CN115536823A - Catalyst for preparing polyester by ring-opening polymerization and method for preparing polyester - Google Patents

Abstract

The invention discloses a catalyst for preparing polyester by ring-opening polymerization and a method for preparing polyester, belonging to the technical field of organic hydrogen bond catalyzed polymer materials. The steps of the invention are (1) in-situ synthesis of amphoteric (thio)urea ion-pair catalysts by diphenylphosphino-substituted (thio)urea and acrylate. (2) Under the reaction conditions, (thio)urea ions double activate the catalyst to the cyclic monomer and the initiator. (3) In the presence of alcohol initiators, (thio)urea ion pairs catalyze the ring-opening polymerization of cyclic monomers to obtain polyesters. The method has the advantages of high efficiency, simple process, low cost, 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

Catalyst for preparing polyester by ring-opening polymerization and method for preparing polyester

technical field

The invention belongs to the technical field of organic catalysis and macromolecular materials, and in particular relates to a method for preparing polyester by ring-opening polymerization of an organic catalyzed cyclic ester.

Background technique

Innovations in petrochemical catalysis and polymerization methods have facilitated 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 and degrade. With the continuous consumption of global fossil energy and the generation of a large amount of plastic pollution, people are urgently seeking a renewable and degradable alternative material. Aliphatic polyesters are a class of biocompatible, biorenewable, and biodegradable materials that can be a good alternative to petroleum-based materials. One of the most efficient methods for the synthesis of aliphatic polyesters is the ring-opening polymerization (ROP) of cyclic esters. Compared with traditional polymer synthesis methods, the preparation of aliphatic polyesters by ring-opening polymerization is an environmentally friendly method with low energy consumption and renewable raw materials, and can obtain polyesters with well-defined structures under mild reaction conditions.

In the catalytic method of ring-opening polymerization, organocatalytic ring-opening polymerization has the advantages of mild reaction conditions, high monomer conversion rate, high product molecular weight and short reaction time, and there is no metal residue in the prepared polymer. It is used in biomedicine, Applications in fields such as food packaging and microelectronic materials are not limited. 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 catalyzed by hydrogen bond catalysts is mild, efficient and free of transesterification, and the obtained polyester has a clear structure and low molecular weight distribution. It is one of the organic catalysts with the most research potential.

Traditional hydrogen bond catalysts often require bases as co/co-catalysts 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 bring some other problems. For example, when metal bases are used as co-/co-catalysts, metal residues may be introduced into the polymer, which affects the application of polymers in metal-sensitive fields such as biomedicine; although organic bases do not introduce metal residues, organic bases are generally expensive , will increase the production cost of the polymer. In addition, the addition of base co-catalysts often increases the probability of side reactions such as transesterification during ring-opening polymerization, so the amount of base addition needs to be strictly controlled.

Contents of the invention

The invention provides a catalyst for preparing polyester by ring-opening polymerization. The invention can synthesize polymers with precise molecular weight more simply, gently and efficiently, and synthesize various biodegradable polymers with precise structures based on organic hydrogen bonding. High molecular polymers, while avoiding the adverse effects of 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 (thio)urea-based monomolecular bifunctional catalytic system. The method has the advantages of simple process, low cost, high reactivity, high reaction rate and controllable process, and the prepared polyester has the advantages of no metal residue, precise molecular weight and low molecular weight distribution.

In order to solve the problems of the technologies described above, the technical scheme adopted in the present invention is as follows:

Based on the diphenylphosphino-substituted (thio)urea provided by the present invention, it reacts with acrylate to form a (thio)urea ion-pair catalyst, and the obtained (thio)urea ion-pair catalyst can be prepared by catalyzing ring-opening polymerization of cyclic esters polyester. Using cyclic esters as reaction monomers, (thio)urea ion pair catalysts as catalysts, and alcohol compounds as initiators, ring-opening polymerization is carried out under room temperature solution environment or high temperature bulk conditions, and polyester is obtained through separation and purification.

A kind of catalyst that is used for ring-opening polymerization to prepare polyester, described catalyst is as the amphoteric (thio) urea ion structure 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, polysubstituted or monosubstituted phenyl, the substituents in the monosubstituted or polysubstituted phenyl selected from methyl, fluoro or trifluoromethyl;

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

^R3 is selected from H, a straight or branched chain alkyl group with 1 to 4 carbon atoms, phenyl or benzyl;

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

Preferably X is selected from O, R is selected from ethyl, isopropyl, tert ^- butyl, cyclohexyl, 3,5-bis(trifluoromethyl)phenyl, 4-methylphenyl, 4-trifluoromethyl phenyl or ⁴ -fluorophenyl, R2 is selected from H, benzyl or isopropyl, ^R3 is selected from methyl, isopropyl, phenyl or benzyl, R4 is selected from methyl, tert ^- butyl , decyl, vinyl, allyl, phenyl or benzyl.

In the catalyst shown in formula I, the (thio)urea structure is a well-known hydrogen bond donor, which can effectively activate the monomer, and the oxyanion moiety can be used to activate the initiator/extended chain end, thereby promoting the opening of the cyclic ester. ring polymerization. First of all, this scheme provides a monomolecular bifunctional catalytic system, which improves the catalytic activity while maintaining the high controllability of the organic hydrogen bond catalyst, and 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-/co-catalyst, which is uncommon in traditional hydrogen bond-catalyzed ring-opening polymerization, avoiding the influence of strong Lewis bases on the reaction, and further ensuring the controllability of polymerization. Finally, this scheme does not require bases as co/promoters, which avoids the metal residue problem of metal bases and the high cost of organic bases in the traditional hydrogen bond catalysis process, and has broader application prospects.

Preferably described 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, using a diphenylphosphino-substituted (thio)urea shown in formula II and an acrylate shown in formula III to synthesize in situ as shown in formula I The shown amphoteric (thio) urea ion pair catalyzes the ring-opening polymerization of cyclic monomers to obtain polyester compounds, and the described diphenylphosphino-substituted (thio) urea as shown in formula II and The reaction process of the 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, polysubstituted or monosubstituted phenyl, the substituents in the monosubstituted or polysubstituted phenyl selected from methyl, fluoro or trifluoromethyl;

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

^R3 is selected from H, a straight or branched chain alkyl group with 1 to 4 carbon atoms, phenyl or benzyl;

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

Preferably, the diphenylphosphino-substituted (thio)ureas shown in formula II can have the structures shown in numbers 1-9:

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

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

(1) lactone monomer shown in formula IV:

Among them, A is [—(CR ¹ R ² )—] _n , n is an integer of 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 Atoms and the same or different groups in the alkyl group substituted by a halogen atom or a hydroxyl group, such as β-propiolactone, γ-butyrolactone, δ-valerolactone, ε-caprolactone, macrocyclic decalactone, Chlorocaprolactone;

(2) or the lactide monomer shown in formula V:

Wherein, 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, have 1 to 5 carbon atoms and The same or different groups in the alkyl group substituted by a halogen atom or a hydroxyl group, such as glycolide, lactide, bromoglycolide, butyrolactide, decanide, macrocyclic dodecide, O-carboxylate Acid internal anhydride.

(3) or the carbonate monomer shown in formula VI:

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

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

The solution environment described in the above preparation method refers to adding a suitable polymerization solvent to the reaction system at room temperature, and these solvents will make the reactants evenly distributed and avoid local reactions. The present invention mainly uses tetrahydrofuran and dichloromethane as solvents, and 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: the initiator is 25-400: 1.

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

The separation and purification described in the above preparation method refers to dissolving the reaction product in a good solvent and then precipitating it with a settling 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, the difference in the non-phosphine-substituted substituents of the (thio)urea part and the difference in the acrylate substituents will affect the catalytic efficiency. The ring-opening polymerization reaction needs to determine the appropriate temperature and temperature variation range according to the property requirements of the polymerization product and the process conditions of the reaction device, so as to ensure that the polymerization reaction can be carried out effectively within a certain temperature range. The controllable 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 the cyclic ester monomer to the initiator determines the target molecular weight of the resulting polyester.

Beneficial effect

The present invention uses (thio)urea-based monomolecular bifunctional catalytic system 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 (thio)urea ion pair, which is a thermally stable active organic catalysts. Therefore, this method can adopt the method of solution polymerization, has an extremely fast reaction rate, and the obtained polymer does not contain metal residues, the molecular weight and terminal structure are controllable, and the molecular weight distribution is narrow;

The method of bulk polymerization can also be adopted without introducing additional reaction solvent in the reaction system, which is beneficial to industrial production, and in the bulk polymerization system, the general reaction temperature is relatively high, which greatly reduces the sensitivity of the reaction system to air and water. Convenient for industrial operation.

The reaction can also be controlled to synthesize the product polyester with high target molecular weight according to the demand, the product yield is high, and there is no monomer residue. Moreover, the catalytic system adopted is 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 that the present invention adopts, beneficial effect is as follows

(1) Utilize the reaction of acrylate and diphenylphosphino-substituted (thio)urea to generate (thio)urea ion-pair catalysts containing oxyanions.

(2) Under the reaction conditions, the (thio)urea part in the catalyst acts as a hydrogen bond donor to activate the cyclic ester, while its oxyanion part acts as a hydrogen bond acceptor to activate the initiator/end of the extended chain.

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

In summary, the method is efficient, simple in process, low in cost, wide in application range, high in reactivity, free of transesterification reaction, free of metal residue in the catalyst, and the prepared polyester has the advantages of precise molecular weight and low molecular weight distribution.

Description of drawings

Embodiments of the present invention are described in detail in conjunction with the accompanying drawings, wherein

Fig. 1. uses (thio) urea ion pair as the ¹ H NMR spectrogram of the polylactide that catalyst prepares;

Fig. 2. use (thio) urea ion pair as the spectrogram of the polylactide that catalyzer prepares in the size exclusion chromatographic analysis;

Fig. 3. use (thio) urea ion pair as the ¹ H NMR spectrogram of the polytrimethylene carbonate that catalyst prepares;

Fig. 4. use (thio) urea ion pair as the spectrogram in the polytrimethylene carbonate size exclusion chromatographic analysis that catalyst prepares;

Fig. 5. uses (thio) urea ion pair as the ¹ H NMR spectrogram of the polyvalerolactone that catalyst prepares;

Fig. 6. The spectrogram in the size exclusion chromatography analysis of polyvalerolactone prepared by using (thio)urea ion pair as a catalyst.

Fig. 7. uses (thio) urea ion pair as the ¹ H NMR spectrogram of the polycaprolactone that catalyst prepares;

Fig. 8. The spectrogram in the size exclusion chromatography analysis of polycaprolactone prepared by using (thio)urea ion pair as a catalyst.

detailed description

The present invention can be further illustrated by the following examples, which are intended to illustrate and not limit the invention. Any person skilled in the art can understand that these embodiments do not limit the present invention in any way, and can make appropriate modifications and data transformations without departing from the essence of the present invention and the scope of the present invention.

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

The acrylates used in the examples have 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 with 2.5ml of 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, the polymer precipitates, centrifuge and vacuum dry to obtain 0.34g of the product, the conversion rate is 96%, the poly-L-lactide The number average molecular weight M _n was 7340 g/mol, the molecular weight distribution PDI was 1.08.

Example 2

In a 10mL polymerization tube, add compound (5) (0.021g, 0.05mmol) and compound (10) (4.5μL, 0.05mmol), dissolve with 2.5ml of 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 h, stop the reaction, slowly drop the reaction solution into cold methanol, and polymers are precipitated. After centrifugation and vacuum drying, 0.31 g of the product is obtained, and the conversion rate is 97%. Poly-L-lactide The number average molecular weight M _n was 6334 g/mol, the molecular weight distribution PDI was 1.09.

Example 3

In a 10mL polymerization tube, add compound (6) (0.024g, 0.05mmol) and compound (10) (4.5μL, 0.05mmol), dissolve with 2.5ml of 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 5 minutes, stop the reaction, slowly drop the reaction solution into cold methanol, and the polymer is precipitated, centrifuged and vacuum-dried to obtain 0.30 g of the product, the conversion rate is 93%, the poly-L-lactide The number average molecular weight M _n was 7991 g/mol, the molecular weight distribution PDI was 1.11. (Attachments 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 with 2.5ml of 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 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 the product 0.11g, the conversion rate is 30%, poly L-lactide The number-average molecular weight M _n of 2472 g/mol, 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 with 2.5ml of 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 15 minutes, stop the reaction, slowly drop the reaction solution into cold methanol, a small amount of polymer precipitates, centrifuge and vacuum dry to obtain the product 0.34g, the conversion rate is 98%, poly L-lactide The number-average molecular weight M _n of the compound is 7567 g/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 with 2.5ml of 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 2 hours, stop the reaction, slowly drop the reaction solution into cold methanol, a small amount of polymer precipitates, centrifuge and vacuum dry to obtain the product 0.32g, the conversion rate is 98%, poly L-lactide The number-average molecular weight M _n of the product is 7643 g/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 with 2.5ml of 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 15 minutes, stop the reaction, slowly drop the reaction solution into cold methanol, a small amount of polymer precipitates, centrifuge and vacuum dry to obtain 0.30 g of the product, the conversion rate is 90%, poly L-lactide The number-average molecular weight M _n of the product is 6974 g/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 with 2.5ml of 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 15 minutes, stop the reaction, slowly drop the reaction solution into cold methanol, a small amount of polymer precipitates, centrifuge and vacuum dry to obtain the product 0.33g, the conversion rate is 96%, poly L-lactide The number-average molecular weight M _n of the product is 6889 g/mol, and the molecular weight distribution PDI is 1.13.

Example 9

In a 10mL polymerization tube, add compound (6) (0.015g, 0.03mmol) and compound (10) (2.7μL, 0.03mmol), dissolve with 2.5ml of 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, the polymer precipitates, centrifuge and vacuum dry to obtain 1.52g of the product, the conversion rate is 95%, the poly-L-lactide The number average molecular weight M _n was 51350 g/mol, the molecular weight distribution PDI was 1.10.

Example 10

In a 10mL polymerization tube, add compound (6) (0.015g, 0.03mmol) and compound (10) (2.7μL, 0.03mmol), dissolve with 0.5ml of dichloromethane, 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, the polymer precipitates, centrifuge and vacuum dry to obtain 0.14g of the product, the conversion rate is 98%, the polytrimethylene carbonate The number average molecular weight M _n is 6306 g/mol, the molecular weight distribution PDI is 1.12. (Attachments 3 and 4)

Ontology aggregation

Example 1

Compound (6) (0.024 g, 0.05 mmol) and compound (10) (4.5 μL, 0.05 mmol) were added to a 10 mL polymerization tube, dissolved in 2.5 ml of dichloromethane, and stirred at room temperature for 10 minutes. The solvent was carefully pumped off 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 the protection of argon. Stir magnetically at 140°C for 2 hours, stop the reaction, add a small amount of dichloromethane dropwise to the resulting mixture to dissolve, then slowly drop the resulting mixture into cold methanol, a polymer precipitates, centrifuge and vacuum dry to obtain 0.27g of the product, transform The ratio was 96%, the number average molecular weight Mn of poly-D-lactide was 6978 g/mol, and the molecular weight distribution PDI was 1.20.

Example 2

Compound (2) (0.035 g, 0.1 mmol) and compound (10) (9.0 μL, 0.1 mmol) were added to a 10 mL polymerization tube, dissolved in 2.5 ml of dichloromethane, and stirred at room temperature for 10 minutes. The solvent was carefully pumped off on a water pump, and glycolide (0.348 g, 3 mmol) and benzyl alcohol (10.0 μL, 0.1 mmol) 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 obtained mixture to dissolve, and then slowly drop the obtained mixture into cold methanol, and a polymer is precipitated. After centrifugation and vacuum drying, 0.28 g of the product is obtained. The conversion rate is 92%, the number average molecular weight M _n of polyglycolide is 3770 g/mol, and the molecular weight distribution PDI is 1.20.

Example 3

Compound (6) (0.048 g, 0.1 mmol) and compound (10) (9.0 μL, 0.1 mmol) were added to a 10 mL polymerization tube, dissolved in 2.5 ml of dichloromethane, and stirred at room temperature for 10 minutes. The solvent was carefully pumped off on a water pump, and L-butyrolactide (1.512 g, 9 mmol) and benzyl alcohol (10.0 μL, 0.1 mmol) were added thereto 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, and then slowly drop the resulting mixture into cold methanol, and a polymer is precipitated. After centrifugation and vacuum drying, 1.2 g of the product is obtained. The conversion rate is 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

Compound (6) (0.048 g, 0.1 mmol) and compound (10) (9.0 μL, 0.1 mmol) were added to a 10 mL polymerization tube, dissolved in 2.5 ml of dichloromethane, and stirred at room temperature for 10 minutes. The solvent was carefully pumped off on a water pump, and trimethylene carbonate (0.306 g, 3 mmol) and benzyl alcohol (10.0 μL, 0.1 mmol) were added thereto under argon protection. Stir magnetically at 60°C for 8 hours, stop the reaction, add a small amount of chloroform to the obtained mixture to dissolve, and then slowly drop the obtained mixture into cold ethanol, and a polymer is precipitated. After centrifugation and vacuum drying, 0.25 g of the product is obtained. The ratio was 88%, the number average molecular weight M _n of polytrimethylene carbonate was 2972 g/mol, and the molecular weight distribution PDI was 1.13.

Example 5

Compound (6) (0.048 g, 0.1 mmol) and compound (10) (9.0 μL, 0.1 mmol) were added to a 10 mL polymerization tube, dissolved in 2.5 ml of dichloromethane, and stirred at room temperature for 10 minutes. The solvent was carefully pumped off on a water pump, and hydroxytrimethylene carbonate (0.714 g, 6 mmol) and isopropanol (7.6 μL, 0.1 mmol) were added thereto under argon protection. Stir magnetically at 60°C for 5 hours, stop the reaction, add a small amount of chloroform to the obtained mixture to dissolve, then slowly drop the mixed solution into cold ethanol, a polymer precipitates, centrifuge and vacuum dry to obtain 0.64g of the product, transform The ratio was 95%, the number average molecular weight M _n of polyhydroxytrimethylene carbonate was 6267 g/mol, and the molecular weight distribution PDI was 1.22.

Example 6

Compound (6) (0.048 g, 0.1 mmol) and compound (10) (9.0 μL, 0.1 mmol) were added to a 10 mL polymerization tube, dissolved in 2.5 ml of dichloromethane, and stirred at room temperature for 10 minutes. The solvent was carefully pumped off on a water pump, and chlorotrimethylene carbonate (0.825 g, 6 mmol) and n-butanol (9.1 μL, 0.1 mmol) were added thereto under argon protection. Stir magnetically at 60°C for 18 hours, stop the reaction, add a small amount of chloroform to the obtained mixture to dissolve, then slowly drop the mixed solution into cold ethanol, a polymer precipitates, centrifuge and vacuum dry to obtain 0.63g of the product, transform The ratio was 96%, the number average molecular weight Mn of polychlorotrimethylene carbonate was 6754 g/mol, and the molecular weight distribution PDI was 1.15.

Example 7

In a 10mL polymerization tube, add δ-valerolactone (0.45mL, 5mmol), compound (6) (0.048 g, 0.1mmol) and compound (10) (9.0μL, 0.1mmol), stir at room temperature for 10 minutes and pour To this was added phenylpropanol (13.6 μL, 0.1 mmol). Stir magnetically at 90°C for 2.5 hours, stop the reaction, add a small amount of dichloromethane dropwise to the obtained mixture to dissolve, filter to remove insoluble matter, and then slowly drop the obtained mixture into cold ethanol, and polymers are precipitated. After drying, 0.33 g of the product was obtained, the conversion rate was 89%, the number average molecular weight M _n of polyvalerolactone was 5660 g/mol, and the molecular weight distribution PDI was 1.14. (Figures 5 and 6)

Example 8

In a 10mL polymerization tube, add γ-chloro-δ-valerolactone (7.60mL, 40mmol), compound (6) (0.048g, 0.1mmol) and compound (10) (9.0μL, 0.1mmol), and stir at room temperature After 10 minutes, phenylpropanol (13.6 μL, 0.1 mmol) was added thereto. Stir magnetically at 90°C for 28 hours, stop the reaction, add a small amount of dichloromethane dropwise to the resulting mixture to dissolve, filter to remove insoluble matter, then slowly drop the resulting mixture into cold ethanol, and polymers are precipitated, centrifuged and vacuum-dried 5.4 g of the 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 10mL polymerization tube, add ε-caprolactone (0.55mL, 5mmol), compound (6) (0.048 g, 0.1mmol) and compound (10) (9.0μL, 0.1mmol), stir at room temperature for 10 minutes To this was added phenylpropanol (13.6 μL, 0.1 mmol). Stir magnetically at 90°C for 36 hours, stop the reaction, add a small amount of dichloromethane dropwise to the resulting mixture to dissolve, then slowly drop the resulting mixture into cold ethanol, a polymer is precipitated, centrifuged and vacuum-dried to obtain 0.44g of the product, The conversion rate was 99%, the number average molecular weight M _n of polycaprolactone was 5138 g/mol, and the molecular weight distribution PDI was 1.10. (accompanying drawing 7,8).

Claims (10)

1. A catalyst for preparing polyester by ring-opening polymerization is characterized in that the catalyst has an amphoteric (thio) urea ion structure shown in a formula I,

wherein

X is selected from O or S;

R ¹ selected from straight chain or branched chain alkyl with 1 to 6 carbon atoms, cyclohexyl, phenyl, polysubstituted or monosubstituted phenyl, wherein the substituent in the monosubstituted or polysubstituted phenyl is selected from methyl, fluoro or trifluoromethyl;

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

R ³ selected from H, straight or branched chain alkyl having 1 to 4 carbon atoms, phenyl or benzyl;

R ⁴ selected from the group consisting of linear or branched alkyl groups having 1 to 10 carbon atoms, vinyl, allyl, phenyl or benzyl.

2. The catalyst of claim 1, wherein X is selected from the group consisting of O and R ¹ Selected from ethyl, isopropyl, tert-butyl, cyclohexyl, 3,5-bis (trifluoromethyl) phenyl, 4-methylphenyl, 4-trifluoromethylphenyl or 4-fluorophenyl, R ² Selected from H, benzyl or isopropyl, R ³ Selected from methyl, isopropyl, phenyl or benzyl, R ⁴ Selected from methyl, tert-butyl, decyl, vinyl, allyl, phenyl or benzyl.

3. The catalyst of claim 1, wherein: the amphoteric (thio) urea ion structure shown in the formula I is as follows:

4. a method for preparing polyester by ring-opening polymerization is characterized in that in the presence of an initiator, diphenylphosphine substituted (thio) urea shown in a formula II and acrylate shown in a formula III are adopted to synthesize amphoteric (thio) urea ion pairs shown in a formula I in situ to catalyze ring-opening polymerization of a cyclic monomer, so that a polyester compound is obtained, wherein the reaction process of the diphenylphosphine substituted (thio) urea shown in the formula II and the acrylate shown in the formula III is as follows:

wherein

X is selected from O or S;

R ¹ selected from straight chain or branched chain alkyl with 1 to 6 carbon atoms, cyclohexyl, phenyl, polysubstituted or monosubstituted phenyl, wherein the substituent in the monosubstituted or polysubstituted phenyl is selected from methyl, fluoro or trifluoromethyl;

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

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

R ⁴ selected from the group consisting of linear or branched alkyl groups having 1 to 10 carbon atoms, vinyl, allyl, phenyl or benzyl.

5. The method of claim 4, wherein the diphenylphosphino-substituted (thio) urea of formula II is selected from the following structures:

the acrylate shown in the formula III is selected from the following structures

6. The method of claim 4, wherein the cyclic ester monomer is selected from the group consisting of:

a lactone monomer represented by formula IV:

wherein, A is [ - (CR) ¹ R ² )—] _m M is an integer of 2 to 10; r ¹ 、R ² Which may be the same or different, R ¹ 、R ² Selected from H, alkyl having 1 to 5 carbon atoms or alkyl having 1 to 5 carbon atoms and substituted with halogen atom or hydroxyl group;

or a lactide monomer of formula V:

wherein A, B are [ - (CR) ¹ R ² )—] _x X is an integer of 0 to 10, A and B are the same or different; r is ¹ 、R ² Which may be the same or different, R ¹ 、R ² Selected from H, alkyl having 1 to 5 carbon atoms or alkyl having 1 to 5 carbon atoms and substituted with halogen atom or hydroxyl group;

or a carbonate monomer of formula VI:

wherein R is ¹ 、R ² Which may be the same or different, R ¹ 、R ² Selected from H, alkyl having 1 to 5 carbon atoms or alkyl having 1 to 5 carbon atoms and substituted with halogen atoms or hydroxyl groups.

7. The method according to claim 4 or 6, wherein the cyclic monomer is selected from one or more of the following: beta-propiolactone, gamma-butyrolactone, delta-valerolactone, epsilon-caprolactone, macrocyclic decalactone, chlorocaprolactone, glycolide, lactide, bromoglycolide, ding Jiaozhi, sebacide, macrocyclic dodecalactone, O-carboxylic acid lactone, 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 acetal or pentaerythritol.

8. The method according to claim 4, wherein the reaction of the method is bulk reaction, and the reaction temperature is 60-150 ℃; when the reaction of the method is solution environment polymerization, the reaction temperature is 20-35 ℃.

9. The process according to claim 8, wherein the reaction of the process is a bulk reaction, the molar ratio of the cyclic monomer to the initiator is selected from the group consisting of 25 to 400; when the reaction of the method for preparing the polyester is solution environment polymerization, the molar ratio of the cyclic ester monomer to the initiator is selected from 25-400.

10. The method according to claim 4, characterized in that the method comprises the following specific steps: reacting a cyclic monomer, diphenylphosphine substituted (thio) urea shown in a formula II, acrylate shown in a formula III and an initiator, after the reaction is finished, adding a good solvent into a mixture obtained by the reaction in bulk polymerization, and slowly adding a precipitation solvent into the mixture in solution polymerization, centrifuging and drying to obtain a product; the good solvent is selected from dichloromethane, trichloromethane, toluene, benzene, acetone or tetrahydrofuran; the precipitation solvent is selected from methanol, ethanol or water.

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