A Schiff base catalyst for the copolymerization of epoxide and carbon disulfide
By introducing functional groups such as methyl and fluorine into the catalyst and modifying the Schiff base catalyst, the problems of large number of by-products and long polymerization time in the copolymerization reaction of epoxide and carbon disulfide were solved, and the preparation of high molecular weight and high purity polycarbonate was achieved.
Patent Information
- Application Number
- CN202510033184.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-09
- Publication Date
- 2025-10-03
- Estimated Expiration
- 2045-01-09
AI Technical Summary
Existing Schiff base catalysts produce many by-products and take a long time to polymerize when catalyzing the copolymerization of epoxide and carbon disulfide, making it difficult to produce high molecular weight and high purity polycarbonate products.
By introducing different numbers of functional groups such as methyl and fluorine into the catalyst, the catalyst is modified to improve its selectivity for the reaction, and Schiff base catalysts for the copolymerization of epoxide and carbon disulfide are prepared.
The reaction selectivity of the catalyst is improved, the target polymer with higher molecular weight and smaller dispersion coefficient is obtained, and the performance of the polycarbonate material is improved.
Smart Images
Figure CN119823364B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of Schiff base catalysts, and in particular to a Schiff base catalyst for the copolymerization reaction of epoxide and carbon disulfide. Background Art
[0002] Polycarbonate is a high molecular polymer containing a carbonate group. Due to its excellent thermal stability, impact resistance, creep resistance, and dielectric properties, it is widely used in sealing plastic lenses, preparing high-performance optical fibers, and treating heavy metal-containing wastewater. It has broad application prospects and has attracted widespread attention from researchers. To further improve the solvent resistance of the material, sulfur atoms can be introduced into the polymer backbone to chemically modify it, giving it the properties of sulfur-containing compounds, giving the material good solvent resistance and antioxidant properties, and improving the stability of the material in application.
[0003] Currently, the main processes for synthesizing polythiocarbonates include the polycondensation of acyl chlorides or carbon disulfide with dithiols, the ring-opening homopolymerization of cyclic thiocarbonates, and the ring-opening copolymerization of epoxides with carbon disulfide. The polycondensation of acyl chlorides with dithiols is the most mature, but this process requires the use of the highly toxic raw material phosgene, which poses a threat to the environment. The copolymerization of epoxides with carbon disulfide involves direct copolymerization in the presence of a catalyst to prepare thiocarbonates. This not only avoids the difficulty of controlling the coupling reaction of epoxides with carbon disulfide to prepare thiocarbonates, but also simplifies the synthesis process and reduces production costs. Furthermore, this process can chemically modify the monomers to produce polythiocarbonates modified with various functional groups. In 2007, Nozaki et al. achieved the copolymerization of cyclopropene oxide with carbon disulfide using a Schiff base-zinc catalyst. The addition of a chromium complex accelerated the copolymerization reaction, resulting in a polymer with high regioregularity. Its excellent performance in catalyzing polythiocarbonate reactions has been used to this day.
[0004] Zinc-coordinated Schiff base catalysts have been repeatedly reported to catalyze CO2 / epoxide coupling reactions. CS2 and CO2 share similar structures, making this catalyst a suitable candidate for CS2 / epoxide coupling reactions. However, these catalysts tend to produce a large number of byproducts when catalyzing CS2 / epoxide copolymerization, and the polymerization process takes a long time to reach the desired high molecular weight. Therefore, modification is necessary to enhance the catalyst's selectivity and activity, thereby increasing the molecular weight and purity of the resulting polycarbonate. Summary of the Invention
[0005] In order to solve the above technical problems, the purpose of the present invention is to provide a Schiff base catalyst for the copolymerization of epoxide and carbon disulfide, which introduces different numbers of functional groups such as methyl and fluorine to improve the selectivity of the catalyst for the reaction.
[0006] The present invention solves the above technical problems with the following technical solution: Provided is a Schiff base catalyst for the copolymerization of epoxide and carbon disulfide, the general structural formula of which is:
[0007]
[0008] wherein X1 and X2 are independently MeO, Me, H or F.
[0009] Furthermore, the copolymerization reaction of epoxide and carbon disulfide uses a Schiff base catalyst, the structural formula of which is:
[0010]
[0011]
[0012] The present invention also provides a method for preparing the Schiff base catalyst for the copolymerization reaction of epoxide and carbon disulfide, comprising the following steps:
[0013] (1) Add the anhydrous ethanol solution of 3,5-di-tert-butyl hydroxybenzoic acid aldehyde dropwise to the anhydrous ethanol solution of the amine reagent, stir and heat under reflux for 4 hours, cool to room temperature, filter, recrystallize from anhydrous ethanol, and dry under reduced pressure to obtain the precursor;
[0014] (2) Adding an ethanol solution of zinc acetate dihydrate to the ethanol solution of the precursor obtained in step (1), heating and reflux at 60° C. with stirring for 5 h under nitrogen protection, cooling to room temperature, transferring to water, and extracting with dichloromethane, drying the organic phase, and then filtering, rotary evaporating, recrystallizing, and filtering in sequence to obtain a Schiff base catalyst for the copolymerization of epoxide and carbon disulfide.
[0015] Furthermore, in step (1), the molar ratio of 3,5-di-tert-butyl hydroxybenzoic acid aldehyde to the amine reagent is 1:2.
[0016] Furthermore, in step (1), the molar concentration of the anhydrous ethanol solution of 3,5-di-tert-butyl hydroxybenzoic acid aldehyde is 10 mmol / 20 mL.
[0017] Furthermore, in step (1), the amine reagent is o-phenylenediamine, 4-methyl o-phenylenediamine, 3,4-dimethyl substituted o-phenylenediamine, 4-fluoro o-phenylenediamine, 3,4-fluoro o-phenylenediamine or 4-ether o-phenylenediamine.
[0018] Furthermore, the amine reagent is one of the following:
[0019]
[0020]
[0021] Furthermore, in step (2), the molar ratio of zinc acetate dihydrate to the precursor is 1:1.
[0022] Furthermore, in step (2), the molar concentration of the ethanol solution of zinc acetate dihydrate is 5 mmol / 6 mL; the molar concentration of the ethanol solution of the precursor is 5 mmol / 12 mL.
[0023] Furthermore, in step (2), the product is rotary evaporated at 50° C. until no liquid is evaporated, and then recrystallized using ethanol / methylene chloride in a volume ratio of 1:1.
[0024] The present invention has the following beneficial effects:
[0025] 1. Improve the reaction selectivity of the catalyst for the copolymerization of epoxide and carbon disulfide by simply modifying the existing catalyst.
[0026] 2. By fine-tuning the catalyst modification unit, the target polymer can obtain a higher molecular weight and a smaller dispersion coefficient. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Figure 1 This is the infrared spectrum of the Schiff base catalyst obtained in Example 1;
[0028] Figure 2 This is the infrared spectrum of the Schiff base catalyst obtained in Example 2;
[0029] Figure 3 This is the infrared spectrum of the Schiff base catalyst obtained in Example 3;
[0030] Figure 4 This is the infrared spectrum of the Schiff base catalyst obtained in Example 4;
[0031] Figure 5 This is the infrared spectrum of the Schiff base catalyst obtained in Example 5;
[0032] Figure 6 This is the infrared spectrum of the Schiff base catalyst obtained in Example 6. DETAILED DESCRIPTION
[0033] The principles and features of the present invention are described below. The examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. In the examples, where specific conditions are not specified, conventional conditions or manufacturer-recommended conditions were used. Reagents or instruments used where the manufacturer is not specified are conventional products that can be purchased commercially.
[0034] Example 1
[0035] A Schiff base catalyst for the copolymerization of epoxide and carbon disulfide, the preparation method of which comprises the following steps:
[0036] (1) A solution of 3,5-di-tert-butyl salicylaldehyde (2.34 g, 10 mmol) in anhydrous ethanol (20 mL) was added dropwise to a solution of o-phenylenediamine (2.16 g, 20 mmol) in anhydrous ethanol, stirred and heated under reflux for 4 h, cooled to room temperature, filtered to remove the solvent, recrystallized from anhydrous ethanol, and dried under reduced pressure to obtain the precursor Salen-0 (5.26 g, 79%). The reaction process is as follows:
[0037]
[0038] (2) A solution of zinc acetate dihydrate (1.09 g, 5 mmol) in ethanol (6 mL) was added to a solution of the precursor (2.767 g, 5 mmol) obtained in step (1) in ethanol (12 mL). The mixture was heated to reflux at 60 ° C with stirring for 5 h under nitrogen protection, cooled to room temperature, transferred to 10 mL of water, and extracted with dichloromethane (3×100 mL). The organic phase was dried, filtered, and rotary evaporated at 50 ° C until no liquid was evaporated. It was recrystallized with ethanol / dichloromethanol with a volume ratio of 1:1 and filtered to obtain Salen-ZnO (2.43 g, 81%), a Schiff base catalyst for the copolymerization of epoxide and carbon disulfide.
[0039] The reaction process is:
[0040]
[0041] Example 2
[0042] A Schiff base catalyst for the copolymerization of epoxide and carbon disulfide, the preparation method of which comprises the following steps:
[0043] (1) A solution of 3,5-di-tert-butyl salicylaldehyde (2.34 g, 10 mmol) in anhydrous ethanol (20 mL) was added dropwise to a solution of 4-methyl-o-phenylenediamine (2.35 g, 20 mmol) in anhydrous ethanol, stirred and heated under reflux for 4 h, cooled to room temperature, filtered to remove the solvent, recrystallized from anhydrous ethanol, and dried under reduced pressure to obtain the precursor Salen-1C (5.14 g, 73%). The reaction process is as follows:
[0044]
[0045] (2) A solution of zinc acetate dihydrate (1.09 g, 5 mmol) in ethanol (6 mL) was added to a solution of the precursor (2.91 g, 5 mmol) obtained in step (1) in ethanol (12 mL). The mixture was heated to reflux at 60 ° C. with stirring for 5 h under nitrogen protection. The mixture was cooled to room temperature, transferred to 10 mL of water, and extracted with dichloromethane (3×100 mL). The organic phase was dried, filtered, and rotary evaporated at 50 ° C. until no liquid was evaporated. The mixture was recrystallized with ethanol / dichloromethanol in a volume ratio of 1:1 and filtered to obtain Salen-Zn1C (2.72 g, 86%), a Schiff base catalyst for the copolymerization of epoxide and carbon disulfide.
[0046] The reaction process is:
[0047]
[0048] Example 3
[0049] A Schiff base catalyst for the copolymerization of epoxide and carbon disulfide, the preparation method of which comprises the following steps:
[0050] (1) A solution of 3,5-di-tert-butyl salicylaldehyde (2.34 g, 10 mmol) in anhydrous ethanol (20 mL) was added dropwise to a solution of 3,4-dimethyl-o-phenylenediamine (2.52 g, 20 mmol) in anhydrous ethanol, stirred and heated under reflux for 4 h, cooled to room temperature, filtered to remove the solvent, recrystallized from anhydrous ethanol, and dried under reduced pressure to obtain the precursor Salen-2C (6.27 g, 85%). The reaction process is as follows:
[0051]
[0052] (2) A solution of zinc acetate dihydrate (1.09 g, 5 mmol) in ethanol (6 mL) was added to a solution of the precursor (3.12 g, 5 mmol) obtained in step (1) in ethanol (12 mL). The mixture was heated to reflux at 60 ° C with stirring for 5 h under nitrogen protection, cooled to room temperature, transferred to 10 mL of water, and extracted with dichloromethane (3×100 mL). The organic phase was dried, filtered, and rotary evaporated at 50 ° C until no liquid was evaporated. It was recrystallized with ethanol / dichloromethanol with a volume ratio of 1:1 and filtered to obtain Salen-Zn2C (1.98 g, 63%), a Schiff base catalyst for the copolymerization of epoxide and carbon disulfide.
[0053] The reaction process is:
[0054]
[0055] Example 4
[0056] A Schiff base catalyst for the copolymerization of epoxide and carbon disulfide, the preparation method of which comprises the following steps:
[0057] (1) A solution of 3,5-di-tert-butyl salicylaldehyde (2.34 g, 10 mmol) in anhydrous ethanol (20 mL) was added dropwise to a solution of 4-fluoro-o-phenylenediamine (2.21 g, 20 mmol) in anhydrous ethanol, stirred and heated under reflux for 4 h, cooled to room temperature, filtered to remove the solvent, recrystallized from anhydrous ethanol, and dried under reduced pressure to obtain the precursor Salen-1F (4.66 g, 69%). The reaction process is as follows:
[0058]
[0059] (2) A solution of zinc acetate dihydrate (1.09 g, 5 mmol) in ethanol (6 mL) was added to a solution of the precursor (2.83 g, 5 mmol) obtained in step (1) in ethanol (12 mL). The mixture was heated to reflux at 60 ° C. and stirred for 5 h under nitrogen protection. The mixture was cooled to room temperature, transferred to 10 mL of water, and extracted with dichloromethane (3×100 mL). The organic phase was dried, filtered, and rotary evaporated at 50 ° C. until no liquid was evaporated. The mixture was recrystallized with ethanol / dichloromethanol with a volume ratio of 1:1 and filtered to obtain Salen-Zn1F (2.72 g, 90%), a Schiff base catalyst for the copolymerization of epoxide and carbon disulfide.
[0060] The reaction process is:
[0061]
[0062] Example 5
[0063] A Schiff base catalyst for the copolymerization of epoxide and carbon disulfide, the preparation method of which comprises the following steps:
[0064] (1) A solution of 3,5-di-tert-butyl salicylaldehyde (2.34 g, 10 mmol) in anhydrous ethanol (20 mL) was added dropwise to a solution of 3,4-fluoro-o-phenylenediamine (2.32 g, 20 mmol) in anhydrous ethanol, stirred and heated under reflux for 4 h, cooled to room temperature, filtered to remove the solvent, recrystallized from anhydrous ethanol, and dried under reduced pressure to obtain the precursor Salen-2F (4.95 g, 71%). The reaction process is as follows:
[0065]
[0066] (2) A solution of zinc acetate dihydrate (1.09 g, 5 mmol) in ethanol (6 mL) was added to a solution of the precursor (2.89 g, 5 mmol) obtained in step (1) in ethanol (12 mL). The mixture was heated to reflux at 60 ° C with stirring for 5 h under nitrogen protection, cooled to room temperature, transferred to 10 mL of water, and extracted with dichloromethane (3×100 mL). The organic phase was dried, filtered, and rotary evaporated at 50 ° C until no liquid was evaporated. It was recrystallized with ethanol / dichloromethanol with a volume ratio of 1:1 and filtered to obtain Salen-Zn2F (2.60 g, 86%), a Schiff base catalyst for the copolymerization of epoxide and carbon disulfide.
[0067] The reaction process is:
[0068]
[0069] Example 6
[0070] A Schiff base catalyst for the copolymerization of epoxide and carbon disulfide, the preparation method of which comprises the following steps:
[0071] (1) A solution of 3,5-di-tert-butyl salicylaldehyde (2.34 g, 10 mmol) in anhydrous ethanol (20 mL) was added dropwise to a solution of 4-ether o-phenylenediamine (2.68 g, 20 mmol) in anhydrous ethanol, stirred and heated under reflux for 4 h, cooled to room temperature, filtered to remove the solvent, recrystallized from anhydrous ethanol, and dried under reduced pressure to obtain the precursor Salen-1O (4.53 g, 58%). The reaction process is as follows:
[0072]
[0073] (2) A solution of zinc acetate dihydrate (1.09 g, 5 mmol) in ethanol (6 mL) was added to a solution of the precursor (3.18 g, 5 mmol) obtained in step (1) in ethanol (12 mL). The mixture was heated under reflux at 60° C. with stirring for 5 h under nitrogen protection. The mixture was cooled to room temperature, transferred to 10 mL of water, and extracted with dichloromethane (3×100 mL). The organic phase was dried, filtered, and rotary evaporated at 50° C. until no liquid was evaporated. The mixture was recrystallized with ethanol / dichloromethanol in a volume ratio of 1:1 and filtered to obtain a Schiff base catalyst for the copolymerization of epoxide and carbon disulfide.
[0074] The reaction process is:
[0075]
[0076] Test example
[0077] 1. The molecular structure of the Schiff base catalysts obtained in Examples 1-6 was determined using a Spectrum Two Fourier infrared spectrometer. Potassium bromide was used to prepare the sample. The catalyst and potassium bromide were dried in a vacuum drying oven before testing. The test results are shown in FIG. Figure 1-6 shown.
[0078] Depend on Figure 1-6 It can be seen that no 3400cm -1 The hydroxyl absorption peak at 1562-1531 cm-1 indicates that the coordination reaction has occurred and the metal has been successfully introduced. At the same time, after the metal is coordinated with the ligand, the C=N double bond absorption peak in the ligand appears at 1562-1531 cm-1. -1 The results show that Examples 1-6 all successfully prepared Schiff base catalysts.
[0079] 2. Bis(triphenylphosphorane)ammonium chloride was selected as the catalyst ligand. The commercially available catalyst, Salen-Cr, was first used to determine the catalyst-to-ligand ratio. It was found that polymerization did not proceed without either the additive or the ligand. Ultimately, the molar ratio of epoxide, carbon disulfide, catalyst, and catalyst ligand was determined to be 1000:1000:1:1. The polymer mass was measured using a TP-114 electronic balance, and the molecular weight and dispersity index were determined using a 1260 InfinityGPC gel permeation chromatography system. The results are shown in Table 1.
[0080] The specific process is as follows: methyl 3,4-epoxycyclohexanecarboxylate (300.00 mg, 1.92 mmol) and carbon disulfide (146 mg, 1.92 mmol) are added to a 50 mL round-bottom flask containing 7 mL of toluene, and a certain proportion of catalyst Salen-ZnX and catalyst ligand bis(triphenylphosphorane)ammonium chloride are added. The mixture is refluxed at 110 ° C for 5 hours under argon protection. After the reaction is completed, it is cooled to room temperature and poured into methanol to precipitate a white solid. The solid product is recrystallized using ethanol / dichloromethane with a volume ratio of 1:3, filtered with a circulating water pump, and dried under reduced pressure at 80 ° C to obtain the target polymer.
[0081] Table 1 Polymer molecular weight and dispersity index
[0082]
[0083] As shown in Table 1, compared to the commercialized catalyst Salen-Cr, the Salen-ZnX catalyst of the present invention achieves a higher molecular weight and the most balanced polymer dispersity index when used as a catalyst. This is presumably because the introduction of side chains provides the catalyst molecule with greater steric hindrance, reducing its nucleophilicity and increasing its catalytic activity. The catalyst Salen-2F, which incorporates two fluorine atoms, achieves the highest polymer molecular weight and the most balanced polymer dispersity index. This can be attributed to the electron-withdrawing properties of the fluorine atoms, which significantly alter the electron cloud density at the metal center, facilitating CHO insertion and thus achieving better catalytic activity. These results demonstrate that the present strategy of introducing different side chains into Schiff base catalysts can yield catalysts with improved performance.
[0084] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.
Claims
1. A Schiff base catalyst for the copolymerization of epoxide and carbon disulfide, characterized in that: Its general structural formula is: wherein X1 and X2 are independently MeO, Me, H or F.
2. The Schiff base catalyst for the copolymerization of epoxide and carbon disulfide according to claim 1, wherein Its structural formula is:
3. The method for preparing a Schiff base catalyst for the copolymerization of epoxide and carbon disulfide according to any one of claims 1 to 2, characterized in that: The following steps are involved: (1) Add the anhydrous ethanol solution of 3,5-di-tert-butyl salicylaldehyde dropwise to the anhydrous ethanol solution of the amine reagent, stir and reflux for 4 hours, cool to room temperature, filter, recrystallize from anhydrous ethanol, and dry under reduced pressure to obtain the precursor; (2) Adding an ethanol solution of zinc acetate dihydrate to the ethanol solution of the precursor obtained in step (1), heating and reflux at 60° C. with stirring for 5 h under nitrogen protection, cooling to room temperature, transferring to water, and extracting with dichloromethane, drying the organic phase, and then filtering, rotary evaporating, recrystallizing, and filtering in sequence to obtain a Schiff base catalyst for the copolymerization of epoxide and carbon disulfide.
4. The method for preparing a Schiff base catalyst for the copolymerization of epoxide and carbon disulfide according to claim 3, wherein: In step (1), the molar ratio of 3,5-di-tert-butyl hydroxybenzoic acid aldehyde to the amine reagent is 1:
2.
5. The method for preparing a Schiff base catalyst for the copolymerization of epoxide and carbon disulfide according to claim 3, wherein: In step (1), the molar concentration of the anhydrous ethanol solution of 3,5-di-tert-butyl hydroxybenzoic acid aldehyde is 10 mmol / 20 mL.
6. The method for preparing a Schiff base catalyst for the copolymerization of epoxide and carbon disulfide according to claim 3, wherein: In step (1), the amine reagent is o-phenylenediamine, 4-methyl o-phenylenediamine, 3,4-dimethyl-substituted o-phenylenediamine, 4-fluoro o-phenylenediamine, 3,4-difluoro o-phenylenediamine or 4-ether o-phenylenediamine.
7. The method for preparing a Schiff base catalyst for the copolymerization of epoxide and carbon disulfide according to claim 3, wherein: In step (2), the molar ratio of zinc acetate dihydrate to the precursor is 1:
1.
8. The method for preparing a Schiff base catalyst for the copolymerization of epoxide and carbon disulfide according to claim 3, wherein: In step (2), the molar concentration of the ethanol solution of zinc acetate dihydrate is 5 mmol / 6 mL; the molar concentration of the ethanol solution of the precursor is 5 mmol / 12 mL.
9. The method for preparing a Schiff base catalyst for the copolymerization of epoxide and carbon disulfide according to claim 3, wherein: In step (2), the product is rotary evaporated at 50° C. until no liquid is evaporated, and then recrystallized using ethanol / methylene chloride in a volume ratio of 1:1.