A method for preparing a crosslinked polymer

Abstract

The application relates to a preparation method of a crosslinked polymer and belongs to the technical field of polymer preparation. The preparation method of the crosslinked polymer provided by the application comprises the following steps: (1) mixing reactant A and reactant B to perform an esterification reaction to obtain an esterification product; (2) dissolving a crosslinking agent in the obtained esterification product and standing for solidification, so that the crosslinked polymer is obtained; the reactant A is a polyether polyol containing at least three hydroxyl groups; the reactant B is 4-(cyclopenta-2,4-dien-1-ylidene) pentanoic acid; and the crosslinking agent contains a maleimide group. The application constructs a fulvene-maleimide D-A reaction system capable of being rapidly crosslinked under low-temperature conditions by end-capping fulvene at the end of a polyether polyol and then adding a crosslinking agent with a maleimide group.

Description

Technical Field

[0001] This invention belongs to the field of polymer preparation technology, and specifically relates to a method for preparing cross-linked polymers. Background Technology

[0002] The Diels-Alder (DA) reaction is a reaction in which a six-membered ring is formed from a diene and a dienophile. It is a [4+2] cycloaddition reaction. Since the atom utilization rate is 100%, no by-products are generated during the reaction. Therefore, the reaction system is very pure without the need for a catalyst, and the cross-linked polymer obtained is also very pure. It has good application prospects in the fields of biology and medicine.

[0003] However, the commonly used DA reaction system (furan-maleimide system) requires high-temperature conditions to proceed (often taking several days), and existing DA reaction systems cannot be used to construct cross-linking systems under low-temperature conditions. Furthermore, the energy consumption at high temperatures is too high, hindering widespread adoption.

[0004] Therefore, it is of great significance to construct a DA crosslinking system that can react under low temperature conditions. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems existing in the prior art and provide a method for preparing crosslinked polymers using a DA reaction system that can be constructed at a lower temperature.

[0006] This invention is achieved through the following technical solution:

[0007] This invention provides a method for preparing a crosslinked polymer, comprising the following steps:

[0008] (1) Mix reactant A and reactant B to carry out esterification reaction to obtain esterified product;

[0009] (2) Dissolve the crosslinking agent in the obtained esterification product, let it stand to solidify, and the crosslinked polymer is obtained;

[0010] The reactant A is a polyether polyol containing at least three hydroxyl groups; the reactant B is 4-(cyclopentan-2,4-diene-1-yl)valeric acid; and the crosslinking agent contains maleimide groups.

[0011] Since the reaction temperature of the DA reaction is related to the structure of the conjugated diene and the dienophile in the reaction system, the stronger the electron-richness of the conjugated diene and the stronger the electron-deficientness of the dienophile, the faster the DA reaction rate and the lower the required reaction temperature. Rich-enene is a cyclic diene with electron-rich conjugated double bonds. Compared with commonly used cyclic conjugated dienes like furans, rich-enene has higher electron-richness, and its DA reaction with maleimide can proceed rapidly at room temperature. This invention uses 4-(cyclopentan-2,4-diene-1-yl)valeric acid containing rich-enene groups to undergo an esterification reaction with a polyether polyol. The polyether polyol is end-capped with rich-enene groups, and the resulting esterification product is a crosslinking monomer. This crosslinking monomer can be crosslinked and cured with a crosslinking agent containing maleimide groups at room temperature (10℃-25℃). The preparation method of this invention is simple and energy-efficient. By introducing a fumonisin-maleimide DA reaction system, a DA crosslinking system that can react rapidly at room temperature without the need for a dispersant is constructed. Since no byproducts are generated after the DA reaction is complete, the crosslinked polymer prepared by the method of this invention can be used to synthesize biomedical materials such as gels for culturing bacteria at room temperature.

[0012] The structural formula of the 4-(cyclopentan-2,4-diene-1-yl)pentanoic acid is shown in Formula I:

[0013]

[0014] As a preferred embodiment of the crosslinking polymer preparation method of the present invention, the preparation method of reactant B includes the following steps: in an inert gas atmosphere, levulinic acid, cyclopentadiene, and pyrrolidine are reacted in a mixed solution of methanol and triethylamine in the dark by stirring, acidification, extraction, washing, and drying to obtain reactant B.

[0015] In a preferred embodiment of the crosslinking polymer preparation method of the present invention, the molecular weight of reactant A is 900-1600.

[0016] The molecular weight of reactant A has little effect on the construction of the crosslinking system. Therefore, the present invention preferably uses reactant A with the above-mentioned molecular weight to construct the crosslinking polymer.

[0017] In a preferred embodiment of the crosslinking polymer preparation method of the present invention, reactant A is polyoxyethyl glycerol ether.

[0018] In a preferred embodiment of the crosslinking polymer preparation method of the present invention, in step (2), the amount of crosslinking agent added is 16%-40% of the mass of the esterification product.

[0019] Adding too little crosslinking agent will prevent film formation, while adding too much crosslinking agent will only result in unreacted crosslinking agent in the system, causing a waste of resources.

[0020] In a preferred embodiment of the crosslinking polymer preparation method of the present invention, the crosslinking agent is 4,4'-bismaleimide diphenylmethane or tris(2-maleimide ethyl)amine.

[0021] The DA crosslinking system constructed by the present invention, based on the fumonisin-maleimide system, can be rapidly constructed at room temperature. When 4,4'-bismaleimide diphenylmethane or tris(2-maleimide ethyl)amine is used as a crosslinking agent, the crosslinking reaction can be carried out under solvent-free and catalyst-free conditions because the agent is soluble in the resulting esterification product. The crosslinking system is more pure, and the crosslinking system constructed by this DA reaction system is extremely pure, showing good prospects in the fields of biology and medicine.

[0022] In a preferred embodiment of the crosslinked polymer preparation method of the present invention, the temperature during static curing in step (2) is 10℃-25℃. The crosslinking system of the present invention can be crosslinked and cured at low temperature to obtain a crosslinked polymer.

[0023] This invention does not limit the ratio of reactant A to reactant B; any reaction involving esterification can be carried out. In one specific embodiment of this invention, the mass ratio of reactant A to reactant B is 4:1.62.

[0024] In a preferred embodiment of the crosslinking polymer preparation method of the present invention, in step (1), the catalyst for the esterification reaction is 4-dimethylaminopyridine (DMAP), and the coupling agent is N,N'-dicyclohexylcarbodiimide (DCC).

[0025] In a preferred embodiment of the crosslinking polymer preparation method of the present invention, in step (1), the reaction temperature of the esterification reaction is 10℃-25℃ and the time is 18h-36h.

[0026] Preferably, in step (1), the solvent for the esterification reaction is an organic solvent; more preferably, the organic solvent is dichloromethane.

[0027] Specifically, the experimental procedure for the esterification reaction is as follows: reactant A and reactant B are dissolved in dichloromethane, then a catalyst and coupling agent are added, and the reaction is carried out at 10℃-25℃ for 18h-36h. After filtration, the solvent is removed by rotary evaporation of the filtrate, the residue is washed, and the product is dried under vacuum to obtain the esterification product.

[0028] Another object of the present invention is to provide a crosslinked polymer obtained by a method for preparing the crosslinked polymer.

[0029] The preparation method of this invention introduces a fumonisin-maleimide DA reaction system, which enables the DA reaction to proceed rapidly at room temperature. The cross-linked polymer obtained after the reaction is complete has no byproducts and can be used to synthesize biomedical materials such as gels for culturing bacteria under room temperature conditions.

[0030] Preferably, the crosslinked polymer has the structural formula shown in Formula II:

[0031]

[0032] In Equation II, n is 6 to 12; R1 is R2 is

[0033] This invention offers the following advantages: By end-capping polyether polyols with olefins and then adding a crosslinking agent with maleimide groups, a rapid crosslinking system of olefin-maleimide DA reaction capable of low-temperature crosslinking is constructed. Since no byproducts are generated after the DA reaction is complete, the crosslinked polymer prepared by this method can be used for the synthesis of biomedical materials such as gels for culturing bacteria at room temperature. Attached Figure Description

[0034] Figure 1 This is the general reaction formula for the esterification reaction of 4-(cyclopentan-2,4-diene-1-yl)valeric acid with polyoxyethyl glycerol ether in Example 1 of the present invention;

[0035] Figure 2 This is the general reaction formula for the crosslinking of the esterified product obtained in Example 1 of the present invention with 4,4'-bismaleimide diphenylmethane via a DA reaction;

[0036] Figure 3 Thermogravimetric analysis curve of the crosslinked polymer in Example 1 of the present invention;

[0037] Figure 4 The 1H NMR spectrum of 4-(cyclopenta-2,4-diene-1-yl)valeric acid and the esterification product obtained by the esterification reaction in Example 1 of this invention.

[0038] Figure 5 The infrared spectra of 4-(cyclopentan-2,4-diene-1-yl)valeric acid and the esterification product obtained by the esterification reaction in Example 1 of the present invention are shown, wherein FXP is 4-(cyclopentan-2,4-diene-1-yl)valeric acid and PEG+FXP is the esterification product.

[0039] Figure 6 The infrared spectra of the esterification product and crosslinked polymer of Example 1 of the present invention are shown, wherein PEG+FXP is the esterification product and PEG+FXP+BMP is the crosslinked polymer. Detailed Implementation

[0040] To better illustrate the objectives, technical solutions, and advantages of this invention, the invention will be further described below with reference to specific embodiments. Those skilled in the art should understand that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0041] Unless otherwise specified, the experimental methods used in the examples are conventional methods; the materials and reagents used are commercially available unless otherwise specified.

[0042] Example 1

[0043] A method for preparing a crosslinked polymer is as follows:

[0044] (1) Dissolve 1.62 g of 4-(cyclopentan-2,4-diene-1-yl)valeric acid and 4 g of polyoxyethyl glycerol ether (molecular weight 1200) in 50 ml of dichloromethane. After complete dissolution, add 3.1 g of N,N'-dicyclohexylcarbodiimide (DCC) and 0.31 g of 4-dimethylaminopyridine (DMAP) to the system and react at 25 °C for 24 h. After the reaction is completed, filter the reaction solution, remove the solvent by rotary evaporation of the filtrate, wash the residue three times with 10 ml of ice-cold ether, and dry under vacuum at room temperature to obtain the esterified product (4-(cyclopentan-2,4-diene-1-yl)valeric acid-terminated polyoxyethyl glycerol ether monomer).

[0045] (2) Dissolve 0.317g of 4,4'-bismaleimide diphenylmethane in 1g of the esterification product obtained in step (1). After the crosslinking agent is completely dissolved, pour it into a polytetrafluoroethylene mold for crosslinking and curing. It can be completely cured at 25°C for 1 hour to obtain the crosslinked polymer.

[0046] The synthesis method of 4-(cyclopentan-2,4-diene-1-yl)valeric acid is as follows:

[0047] Under argon protection, levulinic acid (4.0 g, 34 mmol) and freshly distilled cyclopentadiene (7.1 mL, 92 mmol) were dissolved in methanol (35 mL). Then, a solution of pyrrolidine (0.60 mL, 6.9 mmol) in triethylamine (7.0 mL, 50 mmol) was added dropwise over 10 min with stirring. The solution was stirred in the dark under argon and ambient temperature for 12 h. The mixture was acidified with acetic acid (1.5 mL) and methanol was removed under vacuum. Diethyl ether (100 mL) and water (100 mL) were added to the residue. The organic layer was collected, washed with water (5 × 50 mL) and brine (3 × 50 mL), dried with anhydrous MgSO4, and filtered. The filtrate was concentrated under vacuum. The residue was recrystallized from hexane to give 5.35 g (94.5%) of yellow crystals, which is 4-(cyclopentan-2,4-dien-1-yl)pentanoic acid. Figure 1 The general reaction formula for the esterification reaction of 4-(cyclopent-2,4-diene-1-yl)valeric acid with polyoxyethyl glycerol ether in step (1) to obtain the esterified product; Figure 2 The general formula for the crosslinking reaction of the esterified product obtained in step (1) with 4,4'-bismaleimide diphenylmethane via a DA reaction is given.

[0048] Example 2

[0049] A method for preparing a crosslinked polymer is as follows:

[0050] (1) 1.62 g of 4-(cyclopentan-2,4-diene-1-yl)valeric acid and 4 g of polyoxyethyl glycerol ether (molecular weight 1600) were dissolved in 50 ml of dichloromethane. After complete dissolution, 3.1 g of N,N'-dicyclohexylcarbodiimide (DCC) and 0.31 g of 4-dimethylaminopyridine (DMAP) were added to the system and reacted at 25 °C for 24 h. After the reaction was completed, the reaction solution was filtered, the solvent was removed by rotary evaporation, and the residue was washed three times with 10 ml of ice-cold ether and dried under vacuum at room temperature to obtain the esterified product (4-(cyclopentan-2,4-diene-1-yl)valeric acid-terminated polyoxyethyl glycerol ether monomer); the synthesis method of 4-(cyclopentan-2,4-diene-1-yl)valeric acid was the same as in Example 1.

[0051] (2) Dissolve 0.318g of 4,4'-bismaleimide diphenylmethane in 1g of the esterification product obtained in step (1). After the crosslinking agent is completely dissolved, pour it into a polytetrafluoroethylene mold for crosslinking and curing. It can be completely cured at 25°C for 1 hour to obtain the crosslinked polymer.

[0052] Example 3

[0053] A method for preparing a crosslinked polymer is as follows:

[0054] (1) 1.62 g of 4-(cyclopentan-2,4-diene-1-yl)valeric acid and 4 g of polyoxyethyl glycerol ether (molecular weight 1600) were dissolved in 50 ml of dichloromethane. After complete dissolution, 3.1 g of N,N'-dicyclohexylcarbodiimide (DCC) and 0.31 g of 4-dimethylaminopyridine (DMAP) were added to the system and reacted at 25 °C for 24 h. The reaction solution was filtered after the reaction was completed, the solvent was removed by rotary evaporation of the filtrate, and the residue was washed three times with 10 ml of ice-cold ether and dried under vacuum at room temperature to obtain the esterified product (4-(cyclopentan-2,4-diene-1-yl)valeric acid-terminated polyoxyethyl glycerol ether monomer); the synthesis method of 4-(cyclopentan-2,4-diene-1-yl)valeric acid is the same as in Example 1;

[0055] (2) Dissolve 0.386g of tris(2-maleimide ethyl)amine in 1g of the esterification product obtained in step (1). After the crosslinking agent is completely dissolved, pour it into a polytetrafluoroethylene mold for crosslinking and curing. It can be completely cured at 25°C for 1 hour to obtain the crosslinked polymer.

[0056] Example 4

[0057] A method for preparing a crosslinked polymer is as follows:

[0058] (1) Dissolve 1.62 g of 4-(cyclopentan-2,4-diene-1-yl)valeric acid and 4 g of polyoxyethyl glycerol ether (molecular weight 900) in 50 ml of dichloromethane. After complete dissolution, add 3.1 g of N,N'-dicyclohexylcarbodiimide (DCC) and 0.31 g of 4-dimethylaminopyridine (DMAP) to the system and react at 25 °C for 24 h. After the reaction is complete, filter the reaction solution, remove the solvent by rotary evaporation of the filtrate, wash the residue three times with 10 ml of ice-cold ether, and dry under vacuum at room temperature to obtain the esterified product (4-(cyclopentan-2,4-diene-1-yl)valeric acid-terminated polyoxyethyl glycerol ether monomer); the synthesis method of 4-(cyclopentan-2,4-diene-1-yl)valeric acid is the same as in Example 1.

[0059] (2) Dissolve 0.317g of 4,4'-bismaleimide diphenylmethane in 1g of the esterification product obtained in step (1). After the crosslinking agent is completely dissolved, pour it into a polytetrafluoroethylene mold for crosslinking and curing. It can be completely cured at 25°C for 1 hour to obtain the crosslinked polymer.

[0060] Comparative Example 1

[0061] A method for preparing a crosslinked polymer is as follows:

[0062] (1) Dissolve 1.12 g of 2-furanic acid and 4 g of polyoxyethyl glycerol ether (molecular weight 1200) in 50 ml of dichloromethane. After complete dissolution, add 3.1 g of N,N'-dicyclohexylcarbodiimide (DCC) and 0.31 g of 4-dimethylaminopyridine (DMAP) to the system and react at 25 °C for 24 h. After the reaction is completed, filter the reaction solution, remove the solvent by rotary evaporation of the filtrate, wash the residue three times with 10 ml of ice-cold ether, and dry under vacuum at room temperature to obtain the esterified product (2-furanic acid-terminated polyoxyethyl glycerol ether monomer).

[0063] (2) Dissolve 0.252g of 4,4'-bismaleimide diphenylmethane in 1g of the esterification product obtained in step (1). After the crosslinking agent is completely dissolved, pour it into a polytetrafluoroethylene mold for crosslinking and curing. The crosslinking is completed after reacting at 60°C for 1 day. The crosslinked polymer is obtained.

[0064] Comparative Example 2

[0065] The difference between this comparative preparation method and Example 1 is that reactant A is polyethylene glycol with a molecular weight of 1000. The rest of the preparation method is the same as in Example 1. This preparation method cannot be cured even after reacting at 25°C for 24 hours, and cross-linked polymers cannot be obtained.

[0066] Comparative Example 3

[0067] The difference between this comparative preparation method and Example 1 is that the amount of crosslinking agent added is 10% of the mass of the esterification product. The rest of the preparation method is the same as that in Example 1. This preparation method cannot obtain crosslinked polymers when reacted at 25°C for 24 hours.

[0068] The crosslinked polymer obtained in Example 1 was structurally characterized, and the results are shown below. Figures 3-6 .

[0069] Figure 3 The thermogravimetric analysis curve of the crosslinked polymer in Example 1 is shown in the attached figure. Figure 3 It can be seen that the cross-linking system has two main weight loss plateaus. Due to the strong water absorption of PEG, the first weight loss stage is the stage of polymer water loss, and the second stage is the degradation stage of cross-linked polymer, which starts from 350℃ and ends at 610℃, with a weight loss rate of 54%.

[0070] Figure 4 The 1H NMR spectrum of 4-(cyclopentaenoic-2,4-diene-1-yl)valeric acid and the esterified product obtained in step (1) of Example 1. Figure 4The peak at 6.43 ppm corresponds to the hydrogen atom on the olefinic ring of 4-(cyclopentan-2,4-diene-1-yl)valerate, and is its characteristic peak. In the 1H NMR spectrum of the esterified product, both the hydrogen atom peak of PEG at 3.67 ppm and the characteristic peak of the olefinic ring appear simultaneously. Therefore, the synthesis of the 4-(cyclopentan-2,4-diene-1-yl)valerate-terminated polyoxyethyl glycerol ether monomer can be confirmed.

[0071] Figure 5 The infrared spectra of 4-(cyclopentan-2,4-diene-1-yl)valeric acid and the esterified product obtained in step (1) of Example 1 are shown below. Figure 5 As can be seen from this, the esterification product is 3200 cm⁻¹ -1 The broad peak at 1449 cm⁻¹ has almost disappeared, indicating that the carboxyl group of 4-(cyclopentan-2,4-dien-1-yl)pentanoic acid has reacted, thus confirming the esterification reaction. -1 1352cm -1 The peak at that point corresponds to the conjugated double bond on the olefin ring, which indicates the presence of the olefin ring and confirms the esterification reaction.

[0072] Figure 6 The infrared spectra of the esterified product and crosslinked polymer of Example 1 are shown below. Figure 6 In the middle, the cross-linked polymer is 1449 cm. -1 1352cm -1 The peak at the point indicates the disappearance of the olefinic ring, confirming the occurrence of the DA reaction. The destruction of the conjugated double bond confirms the occurrence of the cross-linking reaction, thus confirming the construction of the cross-linking system.

[0073] Examples 1-4 of this invention successfully constructed a DA crosslinking system under low-temperature conditions, and the crosslinked polymer could be completely cured in 1 hour at 25°C.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a cross-linked polymer, characterized in that, Includes the following steps: (1) Mix reactant A and reactant B to carry out esterification reaction to obtain esterified product; (2) Dissolve the crosslinking agent in the obtained esterification product, let it stand to solidify, and the crosslinked polymer is obtained; Reactant A is polyoxyethyl glycerol ether; reactant B is 4-(cyclopentan-2,4-diene-1-yl)valeric acid; and the crosslinking agent is 4,4'-bismaleimide diphenylmethane. In step (2), the mass of the crosslinking agent is 16%-40% of the mass of the esterification product, and the temperature during static curing is 10℃-25℃. The molecular weight of reactant A is 900-1600.

2. The method for preparing the crosslinked polymer according to claim 1, characterized in that, The preparation method of reactant B includes the following steps: in an inert gas atmosphere, levulinic acid, cyclopentadiene, and pyrrolidine are reacted in a mixed solution of methanol and triethylamine in the dark by stirring, followed by acidification, extraction, washing, and drying to obtain reactant B.

3. The method for preparing the crosslinked polymer according to claim 1, characterized in that, In step (1), the catalyst for the esterification reaction is 4-dimethylaminopyridine, and the coupling agent is N,N'-dicyclohexylcarbodiimide.

4. The method for preparing the crosslinked polymer according to claim 1, characterized in that, In step (1), the esterification reaction is carried out at a temperature of 10℃-25℃ for 18h-36h.

5. A crosslinked polymer prepared by the method of any one of claims 1-4.

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