Hexahydrogen 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 kind of six hydrogen bond self-repairing polyurea and preparation method thereof.A kind of brand-new six hydrogen bond structure is provided, and the lone pair of electrons of sulfydryl in the structure can form hydrogen bond with the hydrogen on amino group, and since the electronegativity of sulfur atom is less than that of nitrogen atom, the hydrogen bond energy formed is small, the material has stronger reworkability and repairability.Sulfur amidoester bond is designed and synthesized, compared with amidoester bond, sulfur amidoester has stronger reworkability and repairability due to containing lower-energy thio-carbamate bond.The high performance of self-repairing polyurea is maintained, and excellent self-repairing function is endowed.The advantages of both six hydrogen bond and sulfur amidoester bond are integrated, the material self-repairing threshold 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] This invention belongs to the field of self-healing materials technology, and specifically relates to a hexa-hydrogen bond self-healing polyurea and its preparation method. Background Technology

[0002] Polyurea materials exhibit diverse forms and excellent overall performance, and are now widely used in the field of engineering materials. However, with the extensive use of polyurea materials, wear and damage caused by various factors during use severely affect their performance and service life. Polyurea possesses excellent physicochemical properties and, as a high-performance material, has wide applications in military, construction, and aerospace fields. However, during the processing and use of polyurea, it is often subjected to external erosion such as light, heat, and mechanical stress, which may lead to damage or cracks on the material surface. This seriously jeopardizes the material's aesthetics, durability, and reliability, ultimately resulting in a series of problems such as low availability and increased maintenance costs. This not only causes significant resource waste but also causes serious environmental pollution.

[0003] The emergence and development of self-healing materials have provided a feasible solution to this problem, among which hydrogen bond-based self-healing methods show great promise. Hydrogen bonds have lower bond energies than reversible covalent bonds; therefore, the reversibility of hydrogen bonds is a key factor in achieving material self-healing. Through heating and cooling processes, hydrogen bonds are broken and reformed, enabling the material to perform self-healing behavior. Currently, a widely used hydrogen bond self-healing system is the UPy system, which contains a quadruple hydrogen bond structure, such as... Figure 1 As shown.

[0004] For example, Chinese patent CN202110997230.X describes a wear-resistant, self-healing waterborne polyurethane based on quadruple hydrogen bonds and aromatic disulfide bonds, and its preparation method, which relates to the field of self-healing polyurethane. An isocyanate-terminated prepolymer is obtained through a prepolymerization reaction of a polymeric diol, a monomer capable of forming quadruple hydrogen bonds, and a diisocyanate. Hydrophilic monomers and monomers containing aromatic disulfide bond structural units are then introduced into the prepolymer to obtain a wear-resistant, self-healing waterborne polyurethane based on quadruple hydrogen bonds and aromatic disulfide bonds. This process is simple and easy to control, suitable for industrial production. The interaction between quadruple hydrogen bonds enhances the movement between molecular chains, thereby improving the toughness and self-healing efficiency of the polyurethane. The high bond energy of aromatic disulfide bonds further improves the strength of the polyurethane while imparting excellent wear resistance, solving the technical defect of traditional polyurethanes where repair efficiency and mechanical properties cannot be simultaneously achieved.

[0005] For example, Chinese patent CN202010347326.7 discloses a self-healing thermoplastic polyurea elastomer and its preparation method. The preparation method of the self-healing thermoplastic polyurea elastomer provided by this invention includes: polymerizing diamine A and diamine B with carbon dioxide to obtain the self-healing thermoplastic polyurea elastomer; wherein diamine A is isophorone diamine; and diamine B is a C4-C10 diaminooxane. This invention uses two specific types of diamines to react simultaneously with carbon dioxide. The urea groups formed by the reaction of C4-C10 diaminooxanes with carbon dioxide produce a regular hydrogen bond structure, while the urea groups formed by the reaction of the asymmetric alicyclic diamine isophorone diamine with carbon dioxide produce an irregular hydrogen bond structure. The combined effect of these two hydrogen bond structures gives the polyurea material high strength, high toughness, good self-healing properties, and transparency.

[0006] The aforementioned patents also have certain defects. For example, in CN202110997230.X, waterborne polyurethane uses water as a medium, and the groups that form hydrogen bonds are dispersed in water. Due to the presence of water, the density of groups per unit volume is diluted, resulting in a low probability of forming hydrogen bonds and thus poor self-healing ability. In CN202010347326.7, the hydrogen bond arrangement is irregular, and the hydrogen bonds are far apart from the groups, resulting in poor bonding force and poor self-healing ability.

[0007] In addition, the technologies used in existing patents are common knowledge in the field, such as disulfide bond exchange reactions, which are commonly used techniques in this field.

[0008] One technical problem this invention aims to solve is to provide a novel tetrahydrobonded self-healing polyurea structure that maintains the high performance of self-healing polyurea while endowing it with excellent self-healing capabilities. The material can be repeatedly repaired and processed without the need for a catalyst and at low temperatures.

[0009] In summary, by combining the advantages of both hexa-hydrogen bonds and thiourethane bonds, the self-healing threshold of materials has been further lowered, and polyurea materials with excellent mechanical properties that can be self-healed and reprocessed at room temperature have been successfully prepared. The mild self-healing capability allows the material to be used more widely. Summary of the Invention

[0010] To address the aforementioned problems, this invention provides a hexa-hydrogen-bonded self-healing polyurea and its preparation method. The thiol groups in the structure can provide lone pairs of electrons to form hydrogen bonds with the 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 small, leading to stronger reprocessability and repairability of the material.

[0011] To achieve the above objectives, this invention proposes a hexa-hydrogen-bonded self-healing polyurea, the structural formula of which is as follows:

[0012]

[0013] On the other hand, this invention proposes a method for preparing a hexa-hydrogen-bonded self-healing polyurea, comprising the following steps:

[0014]

[0015] Furthermore, the synthesis steps of a include: adding 5-10 parts of DMF and 2-6 parts of 6-R-2-thiouracil to a three-necked flask equipped with a magnetic stirrer, thermometer and reflux condenser; purging 1-3 parts of HBr under nitrogen protection; heating and stirring in a water bath at 60°C for 1-2 hours; and distilling off the excess solvent to obtain product a.

[0016] Furthermore, the synthesis steps of b include: adding 3-6 parts of compound a and 1-2 parts of triethylamine sequentially to a three-necked flask containing 30 parts of THF solution, adding 3-6 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 2-4 hours, washing with water, filtering, and drying at 60°C to obtain compound b.

[0017] Furthermore, the synthesis step of c includes: adding 1-5 parts of compound b to a round-bottom flask, adding 30 parts of dry cyclohexane and 0.1 parts of dibutyltin dilaurate, slowly adding 2-10 parts of 2,6-diisocyanate pyridine under nitrogen protection, stirring and refluxing in a 90°C water bath for 5-10 hours, and distilling off the excess solvent to obtain compound c.

[0018] Furthermore, the synthesis step of d includes: preparing 1-3 parts of compound c and 4-12 parts of polyetheramine 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 product d is then dried, sealed, and stored.

[0019] Furthermore, the synthesis steps of e include: adding 8-10 parts of compound d, 1-2 parts of phenol, and 1-2 parts of 48% aqueous solution sequentially to a three-necked flask; heating in an oil bath to 130°C; stirring and refluxing for 2-4 hours; cooling to room temperature; diluting with 30 parts of water; extracting with 15 parts of ethyl acetate; and distilling to dry to obtain compound e.

[0020] Furthermore, the R group in the 6-R-2-thiouracil is a methyl group or its derivative.

[0021] Furthermore, the purity of the triethylamine, p-toluenesulfonyl chloride, and 2,6-diisocyanate pyridine is ≥98%.

[0022] Furthermore, the polyetheramine is a primary amine with bifunctional groups and an average molecular weight of around 2000.

[0023] The beneficial effects of this invention are:

[0024] This invention provides a novel hexa-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 the need for a catalyst and at low temperatures. By combining the advantages of both hexa-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 hexa-hydrogen-bonded self-healing polyurea, the structural formula of which is as follows:

[0028]

[0029] This invention provides a novel six-fold 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 six 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 hexa-hydrogen-bonded self-healing polyurea, comprising the following steps:

[0032]

[0033] The preparation method of hexahydrogen-bonded 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 2,6-diisocyanate pyridine is ≥98%.

[0037] The synthetic 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 2,6-diisocyanate pyridine 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 18 H 12 N5O5S2R. 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] Example 2

[0041] 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%.

[0042] 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 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 2,6-diisocyanate pyridine is ≥98%.

[0043] 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 2,6-diisocyanate pyridine 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 18 H 12 N5O5S2R. Nitrogen content 99%.

[0044] 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.

[0045] 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%.

[0046] Example 3

[0047] 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%.

[0048] 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 2,6-diisocyanate pyridine is ≥98%.

[0049] The synthetic 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 2,6-diisocyanate pyridine 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 18 H 12 N5O5S2R. Nitrogen content 99%.

[0050] 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.

[0051] 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%.

[0052] Comparative Example 1

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] Experimental methods and results:

[0060] 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.

[0061] D% = (L2-L1) / L2×100%;

[0062] L1—Width of the repaired scratch, in mm;

[0063] L2—Initial scratch width, mm;

[0064] The self-healing efficiency of the materials is shown in the table below:

[0065]

[0066] In summary, this embodiment presents a novel six-fold 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 resulting hydrogen bond energy is 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 energy, 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 the need for a catalyst and at low temperatures. By combining the advantages of both six-fold 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.

[0067] 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 hexa-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 hexa-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, where the R group is methyl.

3. The method for preparing a hexa-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 hexa-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 2,6-diisocyanate pyridine 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 hexa-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 hexa-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 hexa-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 2,6-diisocyanate pyridine is ≥98%.

8. The method for preparing a hexa-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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