Catalytic system and synthesis method of segmented copolymer

Abstract

The invention provides a catalytic system. The catalytic system comprises a catalyst with a structure as shown in a formula (I) and an initiator. The catalytic system provided by the invention has relatively high activity on different types of ring-opening polymerization reactions, has very high selectivity on monomers, and can be used for block polymerization reactions with precise and controllable sequences; according to the synthesis method provided by the invention, sequential ring-opening copolymerization of different lactide monomers can be directly realized through a one-pot method, and the AB type segmented copolymer is obtained.

Description

Technical Field

[0001] This invention relates to the field of polymer technology, and in particular to a catalytic system and a method for synthesizing block copolymers. Background Technology

[0002] Block copolymers are polymeric materials composed of two or more different monomers linked by covalent bonds. Due to their unique molecular structure, block copolymers exhibit rich physicochemical properties and distinctive microstructural characteristics, leading to their widespread application in self-assembled nanomaterials, drug delivery systems, coatings, membrane materials, and many other fields. The properties of block copolymers are determined by the physicochemical properties of each block and their interactions, thus offering significant advantages in performance regulation. With the continuous development of polymer materials, the synthesis and application of block copolymers have gradually become a research hotspot.

[0003] Currently, the main methods for synthesizing block copolymers include two-step polymerization and one-step polymerization. In the two-step method, the polymerization segment of the first monomer is synthesized first, and then the polymerization of the second monomer is initiated to form a block structure. This method can effectively control the molecular weight and structure of each block, and typically uses different polymerization techniques such as living radical polymerization, cationic polymerization, and ring-opening polymerization. However, this method usually requires separation, purification, and drying operations between different polymerization stages, increasing process complexity and production costs, and may also lead to lower yields or molecular weight inhomogeneity. Compared with the two-step method, one-step polymerization provides a simpler and more efficient solution. In the one-step method, all monomers and initiators can be added simultaneously in the same reaction system, thereby synthesizing multi-segment block copolymers in a single reaction vessel. This method not only simplifies the operation process but also improves synthesis efficiency and reduces reaction losses. However, most current methods for directly synthesizing block copolymers in one step rely on the significant differences in polymerization activity between different source monomers with large structural differences. For example, Chinese patent document CN114456363A (published on May 10, 2022) discloses a block copolymer composed of epoxide, acid anhydride, ε-caprolactone, and carbon dioxide.

[0004] Although existing synthetic methods have met the requirements for block copolymer synthesis to a certain extent, several problems still need to be solved. In particular, when synthesizing block copolymers with multiple structurally similar monomers in the same reaction system, how to precisely control the polymerization rate of each monomer and avoid alternating reactions and side reactions remains a challenging technical problem. Summary of the Invention

[0005] In view of this, the present invention provides a catalytic system that exhibits high activity for different types of ring-opening polymerization reactions and high selectivity for monomers, and can be used for block polymerization reactions with precise and controllable sequence. The synthesis method provided by the present invention can directly achieve sequential ring-opening copolymerization of different lactide monomers in a one-pot process to obtain AB-type block copolymers.

[0006] The present invention provides a catalytic system comprising a catalyst of formula (I) and an initiator of formula (II).

[0007]

[0008] Where R1 is t Bu, CPhMe2, CPh3, Si(CH3)2C(CH3)3, R2 is H, Me, t Bu, Br, NO2 or CPhMe2;

[0009] X is –CH2-C(CH3)2-CH2-, –(CH2)3-, or –C6H4–CH2-;

[0010]

[0011] Where R is i Pr、 t Bu, Bn, Ph(CH2)2, Ph(CH)Ph or Ph(CH)CH2Ph;

[0012] In some specific embodiments, the initiator has the following structures 2a to 2f:

[0013]

[0014] In some specific embodiments, the catalyst with formula (I) structure specifically has the structure of formula 1a-1j:

[0015]

[0016] In some preferred embodiments, the molar ratio of the catalyst to the initiator is 1:1.

[0017] The catalytic system provided by this invention uses compounds of formula 1a-1j as catalysts and compounds of formula 2a-2f as initiators. The composite catalyst formed in situ in the polymerization solvent by compounds of formula 1a-1j and formula 2a-2f has good activity for the ring-opening polymerization of different lactide monomers and high selectivity for the reactants, laying a good foundation for the subsequent synthesis of block copolymers with precise and controllable sequences.

[0018] This invention provides a method for synthesizing block copolymers with structures shown in formula (III) or (IV), using the catalytic system described in any one of the above technical solutions;

[0019]

[0020] Where n and m are both natural numbers greater than or equal to 10;

[0021] R has one of the following structures:

[0022]

[0023] Its synthesis reaction formula is shown below:

[0024]

[0025] The comonomers of this invention are lactide monomers with similar structures, and the two polymerizable monomers have opposite chirality.

[0026] This invention provides a method for synthesizing block copolymers with structures shown in formula (III) or (IV), comprising the following steps:

[0027] S1) Mix the catalyst with the initiator of formula (I) to obtain a composite catalyst;

[0028] S2) The composite catalyst and lactide monomers of different chirities are mixed and polymerized in the presence of a solvent to obtain the product; the lactide monomers of different chirities include lactide monomer and second comonomer;

[0029] The lactide monomer is selected from the structures shown in formula (IV-1) and formula (IV-2):

[0030]

[0031] The second comonomer is selected from the structures shown in formulas (V-3) and (V-4):

[0032]

[0033] The method for synthesizing structural block copolymers provided by the present invention first involves mixing and stirring the catalyst and initiator described in the above scheme under anhydrous and oxygen-free conditions to directly form a composite catalyst in situ.

[0034] In some preferred embodiments, the molar ratio of the catalyst to the initiator is 1:1.

[0035] The specific catalysts and initiators have been clearly described above in this invention, and will not be repeated here.

[0036] The composite catalyst is mixed with lactide monomers of different chirities and polymerized in the presence of a solvent to obtain the product.

[0037] In some preferred embodiments, the molar ratio of the catalyst, initiator and different chiral lactone monomers is 1:1:(50-1000).

[0038] In some preferred embodiments, the molar ratio of the catalyst, initiator, and different chiral lactone monomers is 1:1:(50-900).

[0039] In some preferred embodiments, the molar ratio of the catalyst, initiator, and different chiral lactone monomers is 1:1:(50-800).

[0040] In some preferred embodiments, the molar ratio of the catalyst, initiator, and different chiral lactone monomers is 1:1:(50-500).

[0041] In some preferred embodiments, the molar ratio of the catalyst, initiator, and different chiral lactone monomers is 1:1:(50-300).

[0042] According to the present invention, the molar ratio of lactide monomer and the second comonomer is 1:1.

[0043] According to the present invention, the concentration of the different chiral lactone monomers in the solvent is 0.5 to 2.0 mol / L.

[0044] Specifically, the concentrations can be 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, and 2.0 mol / L.

[0045] The polymerization solvent used in this invention is preferably dichloromethane, trichloromethane, tetrahydrofuran, toluene, or xylene; more preferably toluene.

[0046] In some embodiments, the temperature of the polymerization reaction is 20 to 100°C, specifically 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, or 100°C.

[0047] The polymerization reaction time is 1 to 120 hours; specifically, it can be 1 hour, 5 hours, 10 hours, 15 hours, 20 hours, 24 hours, 25 hours, 30 hours, 40 hours, 50 hours, 60 hours, 70 hours, 80 hours, 90 hours, 100 hours, 110 hours, or 120 hours.

[0048] The inert gas described in this invention includes, but is not limited to, argon.

[0049] In the synthesis method provided by the present invention, after the polymerization reaction is completed, the present invention preferably slowly drips the obtained polymerization product into an excess of methanol to precipitate the copolymer; the present invention does not have a special limitation on the amount of methanol used, as long as the obtained reaction product can be precipitated in a high yield.

[0050] The specific process for directly synthesizing block copolymers from structurally similar lactide monomers in a single step under catalysis, as provided by this invention, is as follows: Because different lactide monomers in the copolymerization system have different side group structures, their polymerization rates differ. Generally, the larger the side group of the lactide monomer, the slower the polymerization rate. Therefore, when these lactide monomers copolymerize with lactide, the aforementioned catalytic system preferentially coordinates with lactide, completing the ring-opening polymerization of lactide. Thus, the chirality of the entire polymer chain terminal is determined by the chirality of the lactide monomer that preferentially undergoes ring-opening. Therefore, under the dual control of the reactivity ratio and the chain-end mechanism, the lactide monomer preferentially completes ring-opening polymerization. After the lactide is consumed, the lactide monomer with the opposite chirality to lactide continues to undergo ring-opening polymerization under the catalysis of the catalyst, thereby directly forming a block copolyester in a one-pot process. Furthermore, in the preferred technical solution provided by the present invention, multiple different types of chiral lactide monomers can be used as reaction monomers simultaneously, thereby further enriching the sequence structure and functional group positions of the synthesized block copolymer and expanding the application range of the polymerization product. Attached Figure Description

[0051] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of the polymer provided in Example 1 of the present invention;

[0052] Figure 2 This is the hydrogen nuclear magnetic resonance spectrum of the polymer provided in Example 2 of the present invention;

[0053] Figure 3 This is the quantitative carbon spectrum of the polymer provided in Example 1 of the present invention;

[0054] Figure 4 This is the quantitative carbon spectrum of the polymer provided in Example 2 of the present invention. Detailed Implementation

[0055] This invention provides a catalytic system and a method for synthesizing block copolymers. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the desired results. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and fall within the scope of protection of this invention. The methods and applications of this invention have been described through preferred embodiments. Those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0056] It should be understood that the expression “one or more of…” individually includes each of the objects described after the expression, as well as various different combinations of two or more of the described objects, unless otherwise understood from the context and usage. The expression “and / or” combined with three or more described objects should be understood to have the same meaning, unless otherwise understood from the context.

[0057] The terms “including,” “having,” or “containing,” including the use of their grammatical synonyms, should generally be understood as open-ended and non-restrictive, for example, not excluding other unstated elements or steps, unless otherwise specifically stated or understood from the context.

[0058] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural.

[0059] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items.

[0060] It should be understood that the order of the steps or the order in which certain actions are performed is not important as long as the invention remains operational. Furthermore, two or more steps or actions can be performed simultaneously.

[0061] The use of any and all instances or exemplary language such as “e.g.” or “including” in this document is merely intended to better illustrate the invention and is not intended to limit the scope of the invention unless the claims are made. No language in this specification should be construed as indicating that any unclaimed element is essential to the practice of the invention.

[0062] Furthermore, the numerical ranges and parameters used to define the present invention are approximate values, and the relevant values ​​in the specific embodiments have been presented as precisely as possible. However, any value inevitably contains standard deviations due to individual test methods. Therefore, unless explicitly stated otherwise, it should be understood that all ranges, quantities, values, and percentages used in this disclosure are modified with the word "approximately." Here, "approximately" generally means an actual value within plus or minus 10%, 5%, 1%, or 0.5% of a particular value or range.

[0063] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0064] The embodiments and comparative examples of this invention describe some examples, in which the embodiments illustrate certain implementations of the invention. However, this does not mean that the effects of the invention can only be achieved in these examples.

[0065] To further illustrate the present invention, the following detailed description of a catalytic system and a method for synthesizing block copolymers provided by the present invention is provided in conjunction with embodiments.

[0066] Example 1:

[0067] Under anhydrous and oxygen-free conditions, 0.08 mmol of catalyst with structure 1a and 0.08 mmol of initiator with structure 2c were added to a polymerization flask containing 0.5 ml of toluene. The mixture was stirred at room temperature for 5 min. Then, 2.0 mmol of L-lactide and 2.0 mmol of lactide monomer with side chain structure 3a and chirality the same as lactide were added to the polymerization flask. 3.5 ml of toluene was then added, and the polymerization flask was placed in a 60 °C oil bath and stirred for 24 h.

[0068] After polymerization, the reaction mixture was precipitated with 50 ml of ethanol to obtain 0.56 g of polymer. Using polystyrene as a standard, the polymer obtained in this example was analyzed by gel permeation chromatography (GPC) to obtain the number-average molecular weight (Mn) of the copolymer. n The concentration was 12.0 kg / mol, and the molecular weight distribution (D) was 1.20. Quantitative analysis was performed using a 600 M ion exchange rate. 13 The chain regularity of the obtained copolymer was analyzed by ¹³C NMR to obtain the isotacticity P of the polymer chain. m The value is 0.75, indicating that its sequence structure is approximately rich in isotactic copolymers.

[0069] Example 2:

[0070] Under anhydrous and oxygen-free conditions, 0.08 mmol of catalyst with structure 1a and 0.08 mmol of initiator with structure 2c were added to a polymerization flask containing 0.5 ml of toluene. The mixture was stirred at room temperature for 5 min. Then, 2.0 mmol of D-lactide and 2.0 mmol of lactide monomer with side chain structure 3a and chirality opposite to that of lactide were added to the polymerization flask. 3.5 ml of toluene was then added, and the polymerization flask was placed in a 60 °C oil bath and stirred for 24 h.

[0071] After polymerization, the reaction mixture was precipitated with 50 ml of ethanol to obtain 0.58 g of polymer. Using polystyrene as a standard, the polymer obtained in this example was analyzed by gel permeation chromatography (GPC) to obtain the number-average molecular weight (Mn) of the copolymer. n The concentration was 11.7 kg / mol, and the molecular weight distribution (D) was 1.10. Quantitative analysis was performed using a 600 M ion exchange rate. 13 The chain regularity of the obtained copolymer was analyzed by ¹³C NMR to obtain the isotacticity P of the polymer chain. m The value is 0.92, indicating that its sequence structure is an isotactic block copolymer.

[0072] Example 3:

[0073] Under anhydrous and oxygen-free conditions, 0.08 mmol of catalyst with structure 1b and 0.08 mmol of initiator with structure 2c were added to a polymerization flask containing 0.5 ml of toluene. The mixture was stirred at room temperature for 5 min. Then, 2.0 mmol of D-lactide and 2.0 mmol of lactide monomer with side chain structure 3a and chirality opposite to that of lactide were added to the polymerization flask. 3.5 ml of toluene was then added, and the polymerization flask was placed in an oil bath at 60 °C and stirred for 24 h.

[0074] After polymerization, the reaction mixture was precipitated with 50 ml of ethanol to obtain 0.56 g of polymer. Using polystyrene as a standard, the polymer obtained in this example was analyzed by gel permeation chromatography (GPC) to obtain the number-average molecular weight (Mn) of the copolymer. n The concentration was 11.5 kg / mol, and the molecular weight distribution was... The value is 1.11. Quantitative analysis was performed using 600M. 13 The chain regularity of the obtained copolymer was analyzed by ¹³C NMR to obtain the isotacticity P of the polymer chain. m The value is 0.90, indicating that its sequence structure is an isotactic block copolymer.

[0075] Example 4:

[0076] Under anhydrous and oxygen-free conditions, 0.08 mmol of the 1c structure catalyst and 0.08 mmol of the 2c structure initiator were added to a polymerization flask containing 0.5 ml of toluene. The mixture was stirred at room temperature for 5 min. Then, 2.0 mmol of D-lactide and 2.0 mmol of a lactide monomer with a 3a side chain structure and opposite chirality to lactide were added to the polymerization flask. 3.5 ml of toluene was then added, and the polymerization flask was placed in a 60 °C oil bath and stirred for 24 h.

[0077] After polymerization, the reaction mixture was precipitated with 50 ml of ethanol to obtain 0.57 g of polymer. Using polystyrene as a standard, the polymer obtained in this example was analyzed by gel permeation chromatography (GPC) to obtain the number-average molecular weight (Mn) of the copolymer. n The concentration was 11.7 kg / mol, and the molecular weight distribution was... The value is 1.11. Quantitative analysis was performed using 600M. 13 The chain regularity of the obtained copolymer was analyzed by ¹³C NMR to obtain the isotacticity P of the polymer chain. m The value is 0.91, indicating that its sequence structure is an isotactic block copolymer.

[0078] Example 5:

[0079] Under anhydrous and oxygen-free conditions, 0.08 mmol of the 1d-structure catalyst and 0.08 mmol of the 2c-structure initiator were added to a polymerization flask containing 0.5 ml of toluene. The mixture was stirred at room temperature for 5 min. Then, 2.0 mmol of D-lactide and 2.0 mmol of a lactide monomer with a 3a side chain structure and opposite chirality to lactide were added to the polymerization flask. 3.5 ml of toluene was then added, and the polymerization flask was placed in a 60 °C oil bath and stirred for 24 h.

[0080] After polymerization, the reaction mixture was precipitated with 50 ml of ethanol to obtain 0.56 g of polymer. Using polystyrene as a standard, the polymer obtained in this example was analyzed by gel permeation chromatography (GPC) to obtain the number-average molecular weight (Mn) of the copolymer. n The concentration was 12.2 kg / mol, and the molecular weight distribution (D) was 1.12. Quantitative analysis was performed using a 600 M ion exchange rate. 13 The chain regularity of the obtained copolymer was analyzed by ¹³C NMR to obtain the isotacticity P of the polymer chain. m The value is 0.91, indicating that its sequence structure is an isotactic block copolymer.

[0081] Example 6:

[0082] Under anhydrous and oxygen-free conditions, 0.08 mmol of catalyst with structure 1e and 0.08 mmol of initiator with structure 2c were added to a polymerization flask containing 0.5 ml of toluene. The mixture was stirred at room temperature for 5 min. Then, 2.0 mmol of D-lactide and 2.0 mmol of lactide monomer with side chain structure 3a and chirality opposite to that of lactide were added to the polymerization flask. 3.5 ml of toluene was then added, and the polymerization flask was placed in an oil bath at 60 °C and stirred for 24 h.

[0083] After polymerization, the reaction mixture was precipitated with 50 ml of ethanol to obtain 0.56 g of polymer. Using polystyrene as a standard, the polymer obtained in this example was analyzed by gel permeation chromatography (GPC) to obtain the number-average molecular weight (Mn) of the copolymer. n The concentration was 11.1 kg / mol, and the molecular weight distribution (D) was 1.09. Quantitative analysis was performed using a 600 M ion exchange rate. 13 The chain regularity of the obtained copolymer was analyzed by ¹³C NMR to obtain the isotacticity P of the polymer chain. m The value is 0.94, indicating that its sequence structure is an isotactic block copolymer.

[0084] Example 7:

[0085] Under anhydrous and oxygen-free conditions, 0.08 mmol of the 1f-structure catalyst and 0.08 mmol of the 2c-structure initiator were added to a polymerization flask containing 0.5 ml of toluene. The mixture was stirred at room temperature for 5 min. Then, 2.0 mmol of D-lactide and 2.0 mmol of a lactide monomer with a 3a side chain structure and opposite chirality to lactide were added to the polymerization flask. 3.5 ml of toluene was then added, and the polymerization flask was placed in a 60 °C oil bath and stirred for 24 h.

[0086] After polymerization, the reaction mixture was precipitated with 50 ml of ethanol to obtain 0.54 g of polymer. Using polystyrene as a standard, the polymer obtained in this example was analyzed by gel permeation chromatography (GPC) to obtain the number-average molecular weight (Mn) of the copolymer. n The concentration was 10.9 kg / mol, and the molecular weight distribution (D) was 1.13. Quantitative analysis was performed using a 600 M ion exchange rate. 13 The chain regularity of the obtained copolymer was analyzed by ¹³C NMR to obtain the isotacticity P of the polymer chain. m The value is 0.91, indicating that its sequence structure is an isotactic block copolymer.

[0087] Example 8:

[0088] Under anhydrous and oxygen-free conditions, 0.08 mmol of the 1h-structure catalyst and 0.08 mmol of the 2c-structure initiator were added to a polymerization flask containing 0.5 ml of toluene. The mixture was stirred at room temperature for 5 min. Then, 2.0 mmol of D-lactide and 2.0 mmol of a lactide monomer with a 3a side chain structure and opposite chirality to lactide were added to the polymerization flask. 3.5 ml of toluene was then added, and the polymerization flask was placed in a 60°C oil bath and stirred for 24 h.

[0089] After polymerization, the reaction mixture was precipitated with 50 ml of ethanol to obtain 0.54 g of polymer. Using polystyrene as a standard, the polymer obtained in this example was analyzed by gel permeation chromatography (GPC) to obtain the number-average molecular weight (Mn) of the copolymer. n The concentration was 11.1 kg / mol, and the molecular weight distribution (D) was 1.10. Quantitative analysis was performed using a 600 M ion exchange rate. 13 The chain regularity of the obtained copolymer was analyzed by ¹³C NMR to obtain the isotacticity P of the polymer chain. m The value is 0.93, indicating that its sequence structure is an isotactic block copolymer.

[0090] Example 9:

[0091] Under anhydrous and oxygen-free conditions, 0.08 mmol of the 1i structure catalyst and 0.08 mmol of the 2c structure initiator were added to a polymerization flask containing 0.5 ml of toluene. The mixture was stirred at room temperature for 5 min. Then, 2.0 mmol of D-lactide and 2.0 mmol of a lactide monomer with a side chain structure of 3a and chirality opposite to that of lactide were added to the polymerization flask. 3.5 ml of toluene was then added, and the polymerization flask was placed in a 60 °C oil bath and stirred for 24 h.

[0092] After polymerization, the reaction mixture was precipitated with 50 ml of ethanol to obtain 0.56 g of polymer. Using polystyrene as a standard, the polymer obtained in this example was analyzed by gel permeation chromatography (GPC) to obtain the number-average molecular weight (Mn) of the copolymer. n The concentration was 11.2 kg / mol, and the molecular weight distribution (D) was 1.09. Quantitative analysis was performed using a 600 M ion exchange rate. 13 The chain regularity of the obtained copolymer was analyzed by ¹³C NMR to obtain the isotacticity P of the polymer chain. m The value is 0.95, indicating that its sequence structure is an isotactic block copolymer.

[0093] Example 10:

[0094] Under anhydrous and oxygen-free conditions, 0.08 mmol of catalyst with structure 1j and 0.08 mmol of initiator with structure 2c were added to a polymerization flask containing 0.5 ml of toluene. The mixture was stirred at room temperature for 5 min. Then, 2.0 mmol of D-lactide and 2.0 mmol of lactide monomer with side chain structure 3a and chirality opposite to that of lactide were added to the polymerization flask. 3.5 ml of toluene was then added, and the polymerization flask was placed in a 60 °C oil bath and stirred for 24 h.

[0095] After polymerization, the reaction mixture was precipitated with 50 ml of ethanol to obtain 0.55 g of polymer. Using polystyrene as a standard, the polymer obtained in this example was analyzed by gel permeation chromatography (GPC) to obtain the number-average molecular weight (Mn) of the copolymer. n The concentration was 10.9 kg / mol, and the molecular weight distribution (D) was 1.12. Quantitative analysis was performed using a 600 M ion exchange rate. 13 The chain regularity of the obtained copolymer was analyzed by ¹³C NMR to obtain the isotacticity P of the polymer chain. m The value is 0.89, indicating that its sequence structure is rich in isotactic copolymers.

[0096] Example 11:

[0097] Under anhydrous and oxygen-free conditions, 0.08 mmol of the catalyst with structure 1i and 0.08 mmol of the initiator with structure 2a were added to a polymerization flask containing 0.5 ml of toluene. The mixture was stirred at room temperature for 5 min. Then, 2.0 mmol of D-lactide and 2.0 mmol of lactide monomer with side chain structure 3a and chirality opposite to that of lactide were added to the polymerization flask. 3.5 ml of toluene was then added, and the polymerization flask was placed in an oil bath at 60 °C and stirred for 24 h.

[0098] After polymerization, the reaction mixture was precipitated with 50 ml of ethanol to obtain 0.56 g of polymer. Using polystyrene as a standard, the polymer obtained in this example was analyzed by gel permeation chromatography (GPC) to obtain the number-average molecular weight (Mn) of the copolymer. n The concentration was 11.4 kg / mol, and the molecular weight distribution (D) was 1.12. Quantitative analysis was performed using a 600 M ion exchange rate. 13 The chain regularity of the obtained copolymer was analyzed by ¹³C NMR to obtain the isotacticity P of the polymer chain. m The value is 0.95, indicating that its sequence structure is an isotactic block copolymer.

[0099] Example 12:

[0100] Under anhydrous and oxygen-free conditions, 0.08 mmol of the catalyst with structure 1i and 0.08 mmol of the initiator with structure 2a were added to a polymerization flask containing 0.5 ml of toluene. The mixture was stirred at room temperature for 5 min. Then, 2.0 mmol of D-lactide and 2.0 mmol of lactide monomer with side chain structure 3a and chirality opposite to that of lactide were added to the polymerization flask. 1.5 ml of toluene was then added, and the polymerization flask was placed in an oil bath at 60 °C and stirred for 12 h.

[0101] After polymerization, the reaction mixture was precipitated with 50 ml of ethanol to obtain 0.56 g of polymer. Using polystyrene as a standard, the polymer obtained in this example was analyzed by gel permeation chromatography (GPC) to obtain the number-average molecular weight (Mn) of the copolymer. n The concentration was 11.6 kg / mol, and the molecular weight distribution (D) was 1.12. Quantitative analysis was performed using a 600 M ion exchange rate. 13 The chain regularity of the obtained copolymer was analyzed by ¹³C NMR to obtain the isotacticity P of the polymer chain. m The value is 0.94, indicating that its sequence structure is an isotactic block copolymer.

[0102] Example 13:

[0103] Under anhydrous and oxygen-free conditions, 0.08 mmol of the 1i structure catalyst and 0.08 mmol of the 2c structure initiator were added to a polymerization flask containing 0.5 ml of dichloromethane. The mixture was stirred at room temperature for 5 min. Then, 2.0 mmol of D-lactide and 2.0 mmol of a lactide monomer with a 3a side chain structure and opposite chirality to lactide were added to the polymerization flask. 3.5 ml of dichloromethane was then added, and the polymerization flask was placed in an oil bath at 40 °C and stirred for 120 h.

[0104] After polymerization, the reaction mixture was precipitated with 50 ml of ethanol to obtain 0.53 g of polymer. Using polystyrene as a standard, the polymer obtained in this example was analyzed by gel permeation chromatography (GPC) to obtain the number-average molecular weight (Mn) of the copolymer. n The concentration was 10.7 kg / mol, and the molecular weight distribution (D) was 1.11. Quantitative analysis was performed using a 600 M ion exchange rate. 13 The chain regularity of the obtained copolymer was analyzed by ¹³C NMR to obtain the isotacticity P of the polymer chain. m The value is 0.97, indicating that its sequence structure is a highly isotactic block copolymer.

[0105] Example 14:

[0106] Under anhydrous and oxygen-free conditions, 0.08 mmol of the 1i structure catalyst and 0.08 mmol of the 2c structure initiator were added to a polymerization flask containing 0.5 ml of toluene. The mixture was stirred at room temperature for 5 min. Then, 2.0 mmol of D-lactide and 2.0 mmol of a lactide monomer with a side chain structure of 3a and chirality opposite to that of lactide were added to the polymerization flask. 3.5 ml of toluene was then added, and the polymerization flask was placed in an oil bath at 80 °C and stirred for 15 h.

[0107] After polymerization, the reaction mixture was precipitated with 50 ml of ethanol to obtain 0.55 g of polymer. Using polystyrene as a standard, the polymer obtained in this example was analyzed by gel permeation chromatography (GPC) to obtain the number-average molecular weight (Mn) of the copolymer. n The concentration was 10.6 kg / mol, and the molecular weight distribution (D) was 1.10. Quantitative analysis was performed using a 600 M ion exchange rate. 13 The chain regularity of the obtained copolymer was analyzed by ¹³C NMR to obtain the isotacticity P of the polymer chain. m The value is 0.94, indicating that its sequence structure is an isotactic block copolymer.

[0108] Example 15:

[0109] Under anhydrous and oxygen-free conditions, 0.08 mmol of the 1i structure catalyst and 0.08 mmol of the 2c structure initiator were added to a polymerization flask containing 0.5 ml of toluene. The mixture was stirred at room temperature for 5 min. Then, 2.0 mmol of D-lactide and 2.0 mmol of a lactide monomer with a side chain structure of 3a and chirality opposite to that of lactide were added to the polymerization flask. 3.5 ml of toluene was then added, and the polymerization flask was placed in an oil bath at 40 °C and stirred for 100 h.

[0110] After polymerization, the reaction mixture was precipitated with 50 ml of ethanol to obtain 0.54 g of polymer. Using polystyrene as a standard, the polymer obtained in this example was analyzed by gel permeation chromatography (GPC) to obtain the number-average molecular weight (Mn) of the copolymer. n The concentration was 10.4 kg / mol, and the molecular weight distribution (D) was 1.10. Quantitative analysis was performed using a 600 M ion exchange rate. 13 The chain regularity of the obtained copolymer was analyzed by ¹³C NMR to obtain the isotacticity P of the polymer chain. m The value is 0.97, indicating that its sequence structure is a highly isotactic block copolymer.

[0111] Example 16:

[0112] Under anhydrous and oxygen-free conditions, 0.08 mmol of the 1i structure catalyst and 0.08 mmol of the 2c structure initiator were added to a polymerization flask containing 0.5 ml of toluene. The mixture was stirred at room temperature for 5 min. Then, 2.0 mmol of D-lactide and 2.0 mmol of a lactide monomer with a side chain structure of 3a and chirality opposite to that of lactide were added to the polymerization flask. 3.5 ml of toluene was then added, and the polymerization flask was placed at 20 °C and stirred for 240 h.

[0113] After polymerization, the reaction mixture was precipitated with 50 ml of ethanol to obtain 0.52 g of polymer. Using polystyrene as a standard, the polymer obtained in this example was analyzed by gel permeation chromatography (GPC) to obtain the number-average molecular weight (Mn) of the copolymer. n The concentration was 9.7 kg / mol, and the molecular weight distribution was... The value is 1.13. Quantitative analysis was performed using 600M. 13 The chain regularity of the obtained copolymer was analyzed by ¹³C NMR to obtain the isotacticity P of the polymer chain. m The value is 0.94, indicating that its sequence structure is an isotactic block copolymer.

[0114] Example 17:

[0115] Under anhydrous and oxygen-free conditions, 0.04 mmol of the 1i structure catalyst and 0.04 mmol of the 2c structure initiator were added to a polymerization flask containing 0.5 ml of toluene. The mixture was stirred at room temperature for 5 min. Then, 2.0 mmol of D-lactide and 2.0 mmol of a lactide monomer with a side chain structure of 3a and chirality opposite to that of lactide were added to the polymerization flask. 1.5 ml of toluene was then added, and the polymerization flask was placed in a 60 °C oil bath and stirred for 48 h.

[0116] After polymerization, the reaction mixture was precipitated with 50 ml of ethanol to obtain 0.55 g of polymer. Using polystyrene as a standard, the polymer obtained in this example was analyzed by gel permeation chromatography (GPC) to obtain the number-average molecular weight (Mn) of the copolymer. n The concentration was 21.3 kg / mol, and the molecular weight distribution (D) was 1.10. Quantitative analysis was performed using a 600 M ion exchange rate. 13 The chain regularity of the obtained copolymer was analyzed by ¹³C NMR to obtain the isotacticity P of the polymer chain. m The value is 0.94, indicating that its sequence structure is an isotactic block copolymer.

[0117] Example 18:

[0118] Under anhydrous and oxygen-free conditions, 0.008 mmol of the 1i structure catalyst and 0.008 mmol of the 2c structure initiator were added to a polymerization flask containing 0.5 ml of toluene. The mixture was stirred at room temperature for 5 min. Then, 2.0 mmol of D-lactide and 2.0 mmol of a lactide monomer with a side chain structure of 3a and chirality opposite to that of lactide were added to the polymerization flask. 1.5 ml of toluene was then added, and the polymerization flask was placed in an oil bath at 60 °C and stirred for 120 h.

[0119] After polymerization, the reaction mixture was precipitated with 50 ml of ethanol to obtain 0.53 g of polymer. Using polystyrene as a standard, the polymer obtained in this example was analyzed by gel permeation chromatography (GPC) to obtain the number-average molecular weight (Mn) of the copolymer. n The concentration was 90.4 kg / mol, and the molecular weight distribution (D) was 1.11. Quantitative analysis was performed using a 600 M ion exchange rate. 13 The chain regularity of the obtained copolymer was analyzed by ¹³C NMR to obtain the isotacticity P of the polymer chain. m The value is 0.93, indicating that its sequence structure is an isotactic block copolymer.

[0120] Example 19:

[0121] Under anhydrous and oxygen-free conditions, 0.08 mmol of the 1i structure catalyst and 0.08 mmol of the 2c structure initiator were added to a polymerization flask containing 0.5 ml of toluene. The mixture was stirred at room temperature for 5 min. Then, 2.0 mmol of D-lactide and 2.0 mmol of a lactide monomer with a 3e side chain structure and opposite chirality to lactide were added to the polymerization flask. 7.5 ml of toluene was then added, and the polymerization flask was placed in a 60 °C oil bath and stirred for 60 h.

[0122] After polymerization, the reaction mixture was precipitated with 50 ml of ethanol to obtain 0.66 g of polymer. Using polystyrene as a standard, the polymer obtained in this example was analyzed by gel permeation chromatography (GPC) to obtain the number-average molecular weight (Mn) of the copolymer. n The concentration was 12.2 kg / mol, and the molecular weight distribution (D) was 1.14. Quantitative analysis was performed using a 600 M ion exchange rate. 13 The chain regularity of the obtained copolymer was analyzed by ¹³C NMR to obtain the isotacticity P of the polymer chain. m The value is 0.96, indicating that its sequence structure is a highly isotactic block copolymer.

[0123] Example 20:

[0124] Under anhydrous and oxygen-free conditions, 0.08 mmol of the 1i structure catalyst and 0.08 mmol of the 2c structure initiator were added to a polymerization flask containing 0.5 ml of toluene. The mixture was stirred at room temperature for 5 min. Then, 2.0 mmol of D-lactide and 2.0 mmol of a lactide monomer with a side chain structure of 3h and chirality opposite to that of lactide were added to the polymerization flask. 7.5 ml of toluene was then added, and the polymerization flask was placed in a 60°C oil bath and stirred for 60 h.

[0125] After polymerization, the reaction mixture was precipitated with 50 ml of ethanol to obtain 0.78 g of polymer. Using polystyrene as a standard, the polymer obtained in this example was analyzed by gel permeation chromatography (GPC) to obtain the number-average molecular weight (Mn) of the copolymer. n The concentration was 12.5 kg / mol, and the molecular weight distribution (D) was 1.15. Quantitative analysis was performed using a 600 M ion exchange rate. 13 The chain regularity of the obtained copolymer was analyzed by ¹³C NMR to obtain the isotacticity P of the polymer chain. m The value is 0.96, indicating that its sequence structure is a highly isotactic block copolymer.

[0126] Comparative Example 1:

[0127] Under anhydrous and oxygen-free conditions, 0.08 mmol of commercial catalyst Sn(Oct)2 and 0.08 mmol of initiator with a 2c structure were added to a polymerization flask containing 0.5 ml of toluene. The mixture was stirred at room temperature for 5 min. Then, 2.0 mmol of L-lactide and 2.0 mmol of lactide monomer with a 3a side chain structure and the same chirality as lactide were added to the polymerization flask. 3.5 ml of toluene was then added, and the polymerization flask was placed in a 60 °C oil bath and stirred for 24 h.

[0128] After polymerization, the reaction mixture was precipitated with 50 ml of ethanol to obtain 0.58 g of polymer. Using polystyrene as a standard, the polymer obtained in this example was analyzed by gel permeation chromatography (GPC), revealing a number-average molecular weight (Mn) of 10.5 kg / mol and a molecular weight distribution of... The isotacticity (Pm) of the obtained copolymer was 1.41. The chain regularity of the copolymer was analyzed using 600M quantitative 13C NMR, and the isotacticity Pm of the polymer chain was found to be 0.52, indicating that its sequence structure is approximately a random copolymer.

[0129] Comparative Example 2:

[0130] Under anhydrous and oxygen-free conditions, 0.08 mmol of commercial catalyst Sn(Oct)2 and 0.08 mmol of initiator with a 2c structure were added to a polymerization flask containing 0.5 ml of toluene. The mixture was stirred at room temperature for 5 min. Then, 2.0 mmol of L-lactide and 2.0 mmol of lactide monomer with a 3a side chain structure and opposite chirality to lactide were added to the polymerization flask. 3.5 ml of toluene was then added, and the polymerization flask was placed in a 60 °C oil bath and stirred for 24 h.

[0131] After polymerization, the reaction mixture was precipitated with 50 ml of ethanol to obtain 0.60 g of polymer. Using polystyrene as a standard, the polymer obtained in this example was analyzed by gel permeation chromatography (GPC), revealing a number-average molecular weight (Mn) of 11.2 kg / mol and a molecular weight distribution of... The isotacticity (Pm) of the obtained copolymer was 1.38. The chain regularity of the copolymer was analyzed by 600M quantitative 13C NMR, and the isotacticity Pm of the polymer chain was found to be 0.54, indicating that its sequence structure is approximately a random copolymer.

[0132] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A catalytic system comprising a catalyst of formula (I) and an initiator of formula (II); in, R1 is t Bu, CPhMe2, CPh3, Si(CH3)2C(CH3)3, R2 is H, Me, t Bu, Br, NO2 or CPhMe2; X is –CH2–C(CH3)2–CH2–, –(CH2)3-, or –C6H4–CH2–; Where R is i Pr, t Bu, Bn, Ph(CH2)2, Ph(CH)Ph or Ph(CH)CH2Ph.

2. The catalytic system according to claim 1, characterized in that, The initiator has the following structures 2a to 2f:

3. The catalytic system according to claim 1, characterized in that, The catalyst with the structure of formula (I) specifically has the structure of formula 1a-1j:

4. The catalytic system according to claim 1, characterized in that, The molar ratio of the catalyst to the initiator is 1:

1.

5. A method for synthesizing block copolymers with structures shown in formula (III) or (IV), characterized in that, The catalytic system described in any one of claims 1 to 3 is used; Where n and m are both natural numbers greater than or equal to 10; R has one of the following structures:

6. A method for synthesizing block copolymers with structures shown in formula (III) or (IV), characterized in that, Includes the following steps: S1) Mix the catalyst with the initiator of formula (I) to obtain a composite catalyst; S2) The composite catalyst and lactide monomers of different chirities are mixed and polymerized in the presence of a solvent to obtain the product; the lactide monomers of different chirities include lactide monomer and second comonomer; The lactide monomer is selected from the structures shown in formula (V-1) and formula (V-2): The second comonomer is selected from the structures shown in formulas (V-3) and (V-4):

7. The method according to claim 6, characterized in that, The molar ratio of the catalyst, initiator, and different chiral lactide monomers is 1:1:(50-1000).

8. The method according to claim 6, characterized in that, The concentration of the different chiral lactone monomers in the solvent is 0.5–2.0 mol / L.

9. The method according to claim 6, characterized in that, The polymerization solvent is preferably dichloromethane, trichloromethane, tetrahydrofuran, toluene, or xylene.

10. The method according to claim 6, characterized in that, The polymerization reaction is carried out at a temperature of 20–100°C for a time of 1–120 h. The inert gas includes argon.

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