Monomolecular bifunctional organic catalyst as well as preparation method and application thereof

Abstract

The invention discloses a monomolecular bifunctional organic catalyst, the structural formula of which is shown in the following formula (I), in the formula (I), X is selected from a group containing urea or thiourea, the structural formula is shown in the following formula (II), Y is selected from a potassium alkoxide or sodium alkoxide group, the structural formula is shown in the following formula (III), and L is selected from unsubstituted C2-C4 alkyl; the monomolecular bifunctional organic catalyst disclosed by the invention is novel in structure, and has ultrahigh activity and high controllability when catalyzing a ring-opening polymerization reaction of cyclic lactone, the highest conversion number (TON) can reach 900, the highest conversion frequency (TOF) can reach 4860 min <-1 >, and the prepared polymer has high molecular weight and low molecular weight distribution. # imgabs0 #

Description

Technical Field

[0001] The invention relates to the field of catalytic polymerization, in particular to a unimolecular bifunctional organic catalyst and a preparation method thereof and application thereof in catalyzing cyclic lactone. Background Art

[0002] Petroleum-based plastics are widely used in our daily lives, and the global annual production of petrochemical-based plastics is close to 400 million tons. However, petroleum-based plastics cannot be automatically degraded after being released into the environment, leading to serious environmental problems. Therefore, there is an increasing need to develop sustainable polymers to reduce dependence on petrochemical plastics. Ring-opening polymerization (ROP) of cyclic lactones is a method for synthesizing aliphatic polyesters, which are defined as sustainable polymers because they are derived from renewable resources and have biodegradable properties. In order to further expand the application of polyesters, the development of new catalytic methods is a challenging research topic aimed at improving the synthesis efficiency of polymers and the precise control of polymer structure.

[0003] In the catalytic ring-opening polymerization of cyclic lactones, it is often difficult to achieve both reactivity and controllability. Highly active catalysts can accelerate polymerization reactions. However, high activity may also make the reaction difficult to control, easily triggering side reactions such as transesterification, making the molecular weight distribution of the polymer wider, and the properties of the final product difficult to predict. In order to achieve controllable polymerization, it is usually necessary to limit the reaction rate by fine-tuning the reaction conditions or using specially designed catalysts. This approach can ensure that the molecular weight, molecular weight distribution and structure of the polymer are more controllable, but it may also reduce the reaction rate and reduce the reaction efficiency.

[0004] Waymouth's group [Macromolecules 2006, 39, 8574-8583.] developed a thiourea / tertiary amine binary system catalyst that exhibits good control behavior in the ring-opening polymerization (ROP) of cyclic lactones. The synergistic mechanism in this catalytic system is that the tertiary amine activates the initiator / chain end, and the thiourea activates the monomer through hydrogen bonding. The ring-opening polymerization of cyclic lactones undergoes a three-molecular reaction, and the concentrations of thiourea and chain growth species are both low, so the catalytic activity is low. Even if the tertiary amine and thiourea groups are combined in one molecule, the reactivity of the catalytic system is still relatively low.

[0005] In 2016, Waymouth's research group developed an organic catalyst system combining alkoxide and thiourea [Nature Chemistry 2016, 8, 1047-1053.] Compared with the thiourea / tertiary amine binary catalytic system, this catalyst system has improved the catalytic efficiency of hydrogen bond organic catalysts to a certain extent, but the catalytic efficiency is still far lower than that of metal complex systems. The catalytic turnover number (TON) is 90 and the turnover frequency (TOF) is 2. And this binary organic catalyst system usually requires 3 to 5 times the equivalent of (thio) urea catalyst (relative to alkoxide) to activate the initiator / chain end, so as to achieve good control of ROP. Excessive use of organic catalysts will increase production costs, and it is difficult to completely separate or remove them after the reaction, affecting the subsequent product purification steps. Summary of the invention

[0006] In view of the above-mentioned problems existing in the prior art, the present invention discloses a novel monomolecular bifunctional organic catalyst, which has both ultra-high activity and high controllability when catalyzing the ring-opening polymerization reaction of cyclic lactones, with a turnover number (TON) of up to 900 and a turnover frequency (TOF) of up to 4860min-1. The prepared polymer has a high molecular weight and low molecular weight distribution.

[0007] The specific technical solutions are as follows:

[0008] A monomolecular bifunctional organic catalyst for ring-opening polymerization of cyclic lactone, the structural formula of which is shown in the following formula (I):

[0009] X—L—Y (I);

[0010] In formula (I), X is selected from a group containing urea or thiourea, and the structural formula is shown in formula (II) below:

[0011]

[0012] In formula (II):

[0013] N is a nitrogen atom;

[0014] R 1 Selected from C 6 ~C 8 One or more of aromatic groups;

[0015] R 2 Selected from O or S;

[0016] Indicates the connection key;

[0017] Y is selected from potassium alcoholate or sodium alcoholate group, and the structural formula is shown in the following formula (III):

[0018]

[0019] In formula (III):

[0020] O is an oxygen atom;

[0021] R 3 Selected from Na and / or K;

[0022] Indicates the connection key;

[0023] L is selected from unsubstituted C 2 ~C 4 alkyl.

[0024] The present invention is based on long-term research on organic catalytic polymerization and discloses a monomolecular bifunctional organic catalyst that combines (thio)urea and alkoxide in a monomolecular catalyst / initiator, thereby achieving effective intramolecular activation of the initiator / chain end. The catalyst improves catalytic efficiency and high controllability while reducing the amount of (thio)urea required for catalyzing ROP in the existing thiourea / alkoxide binary system.

[0025] Preferably, L is selected from unsubstituted C 3 alkyl.

[0026] Specifically, the structural formula of the monomolecular bifunctional organic catalyst is selected from one or more of the following formulas (I-1) to (I-9):

[0027]

[0028]

[0029] Preferably, the structural formula is selected from the above formula (Ⅰ-1), (Ⅰ-6), (Ⅰ-7) or (Ⅰ-8); further preferably, the structural formula is selected from the above formula (Ⅰ-1), (Ⅰ-6), or (Ⅰ-8); more preferably, the structural formula is selected from the above formula (Ⅰ-1) or (Ⅰ-6).

[0030] Experiments have shown that with the continuous optimization of the structural formula of the single-molecule bifunctional organic catalyst, the catalytic activity and controllability of the catalyst in catalyzing the ring-opening polymerization reaction of cyclic lactones are continuously improved.

[0031] The present invention also discloses a method for preparing the monomolecular bifunctional organic catalyst for the ring-opening polymerization of cyclic lactone, comprising the following steps:

[0032] Will have the following formula W 1 The raw material 1 of the structure has the following formula W 2The raw material 2 of the structure is mixed with solvent A to obtain raw material solution I, and an intermediate product is obtained after Michael addition reaction; the intermediate product, raw material 3 and solvent B are mixed to obtain raw material solution II, and the monomolecular bifunctional organic catalyst is obtained after substitution reaction;

[0033]

[0034] In the formula, O, N, and C represent oxygen atom, nitrogen atom, and carbon atom, respectively;

[0035] R 1 Selected from C 6 ~C 8 One or more aromatic groups; R 2 is selected from a sulfur atom or an oxygen atom; R 3 Selected from unsubstituted C 2 ~C 4 One or more of the alkyl groups.

[0036] Preferred:

[0037] Raw material 1 is selected from one or more of 3,5-bis(trifluoromethyl)phenyl isothiocyanate, 3,4-dichlorophenyl isothiocyanate, 4-(trifluoromethyl)phenyl isothiocyanate, phenyl isothiocyanate, and 3,5-bis(trifluoromethyl)phenyl isothiocyanate;

[0038] Raw material 2 is selected from one or more of 3-amino-1-propanol, 4-amino-1-butanol, and 2-amino-1-ethanol;

[0039] Solvent A is selected from one or more of dichloromethane, tetrahydrofuran, acetone, methanol, ethanol, and isopropanol;

[0040] The molar ratio of raw material 1 to raw material 2 is 1:(1.0-1.1); the concentration of raw material 2 in raw material solution I is 0.8-1.2 mol / L;

[0041] The temperature of the Michael addition reaction is 0-80°C. After the Michael addition reaction, the product undergoes post-treatment processes such as removal of impurities and organic solvents and drying.

[0042] Preferably, the temperature of the Michael addition reaction is 25-60°C.

[0043] Raw material 3 is selected from metallic sodium and / or metallic potassium;

[0044] Solvent B is selected from one or more of tetrahydrofuran, dichloromethane, acetone, methanol, ethanol, toluene and chloroform;

[0045] The molar ratio of the intermediate product to the raw material 3 is 1:(0.9-1.0); the concentration of the intermediate product in the raw material solution II is 1.0-2.0 mol / L;

[0046] The temperature of the substitution reaction is 0-30°C, and after the substitution reaction, impurities and organic solvents are removed, and washing and drying are performed.

[0047] Preferably, the substitution reaction is carried out at room temperature.

[0048] The present invention also discloses the use of the monomolecular bifunctional organic catalyst in catalyzing the ring-opening polymerization reaction of cyclic lactone, specifically:

[0049] The cyclic lactone monomer and the monomolecular bifunctional organic catalyst are mixed and a polymerization reaction is carried out under autogenous pressure.

[0050] It is found through experiments that the unimolecular bifunctional organic catalyst disclosed in the present invention has the advantages of high catalytic efficiency and controllable reaction. On the one hand, it is reflected in that the molecular weight of the prepared polymer can be accurately controlled by regulating the molar ratio of the cyclic lactone monomer (if there are multiple monomers, that is, the total molar number of the multiple monomers) to the initiator. And after testing, the actual number average molecular weight determined by gel permeation chromatography is basically consistent with the theoretical number average molecular weight. On the other hand, it is reflected in that the catalytic efficiency is controlled by regulating the catalyst concentration, reactant concentration, reaction time and reaction temperature.

[0051] Preferably, the cyclic lactone is selected from one or more of L-lactide, valerolactone and caprolactone; more preferably, L-lactide.

[0052] It has been found through experiments that when the cyclic lactone monomer used is L-lactide, the prepared polylactic acid is a stereoregular crystalline polymer.

[0053] Preferably, the molar ratio of the cyclic lactone monomer to the monomolecular bifunctional organic catalyst is 100 to 2000:1. Within this range, the monomolecular bifunctional organic catalyst disclosed in the present invention has excellent catalytic activity.

[0054] More preferably, the molar ratio of the cyclic lactone monomer to the monomolecular bifunctional organic catalyst is 500 to 1000:1.

[0055] When the polymerization reaction is solution polymerization, a solvent commonly used in solution polymerization reactions in the art may also be added.

[0056] Preferably, the polymerization reaction temperature is 25-60°C.

[0057] Compared with the prior art, the present invention has the following advantages:

[0058] (1) The present invention discloses a monomolecular bifunctional organic catalyst that can catalyze the homopolymerization of cyclic lactones, and the catalyst exhibits high activity and good reaction controllability in the ring-opening polymerization (ROP) of cyclic esters. The ultrahigh activity of the organic catalyst is comparable to that of metal complexes, with a turnover number (TON) of up to 900 and a turnover frequency (TOF) of up to 4860 min-1; and the reaction controllability is high, and polyesters with customized structures, predictable molecular weights, narrow molecular weight distributions, less racemization, and minimal transesterification reactions can be prepared. The synthesis process of the catalyst is simple and scalable, and a wide range of ROP activity can be achieved.

[0059] (2) The unimolecular bifunctional organic catalyst disclosed in the present invention catalyzes the ring-opening polymerization of cyclic lactones through a two-molecule reaction in which the concentration of lactone is relatively high, thereby reducing the amount of (thio)urea required for catalyzing ROP in the existing thiourea / alkoxide binary system. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 Schematic diagram of the principle of the monomolecular bifunctional organic catalyst prepared in Example 1;

[0061] Figure 2 The monomolecular bifunctional organic catalyst prepared in Example 1 1 H NMR spectrum;

[0062] Figure 3 The monomolecular bifunctional organic catalyst prepared in Example 2 1 H NMR spectrum;

[0063] Figure 4 The monomolecular bifunctional organic catalyst prepared in Example 3 1 H NMR spectrum;

[0064] Figure 5 The unimolecular bifunctional organic catalyst prepared in Example 4 1 H NMR spectrum;

[0065] Figure 6 The monomolecular bifunctional organic catalyst prepared in Example 5 1 H NMR spectrum;

[0066] Figure 7 The monomolecular bifunctional organic catalyst prepared in Example 6 1 H NMR spectrum;

[0067] Figure 8 The unimolecular bifunctional organic catalyst prepared in Example 7 1 H NMR spectrum;

[0068] Fig. 9 The unimolecular bifunctional organic catalyst prepared in Example 8 1 H NMR spectrum;

[0069] Fig.10 The monomolecular bifunctional organic catalyst prepared in Example 9 1 H NMR spectrum;

[0070] Fig.11 Homonuclear decoupling of the methylene peak of polylactic acid prepared in Application Example 1 1 H NMR spectrum. DETAILED DESCRIPTION

[0071] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

[0072] Example 1 Synthesis of Catalyst 1

[0073] Step 1: Synthesis of 1-(3,5-bis(trifluoromethyl)phenyl)-3-(3-hydroxypropyl)thiourea.

[0074] In N 2 Under atmosphere, 3-amino-1-propanol (0.75 g, 0.01 mol) was added to anhydrous CH 2 Cl 2 3,5-Bis(trifluoromethyl)phenylisothiocyanate (2.71 g, 0.01 mol) was added to the solution (10 mL). The obtained raw material solution I was reacted at 45°C with stirring for 24 hours, and the obtained reaction mixture was concentrated in vacuo. The product was collected and dried in vacuo at 40°C until constant weight (3.38 g, 98% yield).

[0075] Step 2: Synthesis of Catalyst 1

[0076] A Schlenk flask equipped with a stirring bar was charged with a solution of 1-(3,5-bis(trifluoromethyl)phenyl)-3-(3-hydroxypropyl)thiourea (3.46 g, 0.01 mol) in anhydrous tetrahydrofuran (10 mL). 2 Under the atmosphere, sodium (0.22 g, 0.0095 mol) was added. The obtained raw material solution II was placed at 25°C for 4 hours and then cooled to room temperature. The obtained reaction mixture was concentrated in vacuo to obtain a crude solid product, which was further purified by washing with isopropyl ether 3 times. The product was then concentrated in vacuo for 2 hours to obtain 3.58 g of a light yellow solid product (yield of 97%).

[0077] The preparation reaction formula of the catalyst in this embodiment is shown below:

[0078]

[0079] Figure 1 The schematic diagram of the principle of the unimolecular bifunctional organic catalyst prepared in this example. Figure 1 It can be seen that this is a completely new catalyst / initiator structure.

[0080] Catalyst 1 prepared in this example 1 H NMR spectrum Figure 2 shown.

[0081] Example 2 Synthesis of Catalyst 2

[0082] Step 1: 1-(3,5-bis(trifluoromethyl)phenyl)-3-(2-hydroxyethyl)thiourea.

[0083] In N 2 Under atmosphere, 2-amino-1-ethanol (0.61 g, 0.01 mol) was added to anhydrous CH 2 Cl 2 3,5-Bis(trifluoromethyl)phenylisothiocyanate (2.71 g, 0.01 mol) was added to the solution (10 mL). The obtained raw material solution I was reacted at 45°C with stirring for 24 hours, and the obtained reaction mixture was concentrated in vacuo. The product was collected and dried in vacuo at 40°C until constant weight (3.28 g, 99% yield).

[0084] Step 2: Synthesis of Catalyst 2

[0085] A Schlenk flask equipped with a stirring bar was charged with a solution of 1-(3,5-bis(trifluoromethyl)phenyl)-3-(2-hydroxyethyl)thiourea (3.32 g, 0.01 mol) in anhydrous tetrahydrofuran (10 mL). 2 Under the atmosphere, sodium (0.22 g, 0.0095 mol) was added. The obtained raw material solution II was reacted at 25°C for 4 hours and then cooled to room temperature. The obtained reaction mixture was concentrated in vacuo to obtain a crude solid product, which was further purified by washing with isopropyl ether 3 times. The product was then concentrated in vacuo for 2 hours to obtain 3.48 g of a light yellow solid product (yield of 98%). The preparation reaction formula of the catalyst in this example is shown below:

[0086]

[0087] Catalyst 2 prepared in this example 1 H NMR spectrum Figure 3 shown.

[0088] Example 3 Synthesis of Catalyst 3

[0089] Step 1: 1-(3,5-bis(trifluoromethyl)phenyl)-3-(4-hydroxybutyl)thiourea

[0090] In N 2 Under atmosphere, 4-amino-1-butanol (0.89 g, 0.01 mol) was added to anhydrous CH 2 Cl 2 3,5-Bis(trifluoromethyl)phenylisothiocyanate (2.71 g, 0.01 mol) was added to the solution (10 mL). The obtained raw material solution I was reacted at 45°C with stirring for 24 hours, and the obtained reaction mixture was concentrated in vacuo. The product was collected and dried in vacuo at 40°C until constant weight (3.52 g, 98% yield).

[0091] Step 2: Synthesis of Catalyst 3

[0092] A Schlenk flask equipped with a stirring bar was charged with a solution of 1-(3,5-bis(trifluoromethyl)phenyl)-3-(4-hydroxybutyl)thiourea (3.60 g, 0.01 mol) in anhydrous tetrahydrofuran (10 mL). 2 Under atmosphere, sodium (0.22 g, 0.0095 mol) was added. The obtained raw material solution II was reacted at 25°C for 4 hours and then cooled to room temperature. The obtained reaction mixture was concentrated in vacuo to obtain a crude solid product, which was further purified by washing with isopropyl ether 3 times. The product was then concentrated in vacuo for 2 hours to obtain 3.80 g of a yellow solid product (yield of 99%). The preparation reaction formula of the catalyst in this example is shown below:

[0093]

[0094] Catalyst 3 prepared in this example 1 H NMR spectrum Figure 4 shown.

[0095] Example 4 Synthesis of Catalyst 4

[0096] Step 1: 1-(3,5-bis(trifluoromethyl)phenyl)-3-(3-hydroxypropyl)thiourea

[0097] In N 2 Under atmosphere, 3-amino-1-propanol (0.75 g, 0.01 mol) was added to anhydrous CH 2 Cl 2 3,5-Bis(trifluoromethyl)phenylisothiocyanate (2.71 g, 0.01 mol) was added to the solution (10 mL). The obtained raw material solution I was reacted at 45°C with stirring for 24 hours, and the obtained reaction mixture was concentrated in vacuo. The product was collected and dried in vacuo at 40°C until constant weight (3.38 g, 98% yield).

[0098] Step 2: Synthesis of Catalyst 4

[0099] A Schlenk flask equipped with a stirring bar was charged with a solution of 1-(3,5-bis(trifluoromethyl)phenyl)-3-(3-hydroxypropyl)thiourea (3.60 g, 0.01 mol) in anhydrous tetrahydrofuran (10 mL). 2 Under the atmosphere, potassium (0.37 g, 0.0095 mol) was added. The obtained raw material solution II was reacted at 25°C for 4 hours and then cooled to room temperature. The obtained reaction mixture was concentrated in vacuo to obtain a crude solid product, which was further purified by washing with isopropyl ether 3 times. The product was then concentrated in vacuo for 2 hours to obtain 3.80 g of a yellow solid product (yield of 99%). The preparation reaction formula of the catalyst in this embodiment is shown below:

[0100]

[0101] The catalyst 4 prepared in this example 1 H NMR spectrum Figure 5 shown.

[0102] Example 5 Synthesis of Catalyst 5

[0103] Step 1: 1-(3,5-bis(trifluoromethyl)phenyl)-3-(3-hydroxypropyl)urea

[0104] In N 2 Under atmosphere, 3-amino-1-propanol (0.75 g, 0.01 mol) was added to anhydrous CH 2 Cl 2 3,5-bis(trifluoromethyl)phenyl isocyanate (2.55 g, 0.01 mol) was added to the solution (10 mL). The obtained raw material solution I was reacted at 45°C with stirring for 24 hours, and the obtained reaction mixture was concentrated in vacuo. The product was collected and dried in vacuo at 40°C until constant weight (1.95 g, 59% yield).

[0105] Step 2: Synthesis of Catalyst 5

[0106] A Schlenk flask equipped with a stirring bar was charged with a solution of 1-(3,5-bis(trifluoromethyl)phenyl)-3-(3-hydroxypropyl)urea (1.95 g, 0.006 mol) in anhydrous tetrahydrofuran (10 mL). 2 Under the atmosphere, sodium (0.13 g, 0.0057 mol) was added. The obtained raw material solution II was reacted at 25°C for 4 hours and then cooled to room temperature. The obtained reaction mixture was concentrated in vacuo to obtain a crude solid product, which was further purified by washing with isopropyl ether 3 times. The product was then concentrated in vacuo for 2 hours to obtain 2.03 g of a yellow solid product (yield of 98%). The preparation reaction formula of the catalyst in this embodiment is shown below:

[0107]

[0108] The catalyst 5 prepared in this example 1 H NMR spectrum Figure 6 shown.

[0109] Example 6 Synthesis of Catalyst 6

[0110] Step 1: 1-(3,5-bis(trifluoromethyl)phenyl)-3-(3-hydroxypropyl)urea

[0111] The preparation process is exactly the same as step 1 in Example 5.

[0112] Step 2: Synthesis of Catalyst 6

[0113] A Schlenk flask equipped with a stirring bar was charged with a solution of 1-(3,5-bis(trifluoromethyl)phenyl)-3-(3-hydroxypropyl)urea (1.95 g, 0.006 mol) in anhydrous tetrahydrofuran (10 mL). 2 Under the atmosphere, potassium (0.22 g, 0.0057 mol) was added. The obtained raw material solution II was reacted at 25°C for 4 hours and then cooled to room temperature. The obtained reaction mixture was concentrated in vacuo to obtain a crude solid product, which was further purified by washing with isopropyl ether 3 times. The product was then concentrated in vacuo for 2 hours to obtain 2.13 g of a yellow solid product (yield of 98%). The preparation reaction formula of the catalyst in this embodiment is shown below:

[0114]

[0115] The catalyst 6 prepared in this example 1 H NMR spectrum Figure 7 shown.

[0116] Example 7 Synthesis of Catalyst 7

[0117] Step 1: 1-(3,4-dichlorophenyl)-3-(3-hydroxypropyl)thiourea

[0118] In N 2 Under atmosphere, 3-amino-1-propanol (0.75 g, 0.01 mol) was added to anhydrous CH 2 Cl 2 A solution of 3,4-dichlorophenyl isothiocyanate (2.03 g, 0.01 mol) in anhydrous tetrahydrofuran (10 mL) was added to the solution (10 mL). The obtained raw material solution I was reacted at 45°C with stirring for 24 hours, and the obtained reaction mixture was concentrated in vacuo. The product was collected and dried in vacuo at 40°C until constant weight (2.76 g, 99% yield).

[0119] Step 2: Synthesis of Catalyst 7

[0120] A Schlenk flask equipped with a stirring bar was charged with a solution of 1-(3,4-dichlorophenyl)-3-(3-hydroxypropyl)thiourea (2.78 g, 0.01 mol) in anhydrous tetrahydrofuran (10 mL). 2 Under the atmosphere, sodium (0.22g, 0.0095mol) was added. The obtained raw material solution II was reacted at 25°C for 4 hours and then cooled to room temperature. The obtained reaction mixture was concentrated in vacuo to obtain a crude solid product, which was further purified by washing with isopropyl ether 3 times. The product was then concentrated in vacuo for 2 hours to obtain 2.98g of a yellow solid product (yield of 99%). The preparation reaction formula of the catalyst in this embodiment is shown below:

[0121]

[0122] The catalyst 7 prepared in this example 1 H NMR spectrum Figure 8 shown.

[0123] Example 8 Synthesis of Catalyst 8

[0124] Step 1: 1-(3-Hydroxypropyl)-3-(4-(trifluoromethyl)phenyl)thiourea

[0125] In N 2 Under atmosphere, 3-amino-1-propanol (0.75 g, 0.01 mol) was added to anhydrous CH 2 Cl 2 4-(Trifluoromethyl)phenyl isothiocyanate (2.03 g, 0.01 mol) was added to the solution (10 mL). The obtained raw material solution I was reacted at 45°C with stirring for 24 hours, and the obtained reaction mixture was concentrated in vacuo. The product was collected and dried in vacuo at 40°C until constant weight (2.73 g, 98% yield).

[0126] Step 2: Synthesis of Catalyst 8

[0127] A Schlenk flask equipped with a stirring bar was charged with a solution of 1-(3-hydroxypropyl)-3-(4-(trifluoromethyl)phenyl)thiourea (2.78 g, 0.01 mol) in anhydrous tetrahydrofuran (10 mL). 2 Under the atmosphere, sodium (0.22g, 0.0095mol) was added. The obtained raw material solution II was reacted at 25°C for 4 hours and then cooled to room temperature. The obtained reaction mixture was concentrated in vacuo to obtain a crude solid product, which was further purified by washing with isopropyl ether 3 times. The product was then concentrated in vacuo for 2 hours to obtain 2.98g of a yellow solid product (yield of 99%). The preparation reaction formula of the catalyst in this embodiment is shown below:

[0128]

[0129] The catalyst 8 prepared in this example 1 H NMR spectrum Fig. 9 shown.

[0130] Example 9 Synthesis of Catalyst 9

[0131] Step 1: 1-(3-Hydroxypropyl)-3-phenylthiourea

[0132] In N 2 Under atmosphere, 3-amino-1-propanol (0.75 g, 0.01 mol) was added to anhydrous CH 2 Cl 2 Phenyl isothiocyanate (1.35 g, 0.01 mol) was added to the solution (10 mL). The obtained raw material solution I was reacted at 45°C with stirring for 24 hours, and the obtained reaction mixture was concentrated in vacuo. The product was collected and dried in vacuo at 40°C until constant weight (2.05 g, 98% yield).

[0133] Step 2: Synthesis of Catalyst 9

[0134] A Schlenk flask equipped with a stirring bar was charged with a solution of 1-(3-hydroxypropyl)-3-phenylthiourea (2.10 g, 0.01 mol) in anhydrous tetrahydrofuran (10 mL). 2 Under the atmosphere, sodium (0.22g, 0.0095mol) was added. The obtained raw material solution II was reacted at 25°C for 4 hours and then cooled to room temperature. The obtained reaction mixture was concentrated in vacuo to obtain a crude solid product, which was further purified by washing with isopropyl ether 3 times. The product was then concentrated in vacuo for 2 hours to obtain 2.30g of a yellow solid product (yield of 99%). The preparation reaction formula of the catalyst in this embodiment is shown below:

[0135]

[0136] The catalyst 9 prepared in this example 1 H NMR spectrum Fig.10 shown.

[0137] Comparative Example 1 Binary System TU-1 / KOCH 3

[0138] In the article "Fast and selective ring-opening polymerizations by alkoxides and thioureas", Waymouth et al. used the binary catalytic system TU-1 / KOCH 3, the structural formula is as follows:

[0139]

[0140] Comparative Example 2 Binary System TU-1 / NaOCH 3

[0141] In the article "Fast and selective ring-opening polymerizations by alkoxides and thioureas", Waymouth et al. used the binary catalytic system TU-1 / NaOCH 3 , the structural formula is as follows:

[0142]

[0143] Application Example 1: Using catalyst 1 to catalyze the ring-opening of L-lactide to generate polylactic acid (PLLA)

[0144] In N 2 In a glove box under N atmosphere, a 10 mL pressure tube with a magnet was dried in an oven at 110 °C overnight and then immediately placed in the glove box. After keeping under vacuum for 2-3 hours, the pressure tube was moved into N 2 In a glove box with a 10 mL pressure tube equipped with a magnetic pole, catalyst 1 (1.0 mg, 2.76 μmol), L-lactide (L-LA, 200 mg, 1.38 mmol), and dichloromethane (DCM, 1.0 mL) were added. The reaction mixture was stirred at 25 ° C for 5 seconds. A portion of the sample was then taken from the crude product and quenched with benzoic acid to pass through 1 The composition of the crude product was determined by H NMR spectroscopy. The crude product was dissolved in CH 2 Cl 2 The polymer was precipitated from the cooled ethanol. The product was collected by centrifugation, and finally the obtained polymer was dried in a vacuum drying oven at 40°C to constant weight. The molecular weight and molecular weight distribution of the polymer were determined by gel chromatography. The test results are shown in Table 1.

[0145] Fig.11 Homonuclear decoupling of the methylene peak prepared for this application example 1 H NMR spectrum. From this figure, it can be confirmed that the polylactic acid prepared in this application example is crystalline.

[0146] Application Examples 2 to 9: Using Catalysts 2 to 9 to Catalyze the Ring Opening of L-Lactide to Produce PLLA

[0147] The preparation process is basically the same as that of Application Example 1, except that the catalysts of the polymerization reaction are replaced with catalysts 2 to 9 in sequence (the molar ratio of L-LA to each catalyst is 500:1). The molecular weight and molecular weight distribution of the polymers prepared in each application example are determined by gel chromatography, and the test results are shown in Table 1.

[0148] Application Examples 10-12: Using Catalysts 1, 6, and 8 to catalyze the ring-opening of L-lactide to generate PLLA

[0149] The preparation process is basically the same as that of application examples 1, 6, and 8, except that the molar ratio of the monomer to the catalyst in the polymerization reaction is replaced with 1000:1. The specific reaction time is shown in Table 1. The molecular weight and molecular weight distribution of the polymer prepared in each application example are determined by gel chromatography, and the test results are shown in Table 1.

[0150] Application Example 13: Using Catalyst 6 to catalyze the ring-opening of valerolactone to generate polyvalerolactone (PVL)

[0151] In N 2 In a glove box under N atmosphere, a 10 mL pressure tube with a magnet was dried in an oven at 110 °C overnight and then immediately placed in the glove box. After keeping under vacuum for 2-3 hours, the pressure tube was moved into N 2 In a glove box with a 10 mL pressure tube equipped with a magnetic pole, catalyst 6 (6.1 mg, 0.0167 mmol), valerolactone (VL, 500 mg, 5 mmol), and DCM (1.0 mL) were added. The reaction mixture was stirred at 25 ° C for 300 seconds. A portion of the sample was then taken from the crude product and quenched with benzoic acid to obtain a 10 mL solution of 10% ethanol. 1 The composition of the crude product was determined by H NMR spectroscopy. The crude product was dissolved in CH 2 Cl 2 The polymer was precipitated from the cooled ethanol. The product was collected by centrifugation, and finally the obtained polymer was dried in a vacuum drying oven at 40°C to constant weight. The molecular weight and molecular weight distribution of the polymer were determined by gel chromatography. The test results are shown in Table 1.

[0152] Application Example 14: Using Catalyst 6 to catalyze the ring-opening of valerolactone to generate PVL

[0153] The preparation process is basically the same as that of Application Example 13, except that the molar ratio of the monomer to the catalyst is replaced with 500:1, and the reaction mixture is stirred at 60°C for 360s. The molecular weight and molecular weight distribution of the polymer prepared in this application example are measured by gel chromatography, and the test results are shown in Table 1.

[0154] Application Example 15: Using Catalyst 6 to catalyze the ring-opening of caprolactone to generate polycaprolactone (PCL)

[0155] In N 2In a glove box under N atmosphere, a 10 mL pressure tube with a magnet was dried in an oven at 110 °C overnight and then immediately placed in the glove box. After keeping under vacuum for 2-3 hours, the pressure tube was moved into N 2 In a glove box with a 10 mL pressure tube equipped with a magnetic pole, catalyst 6 (5.4 mg, 0.015 mmol), caprolactone (CL, 500 mg, 4.38 mmol), and DCM (1.0 mL) were added. The reaction mixture was stirred at 25 °C for 1200 s. A portion of the sample was then taken from the crude product and quenched with benzoic acid to obtain a 10 mL solution of 10% ethanol. 1 The composition of the crude product was determined by H NMR spectroscopy. The crude product was dissolved in CH 2 Cl 2 The polymer was precipitated from the cooled ethanol. The product was collected by centrifugation, and finally the obtained polymer was dried in a vacuum drying oven at 40°C to constant weight. The molecular weight and molecular weight distribution of the polymer were determined by gel chromatography. The test results are shown in Table 1.

[0156] Application Example 16: Using Catalyst 6 to catalyze the ring-opening of caprolactone to generate PCL

[0157] The preparation process is basically the same as that of Application Example 15, except that the molar ratio of the monomer to the catalyst is replaced with 500:1, and the reaction mixture is stirred at 60°C for 1800s. The molecular weight and molecular weight distribution of the polymer prepared in this application example are measured by gel chromatography, and the test results are shown in Table 1.

[0158] Application Comparative Example 1: Ring-opening of L-lactide to generate PLLA using TU-1 / potassium methoxide binary catalyst system

[0159] The preparation process is basically the same as that of Application Example 1, except that the catalyst of the polymerization reaction is replaced with TU-1 / potassium methoxide (the molar ratio of L-LA to TU-1 and potassium methoxide is 500:5:1) provided in Comparative Example 1, and the reaction mixture is stirred at 25°C for 45 minutes. The molecular weight and molecular weight distribution of the polymer are determined by gel chromatography, and the test results are shown in Table 2.

[0160] Application Comparative Example 2: Ring-opening of L-lactide to generate PLLA using TU-1 / sodium methoxide binary catalyst system

[0161] The preparation process is basically the same as that of Application Example 1, except that the catalyst of the polymerization reaction is replaced with TU-1 / sodium methoxide provided in Comparative Example 2 (the molar ratio of L-LA to TU-1 and sodium methoxide is 200:10:1), and the reaction mixture is stirred at 25° C. for 360 s. The molecular weight and molecular weight distribution of the polymer are determined by gel chromatography, and the test results are shown in Table 2.

[0162] Table 1

[0163]

[0164]

[0165] Note: 1 Conv.(%): Monomer conversion rate is 1 H NMR determination. 2 Turnover number (TON) = (moles of monomer consumed) / (moles of catalyst). 3 Turnover frequency (TOF) = (moles of monomer consumed) / (moles of catalyst·minute). 4 Mn Theo : Theoretical number average molecular weight, according to the formula MW mon ×[M] 0 / [I] 0 ×conv. Calculated. 5 M n GPC : Number average molecular weight, determined by gel permeation chromatography. 6 PDI: Molecular weight distribution, determined by gel permeation chromatography.

[0166] Table 2

[0167]

[0168] The above descriptions are only some specific embodiments of the present invention. It should be pointed out that a person skilled in the art can make many modifications and improvements. All modifications and improvements that do not exceed the scope of protection of the present invention should be regarded as within the scope of protection of the present invention.

Claims

1. A monomolecular bifunctional organic catalyst for ring-opening polymerization of cyclic lactones, characterized in that: The structural formula is shown in the following formula (I): X—L—Y(I) In formula (I), X is selected from a group containing urea or thiourea, and the structural formula is shown in formula (II) below: In formula (II): N is a nitrogen atom; R1 is selected from one or more C6-C8 aromatic groups; R2 is selected from O or S; Indicates the connection key; Y is selected from potassium alcoholate or sodium alcoholate group, and the structural formula is shown in the following formula (III): In formula (III): O is an oxygen atom; R3 is selected from Na and / or K; Indicates the connection key; L is selected from unsubstituted C2-C4 alkyl groups.

2. The unimolecular bifunctional organic catalyst for ring-opening polymerization of cyclic lactone according to claim 1, characterized in that: L is selected from unsubstituted C3 alkyl.

3. The unimolecular bifunctional organic catalyst for ring-opening polymerization of cyclic lactone according to claim 1, characterized in that: The structural formula is selected from one or more of the following formulas (I-1) to (I-9):

4. The unimolecular bifunctional organic catalyst for ring-opening polymerization of cyclic lactone according to claim 3, characterized in that: The structural formula is selected from the above formula (I-1), (I-6), (I-7) or (I-8).

5. The unimolecular bifunctional organic catalyst for ring-opening polymerization of cyclic lactone according to claim 3, characterized in that: The structural formula is selected from the above formula (I-1), (I-6), or (I-8).

6. The unimolecular bifunctional organic catalyst for ring-opening polymerization of cyclic lactone according to claim 3, characterized in that: The structural formula is selected from the above formula (I-1) or (I-6).

7. A method for preparing a monomolecular bifunctional organic catalyst for ring-opening polymerization of cyclic lactone according to claim 1, characterized in that: The steps include: A raw material 1 having a structure of the following formula W1, a raw material 2 having a structure of the following formula W2 and a solvent A are mixed to obtain a raw material solution I, and an intermediate product is obtained after Michael addition reaction; The intermediate product, the raw material 3 and the solvent B are mixed to obtain the raw material solution II, and then the raw material solution II is subjected to a substitution reaction to obtain the monomolecular bifunctional organic catalyst; In the formula, O, N, and C represent oxygen atom, nitrogen atom, and carbon atom, respectively; R1 is selected from one or more C6-C8 aromatic groups; R2 is selected from a sulfur atom or an oxygen atom; and R3 is selected from one or more unsubstituted C2-C4 alkyl groups.

8. The method for preparing a monomolecular bifunctional organic catalyst for ring-opening polymerization of cyclic lactone according to claim 7, characterized in that: Raw material 1 is selected from one or more of 3,5-bis(trifluoromethyl)phenyl isothiocyanate, 3,4-dichlorophenyl isothiocyanate, 4-(trifluoromethyl)phenyl isothiocyanate, phenyl isothiocyanate, and 3,5-bis(trifluoromethyl)phenyl isothiocyanate; Raw material 2 is selected from one or more of 3-amino-1-propanol, 4-amino-1-butanol, and 2-amino-1-ethanol; Solvent A is selected from one or more of dichloromethane, tetrahydrofuran, acetone, methanol, ethanol, and isopropanol; The molar ratio of raw material 1 to raw material 2 is 1:(1.0-1.1); the concentration of raw material 2 in raw material solution I is 0.8-1.2 mol / L; The temperature of the Michael addition reaction is 0-80°C; Raw material 3 is selected from metallic sodium and / or metallic potassium; Solvent B is selected from one or more of tetrahydrofuran, dichloromethane, acetone, methanol, ethanol, toluene and chloroform; The molar ratio of the intermediate product to the raw material 3 is 1:(0.9-1.0); the concentration of the intermediate product in the raw material solution II is 1.0-2.0 mol / L; The temperature of the substitution reaction is 0 to 30°C.

9. Use of the unimolecular bifunctional organic catalyst according to any one of claims 1 to 6 in catalyzing the ring-opening polymerization of cyclic lactones, characterized in that: The cyclic lactone is selected from one or more of L-lactide, valerolactone and caprolactone.

10. Use of the unimolecular bifunctional organic catalyst according to claim 9 in catalyzing the ring-opening polymerization of cyclic lactones, characterized in that: The cyclic lactone is selected from L-lactide.

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