A self-healing polyurethane based on pyridine-metal coordination and a method for preparing the same

Abstract

This invention provides a self-healing polyurethane based on pyridine-metal coordination and its preparation method. The preparation method includes the following steps: 1) dissolving diaminopyridine in an organic solvent to obtain a diaminopyridine solution; mixing the diaminopyridine solution with an isocyanate-based polyurethane prepolymer and performing a chain extension reaction to obtain a rigid aromatic heterocyclic polyurethane solution; 2) adding an iron salt solution dropwise to the rigid aromatic heterocyclic polyurethane solution and reacting to obtain a self-healing polyurethane solution; and sequentially molding and drying the self-healing polyurethane solution to obtain a self-healing polyurethane based on pyridine-metal coordination. The prepared polyurethane can self-heal under mild conditions while maintaining mechanical stability.

Description

Technical Field

[0001] This invention belongs to the field of polymer functional materials technology, specifically relating to a self-healing polyurethane based on pyridine-metal coordination and its preparation method. Background Technology

[0002] Polyurethane materials are widely used in coatings, adhesives, elastomers, and protective coatings due to their designable hard and soft segments and adjustable flexibility and mechanical properties. However, polyurethane films are prone to microcracks and defects under long-term bending, friction, impact, or scratching conditions, leading to a decline in mechanical properties and a shortened service life. Existing polyurethane self-healing methods rely on microcapsules containing repair agents for external repair, which suffers from limited agent reserves, poor efficiency, and poor stability. Internal repair methods, such as disulfide bonds and acylhydrazone bonds, require harsh conditions like high temperature, acid / alkali conditions, or light exposure, limiting their practical application. Summary of the Invention

[0003] To address the problems of existing polyurethane films and flexible protective coatings prepared from them being prone to failure after scratches, cracks, and repeated deformations, as well as insufficient repair efficiency and harsh repair conditions, a self-healing polyurethane based on pyridine-metal coordination and its preparation method are provided. The polyurethane can self-heal cyclically under mild conditions while maintaining mechanical stability.

[0004] This invention is achieved through the following technical solution: In a first aspect, the present invention provides a method for preparing a self-healing polyurethane based on pyridine-metal coordination, comprising the following steps: 1) Dissolve diaminopyridine in an organic solvent to obtain a diaminopyridine solution; stir and mix the diaminopyridine solution with isocyanate-based polyurethane prepolymer to carry out a chain extension reaction to obtain a rigid aromatic heterocyclic polyurethane solution. 2) Add the iron salt solution dropwise to the rigid aromatic heterocyclic polyurethane solution to react and obtain the self-healing polyurethane solution; then mold and dry the self-healing polyurethane solution to obtain the self-healing polyurethane based on pyridine-metal coordination.

[0005] Preferably, in step 1), the diaminopyridine is one or more of 2,6-diaminopyridine, 2,5-diaminopyridine, 2,4-diaminopyridine, 2,3-diaminopyridine, 3,4-diaminopyridine, and 3,5-diaminopyridine.

[0006] Preferably, in step 1), the organic solvent is N,N-dimethylformamide or N,N-dimethylacetamide.

[0007] Preferably, in step 1), the method for preparing the isocyanate-based polyurethane prepolymer is as follows: isophorone diisocyanate, polypropylene glycol and dibutyltin dilaurate are dissolved in N,N-dimethylacetamide and subjected to polymerization reaction, then poly(1,4-butanediol adipate) is added and subjected to polymerization reaction, and then 1,4-butanediol is added and subjected to polymerization reaction to obtain the isocyanate-based polyurethane prepolymer.

[0008] Preferably, in step 1), the amount of diaminopyridine solution is determined according to the content of isocyanate groups in the isocyanate-based polyurethane prepolymer, so as to control the molar ratio of amino groups in diaminopyridine to isocyanate groups in the isocyanate-based polyurethane prepolymer to be 1:1.

[0009] Preferably, in step 1), the reaction conditions for the chain extension reaction are: a temperature of 70~90℃ and a time of 8~12h.

[0010] Preferably, in step 2), the iron salt is one of ferric chloride, ferric sulfate, and ferric nitrate. The solvent in the iron salt solution is one of methanol, ethanol, N,N-dimethylformamide, or N,N-dimethylacetamide. The concentration of the iron salt solution is 180~896 mg / mL.

[0011] Preferably, in step 2), the molar ratio of iron ions in the iron salt solution to pyridine groups in the rigid aromatic heterocyclic polyurethane is (1~3):1.

[0012] Preferably, in step 2), the iron salt solution is added dropwise for 10-30 minutes, the reaction temperature is 25-60°C, and the time is 1-3 hours.

[0013] Preferably, in step 2), the self-healing polyurethane solution is molded and dried sequentially as follows: the self-healing polyurethane solution is poured into a polytetrafluoroethylene plate and left to stand at room temperature for 24~48h, and then vacuum dried at 60~80℃ for 48~72h.

[0014] Secondly, the present invention provides a self-healing polyurethane based on pyridine-metal coordination, obtained by the preparation method described above.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention relates to a method for preparing self-healing polyurethane based on pyridine-metal coordination, relying on the nitrogen and amide nitrogen-oxygen groups of pyridine and Fe... 3+ A double dynamic coordination bond is formed, in which the nitrogen atom of pyridine can provide a lone pair electron with Fe. 3+ Coordinate bonds are formed, and Fe 3 +Furthermore, it can further coordinate with the nitrogen and oxygen groups on the polyurethane amide groups. This dual coordination effect can construct a more stable cross-linked network. Both coordination strengths are moderate, maintaining the integrity of the material structure while allowing for dissociation and recombination under mild conditions. This enables the polyurethane to close cracks at room temperature or under mild heating conditions, without the need for harsh activation methods, thus adapting to various practical needs. The dual-coordinated cross-linked network not only enhances the structural strength of the polyurethane matrix, preventing mechanical property degradation under repeated deformation, but also achieves cyclic repair through the reversible nature of the coordination bonds, effectively extending its service life. The preparation method of this invention uses solution mixing and conventional molding and drying processes. The raw materials used are readily available, and the reaction conditions are mild, facilitating large-scale production. The obtained polyurethane can be directly processed into flexible protective coatings and other components, meeting core requirements such as scratch resistance and bending resistance, significantly reducing the cost of material replacement after failure. Its multi-coordinated design also solves the problem of existing self-healing polyurethanes struggling to balance repairability and mechanical properties.

[0016] Furthermore, by controlling the molar ratio of amino to isocyanate groups to 1:1, it is ensured that the isocyanate groups are completely consumed, thereby avoiding side reactions with solvents in the subsequent iron salt solution or water molecules in the air, which would affect the stability of the subsequent coordination reaction.

[0017] Furthermore, the chain extension reaction conditions of stirring at 70~90℃ for 8~12h can ensure that the amino and isocyanate groups react fully, avoid the residue of unreacted groups, and avoid the burst polymerization caused by high temperature or the incomplete reaction caused by low temperature, thus ensuring the structural stability of the self-healing polyurethane prepolymer.

[0018] Furthermore, the concentration of the iron salt solution is 180~896 mg / mL, which is a concentration range that can balance the dispersion and coordination efficiency of iron ions.

[0019] Furthermore, the molar ratio of iron ions in the iron salt solution to pyridine groups in the rigid aromatic heterocyclic polyurethane is in the range of (1~3):1, which ensures effective coordination and preserves dynamic repair activity.

[0020] Furthermore, the dropping process lasts for 10-30 minutes, and the reaction temperature is 25-60℃, which ensures that iron ions and pyridine are fully coordinated, promotes appropriate cross-linking of the matrix, ensures uniform reaction, and reduces internal defects such as micropores and cracks.

[0021] Furthermore, after standing at room temperature for 24-48 hours, the mixture is poured into a mold, which allows the crosslinked blend solution to slowly level, dissipate air bubbles, and undergo preliminary curing, avoiding surface defects caused by rapid molding. Vacuum drying at 60-80℃ for 48-72 hours can completely remove the solvent, preventing residual air bubbles from affecting performance, while ensuring a dense material structure. The mild temperature will not damage the dynamic coordination bond structure, ensuring stable material performance. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the examples of the present invention or the prior art, the drawings used in the description of the examples or the prior art will be briefly introduced below. Obviously, the drawings described below are some examples of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This invention provides a preparation process for the self-healing polyurethane based on pyridine-metal coordination. Figure 2 The infrared spectra of the rigid aromatic heterocyclic polyurethane and the self-healing polyurethane based on pyridine-metal coordination in Example 2 of this invention are shown. Figure 3 The TGA and DTG spectra (a) of rigid aromatic heterocyclic polyurethane and self-healing polyurethane based on pyridine-metal coordination (with different ratios of iron ions and pyridine groups) in the examples of this invention are shown. Figure 4 The stress-strain curves of rigid aromatic heterocyclic polyurethane and self-healing polyurethane based on pyridine-metal coordination (with different ratios of iron ions and pyridine groups) are shown in the examples of this invention. Figure 5 The images show optical microscope images of the self-healing polyurethane film based on pyridine-metal coordination at different healing times at room temperature in Example 2 of this invention. Detailed Implementation

[0024] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0025] It should be noted that the process equipment or apparatus not specifically mentioned in the following examples all use conventional equipment or apparatus in this field.

[0026] It should be noted that the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or apparatuses. Furthermore, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not intended to limit the order of the method steps or define the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0027] Example 1 A method for preparing a self-healing polyurethane based on pyridine-metal coordination includes the following steps: 1) Preparation of rigid aromatic heterocyclic polyurethane solutions 4.44 g of isophorone diisocyanate, 11.40 g of polypropylene glycol with a relative molecular mass of 2000, and 0.40 g of dibutyltin dilaurate were dissolved in N,N-dimethylacetamide and reacted at 60 °C for 1 h. Then, 2.00 g of poly(1,4-butanediol adipate) with a relative molecular mass of 2000 was added and reacted at 70 °C for 1 h. Following this, 0.20 g of 1,4-butanediol was added and reacted for 1 h to obtain an isocyanate-based polyurethane prepolymer. Finally, 11.87 mL of a 1 mol / L solution of 2,6-diaminopyridine / N,N-dimethylacetamide was added dropwise to the reaction system, and the reaction was carried out at 85 °C for 10 h to obtain a rigid aromatic heterocyclic polyurethane solution.

[0028] 2) Preparation of self-healing polyurethane with pyridine-metal coordination 1.80 g of ferric chloride was dissolved in 10 mL of methanol and then added dropwise (over 30 min) to the above rigid aromatic heterocyclic polyurethane solution. After reacting for 3 h (25 °C), a pyridine-metal coordinated self-healing polyurethane solution was obtained. The solution, after standing for 48 h, was then molded and vacuum dried at 60 °C for 72 h to obtain a pyridine-metal coordinated self-healing polyurethane film.

[0029] Example 2 A method for preparing a self-healing polyurethane based on pyridine-metal coordination includes the following steps: 1) Preparation of rigid aromatic heterocyclic polyurethane solutions 4.44 g of isophorone diisocyanate, 11.40 g of polypropylene glycol with a relative molecular mass of 2000, and 0.40 g of dibutyltin dilaurate were dissolved in N,N-dimethylacetamide and reacted at 60 °C for 1 h. Then, 2.00 g of poly(1,4-butanediol adipate) with a relative molecular mass of 2000 was added and reacted at 70 °C for 1 h. Following this, 0.20 g of 1,4-butanediol was added and reacted for 1 h to obtain an isocyanate-based polyurethane prepolymer. Finally, 11.87 mL of a 1 mol / L solution of 2,6-diaminopyridine / N,N-dimethylacetamide was added dropwise to the reaction system, and the reaction was carried out at 85 °C for 10 h to obtain a rigid aromatic heterocyclic polyurethane solution.

[0030] 2) Preparation of self-healing polyurethane with pyridine-metal coordination 3.60 g of ferric chloride was dissolved in 10 mL of methanol and then added dropwise (over 30 min) to the above rigid aromatic heterocyclic polyurethane solution. After reacting for 3 h (25 °C), a pyridine-metal coordinated self-healing polyurethane solution was obtained. The solution, after standing for 48 h, was then molded and vacuum dried at 60 °C for 72 h to obtain a pyridine-metal coordinated self-healing polyurethane film.

[0031] Example 3 A method for preparing a self-healing polyurethane based on pyridine-metal coordination includes the following steps: 1) Preparation of rigid aromatic heterocyclic polyurethane solutions 4.44 g of isophorone diisocyanate, 11.40 g of polypropylene glycol with a relative molecular mass of 2000, and 0.40 g of dibutyltin dilaurate were dissolved in N,N-dimethylacetamide and reacted at 60 °C for 1 h. Then, 2.00 g of poly(1,4-butanediol adipate) with a relative molecular mass of 2000 was added and reacted at 70 °C for 1 h. Following this, 0.20 g of 1,4-butanediol was added and reacted for 1 h to obtain an isocyanate-based polyurethane prepolymer. Finally, 11.87 mL of a 1 mol / L solution of 2,6-diaminopyridine / N,N-dimethylacetamide was added dropwise to the reaction system, and the reaction was carried out at 85 °C for 10 h to obtain a rigid aromatic heterocyclic polyurethane solution.

[0032] 2) Preparation of self-healing polyurethane with pyridine-metal coordination 5.40 g of ferric chloride was dissolved in 10 mL of methanol and then added dropwise (over 30 min) to the above rigid aromatic heterocyclic polyurethane solution. After reacting for 3 h (25 °C), a pyridine-metal coordinated self-healing polyurethane solution was obtained. The solution, after standing for 48 h, was then molded and vacuum dried at 60 °C for 72 h to obtain a pyridine-metal coordinated self-healing polyurethane film.

[0033] Example 4 A method for preparing a self-healing polyurethane based on pyridine-metal coordination includes the following steps: 1) Preparation of rigid aromatic heterocyclic polyurethane solutions 4.44 g of isophorone diisocyanate, 11.40 g of polypropylene glycol with a relative molecular mass of 2000, and 0.40 g of dibutyltin dilaurate were dissolved in N,N-dimethylacetamide and reacted at 60 °C for 1 h. Then, 2.00 g of poly(1,4-butanediol adipate) with a relative molecular mass of 2000 was added and reacted at 70 °C for 1 h. Following this, 0.20 g of 1,4-butanediol was added and reacted for 1 h to obtain an isocyanate-based polyurethane prepolymer. Finally, 11.87 mL of a 1 mol / L solution of 2,3-diaminopyridine / N,N-dimethylacetamide was added dropwise to the reaction system, and the reaction was carried out at 70 °C for 12 h to obtain a rigid aromatic heterocyclic polyurethane solution.

[0034] 2) Preparation of self-healing polyurethane with pyridine-metal coordination 2.22 g of ferric sulfate was dissolved in 10 mL of methanol and then added dropwise (over 20 min) to the above rigid aromatic heterocyclic polyurethane solution. After reacting for 2 h (50 °C), a pyridine-metal coordinated self-healing polyurethane solution was obtained. The solution, after standing for 36 h, was then molded and vacuum dried at 60 °C for 72 h to obtain a pyridine-metal coordinated self-healing polyurethane film.

[0035] Example 5 A method for preparing a self-healing polyurethane based on pyridine-metal coordination includes the following steps: 1) Preparation of rigid aromatic heterocyclic polyurethane solutions 4.44 g of isophorone diisocyanate, 11.40 g of polypropylene glycol with a relative molecular mass of 2000, and 0.40 g of dibutyltin dilaurate were dissolved in N,N-dimethylacetamide and reacted at 60 °C for 1 h. Then, 2.00 g of poly(1,4-butanediol adipate) with a relative molecular mass of 2000 was added and reacted at 70 °C for 1 h. Following this, 0.20 g of 1,4-butanediol was added and reacted for 1 h to obtain an isocyanate-based polyurethane prepolymer. Finally, 11.87 mL of a 1 mol / L solution of 3,4-diaminopyridine / N,N-dimethylacetamide was added dropwise to the reaction system, and the reaction was carried out at 90 °C for 8 h to obtain a rigid aromatic heterocyclic polyurethane solution.

[0036] 2) Preparation of self-healing polyurethane with pyridine-metal coordination 2.22 g of ferric sulfate was dissolved in 10 mL of methanol and then added dropwise (over 30 min) to the above rigid aromatic heterocyclic polyurethane solution. After reacting for 1 h (60 °C), a pyridine-metal coordinated self-healing polyurethane solution was obtained. The solution, after standing for 48 h, was then molded and vacuum dried at 60 °C for 72 h to obtain a pyridine-metal coordinated self-healing polyurethane film.

[0037] Example 6 A method for preparing a self-healing polyurethane based on pyridine-metal coordination includes the following steps: 1) Preparation of rigid aromatic heterocyclic polyurethane solutions 4.44 g of isophorone diisocyanate, 11.40 g of polypropylene glycol with a relative molecular mass of 2000, and 0.40 g of dibutyltin dilaurate were dissolved in N,N-dimethylacetamide and reacted at 60 °C for 1 h. Then, 2.00 g of poly(1,4-butanediol adipate) with a relative molecular mass of 2000 was added and reacted at 70 °C for 1 h. Following this, 0.20 g of 1,4-butanediol was added and reacted for 1 h to obtain an isocyanate-based polyurethane prepolymer. Finally, 11.87 mL of a 1 mol / L solution of 2,6-diaminopyridine / N,N-dimethylacetamide was added dropwise to the reaction system, and the reaction was carried out at 90 °C for 8 h to obtain a rigid aromatic heterocyclic polyurethane solution.

[0038] 2) Preparation of self-healing polyurethane with pyridine-metal coordination 6.66 g of ferric sulfate was dissolved in 10 mL of methanol and then added dropwise (over 30 min) to the above rigid aromatic heterocyclic polyurethane solution. After reacting for 1 h (60 °C), a pyridine-metal coordinated self-healing polyurethane solution was obtained. The solution, after standing for 48 h, was then molded and vacuum dried at 60 °C for 72 h to obtain a pyridine-metal coordinated self-healing polyurethane film.

[0039] Example 7 A method for preparing a self-healing polyurethane based on pyridine-metal coordination includes the following steps: 1) Preparation of rigid aromatic heterocyclic polyurethane solutions 4.44 g of isophorone diisocyanate, 11.40 g of polypropylene glycol with a relative molecular mass of 2000, and 0.40 g of dibutyltin dilaurate were dissolved in N,N-dimethylacetamide and reacted at 60 °C for 1 h. Then, 2.00 g of poly(1,4-butanediol adipate) with a relative molecular mass of 2000 was added and reacted at 70 °C for 1 h. Following this, 0.20 g of 1,4-butanediol was added and reacted for 1 h to obtain an isocyanate-based polyurethane prepolymer. Finally, 11.87 mL of a 1 mol / L solution of 2,5-diaminopyridine / N,N-dimethylacetamide was added dropwise to the reaction system, and the mixture was reacted at 90 °C for 8 h to obtain a rigid aromatic heterocyclic polyurethane solution.

[0040] 2) Preparation of self-healing polyurethane with pyridine-metal coordination 4.44 g of ferric sulfate was dissolved in 10 mL of methanol and then added dropwise (over 30 min) to the above rigid aromatic heterocyclic polyurethane solution. After reacting for 1 h (60 °C), a pyridine-metal coordinated self-healing polyurethane solution was obtained. The solution, after standing for 48 h, was then molded and vacuum dried at 60 °C for 72 h to obtain a pyridine-metal coordinated self-healing polyurethane film.

[0041] Example 8 A method for preparing a self-healing polyurethane based on pyridine-metal coordination includes the following steps: 1) Preparation of rigid aromatic heterocyclic polyurethane solutions 4.44 g of isophorone diisocyanate, 11.40 g of polypropylene glycol with a relative molecular mass of 2000, and 0.40 g of dibutyltin dilaurate were dissolved in N,N-dimethylacetamide and reacted at 60 °C for 1 h. Then, 2.00 g of poly(1,4-butanediol adipate) with a relative molecular mass of 2000 was added and reacted at 70 °C for 1 h. Following this, 0.20 g of 1,4-butanediol was added and reacted for 1 h to obtain an isocyanate-based polyurethane prepolymer. Finally, 11.87 mL of a 1 mol / L solution of 3,5-diaminopyridine / N,N-dimethylacetamide was added dropwise to the reaction system, and the mixture was reacted at 90 °C for 8 h to obtain a rigid aromatic heterocyclic polyurethane solution.

[0042] 2) Preparation of self-healing polyurethane with pyridine-metal coordination 6.66 g of ferric sulfate was dissolved in 10 mL of methanol and then added dropwise (over 30 min) to the above rigid aromatic heterocyclic polyurethane solution. After reacting for 1 h (60 °C), a pyridine-metal coordinated self-healing polyurethane solution was obtained. The solution, after standing for 48 h, was then molded and vacuum dried at 80 °C for 48 h to obtain a pyridine-metal coordinated self-healing polyurethane film.

[0043] Example 9 A method for preparing a self-healing polyurethane based on pyridine-metal coordination includes the following steps: 1) Preparation of rigid aromatic heterocyclic polyurethane solutions 4.44 g of isophorone diisocyanate, 11.40 g of polypropylene glycol with a relative molecular mass of 2000, and 0.40 g of dibutyltin dilaurate were dissolved in N,N-dimethylacetamide and reacted at 60 °C for 1 h. Then, 2.00 g of poly(1,4-butanediol adipate) with a relative molecular mass of 2000 was added and reacted at 70 °C for 1 h. Following this, 0.20 g of 1,4-butanediol was added and reacted for 1 h to obtain an isocyanate-based polyurethane prepolymer. Finally, 11.87 mL of a 1 mol / L solution of 3,5-diaminopyridine / N,N-dimethylacetamide was added dropwise to the reaction system, and the mixture was reacted at 90 °C for 8 h to obtain a rigid aromatic heterocyclic polyurethane solution.

[0044] 2) Preparation of self-healing polyurethane with pyridine-metal coordination 4.48 g of ferric nitrate was dissolved in 10 mL of methanol and then added dropwise (over 30 min) to the above rigid aromatic heterocyclic polyurethane solution. After reacting for 1 h (60 °C), a pyridine-metal coordinated self-healing polyurethane solution was obtained. The solution, after standing for 36 h, was then molded and vacuum dried at 80 °C for 48 h to obtain a pyridine-metal coordinated self-healing polyurethane film.

[0045] Example 10 A method for preparing a self-healing polyurethane based on pyridine-metal coordination includes the following steps: 1) Preparation of rigid aromatic heterocyclic polyurethane solutions 4.44 g of isophorone diisocyanate, 11.40 g of polypropylene glycol with a relative molecular mass of 2000, and 0.40 g of dibutyltin dilaurate were dissolved in N,N-dimethylacetamide and reacted at 60 °C for 1 h. Then, 2.00 g of poly(1,4-butanediol adipate) with a relative molecular mass of 2000 was added and reacted at 70 °C for 1 h. Following this, 0.20 g of 1,4-butanediol was added and reacted for 1 h to obtain an isocyanate-based polyurethane prepolymer. Finally, 11.87 mL of a 1 mol / L solution of 3,5-diaminopyridine / N,N-dimethylacetamide was added dropwise to the reaction system, and the mixture was reacted at 90 °C for 8 h to obtain a rigid aromatic heterocyclic polyurethane solution.

[0046] 2) Preparation of self-healing polyurethane with pyridine-metal coordination 8.96 g of ferric nitrate was dissolved in 10 mL of methanol and then added dropwise (over 30 min) to the above rigid aromatic heterocyclic polyurethane solution. After reacting for 1 h (60 °C), a pyridine-metal coordinated self-healing polyurethane solution was obtained. The solution, after standing for 48 h, was then molded and vacuum dried at 80 °C for 48 h to obtain a pyridine-metal coordinated self-healing polyurethane film.

[0047] Example 11 A method for preparing a self-healing polyurethane based on pyridine-metal coordination includes the following steps: 1) Preparation of rigid aromatic heterocyclic polyurethane solutions 4.44 g of isophorone diisocyanate, 11.40 g of polypropylene glycol with a relative molecular mass of 2000, and 0.40 g of dibutyltin dilaurate were dissolved in N,N-dimethylacetamide and reacted at 60 °C for 1 h. Then, 2.00 g of poly(1,4-butanediol adipate) with a relative molecular mass of 2000 was added and reacted at 70 °C for 1 h. Following this, 0.20 g of 1,4-butanediol was added and reacted for 1 h to obtain an isocyanate-based polyurethane prepolymer. Finally, 11.87 mL of a 1 mol / L solution of 2,6-diaminopyridine / N,N-dimethylacetamide was added dropwise to the reaction system, and the reaction was carried out at 70 °C for 12 h to obtain a rigid aromatic heterocyclic polyurethane solution.

[0048] 2) Preparation of self-healing polyurethane with pyridine-metal coordination 3.60 g of ferric chloride was dissolved in 10 mL of methanol and then added dropwise (over 20 min) to the above rigid aromatic heterocyclic polyurethane solution. After reacting for 2 h (50 °C), a pyridine-metal coordinated self-healing polyurethane solution was obtained. The solution, after standing for 24 h, was then molded and vacuum dried at 70 °C for 60 h to obtain a pyridine-metal coordinated self-healing polyurethane film.

[0049] Example 12 A method for preparing a self-healing polyurethane based on pyridine-metal coordination includes the following steps: 1) Preparation of rigid aromatic heterocyclic polyurethane solutions 4.44 g of isophorone diisocyanate, 11.40 g of polypropylene glycol with a relative molecular mass of 2000, and 0.40 g of dibutyltin dilaurate were dissolved in N,N-dimethylacetamide and reacted at 60 °C for 1 h. Then, 2.00 g of poly(1,4-butanediol adipate) with a relative molecular mass of 2000 was added and reacted at 70 °C for 1 h. Following this, 0.20 g of 1,4-butanediol was added and reacted for 1 h to obtain an isocyanate-based polyurethane prepolymer. Finally, 11.87 mL of a 1 mol / L solution of 2,6-diaminopyridine / N,N-dimethylacetamide was added dropwise to the reaction system, and the mixture was reacted at 90 °C for 8 h to obtain a rigid aromatic heterocyclic polyurethane solution.

[0050] 2) Preparation of self-healing polyurethane with pyridine-metal coordination 4.60 g of ferric chloride was dissolved in 10 mL of methanol and then added dropwise (over 30 min) to the above rigid aromatic heterocyclic polyurethane solution. After reacting for 1 h (60 °C), a pyridine-metal coordinated self-healing polyurethane solution was obtained. The solution, after standing for 48 h, was then molded and vacuum dried at 60 °C for 72 h to obtain a pyridine-metal coordinated self-healing polyurethane film.

[0051] See Figure 1 This is a synthetic route diagram of the pyridine-metal coordination self-healing polyurethane disclosed in this invention; as can be seen from the diagram, the entire preparation process is simple and can yield a pyridine-metal coordination-based self-healing polyurethane.

[0052] See Figure 2 This is the infrared absorption spectrum of the self-healing polyurethane based on pyridine-metal coordination in Example 2 of this invention; as can be seen from the figure, the rigid aromatic heterocyclic polyurethane absorbs infrared light at 1642 cm⁻¹. -1 The characteristic absorption peak at 1708 cm⁻¹ belongs to the vibrational mode of the C=N bond in free pyridine, while the peak at 1708 cm⁻¹ belongs to the vibrational mode of the C=N bond in free pyridine. -1 The characteristic absorption peak at 1550 cm⁻¹ is attributed to the stretching vibration of the C=O bond in amide band I. -1 The characteristic absorption peak at this location corresponds to the stretching vibration of the CN bond and the deformation vibration of the NH bond in amide band II, indicating that diaminopyridine was successfully introduced into the isocyanate-based polyurethane backbone. For pyridine-metal coordinated self-healing polyurethanes, Fe... 3+ The addition of [something] caused the stretching vibration of the C=N bond to increase from 1642 cm⁻¹. -1 Moved to 1649 cm -1 This indicates that diaminopyridine reacts with Fe 3+ Complexation occurred between them. The characteristic absorption peaks of amide band I and amide band II are located at 1708 cm⁻¹. -1 and 1550 cm -1 Moved to 1698 cm -1 and 1562 cm-1 This indicates that the nitrogen and oxygen on the amide group react with Fe. 3+ The same network interaction also occurred.

[0053] See Figure 3 The figures show the TGA and DTG curves of the self-healing polyurethanes based on pyridine-metal coordination in Examples 1-3 of this invention. As can be seen from the figures, compared with rigid aromatic heterocyclic polyurethanes, the thermal stability of the self-healing polyurethanes based on pyridine-metal coordination is significantly improved, indicating that Fe... 3+ The addition of [a specific ingredient] has a certain promoting effect on improving the thermal stability of polyurethane. Compared with [another ingredient] without Fe [a specific ingredient]... 3+ Compared to rigid aromatic heterocyclic polyurethanes, self-healing polyurethanes based on pyridine-metal coordination exhibit higher thermal decomposition temperatures for the same mass loss, indicating that Fe... 3+ The crosslinking structure formed by coordination with nitrogen and oxygen on diaminopyridine and amide groups effectively increases the crosslinking density between PU chains, further enhancing intermolecular cohesion and thus improving the thermal stability of polyurethane.

[0054] See Figure 4 The figures show the stress-strain curves of the rigid aromatic heterocyclic polyurethane and the self-healing polyurethane based on pyridine-metal coordination in Examples 1-3 of this invention. It can be seen that, relative to the rigid aromatic heterocyclic polyurethane, with different Fe contents... 3+ The addition of Fe increased the tensile strength of self-healing polyurethane to 2.32, 5.16, and 3.15 MPa, respectively, indicating that with the addition of Fe... 3+ With increasing dosage, the tensile strength of self-healing polyurethane first increases and then decreases.

[0055] See Figure 5 The images shown in Example 2 of this invention are before and after self-healing of the pyridine-metal coordination-based self-healing polyurethane film at room temperature using an optical microscope, from 0 to 36 hours. This demonstrates that the pyridine-metal coordination-based self-healing polyurethane film prepared in this invention has good self-healing properties. After 36 hours of repair, the scratches disappear and the microscopic fracture surface returns to a smooth state.

[0056] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of this invention.

Claims

1. A method for preparing a self-healing polyurethane based on pyridine-metal coordination, characterized in that, Includes the following steps: 1) Dissolve diaminopyridine in an organic solvent to obtain a diaminopyridine solution; stir and mix the diaminopyridine solution with isocyanate-based polyurethane prepolymer to carry out a chain extension reaction to obtain a rigid aromatic heterocyclic polyurethane solution. 2) Add the iron salt solution dropwise to the rigid aromatic heterocyclic polyurethane solution to react and obtain the self-healing polyurethane solution; then mold and dry the self-healing polyurethane solution to obtain the self-healing polyurethane based on pyridine-metal coordination.

2. The method for preparing self-healing polyurethane based on pyridine-metal coordination according to claim 1, characterized in that, In step 1), the diaminopyridine is one or more of 2,6-diaminopyridine, 2,5-diaminopyridine, 2,4-diaminopyridine, 2,3-diaminopyridine, 3,4-diaminopyridine and 3,5-diaminopyridine.

3. The method for preparing self-healing polyurethane based on pyridine-metal coordination according to claim 1, characterized in that, In step 1), the preparation method of the isocyanate-based polyurethane prepolymer is as follows: isophorone diisocyanate, polypropylene glycol and dibutyltin dilaurate are dissolved in N,N-dimethylacetamide and subjected to polymerization reaction, then poly(1,4-butanediol adipate) is added and subjected to polymerization reaction, and then 1,4-butanediol is added and subjected to polymerization reaction to obtain isocyanate-based polyurethane prepolymer.

4. The method for preparing self-healing polyurethane based on pyridine-metal coordination according to claim 1, characterized in that, In step 1), the molar ratio of the amino group in the diaminopyridine to the isocyanate group in the isocyanate-based polyurethane prepolymer is 1:

1.

5. The method for preparing self-healing polyurethane based on pyridine-metal coordination according to claim 1, characterized in that, In step 1), the chain extension reaction is carried out at a temperature of 70-90°C for 8-12 hours.

6. The method for preparing self-healing polyurethane based on pyridine-metal coordination according to claim 1, characterized in that, In step 2), the iron salt is one of ferric chloride, ferric sulfate, and ferric nitrate, and the concentration of the iron salt solution is 180~896 mg / mL.

7. The method for preparing self-healing polyurethane based on pyridine-metal coordination according to claim 1, characterized in that, In step 2), the molar ratio of iron ions in the iron salt solution to pyridine groups in the rigid aromatic heterocyclic polyurethane is (1~3):

1.

8. The method for preparing self-healing polyurethane based on pyridine-metal coordination according to claim 1, characterized in that, In step 2), the reaction temperature is 25~60℃ and the time is 1~3h.

9. The method for preparing self-healing polyurethane based on pyridine-metal coordination according to claim 1, characterized in that, In step 2), the self-healing polyurethane solution is molded and dried sequentially as follows: the self-healing polyurethane solution is poured into a polytetrafluoroethylene plate and left to stand at room temperature for 24~48h, and then vacuum dried at 60~80℃ for 48~72h.

10. A self-healing polyurethane based on pyridine-metal coordination, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 9.

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