CN115536823B - Catalyst for preparing polyester by ring-opening polymerization and method for preparing polyester by using catalyst - Google Patents

Abstract

The invention discloses a catalyst for preparing polyester by ring-opening polymerization and a method for preparing polyester by using the catalyst, and belongs to the technical field of organic hydrogen bond catalytic high polymer materials. The method comprises the steps of (1) synthesizing the amphoteric (sulfur) urea ion pair catalyst in situ by diphenyl phosphino substituted (sulfur) urea and acrylic ester. (2) Under the reaction conditions, (thio) urea ions double activate the catalyst for cyclic monomers and initiators. (3) In the presence of an alcohol initiator, (thio) urea ion pairs catalyze ring-opening polymerization of a cyclic monomer to obtain polyester. The method is efficient, simple and convenient in process, low in cost, wide in application range, high in reaction activity, free of transesterification reaction and metal residues in the catalyst, and the prepared polyester has the advantages of being accurate in molecular weight and low in molecular weight distribution.

Description

Catalyst for ring-opening polymerization to prepare polyester and method for preparing polyester

Technical field

The invention belongs to the technical fields of organic catalysis and polymer materials, and specifically relates to a method for preparing polyester through organocatalytic ring-opening polymerization of cyclic esters.

Background technique

Innovations in petrochemical catalysis and polymerization methods have led to the development of petroleum-based materials, one of the most important achievements of the twentieth century. Despite their many advantages, petroleum-based materials cannot be regenerated or degraded. With the continuous consumption of fossil energy around the world and the generation of large amounts of plastic pollution, people are urgently seeking a renewable and degradable alternative material. Aliphatic polyester is a type of material that is biocompatible, biorenewable and biodegradable and can be a good substitute for petroleum-based materials. One of the most efficient methods for synthesizing aliphatic polyesters is the ring-opening polymerization (ROP) of cyclic esters. Compared with traditional polymer synthesis methods, ring-opening polymerization to prepare aliphatic polyester is an environmentally friendly method with low energy consumption and renewable raw materials. It can obtain polyester with a clear structure under mild reaction conditions.

Among the catalytic methods of ring-opening polymerization, organocatalyzed ring-opening polymerization has the advantages of mild reaction conditions, high monomer conversion rate, high product molecular weight, and short reaction time. Moreover, there is no metal residue in the polymer prepared by it, and it is widely used in biomedicine, Applications in areas such as food packaging and microelectronic materials are unrestricted. Because of these advantages, organocatalytic ring-opening polymerization has developed rapidly in the past two decades, and a large number of organic ring-opening polymerization catalysts have emerged. Among them, the ring-opening polymerization reaction catalyzed by hydrogen bonding catalysts is mild, efficient and has no transesterification reaction. The resulting polyester has a clear structure and low molecular weight distribution. It is one of the organic catalysts with the most research potential.

Traditional hydrogen bonding catalysts often require bases as co/cocatalysts to achieve ring-opening polymerization of cyclic esters (Macromolecules 2006, 39, 7863-7871, Nature Chem. 2016, 8, 1047-1053,: Macromolecules 2018, 51, 3203- 3211), and the addition of alkali may cause some other problems. For example, when using metal bases as co/cocatalysts, metal residues may be introduced into the polymer, affecting the application of the polymer in metal-sensitive fields such as biomedicine; although organic bases will not introduce metal residues, organic bases are generally expensive , which will increase the production cost of the polymer. In addition, the addition of alkali co/cocatalysts often increases the probability of side reactions such as transesterification during ring-opening polymerization, so the amount of alkali added needs to be strictly controlled.

Contents of the invention

The invention provides a catalyst for ring-opening polymerization to prepare polyester. The invention can synthesize polymers with precise molecular weights more simply, mildly and efficiently, and synthesize a variety of biodegradable polymers with precise structures based on organic hydrogen bonding. High molecular polymer, while avoiding the adverse effects caused by alkaline reagents participating in ring-opening polymerization.

Another object of the present invention is to provide a method for preparing polyester by ring-opening polymerization of cyclic esters catalyzed by a single-molecule bifunctional catalytic system based on (thio)urea. This method has simple process, low cost, high reactivity, efficient reaction rate and controllable process. The prepared polyester has the advantages of no metal residues, accurate molecular weight and low molecular weight distribution.

In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

Based on the diphenylphosphino-substituted (thio)urea provided by the present invention, it reacts with acrylate to generate a (thio)urea ion pair catalyst, and the obtained (thio)urea ion pair catalyst can catalyze the ring-opening polymerization of cyclic esters. Polyester. Using cyclic ester as the reaction monomer, (thio)urea ion pair catalyst as the catalyst, and alcohol compounds as the initiator, the ring-opening polymerization reaction is carried out in a room temperature solution environment or high temperature bulk condition, and the polyester is obtained through separation and purification.

A catalyst for ring-opening polymerization to prepare polyester, the catalyst having an amphoteric (thio)urea ion structure as shown in formula I,

in

X is selected from O or S;

R ¹ is selected from linear or branched alkyl groups with 1 to 6 carbon atoms, cyclohexyl, phenyl, poly-substituted or mono-substituted phenyl groups, and the substituents in the mono-substituted or poly-substituted phenyl groups Selected from methyl, fluoro or trifluoromethyl;

R ² is selected from H, phenyl, benzyl, isopropyl or tert-butyl;

R ³ is selected from H, linear or branched alkyl with 1 to 4 carbon atoms, phenyl or benzyl;

R ⁴ is selected from linear or branched chain alkyl groups with 1 to 10 carbon atoms, vinyl, allyl, phenyl or benzyl groups.

^Preferably , phenyl or 4-fluorophenyl, R ² is selected from H, benzyl or isopropyl, R ³ is selected from methyl, isopropyl, phenyl or benzyl, R ⁴ is selected from methyl, tert-butyl , decyl, vinyl, allyl, phenyl or benzyl.

In the catalyst shown in Formula I, the (thi)urea structure is a well-known hydrogen bond donor and can effectively activate the monomer. The oxygen anion part can be used to activate the initiator/extending chain end, thereby promoting the opening of the cyclic ester. Ring polymerization. First of all, this solution provides a single-molecule bifunctional catalytic system that maintains high controllability of organic hydrogen bonding catalysts while improving catalytic activity. The resulting polymer has a clear structure and a narrow molecular weight distribution. Secondly, the catalyst selected in this scheme does not require a base as a co-catalyst, which is unusual in traditional hydrogen bond-catalyzed ring-opening polymerization. It avoids the influence of strong Lewis bases on the reaction and further ensures the controllability of the polymerization. Finally, this solution does not require a base as a co/pro-catalyst, avoiding the problem of metal residues of metal bases and the high cost of organic bases in the traditional hydrogen bond catalysis process, and has broader application prospects.

The preferred amphoteric (thio)urea ion structure as shown in formula I is as follows:

A method for preparing polyester by ring-opening polymerization. In the presence of an initiator, a diphenylphosphine-substituted (thio)urea as shown in formula II and an acrylate as shown in formula III are used to synthesize in situ as shown in formula I. The amphoteric (thio)urea ion pair shown in the formula catalyzes the ring-opening polymerization of the cyclic monomer to obtain a polyester compound. The diphenylphosphine-substituted (thio)urea shown in the formula II is identical to the diphenylphosphine-substituted (thio)urea shown in the formula III. The reaction process of acrylate is as follows:

in

X is selected from O or S;

R ¹ is selected from linear or branched alkyl groups with 1 to 6 carbon atoms, cyclohexyl, phenyl, poly-substituted or mono-substituted phenyl groups, and the substituents in the mono-substituted or poly-substituted phenyl groups Selected from methyl, fluoro or trifluoromethyl;

R ² is selected from H, phenyl, benzyl, isopropyl or tert-butyl;

R ³ is selected from H, linear or branched alkyl with 1 to 4 carbon atoms, phenyl or benzyl;

R ⁴ is selected from linear or branched chain alkyl groups with 1 to 10 carbon atoms, vinyl, allyl, phenyl or benzyl groups.

Preferably, the diphenylphosphino-substituted (thio)urea represented by formula II may have structures as shown in numbers 1 to 9:

Also representatively, as shown in formula III, there may be representative acrylate structures as shown in numbers 10 to 19:

The cyclic monomer used in the above preparation method is selected from one or more of the following:

(1) Lactone monomer represented by formula IV:

Wherein, A is [—(CR ¹ R ² )—] _n , n is an integer from 2 to 10; R ¹ and R ² are selected from H, alkyl groups with 1 to 5 carbon atoms and alkyl groups with 1 to 5 carbon atoms. The same or different groups in the alkyl group whose atoms are replaced by halogen atoms or hydroxyl groups, such as β-propiolactone, γ-butyrolactone, δ-valerolactone, ε-caprolactone, macrocyclic decalactone, Chlorinated caprolactone;

(2) Or the lactide monomer represented by formula V:

Among them, A and B are [—(CR ¹ R ² )—] _n , n is an integer from 0 to 10, A and B are the same or different; R ¹ and R ² are selected from H and have 1 to 5 carbon atoms. The same or different groups in an alkyl group substituted by a halogen atom or a hydroxyl group, such as glycolide, lactide, bromoglycolide, butyrolide, decanolide, macrododecide, O-carboxylate intraacid anhydride.

(3) Or the carbonate monomer represented by formula VI:

Wherein, R ¹ and R ² are selected from H, the same or different groups in the alkyl group having 1 to 5 carbon atoms and substituted by halogen atoms or hydroxyl groups, such as trimethylene carbonate, hydroxytrimethylene carbonate, Chlorotrimethylene carbonate.

The initiator used in the above preparation method is an alcohol compound, including methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, benzyl alcohol, phenethyl alcohol, phenylpropanol, and ethylene glycol. , ethylene glycol or pentaerythritol.

The solution environment described in the above preparation method refers to adding appropriate polymerization solvents to the reaction system at room temperature. These solvents will distribute the reactants evenly and avoid local reactions. The present invention mainly uses tetrahydrofuran and dichloromethane as solvents. When the reaction of the method is solution environment polymerization, the reaction temperature is 20-35°C; the reaction feed ratio is mainly selected as cyclic monomer: initiator is 25-400: 1.

The bulk conditions described in the above preparation method mean that no reaction solvent is used and the reaction temperature is relatively high to ensure that the reaction system is in a molten state. The bulk reaction temperature of the present invention is mainly selected to be 60-150°C, and the reaction feed ratio is mainly selected to be Cyclic monomer:initiator is 25~400:1.

The separation and purification described in the above preparation method refers to dissolving the reaction product with a good solvent and then precipitating it with a precipitation solvent. The good solvent used is dichloromethane, chloroform, toluene, benzene, acetone or tetrahydrofuran, preferably dichloromethane. , chloroform or tetrahydrofuran, and the precipitation solvent used is methanol, ethanol or water.

In the present invention, differences in non-phosphine substituents of the (thi)urea part and differences in acrylate substituents will affect the catalytic efficiency. The ring-opening polymerization reaction needs to determine the appropriate temperature and temperature change range based on the property requirements of the polymerization product and the process conditions of the reaction device to ensure that the polymerization reaction proceeds effectively within a certain temperature range. The controlled distribution of polyester terminal structure and molecular weight, such as narrow molecular weight distribution, can be achieved by adding active hydrogen-containing compounds (R-O-H) as initiators to the ring-opening polymerization system. The monomer chain end structures after initiation are: R-O- and -OH, and the feed ratio of cyclic ester monomer to initiator determines the target molecular weight of the resulting polyester.

beneficial effects

The present invention utilizes a single-molecule bifunctional catalytic system based on (thio)urea to catalyze the ring-opening polymerization of cyclic esters to prepare polyester, and the catalyst participating in the ring-opening polymerization reaction in the present invention is a (thio)urea ion pair, which is a thermally stable organic catalyst. Therefore, this method can use solution polymerization and has an extremely fast reaction rate. The resulting polymer does not contain metal residues, has controllable molecular weight and terminal structure, and has a narrow molecular weight distribution;

The method of bulk polymerization can also be used, which does not require the introduction of additional reaction solvents into the reaction system, which is conducive to industrial production. In addition, in the bulk polymerization system, the reaction temperature is generally higher, which greatly reduces the sensitivity of the reaction system to air and water. Convenient for industrial operation.

The reaction can also be used to synthesize product polyester with high target molecular weight in a controlled manner according to demand, with high product yield and no monomer residue. Moreover, the catalytic systems used are all neutral substances, which avoids the direct participation of organic acids and bases in the ring-opening polymerization reaction, avoids the occurrence of transesterification reaction, and further ensures the controllability of the reaction.

The preparation method adopted in the present invention has the following beneficial effects:

(1) Utilize the reaction of acrylate and diphenylphosphine-substituted (thio)urea to generate a (thio)urea ion pair catalyst containing oxygen anions.

(2) Under the reaction conditions, the (thi)urea part of the (thi)urea ion pair catalyst acts as a hydrogen bond donor to activate the cyclic ester, while its oxygen anion part acts as a hydrogen bond acceptor to activate the initiator/end of the growing chain.

(3) In the presence of an alcohol initiator, the (thio)urea ion pair catalyst obtained in step (1) catalyzes the ring-opening polymerization of cyclic ester to obtain polyester.

In summary, this method is highly efficient, simple in process, low in cost, has wide application range, high reactivity, no transesterification reaction, no metal residue in the catalyst, and the prepared polyester has the advantages of precise molecular weight and low molecular weight distribution.

Description of the drawings

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

Figure 1. ¹ H NMR spectrum of polylactide prepared using (thio)urea ion pairs as catalysts;

Figure 2. Spectrum of polylactide prepared using (thio)urea ion pairs as catalysts in size exclusion chromatography;

Figure 3. ¹ H NMR spectrum of polytrimethylene carbonate prepared using (thio)urea ion pair as catalyst;

Figure 4. Spectrum in size exclusion chromatography analysis of polytrimethylene carbonate prepared using (thio)urea ion pairs as catalysts;

Figure 5. ¹ H NMR spectrum of polyvalerolactone prepared using (thio)urea ion pair as catalyst;

Figure 6. Spectrum in size exclusion chromatography analysis of polyvalerolactone prepared using (thio)urea ion pair as catalyst.

Figure 7. ¹ H NMR spectrum of polycaprolactone prepared using (thio)urea ion pair as catalyst;

Figure 8. Spectrum in size exclusion chromatography analysis of polycaprolactone prepared using (thio)urea ion pair as catalyst.

Detailed ways

The present invention can be further illustrated by the following examples, which are intended to illustrate rather than limit the present invention. Anyone of ordinary skill in the art can understand that these embodiments do not limit the present invention in any way, and appropriate modifications and data transformations can be made without violating the essence of the present invention and deviating from the scope of the present invention.

The diphenylphosphino-substituted (thio)urea used in the examples has the following structure:

The acrylate used in the examples has the following structure:

solution polymerization

Example 1

In a 10mL polymerization tube, add compound (3) (0.018g, 0.05mmol) and compound (10) (4.5μL, 0.05mmol), dissolve them in 2.5ml dichloromethane, stir at room temperature for 10 minutes, and then add L - Lactide (0.360 g, 2.5 mmol) and phenylpropanol (6.8 μL, 0.05 mmol). Under the protection of argon, stir at room temperature for 4 hours, stop the reaction, slowly drop the reaction solution into cold methanol, and the polymer will precipitate. After centrifugation and vacuum drying, 0.34g of the product is obtained. The conversion rate is 96%. The poly-L-lactide The number average molecular weight M _n is 7340g/mol, and the molecular weight distribution PDI is 1.08.

Example 2

In a 10mL polymerization tube, add compound (5) (0.021g, 0.05mmol) and compound (10) (4.5μL, 0.05mmol), dissolve them in 2.5ml dichloromethane, stir at room temperature for 10 minutes, and then add L - Lactide (0.360 g, 2.5 mmol) and phenylpropanol (6.8 μL, 0.05 mmol). Under the protection of argon, stir at room temperature for 1 hour, stop the reaction, slowly drop the reaction solution into cold methanol, and the polymer will precipitate. After centrifugation and vacuum drying, 0.31g of the product is obtained. The conversion rate is 97%. The poly-L-lactide The number average molecular weight M _n is 6334g/mol, and the molecular weight distribution PDI is 1.09.

Example 3

In a 10mL polymerization tube, add compound (6) (0.024g, 0.05mmol) and compound (10) (4.5μL, 0.05mmol), dissolve them in 2.5ml dichloromethane, stir at room temperature for 10 minutes, and then add L - Lactide (0.360 g, 2.5 mmol) and phenylpropanol (6.8 μL, 0.05 mmol). Under argon protection, stir at room temperature for 5 minutes, stop the reaction, slowly drop the reaction solution into cold methanol, and the polymer will precipitate. After centrifugation and vacuum drying, 0.30g of the product is obtained. The conversion rate is 93%. The poly-L-lactide The number average molecular weight M _n is 7991g/mol, and the molecular weight distribution PDI is 1.11. (Appendix Pictures 1 and 2)

Example 4

In a 10mL polymerization tube, add compound (6) (0.024g, 0.05mmol) and compound (11) (5.3μL, 0.05mmol), dissolve them in 2.5ml dichloromethane, stir at room temperature for 10 minutes, and then add L - Lactide (0.360 g, 2.5 mmol) and phenylpropanol (6.8 μL, 0.05 mmol). Under argon protection, stir at room temperature for 24 hours, stop the reaction, slowly drop the reaction solution into cold methanol, a small amount of polymer precipitates, centrifuge and vacuum dry to obtain 0.11g of product, the conversion rate is 30%, poly-L-lactide The number average molecular weight _Mn is 2472g/mol, and the molecular weight distribution PDI is 1.16.

Example 5

In a 10mL polymerization tube, add compound (6) (0.024g, 0.05mmol) and compound (13) (5.4μL, 0.05mmol), dissolve them in 2.5ml dichloromethane, stir at room temperature for 10 minutes, and then add L - Lactide (0.360 g, 2.5 mmol) and phenylpropanol (6.8 μL, 0.05 mmol). Under argon protection, stir at room temperature for 15 minutes. Stop the reaction. Slowly drip the reaction solution into cold methanol. A small amount of polymer precipitates. After centrifugation and vacuum drying, 0.34g of the product is obtained. The conversion rate is 98%. Poly-L-lactide The number average molecular weight _Mn is 7567g/mol, and the molecular weight distribution PDI is 1.12.

Example 6

In a 10mL polymerization tube, add compound (6) (0.024g, 0.05mmol) and compound (14) (7.3μL, 0.05mmol), dissolve them in 2.5ml dichloromethane, stir at room temperature for 10 minutes, and then add L - Lactide (0.360 g, 2.5 mmol) and phenylpropanol (6.8 μL, 0.05 mmol). Under argon protection, stir at room temperature for 2 hours, stop the reaction, slowly drop the reaction solution into cold methanol, a small amount of polymer precipitates, and obtain 0.32g of product after centrifugation and vacuum drying. The conversion rate is 98%. Poly-L-lactide The number average molecular weight _Mn is 7643g/mol, and the molecular weight distribution PDI is 1.12.

Example 7

In a 10mL polymerization tube, add compound (6) (0.024g, 0.05mmol) and compound (15) (7.2μL, 0.05mmol), dissolve them in 2.5ml dichloromethane, stir at room temperature for 10 minutes, and then add L - Lactide (0.360 g, 2.5 mmol) and phenylpropanol (6.8 μL, 0.05 mmol). Under argon protection, stir at room temperature for 15 minutes. Stop the reaction. Slowly drop the reaction solution into cold methanol. A small amount of polymer precipitates. After centrifugation and vacuum drying, 0.30g of the product is obtained. The conversion rate is 90%. Poly-L-lactide The number average molecular weight _Mn is 6974g/mol, and the molecular weight distribution PDI is 1.14.

Example 8

In a 10mL polymerization tube, add compound (6) (0.024g, 0.05mmol) and compound (19) (7.5μL, 0.05mmol), dissolve them in 2.5ml dichloromethane, stir at room temperature for 10 minutes, and then add L - Lactide (0.360 g, 2.5 mmol) and phenylpropanol (6.8 μL, 0.05 mmol). Under argon protection, stir at room temperature for 15 minutes. Stop the reaction. Slowly drop the reaction solution into cold methanol. A small amount of polymer precipitates. After centrifugation and vacuum drying, 0.33g of the product is obtained. The conversion rate is 96%. Poly-L-lactide The number average molecular weight _Mn is 6889g/mol, and the molecular weight distribution PDI is 1.13.

Example 9

In a 10 mL polymerization tube, add compound (6) (0.015 g, 0.03 mmol) and compound (10) (2.7 μL, 0.03 mmol), dissolve them in 2.5 ml dichloromethane, stir at room temperature for 10 minutes, and then add L - Lactide (1.730 g, 12 mmol) and phenylpropanol (4.08 μL, 0.03 mmol). Under the protection of argon, stir at room temperature for 4 hours, stop the reaction, slowly drop the reaction solution into cold methanol, and the polymer will precipitate. After centrifugation and vacuum drying, 1.52g of the product is obtained. The conversion rate is 95%. The poly-L-lactide The number average molecular weight M _n is 51350g/mol, and the molecular weight distribution PDI is 1.10.

Example 10

In a 10mL polymerization tube, add compound (6) (0.015g, 0.03mmol) and compound (10) (2.7μL, 0.03mmol), dissolve them in 0.5ml methylene chloride, stir at room temperature for 10 minutes, and then add Sanya Methyl carbonate (0.153 g, 1.5 mmol) and phenylpropanol (4.08 μL, 0.03 mmol). Under the protection of argon, stir at room temperature for 4 hours, stop the reaction, slowly drop the reaction solution into cold methanol, and the polymer will precipitate. After centrifugation and vacuum drying, 0.14g of the product is obtained. The conversion rate is 98%. The polytrimethylene carbonate is The number average molecular weight M _n is 6306g/mol, and the molecular weight distribution PDI is 1.12. (Appendix Pictures 3 and 4)

ontology aggregation

Example 1

In a 10 mL polymerization tube, compound (6) (0.024 g, 0.05 mmol) and compound (10) (4.5 μL, 0.05 mmol) were added, dissolved in 2.5 ml of methylene chloride, and stirred at room temperature for 10 minutes. The solvent was carefully removed on a water pump, and D-lactide (0.360 g, 2.5 mmol) and pentaerythritol (4.9 μL, 0.05 mmol) were added thereto under argon protection. Stir magnetically at 140°C for 2 hours, stop the reaction, add a small amount of methylene chloride dropwise to the resulting mixture to dissolve, then slowly drop the resulting mixture into cold methanol, and polymer will precipitate. After centrifugation and vacuum drying, 0.27g of the product is obtained. Transform The rate is 96%, the number average molecular weight Mn of polyD-lactide is 6978g/mol, and the molecular weight distribution PDI is 1.20.

Example 2

In a 10 mL polymerization tube, compound (2) (0.035 g, 0.1 mmol) and compound (10) (9.0 μL, 0.1 mmol) were added, dissolved in 2.5 ml of methylene chloride, and stirred at room temperature for 10 minutes. The solvent was carefully removed on a water pump, and glycolide (0.348g, 3mmol) and benzyl alcohol (10.0 μL, 0.1mmol) were added thereto under argon protection. Stir magnetically at 130°C for 22 hours, stop the reaction, add a small amount of tetrahydrofuran dropwise to the resulting mixture to dissolve, then slowly drop the resulting mixture into cold methanol, and polymer will precipitate. After centrifugation and vacuum drying, 0.28g of the product is obtained. The conversion rate is 92%, the number average molecular weight _Mn of polyglycolide is 3770g/mol, and the molecular weight distribution PDI is 1.20.

Example 3

In a 10 mL polymerization tube, compound (6) (0.048 g, 0.1 mmol) and compound (10) (9.0 μL, 0.1 mmol) were added, dissolved in 2.5 ml of methylene chloride, and stirred at room temperature for 10 minutes. Carefully remove the solvent on a water pump, and add L-butyrolide (1.512g, 9mmol) and benzyl alcohol (10.0 μL, 0.1mmol) under argon protection. Stir magnetically at 150°C for 12 hours, stop the reaction, add a small amount of tetrahydrofuran dropwise to the resulting mixture to dissolve, then slowly drop the resulting mixture into cold methanol, polymer will precipitate, centrifuge and vacuum dry to obtain 1.2g of product, conversion rate 98%, the number average molecular weight M _n of poly-L-butyrolactide is 14730 g/mol, and the molecular weight distribution PDI is 1.23.

Example 4

In a 10 mL polymerization tube, compound (6) (0.048 g, 0.1 mmol) and compound (10) (9.0 μL, 0.1 mmol) were added, dissolved in 2.5 ml of methylene chloride, and stirred at room temperature for 10 minutes. Carefully remove the solvent on a water pump, and add trimethylene carbonate (0.306g, 3mmol) and benzyl alcohol (10.0μL, 0.1mmol) under argon protection. Stir magnetically at 60°C for 8 hours. Stop the reaction. Add a small amount of chloroform to the resulting mixture to dissolve it. Then slowly drop the resulting mixture into cold ethanol. The polymer will precipitate. After centrifugation and vacuum drying, 0.25g of the product is obtained. Transform The rate is 88%, the number average molecular weight _Mn of polytrimethylene carbonate is 2972g/mol, and the molecular weight distribution PDI is 1.13.

Example 5

In a 10 mL polymerization tube, compound (6) (0.048 g, 0.1 mmol) and compound (10) (9.0 μL, 0.1 mmol) were added, dissolved in 2.5 ml of methylene chloride, and stirred at room temperature for 10 minutes. The solvent was carefully removed on a water pump, and hydroxytrimethylene carbonate (0.714g, 6mmol) and isopropanol (7.6μL, 0.1mmol) were added thereto under argon protection. Stir magnetically for 5 hours at 60°C to stop the reaction. Add a small amount of chloroform to the resulting mixture to dissolve it. Then slowly drop the mixture into cold ethanol. The polymer will precipitate. After centrifugation and vacuum drying, 0.64g of the product is obtained. Transform The rate is 95%, the number average molecular weight _Mn of polyhydroxytrimethylene carbonate is 6267g/mol, and the molecular weight distribution PDI is 1.22.

Example 6

In a 10 mL polymerization tube, compound (6) (0.048 g, 0.1 mmol) and compound (10) (9.0 μL, 0.1 mmol) were added, dissolved in 2.5 ml of methylene chloride, and stirred at room temperature for 10 minutes. Carefully remove the solvent on a water pump, and add chlorotrimethylene carbonate (0.825g, 6mmol) and n-butanol (9.1μL, 0.1mmol) under argon protection. Stir magnetically for 18 hours at 60°C to stop the reaction. Add a small amount of chloroform to the resulting mixture to dissolve it. Then slowly drop the mixture into cold ethanol. The polymer will precipitate. After centrifugation and vacuum drying, 0.63g of the product is obtained. Transform The rate is 96%, the number average molecular weight Mn of polychlorotrimethylene carbonate is 6754g/mol, and the molecular weight distribution PDI is 1.15.

Example 7

In a 10 mL polymerization tube, add δ-valerolactone (0.45 mL, 5 mmol), compound (6) (0.048 g, 0.1 mmol) and compound (10) (9.0 μL, 0.1 mmol), and stir at room temperature for 10 minutes. Phenylpropanol (13.6 μL, 0.1 mmol) was added. Stir magnetically for 2.5 hours at 90°C to stop the reaction. Add a small amount of methylene chloride dropwise to the resulting mixture to dissolve it. Filter to remove insoluble matter. Then slowly drop the resulting mixture into cold ethanol. If the polymer precipitates, centrifuge and vacuum. After drying, 0.33 g of the product was obtained, with a conversion rate of 89%. The number average molecular weight M _n of polyvalerolactone was 5660 g/mol, and the molecular weight distribution PDI was 1.14. (Appendix Pictures 5 and 6)

Example 8

In a 10 mL polymerization tube, add γ-chloro-δ-valerolactone (7.60 mL, 40 mmol), compound (6) (0.048 g, 0.1 mmol) and compound (10) (9.0 μL, 0.1 mmol), and stir at room temperature. After 10 minutes, phenylpropanol (13.6 μL, 0.1 mmol) was added. Stir magnetically for 28 hours at 90°C, stop the reaction, add a small amount of methylene chloride dropwise to the resulting mixture to dissolve, filter to remove insoluble matter, then slowly drop the resulting mixture into cold ethanol, if the polymer precipitates, centrifuge and vacuum dry 5.4 g of product was obtained, the conversion rate was 84%, the number average molecular weight M _n of the obtained polymer was 45740 g/mol, and the molecular weight distribution PDI was 1.25.

Example 9

In a 10 mL polymerization tube, add ε-caprolactone (0.55 mL, 5 mmol), compound (6) (0.048 g, 0.1 mmol) and compound (10) (9.0 μL, 0.1 mmol), and stir at room temperature for 10 minutes. Phenylpropanol (13.6 μL, 0.1 mmol) was added. Stir magnetically for 36 hours at 90°C to stop the reaction. Add a small amount of methylene chloride dropwise to the resulting mixture to dissolve it. Then slowly drop the resulting mixture into cold ethanol. The polymer will precipitate. After centrifugation and vacuum drying, 0.44g of the product is obtained. The conversion rate is 99%, the number average molecular weight _Mn of polycaprolactone is 5138g/mol, and the molecular weight distribution PDI is 1.10. (Appendix Figures 7 and 8).

Claims (10)

1. A catalyst for preparing polyester by ring-opening polymerization, characterized in that the catalyst has an amphoteric (thio)urea ion structure as shown in formula I, in X is selected from O or S; R ¹ is selected from linear or branched alkyl groups with 1 to 6 carbon atoms, cyclohexyl, phenyl, poly-substituted or mono-substituted phenyl groups, and the substituents in the mono-substituted or poly-substituted phenyl groups Selected from methyl, fluoro or trifluoromethyl; R ² is selected from H, phenyl, benzyl, isopropyl or tert-butyl; R ³ is selected from H, linear or branched alkyl with 1 to 4 carbon atoms, phenyl or benzyl; R ⁴ is selected from linear or branched chain alkyl groups with 1 to 10 carbon atoms, vinyl, allyl, phenyl or benzyl groups. 2. The catalyst according to claim 1, wherein X is selected from O and ^R is selected from ethyl, isopropyl, tert-butyl, cyclohexyl, 3,5-bis(trifluoromethyl)benzene base, 4-methylphenyl, 4-trifluoromethylphenyl or 4-fluorophenyl, R ² is selected from H, benzyl or isopropyl, R ³ is selected from methyl, isopropyl, phenyl Or benzyl, R ⁴ is selected from methyl, tert-butyl, decyl, vinyl, allyl, phenyl or benzyl. 3. The catalyst according to claim 1, characterized in that: the amphoteric (thio)urea ion structure shown in formula I is as follows: 4. A method for preparing polyester by ring-opening polymerization, characterized in that, in the presence of an initiator, a diphenylphosphine-substituted (thio)urea as shown in formula II and an acrylic acid ester as shown in formula III are used. The amphoteric (thio)urea ion pair shown in the formula I is synthesized in situ to catalyze the ring-opening polymerization of the cyclic monomer to obtain a polyester compound, such as the diphenylphosphino-substituted (thio)urea shown in the formula II and the formula The reaction process of the acrylate shown in III is as follows: in X is selected from O or S; R ¹ is selected from linear or branched alkyl groups with 1 to 6 carbon atoms, cyclohexyl, phenyl, poly-substituted or mono-substituted phenyl groups, and the substituents in the mono-substituted or poly-substituted phenyl groups Selected from methyl, fluoro or trifluoromethyl; R ² is selected from H, phenyl, benzyl, isopropyl or tert-butyl; R ³ is selected from H, linear or branched alkyl with 1 to 4 carbon atoms, phenyl or benzyl; R ⁴ is selected from linear or branched chain alkyl groups with 1 to 10 carbon atoms, vinyl, allyl, phenyl or benzyl groups. 5. The method according to claim 4, characterized in that the diphenylphosphino-substituted (thio)urea as shown in Formula II is selected from the following structures: The acrylate represented by formula III is selected from the following structures 6. The method according to claim 4, characterized in that the cyclic ester monomer is selected from the following: Lactone monomer represented by formula IV: Wherein, A is [—(CR ¹ R ² )—] _m , m is an integer from 2 to 10; R ¹ and R ² can be the same or different, R ¹ and R ² are selected from H and have 1 to 5 carbon atoms. an alkyl group or an alkyl group having 1 to 5 carbon atoms and substituted by a halogen atom or a hydroxyl group; Or the lactide monomer represented by formula V: Among them, A and B are both [—(CR ¹ R ² )—] _x , x is an integer from 0 to 10, A and B are the same or different; R ¹ and R ² can be the same or different, choose R ¹ and R ² From H, an alkyl group having 1 to 5 carbon atoms or an alkyl group having 1 to 5 carbon atoms substituted by a halogen atom or a hydroxyl group; Or the carbonate monomer represented by formula VI: Among them, R ¹ and R ² can be the same or different, and R ¹ and R ² are selected from H, an alkyl group with 1 to 5 carbon atoms or an alkyl group with 1 to 5 carbon atoms substituted by a halogen atom or a hydroxyl group. 7. The method according to claim 4 or 6, characterized in that the cyclic monomer is selected from one or more of the following: β-propiolactone, γ-butyrolactone, δ-pentanolactone Lactone, ε-caprolactone, macrolide, chlorocaprolactone, glycolide, lactide, bromoglycolide, butyrolide, decanolide, macrolide, O-carboxylic anhydride, trimethylene carbonate, hydroxytrimethylene carbonate, chlorotrimethylene carbonate; the initiator is selected from methanol, ethanol, n-propanol, isopropanol, n-butanol, Tert-butanol, benzyl alcohol, phenethyl alcohol, phenylpropanol, ethylene glycol, ethylene glycol or pentaerythritol. 8. The method according to claim 4, characterized in that when the reaction of the method is bulk reaction, the reaction temperature is 60-150°C; when the reaction of the method is solution environment polymerization, the reaction temperature is 20-35 ℃. 9. The method according to claim 8, characterized in that when the reaction of the method is a bulk reaction, the molar ratio of the cyclic monomer to the initiator is selected from 25 to 400:1; When the reaction of the ester method is solution environment polymerization, the molar ratio of the cyclic ester monomer to the initiator is selected from 25 to 400:1. 10. The method according to claim 4, characterized in that the specific steps of the method include: cyclic monomer, diphenylphosphino-substituted (thio)urea shown in formula II and acrylic acid shown in formula III The ester and initiator react. After the reaction is completed, if it is bulk polymerization, add a good solvent to the reaction mixture. After the mixture is dissolved, add the precipitating solvent to the reaction system; if it is solution polymerization, directly add it to the reaction system. Add a precipitation solvent, centrifuge and dry to obtain the product; the good solvent is selected from dichloromethane, chloroform, toluene, benzene, acetone or tetrahydrofuran; the precipitation solvent is selected from methanol, ethanol or water.