Hydrated boric acid ester micromolecule with boron-nitrogen coordination bond, polyurethane elastomer material and preparation method of hydrated boric acid ester micromolecule and polyurethane elastomer material

Abstract

The invention relates to a hydrated borate micromolecule with a boron-nitrogen coordination bond, a polyurethane elastomer material and a preparation method thereof, and the preparation method comprises the following steps: S1, dissolving and reacting 1, 4-benzene diboronic acid and a polyfunctional group amine compound at room temperature through a solution reaction to form a rigid eight-membered ring intramolecular boron-nitrogen coordination micromolecule NCBW-X; s2, polyester (polycaprolactone, polybutylene terephthalate, polylactic acid and the like) or polyether (polytetrahydrofuran, polypropylene ether polyol and the like) and diisocyanate (isophorone diisocyanate, toluene diisocynate and the like) react in a dry solvent at 80 DEG C by using a catalyst to form a prepolymer; hydrazide and NCBW-X are added into the obtained prepolymer for chain extension; the water resistance and the acid and alkali resistance of the material are enhanced through the boron-nitrogen coordination structure characteristic; and the prepared polyurethane elastomer material has very strong self-repairing efficiency and environmental adaptability.

Description

Technical Field

[0001] The invention belongs to the technical field of high-performance solvent-resistant elastomers in new materials, and relates to a hydrated borate small molecule with boron-nitrogen coordination bonds and a polyurethane elastomer material and a preparation method thereof, and in particular to a hydrated borate small molecule and a polyurethane elastomer material containing synergistic effects of hydrogen bonds and coordination bonds and a preparation method thereof. Background Art

[0002] Supramolecular elastomers have the properties of repairability and recyclability, which help to extend the service life of elastomer materials, thus having a positive impact on building a sustainable society. However, dynamic cross-linked supramolecular elastomers based on non-covalent interactions face challenges in mechanical strength, thermal stability and solvent resistance. This is because the weak and reversible nature of non-covalent bonds limits their performance in practical applications. In addition, the polar groups in supramolecular elastomers are sensitive to water, resulting in a significant decrease in mechanical properties in humidity or aqueous solutions, which is difficult to meet practical needs. Current research focuses on improving the mechanical strength, thermal stability and solvent resistance of supramolecular elastomers. At the same time, due to the extreme sensitivity of isocyanates to humidity, side reactions are prone to occur during the isocyanate curing reaction, affecting the network structure of the polymer, resulting in a decrease in the mechanical properties of the adhesive network. At the same time, reversible non-covalent bonds are generally dominated by some weak intermolecular interactions (including hydrogen bonds, coordination bonds and π-π stacking interactions, etc.). By adopting different non-covalent bonds, such as hydrogen bonds, ionic bonds, coordination bonds, etc., and adjusting the chemical structure, we are committed to improving the wet and thermal stability, solvent resistance and overall performance, thereby promoting the practical application of supramolecular elastomers in complex environments.

[0003] Although borate esters and boron ethers have been successfully used to construct various self-healing materials and reprocessable thermosetting materials, since borate esters and boron ethers are very sensitive to water or alcohol, the materials usually have poor water resistance. There are currently two main methods to improve the water resistance of borate ester and boron ether polymers:

[0004] (1) Introducing nitrogen-containing electron donors, such as amines and pyridine, to form BN coordination bonds with borate esters or boron ethers;

[0005] (2) Using hydrophobic material as the matrix.

[0006] Previous studies have found that even if BN coordination bonds are formed, polyurethane materials still have poor humidity stability, but the rapid reversible breakage and reorganization of BN coordination bonds can effectively absorb stretching energy.

[0007] Therefore, it is necessary to design a new method to synergistically construct room-temperature self-healing polymer materials by dynamic borate and BN coordination bonds, so as to solve the problems of insufficient self-healing ability and poor environmental stability in existing polyurethane materials due to the lack of synergistic effects of hydrogen bonds and coordination bonds, and the contradiction between the room-temperature self-healing mechanical properties and self-healing properties of polyurethane materials. Summary of the invention

[0008] In view of this, in order to solve the problem of insufficient self-repairing ability and poor environmental stability in existing polyurethane materials due to the lack of synergistic effect of hydrogen bonds and coordination bonds, which leads to contradictions between the room temperature self-repairing mechanical properties and self-repairing properties of polyurethane materials, the present invention provides a hydrated borate ester small molecule with boron-nitrogen coordination bonds and a polyurethane elastomer material and a preparation method thereof. The polyurethane elastomer material prepared by the method has strong self-repairing efficiency and environmental adaptability, is a high-strength, high-toughness, tear-resistant thermoplastic polyurethane elastomer that can self-repair at room temperature, and has good potential in waterproof and acid- and alkali-resistant polyurethane elastomer materials.

[0009] In order to achieve the above object, the present invention provides the following technical solutions:

[0010] A hydrated borate ester small molecule with a boron-nitrogen coordination bond, the hydrated borate ester small molecule is synthesized from boric acid and its derivatives and a multifunctional amine compound, and its chemical structure is generally as follows:

[0011]

[0012] The synthetic route is:

[0013]

[0014] Among them, the general chemical structure formula of boric acid and its derivatives is as follows:

[0015]

[0016] R 1 It is represented by a substituent, selected from any one of the electron donating groups such as hydrogen (-H), ortho-hydroxyl (m-OH), para-hydroxyl (p-OH), ortho-amino (m-NH2) and para-amino (p-NH2), wherein n represents multiple boronic acid groups, n≥2; Boric acid and its derivatives are all boronic acids with aromatic rings (such as benzene ring, biphenyl, thiophene, pyridine, pyrazole, carbazole, etc.), wherein m, p represents -OH or -NH2 located at the ortho or para position of the aromatic ring; its main examples are as follows:

[0017]

[0018] The general chemical structure of multifunctional amine compounds is as follows:

[0019]

[0020] R 2 It is represented by a substituent, which is a carbon chain or carbon chains of different lengths terminated by amino (-NH2), hydroxyl (-OH), alkenyl, alkynyl, carboxyl, etc.; its main examples are as follows:

[0021]

[0022] The main examples of the formed boron-nitrogen coordinated small molecule NCBW-X are as follows:

[0023]

[0024] The method for preparing the polyurethane elastomer material based on the above-mentioned hydrated borate ester small molecule having a boron-nitrogen coordination bond comprises the following steps:

[0025] S1. Synthesis of boron-nitrogen coordinated small molecules: Boric acid and its derivatives are dissolved and reacted with multifunctional amine compounds at room temperature through a solution reaction to form a boron-nitrogen coordinated small molecule NCBW-X (X=1, 2, 3...) with an eight-membered ring structure, wherein the boron-nitrogen coordination causes the eight-membered ring to split into two five-membered rings, so that the rigid eight-membered ring can exist stably. The rigid eight-membered ring forms a coordination system when it meets water, thereby improving the hydrolysis resistance of boric esters;

[0026] S2. Synthesize polyurethane elastomer material: Under nitrogen protection, the soft segment (such as polycaprolactone PCL, polytetramethylene diisocyanate PTEMG, polypropylene glycol PPG and other terminal hydroxyl-terminated substances) is dissolved in a three-necked flask, and the hard segment diisocyanate (such as isophorone diisocyanate IPDI, hexamethylene diisocyanate HDI, toluene diisocyanate TDI and other terminal isocyanate-terminated substances) is added through a syringe. After adding the diisocyanate, wait until it is evenly mixed before adding The isocyanate-terminated prepolymer is obtained by stirring the mixture in a nitrogen atmosphere at 80° C. for 3 hours with 0.1 wt% of dibutyltin dilaurate as a catalyst; after cooling to 50° C., the NCBW-X prepared in step S1 is added, and the reaction is continued for 6 hours, and then the solution is poured into a polytetrafluoroethylene mold, and dried at 70° C. to obtain a polyurethane elastomer material containing NCBW-X boron-nitrogen coordination bonds, wherein the soft segment: hard segment: NCBW-X=1:2:1.

[0027] During the preparation of isocyanate-terminated prepolymers, the control of temperature and time is crucial to the mechanical properties and self-healing characteristics of the final material; adjusting the temperature to 40°C can ensure that ADH will not agglomerate due to high temperature, and further increasing the temperature allows NCBW-X to fully react and the unreacted isocyanate groups to be completely consumed to form the expected polyurethane network structure.

[0028] The waterproof acid-base resistant polyurethane elastomer material is formed by the synergistic effect of dynamic covalent bonds and non-covalent bonds, wherein the dynamic covalent boron-nitrogen coordination bond is composed of ligands such as borate and nitrogen-containing electron donors; the non-covalent hydrogen bond is formed between molecules by ADH, the mechanical properties of the material are optimized, and it has high strength and high elasticity, and at the same time, it has significant improvements in water resistance and solvent resistance, and can be immersed in 2 mol / L HCl and NaOH with pH=10 for one month, and still has excellent performance; the self-healing behavior of the material is realized under water wetting at 80°C, the self-healing efficiency reaches the expected value within a certain time, and the mechanical integrity of the material is effectively restored; the material has a wide range of applications, and is suitable for complex environments in the field of high-performance solvent-resistant elastomer technology, such as applications in high humidity and water.

[0029] The principle and beneficial effect of this basic scheme are: the material is mainly composed of polycaprolactone (PCL) and isophorone diisocyanate (IPDI) as prepolymers, and the prepolymers, adipic acid dihydrazide (ADH) and boron nitrogen coordination small molecules (NCBW-1 or NCBW-2) constitute the final elastomer. By adding ADH and NCBW-X to the prepolymer, a network structure containing both hydrogen bonds and metal coordination is formed. This design not only enhances the mechanical properties of the polyurethane material, but also gives it excellent self-healing ability and waterproof properties.

[0030] Among them, polycaprolactone (PCL) and isophorone diisocyanate (IPDI) provide the basic polymer skeleton and physical properties as soft segment and hard segment respectively; adipic acid dihydrazide (ADH), as the main source of hydrogen bonds, forms strong hydrogen bonds with the amino acid residues of the polymer chain, enhances the cohesion of the material and promotes phase separation; boron nitrogen coordination small molecules (NCBW-X) provide additional mechanical property enhancement and dynamic self-healing mechanism by forming metal coordination bonds with electron-rich nitrogen atoms in the polymer.

[0031] Furthermore, the multifunctional amine compound in step S1 is triethanolamine, the solvent used for the solution reaction is one of methanol or ethanol, and the boron-nitrogen coordination small molecule formed is NCBW-1. The specific synthesis method includes the following steps: at room temperature, 1,4-phenyldiboric acid and triethanolamine are dissolved in methanol respectively, and then the triethanolamine solution is transferred to a single-necked flask, and then the methanol solution of 1,4-dihydroxyborophene is added dropwise. A white precipitate begins to form within 1 minute after the addition, and the reaction stops after 5 minutes without further heating. Finally, the precipitate is filtered and washed with ethanol two to three times.

[0032] Furthermore, the multifunctional amine compound in step S1 is diethanolamine, the solvent used for the solution reaction is one of methanol or ethanol, and the boron-nitrogen coordination small molecule formed is NCBW-2. The specific synthesis method includes the following steps: at room temperature, 1,4-phenyldiboric acid and diethanolamine are dissolved in ethanol respectively, and then the diethanolamine solution is transferred to a single-necked flask, and then the ethanol solution of 1,4-dihydroxyborophene is added dropwise. A white precipitate begins to form within 1 minute after the addition, and the reaction stops after 5 minutes without further heating. Finally, the precipitate is filtered and washed with ethanol two to three times.

[0033] Furthermore, in step S2, the hydroxyl-terminated soft segment is one of polycaprolactone PCL, polybutylene terephthalate, and polylactic acid polyesters, or one of polytetrahydrofuran PTEMG and polypropylene ether polyol polyethers, and the isocyanate-terminated diisocyanate hard segment is one of isophorone diisocyanate IPDI, hexamethylene diisocyanate HDI, and toluene diisocyanate TDI.

[0034] Further, step S2 contains the synthesis of boron-nitrogen coordinated small molecule NCBW-1 elastomer, which specifically includes the following steps: under nitrogen protection, polycaprolactone is dissolved in a three-necked flask, isophorone diisocyanate is added through a syringe, IPDI is added and mixed evenly, and then dibutyltin dilaurate accounting for 0.1wt% of the mass of IPDI / PCL-2000 is added as a catalyst, and stirred in a nitrogen atmosphere at 80°C for 3h to obtain an isocyanate-terminated prepolymer; after cooling to about 50°C, adipic acid dihydrazide is added and the temperature is raised to 80°C and the reaction is continued for 2h, and then the NCBW-1 prepared in step S1 is added thereto, and the reaction is continued for 6h, and then the solution is poured into a polytetrafluoroethylene mold, and dried at 70°C to prepare a polyurethane elastomer containing dynamic ionic bonds, which is recorded as PCL-IPDI-ADH-NCBW-1.

[0035] Further, step S2 contains the synthesis of boron-nitrogen coordinated small molecule NCBW-2 elastomer, which specifically includes the following steps: under nitrogen protection, weigh polycaprolactone and dissolve it in a three-necked flask, add isophorone diisocyanate through a syringe, add IPDI and mix well, then add dibutyltin dilaurate accounting for the mass of IPDI / PCL-2000 and 0.1wt% as a catalyst, stir for 3 hours in a nitrogen atmosphere at 80°C to obtain an isocyanate-terminated prepolymer; after cooling to about 50°C, add adipic acid dihydrazide and heat to 80°C to continue the reaction for 2 hours, then add the NCBW-2 prepared in step S1, continue the reaction for 6 hours, pour the solution into a polytetrafluoroethylene mold, and dry it at 70°C to prepare a polyurethane elastomer containing dynamic ionic bonds, which is recorded as PCL-IPDI-ADH-NCBW-2.

[0036] The waterproof and acid- and alkali-resistant polyurethane elastomer material is prepared by the method for preparing the polyurethane elastomer material of hydrated borate small molecules with boron-nitrogen coordination bonds.

[0037] Furthermore, the waterproof and acid- and alkali-resistant polyurethane elastomer material introduces adipic acid dihydrazide and NCBW-X as chain extenders, and the quadruple hydrogen bonding effect constructed therein is beneficial to improving the elongation at break of the material and maintaining a considerable tensile strength.

[0038] Furthermore, the waterproof and acid- and alkali-resistant polyurethane elastomer material can withstand 2 mol / l HCl, saturated NaCl, and pH=10 NaOH solutions.

[0039] The beneficial effects of the present invention are:

[0040] 1. The hydrated borate ester small molecule with boron-nitrogen coordination bond disclosed in the present invention is formed by dissolving and reacting boric acid and its derivatives with multifunctional amine compounds at room temperature through solution reaction to form a boron-nitrogen coordination small molecule NCBW-X; when selecting boric acid and its derivatives, boric acid and derivatives with aromatic ring structures are selected, which is conducive to the construction of high-strength small molecules, such as phenylboronic acid, biphenylboronic acid, thiopheneboronic acid, pyridineboronic acid, pyrazoleboronic acid, carbazoleboronic acid, etc. The characteristics of these boric acid derivatives are that the functional groups on the aromatic ring (such as hydroxyl-OH or amino-NH2) are located in the ortho or para position of the ring; the selection of multifunctional amine compounds, such as N,N-di(2-hydroxyethyl)amine derivatives; the nitrogen atom (N) connects two 2-hydroxyethyl (-CH2CH2OH) groups. R 2 Represents a variable substituent, which can be one of the following two forms: a substituent having a (-CH2)m structural unit and a hydroxyl group (-OH) at the terminal; a substituent having a (-CH2)m structural unit and an amino group (-NH2) at the terminal.

[0041] Boron-nitrogen coordinated small molecules can not only be used to modify traditional polymer materials to improve the mechanical properties and heat resistance of materials, but also enhance the durability and safety of materials by introducing self-repairing functions. This self-repairing function enables the material to restore its original performance under appropriate stimulation after being physically or chemically damaged, which has great economic value and social significance for reducing maintenance costs and extending the life of materials. These characteristics of boron-nitrogen coordinated small molecules enable them to show broad application prospects in many fields. In polyurethane materials, the interaction between hard segments and soft segments can be improved and the microscopic phase separation structure of the material can be optimized to obtain better mechanical properties and processing performance.

[0042] 2. The polyurethane elastomer material of hydrated borate small molecules with boron-nitrogen coordination bonds disclosed in the present invention introduces multiple hydrogen bond structural units and boron-nitrogen coordination small molecules into the main chain through chain extension reaction, and introduces borate and nitrogen-containing electron donors that can form coordination into the polyurethane main chain respectively through molecular design to prepare thermoplastic polyurethane elastomer materials based on the synergistic effect of dynamic borate and BN coordination bonds. BN coordination bonds construct intramolecular and intermolecular supramolecular effects in polyurethane elastomers: intermolecular BN coordination bonds promote the folding of polymer chains, giving the material ultra-high mechanical properties; intermolecular BN coordination bonds act as physical crosslinking points, significantly improving the mechanical strength of the material. At the same time, the reversible fracture and recombination mechanism of BN coordination bonds can effectively absorb external energy, and polyurethane exhibits excellent notch insensitivity and outstanding puncture resistance. In addition, the high reversibility of borate, BN coordination bonds and hydrogen bonds gives polyurethane elastomers excellent room temperature self-healing properties.

[0043] 3. The polyurethane elastomer material of hydrated borate ester small molecules with boron-nitrogen coordination bonds disclosed in the present invention mainly consists of polycaprolactone (PCL) and isophorone diisocyanate (IPDI) as prepolymers, adipic acid dihydrazide (ADH) and boron-nitrogen coordination small molecules (NCBW-1 or NCBW-2) as the final elastomer. By adding ADH and NCBW-X to the prepolymer, a network structure containing both hydrogen bonds and metal coordination is formed. Such a design not only enhances the mechanical properties of the polyurethane material, but also gives it excellent self-healing ability and waterproof and acid-base resistance.

[0044] 4. The polyurethane elastomer material of hydrated borate ester small molecules with boron-nitrogen coordination bonds disclosed in the present invention is constructed by the nucleophilic addition reaction of 1,4-phenylenediboronic acid and diethanolamine or triethanolamine. The small molecule is characterized by containing a boron-nitrogen coordinated 8-membered ring. The material is composed of a main chain composed of a polycaprolactone (PCL) substrate and isophorone diisocyanate (IPDI), wherein PCL is composed of a long-chain polyester with a molecular weight of about 2000; the material introduces adipic acid dihydrazide (ADH) and boron-nitrogen coordinated small molecules NCBW-1 or NCBW-2 into the main chain to form a supramolecular network structure with synergistic effects of hydrogen bonds and coordination bonds. The introduction of adipic acid dihydrazide to construct a quadruple hydrogen bond is beneficial to improving the elongation at break. The boron-nitrogen coordinated rigid octagonal ring of NCBW-X can improve waterproofness, acid and alkali resistance and has a self-repairing function. The prepared polyurethane elastomer material has strong self-healing efficiency and environmental adaptability. Compared with other borate elastomers, its boron-nitrogen coordinated structural characteristics enhance its waterproofness and acid-base resistance. The material can withstand 2 mol / l HCl, saturated NaCl, and pH=10 NaOH solution.

[0045] The polyurethane elastomer material constructed as above exhibits high tensile strength, high elongation at break and high elastic modulus in terms of mechanical properties, and has self-healing properties at room temperature; the special design of the boron-nitrogen coordination bonds in the material enables the coordination bonds to break and reorganize quickly after the material is mechanically damaged, thereby absorbing and dispersing tensile energy, effectively improving the material's tear and puncture resistance; the material preparation process is carried out in a water-free and oxygen-free environment to ensure the integrity and stability of the formed polyurethane network structure.

[0046] 5. In the waterproof and acid- and alkali-resistant polyurethane elastomer material with synergistic hydrogen bonds and coordination bonds disclosed in the present invention, adipic acid dihydrazide provides a multiple hydrogen bond system for the composite material, and the boron-nitrogen small molecule compound containing a coordination bond structure attacks the boron atom in the boric acid molecule through the secondary amino group as a nucleophilic reagent to form a new boron-nitrogen coordination bond. Its advantage is that when the eight-ring borate elastomer system formed by boron-nitrogen coordination is soaked in water, acid, alkali, or salt for a long time, the borate will not open the ring and cleave into boric acid and the corresponding alcohol due to the attack of the CO bond by water molecules. Instead, the B atom of the borate will coordinate with the O atom of the water molecule, changing the original BN bond length, thereby increasing the original tight eight-membered ring crosslinking density, making it difficult for water molecules to enter. At the same time, the borate system can be made to have higher dynamics by changing the temperature, which is specifically reflected in that the presence of boron-nitrogen coordination at room temperature will not cause the borate to cleave, but at 80°C , the higher temperature makes the CO bond of borate ester attacked by water molecules and cracked. Due to the high dynamics of borate ester, it can achieve self-repair at this temperature. Based on the above advantages, the elastomer can realize the dynamic reversible system of non-covalent bonds formed by hydrogen bonds and coordination bonds. First, the terminal hydroxyl polycaprolactone and diisocyanate are prepolymerized, and then the chain extender containing multiple hydrogen bond systems and the chain extender containing boron nitrogen with coordination bond structure are added to extend the chain, and two terminal hydroxyl polymers containing different chain extenders are obtained. The chain extender ratio in the two terminal hydroxyl polymers containing different chain extenders is adjusted. Furthermore, the construction of the non-covalent dynamic reversible system with the synergistic effect of hydrogen bonds and coordination bonds is conducive to the improvement of the microphase separation structure and solvent resistance of the polyurethane system, solving the problems of poor solvent resistance of polyester elastomers and poor mechanical properties under the non-covalent dynamic reversible system.

[0047] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0049] Figure 1 The synthetic route of the boron-nitrogen coordinated small molecule of the present invention is as follows;

[0050] Figure 2 is a synthetic route of the boron-nitrogen coordinated small molecule in the embodiment of the present invention, wherein Figure 2 (a) shows the synthesis of the boron-nitrogen coordinated small molecule NCBW-1. Figure 2 (b) shows the synthesis of the boron-nitrogen coordinated small molecule NCBW-2;

[0051] Figure 3 The synthetic route of the waterproof and acid- and alkali-resistant polyurethane elastomer material (PCL-IPDI-ADH-NCBW-1) or (PCL-IPDI-ADH-NCBW-2) containing the synergistic effect of hydrogen bonds and coordination bonds in the embodiment of the present invention;

[0052] Figure 4 is the boron-nitrogen coordinated small molecule NCBW-1 in Example 1 of the present invention 1 H-NMR and 13 C-NMR spectrum, where Figure 4 (a) is the boron-nitrogen coordinated small molecule NCBW-1 1 H-NMR spectrum, Figure 4 (b) is the boron-nitrogen coordinated small molecule NCBW-1 13 C-NMR spectrum;

[0053] Figure 5 is the boron-nitrogen coordinated small molecule NCBW-2 in Example 2 of the present invention 1 H-NMR and 13 C-NMR (b), where Figure 5 (a) is the boron-nitrogen coordinated small molecule NCBW-2 1 H-NMR spectrum, Figure 5 (b) is the boron-nitrogen coordinated small molecule NCBW-2 13 C-NMR spectrum;

[0054] Figure 6 FTIR comparison diagram of the waterproof and acid- and alkali-resistant polyurethane elastomer materials (PCL-IPDI-ADH-NCBW-1) and (PCL-IPDI-ADH-NCBW-2) with synergistic effects of hydrogen bonds and coordination bonds in the embodiment of the present invention;

[0055] Figure 7 This is a comparison diagram of the stress-strain curves of the waterproof and acid- and alkali-resistant polyurethane elastomer materials (PCL-IPDI-ADH-NCBW-1) and (PCL-IPDI-ADH-NCBW-2) with synergistic effects of hydrogen bonds and coordination bonds in the embodiments of the present invention. DETAILED DESCRIPTION

[0056] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0057] Self-repairing ability refers to the ability of the material to quickly self-repair at 80°C under water drive, and to recover most of its original mechanical properties within a few hours, with a self-repair efficiency of more than 90%. Mechanical properties refer to the material's tensile strength of more than 55MPa and elongation at break of more than 1400%, demonstrating its excellent mechanical properties. Waterproof performance refers to the material's ability to maintain stable performance after being immersed in 2mol / L HCl or NaOH solution with pH=10 for a long time, showing excellent chemical stability and waterproofness.

[0058] Figure 1 The synthetic route of the boron-nitrogen coordination small molecule of the present invention; borate ester small molecule is a special compound generated by the reaction of a boric acid group and a multifunctional amine compound. These small molecules can form stable boron-nitrogen coordination bonds with nitrogen-containing compounds (such as amines, amides, etc.). This coordination bond is reversible and can be broken and re-formed when subjected to specific stimuli (such as heat, chemistry, mechanical action, etc.). Therefore, the boron-nitrogen coordination bond can not only improve the mechanical properties of the material, but also give it dynamic reversibility, so that the material can self-repair when damaged, and has the potential for multiple cycles.

[0059] The present invention aims to improve the mechanical strength, self-repairing ability and environmental adaptability of polyurethane materials by synthesizing small molecules containing boron and nitrogen coordination (i.e., NCBW-X) and applying them to polyurethane materials. By introducing boron and nitrogen coordination bonds, the material of the present invention has excellent mechanical properties, such as high tensile strength, high elongation at break and good tear resistance. At the same time, the material can achieve effective self-repair after being damaged through dynamic fracture and recombination of boron and nitrogen bonds. In addition, the material of the present invention exhibits excellent chemical stability in environments such as solvents and has good solvent tolerance.

[0060] Embodiment 1

[0061] like Figure 2 , Figure 3 The preparation method of the waterproof and acid- and alkali-resistant polyurethane elastomer material containing the boron-nitrogen coordinated small molecule NCBW-1 shown comprises the following steps:

[0062] S1. Synthesis of boron-nitrogen coordinated small molecules: Figure 2(a) Synthesis of NCBW-1 shown: 1,4-phenylenediboronic acid (10 g, 0.06 mol) and triethanolamine (12.7 g, 0.12 mol) were dissolved in methanol (about 75 ml) at room temperature. Subsequently, the triethanolamine solution was transferred to a 250 ml single-necked flask. Then the methanol solution of 1,4-dihydroxyborophene was added dropwise. A white precipitate began to form within 1 minute after the addition. The reaction stopped after 5 minutes without further heating. Finally, the precipitate was filtered and washed with ethanol two to three times. This procedure gave a white solid product with a yield of 95%; Figure 4 is the boron-nitrogen coordinated small molecule NCBW-1 of this example 1 H-NMR and 13 C-NMR spectrum, where Figure 4 (a) is the boron-nitrogen coordinated small molecule NCBW-1 1 H-NMR spectrum, Figure 4 (b) is the boron-nitrogen coordinated small molecule NCBW-1 13 C-NMR spectrum.

[0063] S2. Synthesize waterproof and acid- and alkali-resistant polyurethane elastomers with synergistic effects of hydrogen bonds and coordination bonds: Figure 2 As shown in the figure, under nitrogen protection, 20.0g of polycaprolactone (PCL-2000, 0.01mol) was weighed into a 250ml three-necked flask, and 6.67g of isophorone diisocyanate (IPDI, 0.03mol, dissolved in a small amount of DMF) was added through a syringe. After adding IPDI and mixing evenly, 0.1wt% of dibutyltin dilaurate was added as a catalyst, and the mixture was stirred for 3h in a nitrogen atmosphere at 80°C to obtain an isocyanate-terminated prepolymer; after cooling to about 40°C, 1.74g of adipic acid dihydrazide (ADH, 0.01mol) was added, the temperature was raised to 80°C, and the reaction was continued for 2h, and then NCBW-1 was added thereto. 3.92 g (NCBW-1, 0.01 mol), after continuing the reaction for 6 h, the solution was poured into a polytetrafluoroethylene mold and dried at 70 °C to prepare a polyurethane elastomer containing dynamic ionic bonds, which was recorded as PCL-IPDI-ADH-NCBW-1.

[0064] Embodiment 2

[0065] like Figure 2 , Figure 3 The preparation method of the waterproof and acid- and alkali-resistant polyurethane elastomer material containing the boron-nitrogen coordinated small molecule NCBW-2 shown comprises the following steps:

[0066] S1. Synthesis of boron-nitrogen coordinated small molecules: Figure 2(b) Synthesis of NCBW-2 shown: 1,4-phenylenediboronic acid (10 g, 0.06 mol) and diethanolamine (18.4 g, 0.12 mol) were dissolved in ethanol (about 75 ml) at room temperature. Subsequently, the diethanolamine solution was transferred to a 250 ml single-necked flask. The ethanol solution of 1,4-dihydroxyborophene was then added dropwise. A white precipitate began to form within 1 minute after the addition. The reaction stopped after 5 minutes without further heating. Finally, the precipitate was filtered and washed with ethanol two to three times. This procedure gave a white solid product with a yield of 95%; Figure 5 is the boron-nitrogen coordinated small molecule NCBW-2 of this embodiment. 1 H-NMR and 13 C-NMR (b), where Figure 5 (a) is the boron-nitrogen coordinated small molecule NCBW-2 1 H-NMR spectrum, Figure 4 (b) is the boron-nitrogen coordinated small molecule NCBW-2 13 C-NMR spectrum.

[0067] S2. Synthesize waterproof and acid- and alkali-resistant polyurethane elastomers with synergistic effects of hydrogen bonds and coordination bonds: Figure 2 As shown in the figure, under nitrogen protection, 20.0g of polycaprolactone (PCL-2000, 0.01mol) was weighed into a 250mL three-necked flask, and 6.67g of isophorone diisocyanate (IPDI, 0.03mol, dissolved in a small amount of DMF) was added through a syringe. After adding IPDI and mixing evenly, 0.1wt% of dibutyltin dilaurate was added as a catalyst, and the mixture was stirred for 3h in a nitrogen atmosphere at 80°C to obtain an isocyanate-terminated prepolymer; after cooling to about 40°C, 1.74g of adipic acid dihydrazide (ADH, 0.01mol) was added, the temperature was raised to 80°C, and the reaction was continued for 2h, and then NCBW-2 was added thereto. 3.04 g (NCBW-2, 0.01 mol), and after continuing the reaction for 6 h, the solution was poured into a polytetrafluoroethylene mold and dried at 70 °C to prepare a polyurethane elastomer containing dynamic ionic bonds, which was recorded as PCL-IPDI-ADH-NCBW-2.

[0068] Figure 6The FTIR comparison diagram of the waterproof and acid-alkali resistant polyurethane elastomer materials (PC L-IPDI-ADH-NCBW-1) and (PCL-IPDI-ADH-NCBW-2) with synergistic effects of hydrogen bonds and coordination bonds in Example 1 and Example 2, about 2260cm-1 indicates that the isocyanate reaction is complete, about 3300cm-1 corresponds to the stretching vibration of hydrogen bonds NH or OH bonds, and the peak of about 2900cm-1 may represent the stretching vibration of CH bonds in the range of 1600-1500cm-1 or C=O. The peak of 1100cm-1 corresponds to the vibration of CN bonds, the peak of 1368cm-1 corresponds to the stretching vibration of BO bonds, and the vibration of BN coordination is between 689-860cm-1.

[0069] Figure 7 The mechanical properties of the waterproof and acid-alkali resistant polyurethane elastomer materials (PC L-IPDI-ADH-NCBW-1) and (PCL-IPDI-ADH-NCBW-2) with synergistic hydrogen bonds and coordination bonds in Example 1 and Example 2 are compared. The tensile strength, elastic modulus, elongation at break and toughness of Example PCL-IPDI-ADH-NCBW-1 are 55.57MPa, 35.66MPa, 1403% and 351.80MJ / m 3 The embedding of the boron-nitrogen coordinated macrocyclic ring will increase the tensile strength and elastic modulus of the elastomer. Due to the embedding of the rigid octagonal ring, the movement of the soft segment is restricted and the ductility of the material is reduced. The rigid ring participates in the construction of the hard segment, and the tensile strength and elastic modulus increase. Finally, the toughness of the material decreases less and still maintains good toughness.

[0070] The interaction of dynamic covalent bonds and non-covalent bonds in this waterproof and acid-resistant polyurethane elastomer material gives the material self-healing ability at room temperature; by precisely controlling the chemical composition and reaction conditions, the material has excellent self-healing ability at room temperature while maintaining high mechanical properties; the boron-nitrogen coordination bonds and hydrogen bonds in the material work together to provide the composite material with excellent tensile, tear and puncture resistance; the material shows changes in characteristic peaks at specific wavelengths in the FTIR spectrum, proving the formation of expected chemical bonds in the chemical structure; in mechanical properties tests, the material showed a tensile strength of more than 55MPa and an elongation at break of more than 1400%, as well as a high recovery rate under specific conditions.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A hydrated borate ester small molecule having a boron-nitrogen coordination bond, characterized in that: The hydrated borate ester small molecule is synthesized from boric acid and its derivatives and multifunctional amine compounds, and its chemical structure is as follows: The synthetic route is: Among them, the general chemical structure formula of boric acid and its derivatives is as follows: R 1 It is represented by a substituent, selected from any one of the electron donating groups of hydrogen (-H), ortho-hydroxyl (m-OH), para-hydroxyl (p-OH), ortho-amino (m-NH2) and para-amino (p-NH2), wherein n represents a plurality of boronic acid groups n≥2; The general chemical structure of multifunctional amine compounds is as follows: R 2 It is represented as a substituent, which is a carbon chain or carbon chains of different lengths terminated with an amino (-NH2), hydroxyl (-OH), alkenyl, alkynyl, or carboxyl group.

2. A method for preparing a polyurethane elastomer material based on a hydrated borate ester small molecule having a boron-nitrogen coordination bond according to claim 1, characterized in that: The following steps are involved: S1. Synthesis of boron-nitrogen coordination small molecules: Boric acid and its derivatives are dissolved and reacted with multifunctional amine compounds at room temperature through solution reaction to form a boron-nitrogen coordination small molecule NCBW-X (X=1, 2, 3...) with an eight-membered ring structure, wherein the boron-nitrogen coordination causes the eight-membered ring to split into two five-membered rings, so that the rigid eight-membered ring can exist stably. The rigid eight-membered ring forms a coordination system when it meets water, thereby improving the hydrolysis resistance of boric esters; S2. Synthesis of polyurethane elastomer material: Under nitrogen protection, the hydroxyl-terminated soft segment was dissolved in a three-necked flask, and the isocyanate-terminated diisocyanate hard segment was added through a syringe. After the diisocyanate was added and mixed evenly, 0.1wt% of dibutyltin dilaurate was added as a catalyst, and the mixture was stirred in a nitrogen atmosphere at 80°C for 3 h to obtain an isocyanate-terminated prepolymer; after cooling to 50°C, the NCBW-X prepared in step S1 was added, and the reaction was continued for 6 h, and then the solution was poured into a polytetrafluoroethylene mold, and dried at 70°C to prepare a polyurethane elastomer material containing NCBW-X boron-nitrogen coordination bonds, wherein the soft segment: hard segment: NCBW-X = 1:2:

1.

3. The method for preparing the polyurethane elastomer material according to claim 2, characterized in that: In step S1, the boric acid and its derivatives are 1,4-phenylenediboronic acid, the multifunctional amine compound is triethanolamine, the solvent used for the solution reaction is methanol, and the boron-nitrogen coordination small molecule formed is NCBW-1. The specific synthesis method includes the following steps: at room temperature, 1,4-phenylenediboronic acid and triethanolamine are dissolved in methanol respectively, then the triethanolamine solution is transferred to a single-necked flask, and then a methanol solution of 1,4-dihydroxyborophene is added dropwise, and a white precipitate begins to form within 1 minute after the addition, and the reaction stops after 5 minutes without further heating. Finally, the precipitate is filtered and washed with ethanol two to three times.

4. The method for preparing the polyurethane elastomer material according to claim 2, characterized in that: Step S1: Boric acid and its derivatives are 1,4-phenylenediboronic acid, the multifunctional amine compound is diethanolamine, the solvent used for the solution reaction is ethanol, and the boron-nitrogen coordination small molecule formed is NCBW-2. The specific synthesis method includes the following steps: at room temperature, 1,4-phenylenediboronic acid and diethanolamine are dissolved in ethanol respectively, then the diethanolamine solution is transferred to a single-necked flask, and then the ethanol solution of 1,4-dihydroxyborophene is added dropwise. A white precipitate begins to form within 1 minute after the addition, and the reaction stops after 5 minutes without further heating. Finally, the precipitate is filtered and washed with ethanol two to three times.

5. The method for preparing the polyurethane elastomer material according to claim 3 or 4, characterized in that: In step S2, the hydroxyl-terminated soft segment is one of polycaprolactone PCL, polybutylene terephthalate, polylactic acid polyesters or one of polytetrahydrofuran PTEMG and polypropylene ether polyol polyethers, and the isocyanate-terminated diisocyanate hard segment is one of isophorone diisocyanate IPDI, hexamethylene diisocyanate HDI, and toluene diisocyanate TDI.

6. The method for preparing the polyurethane elastomer material according to claim 5, characterized in that: In step S2, the soft segment terminated by terminal hydroxyl groups is polycaprolactone, and the isocyanate-terminated diisocyanate hard segment is isophorone diisocyanate. The synthesis of the boron-nitrogen coordinated small molecule NCBW-1 elastomer in step S2 specifically includes the following steps: under nitrogen protection, polycaprolactone is dissolved in a three-necked flask, isophorone diisocyanate is added through a syringe, IPDI is added and mixed evenly, and then dibutyltin dilaurate accounting for 0.1wt% of the mass of IPDI / PCL-2000 is added as a catalyst, and stirred in a nitrogen atmosphere at 80° C. for 3 h to obtain an isocyanate-terminated prepolymer; after cooling to 50° C., hydrazide is added and the temperature is raised to 80° C. to continue the reaction for 2 h, and then the NCBW-1 prepared in step S1 is added thereto, and after continuing the reaction for 6 h, the solution is poured into a polytetrafluoroethylene mold and dried at 70° C. to prepare a polyurethane elastomer containing dynamic ionic bonds, which is recorded as PCL-IPDI-ADH-NCBW-1.

7. The method for preparing the polyurethane elastomer material according to claim 5, characterized in that: In step S2, the soft segment terminated by terminal hydroxyl groups is polycaprolactone, and the isocyanate-terminated diisocyanate hard segment is isophorone diisocyanate. The synthesis of the boron-nitrogen coordinated small molecule NCBW-2 elastomer in step S2 specifically includes the following steps: under nitrogen protection, weighing polycaprolactone and dissolving it in a three-necked flask, adding isophorone diisocyanate through a syringe, adding IPDI and mixing evenly, then adding dibutyltin dilaurate accounting for the mass of IPDI / PCL-2000 and 0.1wt% as a catalyst, stirring at 80°C in a nitrogen atmosphere for 3 h to obtain an isocyanate-terminated prepolymer; after cooling to 50°C, adding hydrazide and heating to 80°C to continue the reaction for 2 h, then adding the NCBW-2 prepared in step S1, continuing the reaction for 6 h, pouring the solution into a polytetrafluoroethylene mold, and drying at 70°C to prepare a polyurethane elastomer containing dynamic ionic bonds, which is recorded as PCL-IPDI-ADH-NCBW-2.

8. The method for preparing the polyurethane elastomer material according to claim 6 or 7, characterized in that: The hydrazide is a difunctional hydrazide group, wherein the quadruple hydrogen bond provides a stronger intermolecular force, so that the polyurethane elastomer has better strength and toughness under the action of tensile and bending external forces. It is preferably one of adipic acid dihydrazide, sebacic acid dihydrazide and dodecanedioic acid dihydrazide.

9. The polyurethane elastomer material prepared by the method for preparing the polyurethane elastomer material according to claim 6 or 7.

10. The polyurethane elastomer material according to claim 8, characterized in that: The hydrazide is adipic acid dihydrazide. The polyurethane elastomer material introduces adipic acid dihydrazide and NCBW-X as chain extenders. The quadruple hydrogen bonding effect constructed by the polyurethane elastomer is beneficial to improving the elongation at break of the material and maintaining a considerable tensile strength.

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