monomer shown in Formula I [2.1.1] undergoes a ring-opening polymerization reaction, wherein the initiator is an alcohol compound.

9. The preparation method according to claim 7, characterized in that, The polyester shown in Formula II is a cyclic polymer, which reacts with metal catalysts La1, Y2, or... t BuOK catalyzes the ring-opening polymerization of the bridged cyclic lactone monomer shown in Formula I [2.1.1].

10. A method for recycling a polymer, wherein the polymer is a polyester as shown in Formula II, wherein the polymer and a catalyst are prepared into a solution and heated, or the polymer and the catalyst are mixed and heated to a molten state to achieve the conversion of the polymer into a monomer; in, n represents the degree of polymerization; R represents hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C6-C12 aryl; the substituents in R are C1-C12 alkyl, C1-C12 alkoxy, and / or halogens; the catalyst is selected from Sn(Oct)2, ZnCl2, YCl3, LaCl3, TBD, DMAP, etc. t One of BuOK, Y1, Y2, Zn1, La1, and Y(CH2SiMe3)3(THF)2, and one of the solvents used, namely toluene, xylene, and 1,2-dichlorobenzene; wherein, Y1, Y2, Zn1, La1, and t The structure of BuOK is shown below:

11. A recyclable polyester having the general structural formula shown in Formula III: In Formula III, n and m are the degrees of polymerization; x is an integer greater than or equal to 1; R is hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C6-C12 aryl, and the substituents in R are C1-C12 alkyl, C1-C12 alkoxy, and / or halogen; R 1 It is one or more of hydrogen, C1-C12 alkyl, C1-C12 alkoxy, halogen, and C6-C12 aryl.

12. The recyclable polyester as claimed in claim 11, characterized in that, R is selected from the following structures: Where n is an integer greater than or equal to 0; X represents a halogen, selected from F, Cl, Br, and I.

13. The method for preparing the recyclable polyester according to claim 11, wherein the reaction formula is as follows: The preparation is carried out using either a one-pot feeding method or a sequential feeding method, wherein: One-pot feeding: The bridged ring lactone monomer shown in Formula I [2.1.1] is mixed with the second lactone monomer, and then a metal catalyst and an initiator are added. The ring-opening copolymerization reaction is carried out in an organic solvent to obtain the random copolymer or block copolymer shown in Formula III. Sequential feeding: A lactone monomer is first mixed with a metal catalyst and an initiator in an organic solvent to generate a first homopolymer, and then a second lactone monomer is added to the system to generate a second polymer, resulting in a block copolymer as shown in Formula III.

14. The preparation method according to claim 13, characterized in that, The metal catalyst is selected from one of the following compounds: The initiator is an alcohol compound; the organic solvent is one or more of dichloromethane, chloroform, toluene, and tetrahydrofuran; the polymerization reaction is carried out under an inert gas atmosphere.

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