Quadruple hydrogen bond self-healing polyurea and preparation method thereof

Abstract

The present application relates to the technical field of self-repairing materials, in particular to a quadruple hydrogen bond self-repairing polyurea and a preparation method thereof. A novel quadruple hydrogen bond structure is provided, and the sulfydryl in the structure can provide a lone pair of electrons to form a hydrogen bond with the hydrogen on the amino group. Since the electronegativity of the sulfur atom is smaller than that of the nitrogen atom, the hydrogen bond energy formed is small, and the material has stronger reworkability and repairability. A sulfur amine ester bond is designed and synthesized, and compared with the urethane bond, the sulfur amine ester has stronger reworkability and repairability due to the lower energy of the thiourethane bond. The high performance of the self-repairing polyurea is maintained, and excellent self-repairing function is imparted. The advantages of both the quadruple hydrogen bond and the sulfur amine ester bond are combined, the self-repairing threshold of the material is further reduced, and the polyurea material with excellent mechanical properties, which can be self-repaired and reworked at room temperature, is successfully prepared. The mild self-repairing ability makes the material more widely used.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of self-repairing materials, and particularly relates to a quadruple hydrogen bond self-repairing polyurea and a preparation method thereof. BACKGROUND

[0002] Polyurea materials have various forms and excellent comprehensive performance, and have been widely used in the field of engineering materials. With the large use of polyurea materials, wear and damage caused by various factors during use seriously affect the performance and service life of the polyurea materials. Polyurea has excellent physical and chemical properties, and is widely used in the fields of military, construction, aerospace, etc. However, polyurea is often subjected to external erosion such as light, heat and mechanical stress during processing and use, which may cause damage or cracks on the surface of the material, seriously endangering the appearance, durability and reliability of the material, and finally leading to a series of problems such as low availability of polyurea materials and increased maintenance costs. Not only does it cause great waste of resources, but also causes serious pollution to the environment.

[0003] The emergence and development of self-repairing materials provide a feasible solution to this problem, and the hydrogen bond self-repairing method has great development prospects. The hydrogen bond has lower bond energy than the reversible covalent bond, and therefore, the reversibility of the hydrogen bond is a key factor for realizing material self-repairing. Through heating and cooling processes, the hydrogen bond is destroyed and recombined, which enables the material to complete self-healing behavior. The most widely used hydrogen bond self-repairing system is a UPy system containing a quadruple hydrogen bond structure, as shown in Figure 1 .

[0004] For example, Chinese Patent CN202110997230.X discloses a wear-resistant self-repairing waterborne polyurethane based on quadruple hydrogen bonds and aromatic disulfide bonds and a preparation method thereof, and relates to the field of self-repairing polyurethane. An isocyanate group-terminated prepolymer is obtained by pre-polymerization of a polymer diol, a monomer capable of forming a quadruple hydrogen bond and a diisocyanate. A hydrophilic monomer and a monomer containing an aromatic disulfide bond structure unit are introduced into the prepolymer to obtain a wear-resistant self-repairing waterborne polyurethane based on quadruple hydrogen bonds and aromatic disulfide bonds. The process is simple and easy to control, and is suitable for industrial production. The interaction between the quadruple hydrogen bonds improves the movement between the molecular chains, thereby improving the toughness and self-repairing efficiency of the polyurethane. The high bond energy of the aromatic disulfide bond is used to further improve the strength of the polyurethane while imparting excellent wear resistance to the polyurethane, thereby solving the technical defect that the repair efficiency and mechanical properties of traditional polyurethane cannot be simultaneously considered.

[0005] For example, Chinese patent CN202010347326.7 discloses a self-repairing thermoplastic polyurea elastomer and a preparation method thereof. The preparation method of the self-repairing thermoplastic polyurea elastomer provided by the present application comprises: polymerizing diamine A and diamine B with carbon dioxide to obtain a self-repairing thermoplastic polyurea elastomer; the diamine A is isophorone diamine; and the diamine B is C4-C10 diamino-oxaalkane. The present application adopts two specific types of diamines to react with carbon dioxide, wherein the urea group formed by the reaction of C4-C10 diamino-oxaalkane and carbon dioxide produces a regular hydrogen bond structure, and the urea group formed by the reaction of the asymmetric alicyclic diamine isophorone diamine and carbon dioxide produces an irregular hydrogen bond structure. The two hydrogen bond structures jointly act to make the polyurea material have high strength, high toughness, good self-repairing performance and transparency.

[0006] There are still some defects in the above-mentioned patents, for example: in CN202110997230.X, the water-based polyurethane is formed by using water as the medium, and the hydrogen bond groups are dispersed and arranged in water. Due to the presence of water, the group density per unit volume is diluted, the probability of forming hydrogen bonds is small, and therefore the self-repairing ability is poor. In CN202010347326.7, the hydrogen bonds are irregularly arranged, the hydrogen bonds are far apart from the groups, the binding force formed is poor, and the self-repairing ability is poor.

[0007] In addition, the technology used in the existing patents is common sense in the known field, such as disulfide bond exchange reaction, which is a commonly used technical means in the field.

[0008] One of the technical problems to be solved by the present application is to provide a novel four-hydrogen bond self-repairing polyurea, which maintains the high performance of the self-repairing polyurea and endows it with excellent self-repairing function. The material can be repaired and reprocessed repeatedly at low temperature without the need for a catalyst.

[0009] In summary, the advantages of four hydrogen bonds and thioamide bonds are combined to further reduce the self-repairing threshold of the material, and a polyurea material with excellent mechanical properties, which can be self-repaired and reprocessed at room temperature, is successfully prepared. The self-repairing ability under mild conditions makes the material more widely applicable. SUMMARY

[0010] To solve the above problems, the present application provides a four-hydrogen bond self-repairing polyurea and a preparation method thereof. The sulfhydryl group in the structure can provide a lone pair of electrons to form a hydrogen bond with the hydrogen on the amino group. Since the electronegativity of sulfur atom is smaller than that of nitrogen atom, the hydrogen bond energy formed is small, and the material has stronger reprocessability and repairability.

[0011] To achieve the above-mentioned purpose, the present application provides a four-hydrogen bond self-repairing polyurea, and the structural formula of the four-hydrogen bond self-repairing polyurea is as follows:

[0012]

[0013] In another aspect, the present application provides a preparation method of quadruple hydrogen bond self-repairing polyurea, comprising the following steps, as follows:

[0014]

[0015] Further, the synthesis step of a comprises: adding 5-10 parts of DMF into a three-necked flask equipped with a magnetic stirrer, a thermometer and a reflux condenser, then adding 2-6 parts of 6-R group-2-thiouracil, under nitrogen protection, passing 1-3 parts of HBr, heating in a 60℃ water bath and stirring for 1-2 hours, and distilling the excess solvent to obtain the product a.

[0016] Further, the synthesis step of b comprises: adding 3-6 parts of compound a and 1-2 parts of triethylamine into a three-necked flask containing 30 parts of THF solution, dropwise adding 3-6 parts of p-toluenesulfonyl chloride solution, adding 10 parts of dry THF into the solution, stirring in a 0℃ ice bath for 2-4 hours, washing with water, filtering, and drying at 60℃ to obtain compound b.

[0017] Further, the synthesis step of c comprises: adding 1-5 parts of compound b into a round-bottom flask, adding 30 parts of dry cyclohexane and 0.1 part of dibutyltin dilaurate, slowly and dropwise adding 2-10 parts of hexamethylene diisocyanate (HDI) under nitrogen protection, stirring in a 90℃ water bath for 5-10 hours, and distilling the excess solvent to obtain compound c.

[0018] Further, the synthesis step of d comprises: configuring 1-3 parts of compound c and 4-12 parts of polyether amine in a three-necked flask, and performing oil bath heating, which needs high-purity nitrogen protection, preheating at 50℃ for 1 hour, and then reacting at 80℃ for 2 hours. The obtained product d is dried and stored in a sealed state.

[0019] Further, the synthesis step of e comprises: adding 8-10 parts of compound d, 1-2 parts of phenol and 1-2 parts of 48% aqueous solution into a three-necked flask in sequence, heating in an oil bath to 130℃, stirring for 2-4 hours, cooling to room temperature, diluting with 30 parts of water, extracting with 15 parts of ethyl acetate, and distilling and drying to obtain compound e.

[0020] Further, the R group in the 6-R group-2-thiouracil is methyl and its derivatives.

[0021] Further, the purity of the triethylamine, p-toluenesulfonyl chloride and HDI is greater than or equal to 98%.

[0022] Further, the polyether amine is a bifunctional primary amine with an average molecular weight of about 2000.

[0023] The present application has the following beneficial effects:

[0024] This invention provides a novel quadruple hydrogen bond structure. The thiol group in the structure provides lone pair electrons to form hydrogen bonds with hydrogen atoms on the amino group. Because the electronegativity of sulfur atoms is lower than that of nitrogen atoms, the resulting hydrogen bond energies are low, leading to stronger reprocessability and repairability of the material. Furthermore, a thiourethane bond was designed and synthesized. Compared to urethane bonds, thiourethanes, due to the presence of thiourethane bonds with even lower bond energies, exhibit stronger reprocessability and repairability. This maintains the high performance of self-healing polyurea and endows it with excellent self-healing capabilities. The material can be repaired and repeatedly processed without catalysts and at low temperatures. By combining the advantages of both quadruple hydrogen bonds and thiourethane bonds, the self-healing threshold of the material is further lowered, successfully preparing a room-temperature self-healing and reprocessable polyurea material with excellent mechanical properties. The mild self-healing capability allows for wider applications of the material. Attached Figure Description

[0025] Figure 1 The diagram shows the quadruple hydrogen bond structure of the UPy system used in the prior art. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] This invention provides a quadruple hydrogen-bonded self-healing polyurea, the structural formula of which is as follows:

[0028]

[0029] This invention provides a novel quadruple hydrogen bond structure. The thiol group in the structure provides lone pair electrons to form hydrogen bonds with hydrogen atoms on the amino group. Because the electronegativity of sulfur atoms is lower than that of nitrogen atoms, the resulting hydrogen bond energies are low, leading to better reprocessability and repairability of the material. Furthermore, a thiourethane bond was designed and synthesized. Compared to urethane bonds, thiourethanes exhibit even better reprocessability and repairability due to the presence of thiocarbamate bonds with lower bond energies.

[0030] Specifically, the self-healing function of the material is achieved through the reversibility of quadruple hydrogen bonds. The self-healing group is located on the polyurea molecular backbone and is an intrinsic functional group.

[0031] On the other hand, the present invention also proposes a method for preparing a fourfold hydrogen-bonded self-healing polyurea, comprising the following steps:

[0032]

[0033] The preparation method of quadruple hydrogen bond self-healing polyurea will be described in detail below with reference to specific embodiments and comparative examples.

[0034] Example 1

[0035] The synthesis steps of compound a include: adding 5 parts DMF and 2 parts 6-R-2-thiouracil to a three-necked flask equipped with a magnetic stirrer, thermometer, and reflux condenser; purging 1 part HBr under nitrogen protection; heating and stirring in a 60°C water bath for 1 hour; distilling off excess solvent to obtain 2-mercapto-6-methylpyrimidin-4(3H)one, which is product a, with the chemical formula C4H3N2OSR. Mass spectrum m / z: 142.02 (100.0%), 143.02 (5.4%), 144.02 (4.5%). Elemental analysis: C, 42.24; H, 4.25; N, 19.70; O, 11.25; S, 22.55. Specifically, the R group in the 6-R-2-thiouracil is a methyl group or its derivative. Nitrogen content: 99%.

[0036] The synthetic steps of compound b include: adding 3 parts of 2-mercapto-6-methylpyrimidin-4(3H)one and 1 part of triethylamine sequentially to a three-necked flask containing 30 parts of THF solution, followed by the dropwise addition of 3 parts of p-toluenesulfonyl chloride solution, and then adding 10 parts of dry THF to the solution. The mixture is then stirred in an ice bath at 0°C for 2 hours, washed with water, filtered, and dried at 60°C to obtain 2-mercapto-6-methyl-3-toluenesulfonylpyrimidin-4(3H)one, thus yielding compound b, with the chemical formula: C 11 H9N2O3S2R. Mass spectrum m / z: 296.03 (100.0%), 297.03 (13.0%), 298.02 (9.0%), 297.03 (1.6%). Elemental analysis: C, 48.63; H, 4.08; N, 9.45; O, 16.20; S, 21.64. Specifically, the purity of the triethylamine, p-toluenesulfonyl chloride, and HDI is ≥98%.

[0037] The synthesis steps of compound c include: adding 1 part of 2-mercapto-6-methyl-3-toluenesulfonylpyrimidin-4(3H)one to a round-bottom flask, adding 30 parts of dry cyclohexane and 0.1 parts of dibutyltin dilaurate, and slowly adding 2 parts of HDI (hexamethylene diisocyanate) dropwise under nitrogen protection. The mixture is then stirred and refluxed in a 90°C water bath for 5-10 hours. Excess solvent is distilled off to obtain the thiouric acid ester compound, i.e., compound c, with the chemical formula: C 19 H 21 N4O5S2R. Nitrogen content 99%.

[0038] The synthesis steps of compound d include: preparing 1 part of a thiouric acid ester compound and 4 parts of polyetheramine D2000 in a three-necked flask, heating in an oil bath under high-purity nitrogen protection, preheating at 50°C for 1 hour, and then reacting at 80°C for 2 hours. The resulting urea-bonded compound (product d) is dried, sealed, and stored. Specifically, the polyetheramine is a bifunctional primary amine with an average molecular weight of approximately 2000.

[0039] The synthesis steps of compound e include: adding 8 parts of a urea-bonded compound, 1 part of phenol, and 1 part of 48% HBr (48% aqueous solution) sequentially to a three-necked flask; heating in an oil bath to 130°C; stirring and refluxing for 2 hours; cooling to room temperature; diluting with 30 parts of water; extracting with 15 parts of ethyl acetate; and distilling to dry, thus obtaining the self-healing polyurea, i.e., compound e. The nitrogen content is 99%.

[0040] In this embodiment, the purity of triethylamine, p-toluenesulfonyl chloride, and HDI is ≥98%.

[0041] Example 2

[0042] The synthesis steps of compound a include: adding 7 parts DMF and 4 parts 6-R-2-thiouracil to a three-necked flask equipped with a magnetic stirrer, thermometer, and reflux condenser; purging 2 parts HBr under nitrogen protection; heating and stirring in a 60°C water bath for 1-2 hours; distilling off excess solvent to obtain 2-mercapto-6-methylpyrimidin-4(3H)one, which is product a, with the chemical formula C4H3N2OSR. Mass spectrum m / z: 142.02 (100.0%), 143.02 (5.4%), 144.02 (4.5%). Elemental analysis: C, 42.24; H, 4.25; N, 19.70; O, 11.25; S, 22.55. Specifically, the R group in the 6-R-2-thiouracil is a methyl group or its derivative. Nitrogen content: 99%.

[0043] The synthetic steps of compound b include: adding 5 parts of 2-mercapto-6-methylpyrimidin-4(3H)one and 1.5 parts of triethylamine sequentially to a three-necked flask containing 30 parts of THF solution, followed by the dropwise addition of 4.5 parts of p-toluenesulfonyl chloride solution, and then adding 10 parts of dry THF to the solution. The mixture is then stirred in an ice bath at 0°C for 3 hours, washed with water, filtered, and dried at 60°C to obtain 2-mercapto-6-methyl-3-toluenesulfonylpyrimidin-4(3H)one, thus yielding compound b, with the chemical formula: C 11H9N2O3S2R. Mass spectrum m / z: 296.03 (100.0%), 297.03 (13.0%), 298.02 (9.0%), 297.03 (1.6%). Elemental analysis: C, 48.63; H, 4.08; N, 9.45; O, 16.20; S, 21.64. Specifically, the purity of the triethylamine, p-toluenesulfonyl chloride, and HDI is ≥98%.

[0044] The synthesis steps of compound c include: adding 3 parts of 2-mercapto-6-methyl-3-toluenesulfonylpyrimidin-4(3H)one to a round-bottom flask, adding 30 parts of dry cyclohexane and 0.1 parts of dibutyltin dilaurate, and slowly adding 6 parts of HDI (hexamethylene diisocyanate) dropwise under nitrogen protection. The mixture is then stirred and refluxed in a 90°C water bath for 7.5 h. Excess solvent is distilled off to obtain the thiouric acid ester compound, i.e., compound c, with the chemical formula: C 19 H 21 N4O5S2R. Nitrogen content 99%.

[0045] The synthesis steps of compound d include: preparing 2 parts of a thiouric acid ester compound and 8 parts of polyetheramine D2000 in a three-necked flask, heating in an oil bath under high-purity nitrogen protection, preheating at 50°C for 1 hour, and then reacting at 80°C for 2 hours. The resulting urea-bonded compound (product d) is dried, sealed, and stored. Specifically, the polyetheramine is a bifunctional primary amine with an average molecular weight of approximately 2000.

[0046] The synthesis steps of compound e include: in a three-necked flask, adding 9 parts of a urea-bonded compound, 1.5 parts of phenol, and 1.5 parts of 48% HBr (48% aqueous solution) sequentially; heating in an oil bath to 130°C; stirring and refluxing for 3 hours; cooling to room temperature; diluting with 30 parts of water; extracting with 15 parts of ethyl acetate; and distilling to dry, thus obtaining the self-healing polyurea, i.e., compound e. The nitrogen content is 99%.

[0047] Example 3

[0048] The synthesis steps of compound a include: adding 10 parts DMF and 6 parts 6-R-2-thiouracil to a three-necked flask equipped with a magnetic stirrer, thermometer, and reflux condenser; purging 3 parts HBr under nitrogen protection; heating and stirring in a 60°C water bath for 2 hours; distilling off excess solvent to obtain 2-mercapto-6-methylpyrimidin-4(3H)one, which is product a, with the chemical formula C4H3N2OSR. Mass spectrum m / z: 142.02 (100.0%), 143.02 (5.4%), 144.02 (4.5%). Elemental analysis: C, 42.24; H, 4.25; N, 19.70; O, 11.25; S, 22.55. Specifically, the R group in the 6-R-2-thiouracil is a methyl group or its derivative. Nitrogen content: 99%.

[0049] The synthetic steps of compound b include: adding 6 parts of 2-mercapto-6-methylpyrimidin-4(3H)one and 2 parts of triethylamine sequentially to a three-necked flask containing 30 parts of THF solution, followed by the dropwise addition of 6 parts of p-toluenesulfonyl chloride solution, and then adding 10 parts of dry THF to the solution. The mixture is then stirred in an ice bath at 0°C for 4 hours, washed with water, filtered, and dried at 60°C to obtain 2-mercapto-6-methyl-3-toluenesulfonylpyrimidin-4(3H)one, thus yielding compound b, with the chemical formula: C 11 H9N2O3S2R. Mass spectrum m / z: 296.03 (100.0%), 297.03 (13.0%), 298.02 (9.0%), 297.03 (1.6%). Elemental analysis: C, 48.63; H, 4.08; N, 9.45; O, 16.20; S, 21.64. Specifically, the purity of the triethylamine, p-toluenesulfonyl chloride, and HDI is ≥98%.

[0050] The synthesis steps of compound c include: adding 5 parts of 2-mercapto-6-methyl-3-toluenesulfonylpyrimidin-4(3H)one to a round-bottom flask, adding 30 parts of dry cyclohexane and 0.1 parts of dibutyltin dilaurate, and slowly adding 10 parts of HDI (hexamethylene diisocyanate) dropwise under nitrogen protection. The mixture is then stirred and refluxed in a 90°C water bath for 10 hours. Excess solvent is distilled off to obtain the thiouric acid ester compound, i.e., compound c, with the chemical formula: C 19 H 21 N4O5S2R. Nitrogen content 99%.

[0051] The synthesis steps of compound d include: preparing 3 parts of a thiouric acid ester compound and 12 parts of polyetheramine D2000 in a three-necked flask, heating in an oil bath under high-purity nitrogen protection, preheating at 50°C for 1 hour, and then reacting at 80°C for 2 hours. The resulting urea-bonded compound (product d) is dried, sealed, and stored. Specifically, the polyetheramine is a bifunctional primary amine with an average molecular weight of approximately 2000.

[0052] The synthesis steps of compound e include: in a three-necked flask, adding 10 parts of a urea-bonded compound, 2 parts of phenol, and 2 parts of 48% HBr (48% aqueous solution) sequentially; heating in an oil bath to 130°C; stirring and refluxing for 4 hours; cooling to room temperature; diluting with 30 parts of water; extracting with 15 parts of ethyl acetate; and distilling to dry, thus obtaining the self-healing polyurea, i.e., compound e. The nitrogen content is 99%.

[0053] Comparative Example 1

[0054] In this comparative example, compared to Example 1, the polyetheramine used has a trifunctionality of 330N. Due to the increased molecular weight and steric hindrance, hydrogen bond formation is more difficult, resulting in decreased material processing performance and repairability. Details are as follows.

[0055] The synthesis steps of compound a include: adding 5 parts of DMF and 2 parts of 6-R-2-thiouracil to a three-necked flask equipped with a magnetic stirrer, thermometer and reflux condenser; passing 1 part of HBr under nitrogen protection; heating and stirring in a water bath at 60°C for 1 hour; distilling off the excess solvent to obtain 2-mercapto-6-methylpyrimidin-4(3H)one, which is product a.

[0056] The synthesis steps of compound b include: adding 3 parts of 2-mercapto-6-methylpyrimidin-4(3H)one and 1 part of triethylamine to a three-necked flask containing 30 parts of THF solution, adding 3 parts of p-toluenesulfonyl chloride solution dropwise, adding 10 parts of dry THF to the solution, stirring the mixture in an ice bath at 0°C for 2 hours, washing with water, filtering, and drying at 60°C to obtain 2-mercapto-6-methyl-3-toluenesulfonylpyrimidin-4(3H)one, thus obtaining compound b.

[0057] The synthesis steps of compound c include: adding 1 part of 2-mercapto-6-methyl-3-toluenesulfonylpyrimidin-4(3H)one to a round-bottom flask, adding 30 parts of dry cyclohexane and 0.1 parts of dibutyltin dilaurate, and slowly adding 2 parts of HDI (hexamethylene diisocyanate) dropwise under nitrogen protection. The mixture is then stirred and refluxed in a 90°C water bath for 5-10 hours. The excess solvent is distilled off to obtain the thiouric acid ester compound, which is compound c.

[0058] Prepare a mixture of 1 part thiouric acid ester compound and 12 parts polyetheramine 330N in a three-necked flask, and heat in an oil bath under high-purity nitrogen protection. Preheat at 50°C for 1 hour, then react at 80°C for 2 hours. Dry and seal the resulting urea bond product for storage.

[0059] In a three-necked flask, 8 parts of urea-bonded compound, 2 parts of phenol, and 2 parts of HBr (48% aqueous solution) were added sequentially. The mixture was heated in an oil bath to 130°C and stirred under reflux for 2 hours. After cooling to room temperature, the mixture was diluted with 30 parts of water, extracted with 15 parts of ethyl acetate, and dried by distillation to obtain self-healing polyurea.

[0060] Experimental methods and results:

[0061] A 1mm thick self-healing polyurea sample was prepared. The material was scratched with a clean blade, and after a set time and temperature, it was placed under a polarizing microscope to observe changes in the scratches. The self-healing efficiency of the material was calculated using the apparent self-healing formula.

[0062] D% = (L2-L1) / L2×100%;

[0063] L1—Width of the repaired scratch, in mm;

[0064] L2—Initial scratch width, mm;

[0065] The self-healing efficiency of the materials is shown in the table below:

[0066]

[0067] In summary, this embodiment presents a novel quadruple hydrogen bond structure. The thiol group in the structure provides lone pair electrons to form hydrogen bonds with the hydrogen atoms on the amino group. Due to the lower electronegativity of the sulfur atom compared to the nitrogen atom, the hydrogen bond energy is low, resulting in stronger reprocessability and repairability of the material. Furthermore, a thiourethane bond was designed and synthesized. Compared to urethane bonds, thiourethanes, due to the presence of thiourethane bonds with lower bond energy, exhibit even stronger reprocessability and repairability. This maintains the high performance of self-healing polyurea and endows it with excellent self-healing capabilities. The material can be repaired and repeatedly processed without catalysts and at low temperatures. By combining the advantages of both quadruple hydrogen bonds and thiourethane bonds, the self-healing threshold of the material is further lowered, successfully preparing a room-temperature self-healing and reprocessable polyurea material with excellent mechanical properties. The mild self-healing capability allows for wider applications.

[0068] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a fourfold hydrogen-bonded self-healing polyurea, characterized in that, Includes the following steps: In this case, R group is a methyl group.

2. The method for preparing a quadruple hydrogen-bonded self-healing polyurea according to claim 1, characterized in that, The synthesis steps of 'a' include: In a three-necked flask equipped with a magnetic stirrer, thermometer, and reflux condenser, add 5-10 parts of DMF, then add 2-6 parts of 6-R-2-thiouracil. Under nitrogen protection, introduce 1-3 parts of HBr, heat and stir in a 60°C water bath for 1-2 hours, and distill off the excess solvent to obtain product a, wherein the R group is methyl.

3. The method for preparing a quadruple hydrogen-bonded self-healing polyurea according to claim 2, characterized in that, The synthesis steps of b include: In a three-necked flask containing 30 parts of THF solution, 3-6 parts of compound a and 1-2 parts of triethylamine were added sequentially, followed by 3-6 parts of p-toluenesulfonyl chloride solution. 10 parts of dry THF were added to the solution, and the mixture was stirred in an ice bath at 0°C for 2-4 hours. The mixture was washed with water, filtered, and dried at 60°C to obtain compound b.

4. The method for preparing a quadruple hydrogen-bonded self-healing polyurea according to claim 3, characterized in that, The synthesis steps of c include: Add 1-5 parts of compound b to a round-bottom flask, add 30 parts of dry cyclohexane and 0.1 parts of dibutyltin dilaurate, and slowly add 2-10 parts of hexamethylene diisocyanate (HDI) dropwise under nitrogen protection. Place the flask in a 90°C water bath and stir under reflux for 5-10 hours. Distill off the excess solvent to obtain compound c.

5. The method for preparing a quadruple hydrogen-bonded self-healing polyurea according to claim 4, characterized in that, The synthesis steps of d include: Prepare 1-3 parts of compound c and 4-12 parts of polyetheramine in a three-necked flask, and heat in an oil bath. High-purity nitrogen is required for protection during the heating process. Preheat at 50°C for 1 hour, then react at 80°C for 2 hours. Dry and seal the product d obtained from the reaction for storage.

6. The method for preparing a quadruple hydrogen-bonded self-healing polyurea according to claim 5, characterized in that, The synthesis steps of e include: In a three-necked flask, 8-10 parts of compound d, 1-2 parts of phenol, and 1-2 parts of 48% aqueous hydrogen bromide solution were added sequentially. The mixture was heated in an oil bath to 130°C and stirred under reflux for 2-4 hours. After cooling to room temperature, the mixture was diluted with 30 parts of water, extracted with 15 parts of ethyl acetate, and dried by distillation to obtain compound e.

7. The four-fold hydrogen-bonded self-healing polyurea and its preparation method according to claim 4, characterized in that, The purity of the triethylamine, p-toluenesulfonyl chloride, and HDI is ≥98%.

8. The method for preparing a quadruple hydrogen-bonded self-healing polyurea according to claim 5, characterized in that, The polyetheramine is a primary amine with bifunctional groups and an average molecular weight of 2000.

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