A method for synthesizing end group functionalized polyesters

Abstract

The application relates to a synthesis method of end group functionalized polyester, and belongs to the technical field of polymer synthesis. In the application, ring ester monomers and single alcohol initiators containing different functional groups are polymerized at a low monomer initiator ratio, ring-opening polymerization is first carried out to generate low-molecular-weight end group functionalized polyester, cascade condensation polymerization occurs between the end group functionalized polyester, the initiator is removed, and end group functionalized polyester with a higher molecular weight is generated. Compared with the existing ring-opening polymerization technology, the synthesis method has the characteristics of fast polymerization speed, high monomer conversion rate and high end group functionalization degree, and can be used for synthesizing high end group functionalized polyester at a high monomer conversion rate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polymer synthesis, and particularly relates to a synthesis method of end-functionalized polyester. BACKGROUND

[0002] Aliphatic polyesters are widely used in medical and packaging fields, such as drug delivery systems, surgical sutures and plastic straws, due to their good biodegradability, biocompatibility and stability. Although traditional aliphatic polyesters are consistent with the current concept of green chemistry, the structural simplicity and lack of controllable sites also limit the application of aliphatic polyesters in many aspects. Therefore, it is necessary to develop end-functionalized aliphatic polyesters for modification, and the end-functionalized polyesters can be used for the next reaction to introduce other functional groups or prepare block, brush and other polymers, so as to further expand the application range of aliphatic polyesters.

[0003] At present, the synthesis of end-functionalized aliphatic polyesters generally uses ring-opening polymerization, that is, an alcohol or an amine containing a functional group is used as an initiator, and a cyclic ester is used as a monomer. The σ bond of the cyclic monomer is broken and then ring-opening to form a linear polymer. Theoretically, the molecular weight of the polyester obtained by ring-opening polymerization of small ring lactone is consistent with the formula:

[0004] M n,ROP =R×FW M ×Conv.+FW I

[0005] Wherein, FW M is the molecular weight of the monomer lactone, FW I is the molecular weight of the initiator, and R is the molar ratio of the monomer and the initiator. Therefore, the molecular weight of the polyester is generally controlled by adjusting the molar ratio of the monomer and the initiator and the monomer conversion rate in the ordinary ring-opening polymerization.

[0006] End group functionalized polyesters are usually prepared by ring-opening polymerization of cyclic lactones or lactides using an initiator containing functional groups. They are generally carried out in bulk or in solution. The temperature of bulk polymerization is generally 100-150 °C, while in solution polymerization, low temperature is used to reduce the transesterification side reaction. Although the synthesis conditions are mild, the reaction time is long, the monomer conversion is low, the atomic economic efficiency is low, and the molecular weight of the prepared polyester is also low (usually only a few thousand Da). When high molecular weight polyester with a molecular weight greater than 10000 Da needs to be prepared, the molar ratio of monomer to initiator needs to be increased (usually > 200 considering the conversion rate of monomer), which will make the reaction time longer, and trace impurities in the system will also participate in the reaction, more side reactions will occur, ultimately leading to the decrease of the degree of end group functionalization of the polyester and the difficulty of controlling the molecular weight.

[0007] The synthesis of end group functionalized aliphatic polyesters can also be synthesized by condensation polymerization. For example, Chinese invention patent (CN113527648A) discloses a polyester with functional groups at the end of the long chain and a preparation method thereof. The invention first prepares a polyester with bromine group at the end of the long chain, then the bromine group reacts with the carboxyl group in a series of carboxylic acids containing functional groups, removes hydrogen bromide, and generates long chain polyester containing functional groups at the end. Although this invention can achieve the functionalization of both ends of the polyester, the reaction period is long, the operation is complicated, and the degree of end group functionalization is unknown.

[0008] Based on the above analysis, there is an urgent need to develop a method that can quickly and efficiently prepare high-end group functionalized polyesters at high monomer conversion, thereby reducing costs and broadening the application prospects of polyesters. SUMMARY

[0009] To address the shortcomings of existing technologies, this invention provides a method for synthesizing end-functionalized polyesters. It employs a cyclic ester monomer and a monool initiator containing functional groups at a low monomer-to-initiator ratio, cascading ring-opening polymerization and condensation polymerization within the system to synthesize high-molecular-weight end-functionalized polyesters with high monomer conversion. This invention uses a low cyclic ester / initiator ratio, i.e., increasing the initiator concentration to accelerate the ring-opening polymerization rate and improve monomer conversion, resulting in low-molecular-weight end-functionalized polyesters. Then, through condensation polymerization between the end-functionalized polyesters, the initiator molecules are removed, allowing the molecular weight to continue increasing, yielding higher-molecular-weight end-functionalized polyesters. This method, through the cascading of ring-opening and condensation polymerization, overcomes the limitation that ring-opening polymerization can only synthesize low-molecular-weight polyesters at low monomer-to-initiator ratios. It also solves the problems of low monomer conversion, low functionalization degree of functional groups, and long reaction time encountered in existing technologies that use high monomer-to-initiator ratios to synthesize high-molecular-weight end-functionalized polyesters. The advantages of this invention are that the reaction steps are simple, the reaction is fast, the monomer conversion rate is high, and the end-group functionalization of the obtained polymer is high.

[0010] This invention is achieved through the following technical solution:

[0011] The purpose of this invention is to provide a method for synthesizing end-functionalized polyesters, comprising the following steps: a cyclic ester monomer and a monool initiator containing functional groups undergo a polymerization reaction under the action of a catalyst to generate end-functionalized polyesters; the structure of the end-functionalized polyesters is as follows:

[0012] ;

[0013] Wherein, R comes from cyclic ester monomers, including small-ring lactones and lactides and their derivatives; R1 comes from a monool initiator containing a functional group; m is the molar ratio of the cyclic ester monomer to the monool initiator containing the functional group, where m is 3~50; n is the number of polycondensation steps, where n>1.

[0014] In one embodiment of the present invention, the polymerization reaction includes cascaded ring-opening polymerization and condensation polymerization; the polymerization reaction is as follows: a monool initiator containing functional groups performs ring-opening polymerization on a cyclic ester to generate a low molecular weight polyester with terminal functionalization; the resulting low molecular weight polyesters undergo cascaded condensation polymerization to remove the initiator, yielding a polyester with terminal functional groups. The reaction mechanism diagram is shown below. Figure 1 As shown. Based on the role of functional monools in the polymerization process, it can also be called initiation-elimination cascade polymerization.

[0015] In one embodiment of the present invention, the cyclic ester monomer is one or more selected from lactones and their derivatives, lactides and their derivatives; the general chemical structural formula of the cyclic ester monomer is:

[0016] ;

[0017] Where R is (CH2) a When (CH2O(CH2)2), the cyclic ester monomer is a lactone, a is 2, 4, or 5; R is ((CH2)2) / (CH2O(CH2)2). b OCO(CH2) b When b is 1 or 2, the cyclic ester monomer is a lactone.

[0018] In one embodiment of the present invention, the cyclic ester monomer is selected from one or more of ε-caprolactone, δ-valerolactone, proprolactone, p-dioxanone and other lactones or their derivatives, glycolide and other lactones or their derivatives.

[0019] In one embodiment of the present invention, the boiling point of the monool initiator containing functional groups is less than 300 °C under normal pressure.

[0020] In one embodiment of the present invention, the monool initiator containing a functional group is one of the following: alkyl-based n-butanol, alkyl-based n-hexanol, alkenyl-based 3-buten-1-ol, alkynyl-based 3-butyn-1-ol, ether-based ethylene glycol monovinyl ether, aromatic-based benzyl alcohol, aromatic-based phenethyl alcohol, halogenated hydrocarbon-based 2-bromoethanol, and halogenated hydrocarbon-based 2,2,2-trichloroethanol.

[0021] In one embodiment of the present invention, the functional group includes, but is not limited to, alkyl, alkenyl, alkynyl, etheryl, aromatic, and halogenated hydrocarbon groups.

[0022] In one embodiment of the invention, the molar ratio of the cyclic ester monomer to the monool initiator containing the functional group is 3:1 to 50:1, for example, 3:1, 5:1, 10:1, 20:1, 30:1, 40:1, 50:1, and any ratio between two of these. The polyester molecular weight is greater than the theoretical molecular weight calculated based on the complete conversion of the ring-opening monomer.

[0023] In one embodiment of the present invention, the catalyst is a metal salt catalyst, and is one or more selected from titanate, stannous octoate, antimony glycol, dibutyltin oxide, and antimony acetate. Preferably, the catalyst is selected from titanate.

[0024] In one embodiment of the present invention, the amount of catalyst used is 0.01 wt% to 4 wt% of the cyclic ester monomer. Specifically, it is 0.01 wt%, 0.02 wt%, 0.05 wt%, 0.1 wt%, 0.5 wt%, 1 wt%, 4 wt%, and any value or range between any two points.

[0025] In one embodiment of the invention, the polymerization reaction is carried out in an inert gas or vacuum atmosphere.

[0026] In one embodiment of the present invention, the polymerization reaction is carried out at a temperature of 150 ℃ to 250 ℃ for a time of 0.5 h to 5 h.

[0027] In one embodiment of the present invention, the polymerization reaction is fast and the conversion rate of the cyclic ester monomer is very high, reaching over 99% within 1 hour.

[0028] In one embodiment of the present invention, the end-functionalized polyester end has a high degree of functionalization, exceeding 99%.

[0029] The technical solution of the present invention has the following advantages compared with the prior art:

[0030] This invention provides a method for synthesizing end-functionalized polyesters. The initiation-elimination cascade polymerization method provided by this invention has the characteristics of fast polymerization speed and simple operation. It can synthesize polyesters with high end-functionalization and relatively high molecular weight under low monomer / initiator molar ratio and high monomer conversion rate. Its monomer conversion rate can exceed 99% and the end-functionalization degree is close to 100%. Attached Figure Description

[0031] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein:

[0032] Figure 1 The reaction equation mechanism diagram is shown below; where m is the molar ratio of the cyclic ester monomer to the monool initiator containing the functional group, and m is 3~50; n is the number of polycondensation steps, and n>1;

[0033] Figure 2 This is the quantitative 1H NMR spectrum of polyester P-1 obtained in Example 1 of the present invention;

[0034] Figure 3 This is the macromolecular mass spectrum of polycaprolactone obtained in Example 1 of the present invention;

[0035] Figure 4 This is the GPC diagram of the polycaprolactone obtained in Example 1 of the present invention;

[0036] Figure 5 The quantitative 1H NMR spectrum of polyester P-2 obtained in Example 2 of this invention;

[0037] Figure 6 This is the quantitative 1H NMR spectrum of polyester P-3 obtained in Example 3 of the present invention;

[0038] Figure 7This is the quantitative 1H NMR spectrum of polyester P-4 obtained in Example 4 of the present invention;

[0039] Figure 8 The quantitative 1H NMR spectrum of polyester P-5 obtained in Example 5 of this invention;

[0040] Figure 9 This is the macromolecular mass spectrum of polyester P-7 obtained in Example 7 of the present invention;

[0041] Figure 10 This is the quantitative 1H NMR spectrum of polyester P-11 obtained in Comparative Example 1 of the present invention. Detailed Implementation

[0042] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0043] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used are commercially available.

[0044] The CAS numbers of the reagents used in this invention are listed below:

[0045] Table 1

[0046]

[0047] In the following embodiments of the present invention, an Agilent 600 MHz DD2 superconducting nuclear magnetic resonance spectrometer was used, deuterated trichloromethane (CDCl3) was used as the solvent, and tetramethylsilane (TMS) was used as the internal standard. The test temperature was 25 °C, and the sample concentration was 10 mg / mL. Acquisition conditions: pulse angle 90°, relaxation time 25 s, number of scans 64, and [further details needed]. 13 C performs decoupling.

[0048] In the following embodiments of the present invention, a Bruker Ultrafle Xtreme matrix-assisted laser desorption / ionization time-of-flight mass spectrometer (MALDI-TOF-MS) was used for testing. The tests were performed in reflectance mode. The matrix used was trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-propenylidene]malonitrile (DCTB), and the cation salt was sodium trifluoroacetate (CF3COONa).

[0049] In the following embodiments of the present invention, a Waters volume exclusion chromatography system was used for determination. The volume exclusion chromatography system consisted of a 1515 pump, a 2707 autosampler, and an RI 2414 differential detector, and was equipped with three PL Mixed-C columns. The mobile phase was CHCl3, the flow rate was 1.0 mL / min, the test temperature was 35 °C, and the molecular weight was calibrated using narrowly distributed polystyrene as a standard.

[0050] Example 1

[0051] This example provides a method for synthesizing terminal-functionalized polycaprolactone P-1, the specific steps of which are as follows:

[0052] 22.83 g ε-caprolactone, 0.74 g n-butanol and 4.56 μL Ti(n-C4H9O)4 were added to a reaction flask, nitrogen gas was introduced, mechanical stirring was performed, and the mixture was heated to 220 °C for 120 min to obtain butoxy-terminated functionalized polyester P-1.

[0053] Quantitative proton NMR spectroscopy was performed on P-1, and its NMR spectrum is as follows: Figure 2 As shown. NMR calculations showed a monomer conversion rate greater than 99%, and end-group analysis yielded a molecular weight of 13.45 kg / mol. The degree of end-group functionalization was determined by the integral area (It) of the hydrogen atoms at the butoxy-terminal methyl group. a The integral area of ​​hydrogen atoms in the methylene groups attached to the hydroxyl groups at the ends of the polycaprolactone chain (I) c The theoretical value I is obtained by calculation. a / I c The value is 3 / 2, and the measured value is 3.0 / 2.0, indicating that the functionalization degree of the end base is approximately 100%.

[0054] P-1 was subjected to matrix-assisted laser desorption / ionization time-of-flight mass spectrometry (MALDI-TOF-MS) analysis, such as... Figure 3 As shown, the peak values ​​of two adjacent molecular ions differ by 114.14, consistent with the molecular weight of the repeating unit of caprolactone. The corresponding molecular ion peak ([M+Na)) can be calculated from the structure of polycaprolactone with a n-butoxy terminal group. +The theoretical value of the peak is 114.14m + 74.14 + 23.00. Taking the peak with a mass-to-charge ratio of 4776.58 as an example, it can be attributed to the corresponding PCL peak with repeating unit 41 (theoretical value 4776.88), further proving that butoxy groups were successfully introduced into the polymer chain ends. The molecular ion peaks in the mass spectrum can all be attributed to PCLs with butoxy groups at the end containing different numbers of caprolactone repeating units. There are no other impurity peaks, indicating that the obtained PCL has a high degree of end-group functionalization, which is consistent with the NMR results.

[0055] P-1 was tested by gel permeation chromatography (GPC), such as... Figure 4 As shown, it exhibits a single peak with a molecular weight of 23.85 kg / mol, which differs from the molecular weight measured by NMR. This is because GPC yields a relative molecular weight. The dispersion is 2.0, which falls within the dispersion range for condensation polymerization.

[0056] Example 2

[0057] This example provides a method for synthesizing end-functionalized polycaprolactone P-2, the specific steps of which are as follows:

[0058] 22.83 g ε-caprolactone, 1.02 g n-hexanol and 4.56 μL Ti(n-C4H9O)4 were added to a reaction flask, nitrogen gas was introduced, mechanical stirring was performed, and the mixture was heated to 240 °C for 180 min to obtain hexyloxy-terminated functionalized polyester P-2.

[0059] Quantitative proton NMR spectroscopy of P-2 was performed, and its NMR spectrum is as follows: Figure 5 As shown. NMR calculations showed a monomer conversion rate greater than 99%, and end-group analysis yielded a molecular weight of 12.15 kg / mol. The degree of end-group functionalization was determined by the integral area of ​​the hydrogen atoms at the hexyloxy-terminal methyl group (I0.05). a The integral area of ​​hydrogen atoms in the methylene groups attached to the hydroxyl groups at the ends of the polycaprolactone chain (I) c The theoretical value I is obtained by calculation. a / I c The value is 3 / 2, and the measured value is 3.0 / 2.0, indicating that the functionalization degree of the end base is approximately 100%.

[0060] Example 3

[0061] This example provides a method for synthesizing end-functionalized polycaprolactone P-3, the specific steps of which are as follows:

[0062] 22.83 g of ε-caprolactone, 0.72 g of 3-buten-1-ol and 4.56 μL of Ti(n-C4H9O)4 were added to a reaction flask, nitrogen gas was introduced, mechanical stirring was performed, and the mixture was heated to 200 °C for 90 min to obtain butenoxy-terminated functionalized polyester P-3.

[0063] Quantitative proton NMR spectroscopy of P-3 was performed, and its NMR spectrum is as follows: Figure 6 As shown. NMR calculations showed a monomer conversion rate greater than 99%, and end-group analysis yielded a molecular weight of 11.39 kg / mol. The degree of end-group functionalization was determined by the integral area of ​​the hydrogen atoms in the butenoxy-terminal double bond (Ik). a The integral area of ​​hydrogen atoms in the methylene groups attached to the hydroxyl groups at the ends of the polycaprolactone chain (I) c The theoretical value I is obtained by calculation. a / I c The value is 2 / 2, and the measured value is 2.0 / 2.0, indicating that the functionalization degree of the end base is approximately 100%.

[0064] Example 4

[0065] This example provides a method for synthesizing end-functionalized polycaprolactone P-4, the specific steps of which are as follows:

[0066] 22.83 g of ε-caprolactone, 0.70 g of 3-butyn-1-ol and 22.83 μL of Ti(n-C4H9O)4 were added to a reaction flask, nitrogen gas was introduced, mechanical stirring was performed, and the mixture was heated to 200 °C for 120 min to obtain butynoxy-terminated functionalized polyester P-4.

[0067] Quantitative proton NMR spectroscopy of P-4 was performed, and its NMR spectrum is as follows: Figure 7 As shown. NMR calculations showed a monomer conversion rate greater than 99%, and end-group analysis yielded a molecular weight of 21.23 kg / mol. The degree of end-group functionalization was determined by the integral area of ​​the hydrogen atoms in the butyrynoxy-terminal triple bond (I0.05). a The integral area of ​​hydrogen atoms in the methylene groups attached to the hydroxyl groups at the ends of the polycaprolactone chain (I) c The theoretical value I is obtained by calculation. a / I c The value is 1 / 2, and the measured value is 1.0 / 2.0, indicating that the functionalization degree of the end base is approximately 100%.

[0068] Example 5

[0069] This example provides a method for synthesizing end-functionalized polycaprolactone P-5, the specific steps of which are as follows:

[0070] 22.83 g ε-caprolactone, 1.25 g 2-bromoethanol and 4.56 μL Ti(i-C3H7O)4 were added to a reaction flask, nitrogen gas was introduced, mechanical stirring was performed, and the mixture was heated to 180 °C for 120 min to obtain halogen-terminated functionalized polyester P-5.

[0071] Quantitative proton NMR spectroscopy was performed on P-5, and its NMR spectrum is as follows: Figure 8 As shown. NMR calculations showed a monomer conversion rate greater than 99%, and end-group analysis yielded a molecular weight of 26.47 kg / mol. The degree of end-group functionalization was determined by the integral area (I0.05) of the hydrogen atoms in the methylene group linked to bromine. a The integral area of ​​hydrogen atoms in the methylene groups attached to the hydroxyl groups at the ends of the polycaprolactone chain (I) c The theoretical value I is obtained by calculation. a / I c The value is 2 / 2, and the measured value is 2.0 / 2.0, indicating that the functionalization degree of the end base is approximately 100%.

[0072] Example 6

[0073] This example provides a method for synthesizing end-functionalized polycaprolactone P-6, the specific steps of which are as follows:

[0074] 22.83 g of ε-caprolactone, 0.88 g of ethylene glycol monovinyl ether and 22.83 μL of Ti(n-C4H9O)4 were added to a reaction flask, nitrogen gas was introduced, mechanical stirring was performed, and the mixture was heated to 200 °C for 120 min to obtain ethylene-oxy-terminated functionalized polyester P-6.

[0075] Quantitative nuclear magnetic resonance (NMR) spectroscopy of P-6 revealed a monomer conversion greater than 99% based on NMR calculations. Its molecular weight was calculated to be 24.80 kg / mol using end-group analysis. The degree of end-group functionalization was determined by the integral area (I²) of the hydrogen atoms of the methine group linked to the ether bond in the ethylene group. a The integral area of ​​hydrogen atoms in the methylene groups attached to the hydroxyl groups at the ends of the polycaprolactone chain (I) c The theoretical value I is obtained by calculation. a / I c The value is 1 / 2, and the measured value is 1.0 / 2.0, indicating that the functionalization degree of the end base is approximately 100%.

[0076] Example 7

[0077] This example provides a method for synthesizing terminal-functionalized polyvalerone P-7, the specific steps of which are as follows:

[0078] 10.01 g δ-valerol, 0.37 g n-butanol and 2.00 μL Ti(n-C4H9O)4 were added to a reaction flask, nitrogen gas was introduced, mechanical stirring was performed, and the mixture was heated to 200 °C for 120 min to obtain a functionalized polyester P-7 with butoxy-terminated ends.

[0079] Quantitative proton NMR spectroscopy and macromolecular mass spectrometry characterization of P-7 were performed, such as... Figure 9 As shown, NMR calculations revealed a monomer conversion rate greater than 99%, and the degree of terminal functionalization was determined by the integral area of ​​the hydrogen atoms at the butoxy-terminal methyl group (It). a The integral area of ​​hydrogen atoms in the methylene groups attached to the hydroxyl groups at the ends of the polycaprolactone chain (I) c The theoretical value I is obtained by calculation. a / I c The value is 3 / 2, and the measured value is 3.0 / 2.0, indicating that the functionalization degree of the end base is approximately 100%.

[0080] Example 8

[0081] This example provides a method for synthesizing end-functionalized polyglycolic acid P-8, the specific steps of which are as follows:

[0082] 11.60 g glycolide, 1.08 g benzyl alcohol and 2.32 μL Ti(n-C4H9O)4 were added to a reaction flask, nitrogen gas was introduced, mechanical stirring was performed, and the mixture was heated to 200 °C for 120 min to obtain functionalized polyester P-8 with benzyl groups at the end.

[0083] Quantitative nuclear magnetic resonance (NMR) spectroscopy and macromolecular mass spectrometry characterization were performed on P-8. NMR calculations showed that its monomer conversion rate was greater than 99%, and the degree of end-group functionalization was determined by the integral area of ​​the hydrogen atoms on the benzene ring (I0). a The integral area of ​​hydrogen atoms in the methylene groups attached to the hydroxyl groups at the ends of the polyethylene glycol chain (I) c The theoretical value is obtained by calculation, and is I. a / I c The value is 5 / 2, and the measured value is 5.0 / 2.0, indicating that the functionalization degree of the end base is approximately 100%.

[0084] Example 9

[0085] This example provides a method for synthesizing terminal-functionalized poly(p-dioxanone) P-9, the specific steps of which are as follows:

[0086] Add 5.10 g of p-dioxanone, 0.74 g of n-butanol and 0.20 g of stannous octoate to a reaction flask, purge with nitrogen, stir mechanically, heat to 160 °C and react for 120 min to obtain functionalized polyester P-9.

[0087] Quantitative nuclear magnetic resonance (NMR) spectroscopy of P-9 showed that its monomer conversion rate was greater than 99%, and the degree of functionalization was determined by the integral area of ​​the hydrogen atoms at the butoxy-terminal methyl group (It). a The integral area of ​​hydrogen atoms in the methylene group at the end of the poly(p-dioxanone) chain, which is attached to a hydroxyl group (I) c The theoretical value is obtained by calculation, and is I. a / I c The value is 3 / 2, and the measured value is 3.0 / 2.0, indicating that the functionalization degree of the end base is approximately 100%.

[0088] Example 10

[0089] This example provides a method for synthesizing end-functionalized polycaprolactone P-10 with a low monomer / initiator molar ratio. The specific steps are as follows:

[0090] 10.27 g ε-caprolactone, 2.23 g n-butanol and 10.27 μL Ti(n-C4H9O)4 were added to the reaction flask, nitrogen gas was introduced, mechanical stirring was performed, the mixture was heated to 180 °C, vacuum was applied, and the reaction was continued for 30 min to obtain functionalized polyester P-10.

[0091] Quantitative nuclear magnetic resonance (NMR) spectroscopy of P-10 revealed a monomer conversion greater than 99% based on NMR calculations, and a molecular weight of 6.05 kg / mol calculated using end-group analysis. The degree of end-group functionalization was determined by the integral area (I²) of the hydrogen atoms at the butoxy-terminal methyl group. a The integral area of ​​hydrogen atoms in the methylene groups attached to the hydroxyl groups at the ends of the polycaprolactone chain (I) c The theoretical value is obtained by calculation, and is I. a / I c The value is 3 / 2, and the measured value is 3.0 / 2.0, indicating that the functionalization degree of the end base is approximately 100%.

[0092] Comparative Example 1

[0093] This comparative example provides a synthetic method for preparing end-functionalized polycaprolactone P-11 using ring-opening polymerization. The specific steps are as follows:

[0094] Add 80 mL of toluene, 22.83 g of ε-caprolactone, 0.07 g of n-butanol and 228.28 μL of stannous octoate to a reaction flask, heat to 90 °C and react for 24 h to obtain functionalized polyester P-11.

[0095] Quantitative proton NMR spectroscopy was performed on P-11, such as... Figure 10 As shown, NMR calculations revealed a monomer conversion rate of less than 60%, and end-group analysis yielded a molecular weight of 3.52 kg / mol. The degree of end-group functionalization was determined by the integral area (It) of the hydrogen atoms at the butoxy-terminal methyl group. aThe integral area of ​​hydrogen atoms in the methylene groups attached to the hydroxyl groups at the ends of the polycaprolactone chain (I) c The theoretical value is obtained by calculation, and is I. a / I c The value is 3 / 2, and the measured value is 0.9 / 2.0, indicating that the functionalization degree of the end group is about 30%.

[0096] Comparative Example 2

[0097] This comparative example provides a method for preparing end-functionalized polycaprolactone at low temperature, similar to Example 1, except that the heating temperature is adjusted to 120°C. The specific steps are as follows:

[0098] 22.83 g of ε-caprolactone, 0.74 g of n-butanol and 4.56 μL of Ti(n-C4H9O)4 were added to a reaction flask, nitrogen gas was introduced, mechanical stirring was performed, and the mixture was heated to 120 °C for 120 min to obtain product P-12, which is a liquid at room temperature.

[0099] Quantitative nuclear magnetic resonance (NMR) spectroscopy and macromolecular mass spectrometry characterization of P-12 revealed that no end-functionalized polycaprolactone was obtained.

[0100] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for synthesizing end-functionalized polyesters, characterized in that, Includes the following steps: Cyclic ester monomers and monool initiators containing functional groups undergo polymerization under the action of a catalyst to generate end-functionalized polyesters; the structure of the end-functionalized polyesters is as follows: ； Wherein, R comes from the cyclic ester monomer; R1 comes from the monool initiator containing a functional group; m is the molar ratio of the cyclic ester monomer to the monool initiator containing a functional group, where m is 3~50; n is the number of polycondensation steps, where n>1; The polymerization reaction includes cascaded ring-opening polymerization and condensation polymerization; The polymerization reaction is carried out in an inert gas or vacuum atmosphere.

2. The method for synthesizing end-functionalized polyester according to claim 1, characterized in that, The cyclic ester monomer is one or both of lactone and lactide; the lactone is one or more of ε-caprolactone, valproic acid lactone, proprolactone, and p-dioxanone; the lactide is glycolide and / or lactide.

3. The method for synthesizing end-functionalized polyester according to claim 1, characterized in that, The boiling point of the monool initiator containing the functional group is less than 300 °C under normal pressure.

4. The method for synthesizing end-functionalized polyester according to claim 1, characterized in that, The functional groups include one or more of alkyl, alkenyl, alkynyl, etheryl, aromatic, and halogenated hydrocarbon groups.

5. The method for synthesizing end-functionalized polyester according to claim 1, characterized in that, The molar ratio of the cyclic ester monomer to the monool initiator containing the functional group is 3:1 to 50:

1.

6. The method for synthesizing end-functionalized polyester according to claim 1, characterized in that, The catalyst is one or more of titanate, stannous octoate, dibutyltin oxide, antimony glycolate, and antimony acetate.

7. The method for synthesizing end-functionalized polyester according to claim 1, characterized in that, The amount of catalyst used is 0.01% of the cyclic ester monomer. wt ~4 wt %.

8. The method for synthesizing end-functionalized polyester according to claim 1, characterized in that, The polymerization reaction is carried out at a temperature of 150 ℃ to 250 ℃ for a time of 0.5 h to 5 h.

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