A visible light-responsive dynamically covalently crosslinked self-healing polyurethane and its preparation method

Abstract

This invention discloses a visible-light-responsive dynamically covalently cross-linked self-healing polyurethane and its preparation method, belonging to the field of self-healing materials technology. The material is prepared by reacting diisocyanate, long-chain diol, butanediol, trimethylolpropane, and a monool containing an azophenylboronic acid structure in a certain proportion at 60°C. This invention achieves visible-light-responsive self-healing of the polyurethane material by introducing a visible-light-responsive azophenylboronic acid structure into the polyurethane and utilizing the photoresponsive cis-trans isomerization of the azo structure to regulate the reversible breakage and recombination of the boron-oxygen hexacyclic ring. The visible-light-responsive dynamically covalently cross-linked self-healing polyurethane material prepared by this invention maintains high mechanical strength (16.47 MPa) while exhibiting a strength self-healing efficiency of 95.8% after 8 hours of visible light irradiation, showing broad application prospects in smart materials, anti-corrosion coatings, and other fields.

Description

Technical Field

[0001] This invention relates to the field of self-healing materials technology, and in particular to a visible light-responsive dynamic covalent crosslinked self-healing polyurethane and its preparation method. Background Technology

[0002] Self-healing polymer materials can spontaneously heal microcracks after damage, significantly extending service life and reducing maintenance costs, demonstrating great engineering application potential in fields such as flexible electronics and smart protective coatings. Among various self-healing strategies, photo-responsive self-healing has attracted much attention due to its advantages such as non-contact actuation, precise spatiotemporal control, and rapid response. However, most photoresponsive self-healing polymers mainly rely on non-covalent interactions to build dynamic cross-linked networks, and this physical cross-linking mechanism leads to generally low strength in existing systems. In addition, traditional photoresponsive systems mostly rely on high-energy ultraviolet light for actuation; long-term irradiation not only poses certain health risks but also induces oxidation and irreversible degradation of the polymer matrix, severely shortening the long-term service life of the material and limiting the application of photoresponsive self-healing materials.

[0003] This invention introduces an azobenzeneboronic acid structure into polyurethane and utilizes the photoresponsive reversible isomerization of the azo structure to regulate the reversible breakage and recombination of the boron-oxygen hexacyclic ring, thus preparing a visible-light-responsive dynamically covalently crosslinked self-healing polyurethane material. This polyurethane material exhibits excellent mechanical strength and highly efficient visible-light-responsive self-healing properties, showing broad application prospects in the field of smart polymers. Summary of the Invention

[0004] To address the challenges of low repair efficiency, the need for high-energy ultraviolet light irradiation, and low mechanical strength in existing photoresponsive self-healing materials, this invention proposes a visible light-responsive dynamic covalent crosslinked self-healing polyurethane material and its preparation method.

[0005] To achieve the above objectives, the present invention employs the following technical solution: A visible light-responsive, dynamically covalently crosslinked, self-healing polyurethane material, characterized in that the polyurethane material is obtained by reacting diisocyanate, long-chain diol, butanediol, trimethylolpropane, and a monool containing azophenylboronic acid in a molar ratio of 1:0.2-0.6:0.1-0.6:0.01-0.2:0.02-0.15, and the general structural formula of the polyurethane is: ; In the formula, the value of m ranges from 1 to 6; In the formula, R1 is one or more of the following structural formulas; ; In the formula, R2 is one or more of the following structural formulas; ; In the formula, the value of n ranges from 3 to 40; Furthermore, the visible light-responsive dynamic covalent crosslinked self-healing polyurethane material is characterized in that the monool containing the azophenylboronic acid structure has the following general structural formula; ; In the formula, the value of m ranges from 1 to 6; Furthermore, the visible light-responsive dynamic covalent crosslinked self-healing polyurethane material and its preparation method are characterized by comprising the following steps: S1. Preparation of monools containing azophenylboronic acid structure: Monophenols containing azophenylboronic acid structure, chlorosubstituted alkyl alcohols, potassium carbonate and potassium iodide were added to a round-bottom flask in a molar ratio of 1:1.2:2.4:0.4, dissolved in N,N-dimethylformamide, and stirred at 80°C for 12 hours. After the reaction was completed, the monools containing azophenylboronic acid structure were obtained by extraction, washing and drying. S2. Preparation of visible light responsive dynamic covalent crosslinked self-healing polyurethane: Under nitrogen protection, diisocyanate, long-chain diol, and butanediol were dissolved in N,N-dimethylformamide, and then the catalyst dibutyltin dilaurate was added. The reaction was carried out at 60°C for 2-4 hours. Then, trimethylolpropane was added dropwise and the reaction was continued for 1-2 hours. Finally, a monool containing azophenylboronic acid structure was added and the reaction was carried out for 1 hour to obtain visible light responsive dynamic covalent crosslinked self-healing polyurethane.

[0006] Compared with the prior art, the advantages of the present invention are: Firstly, this invention introduces an azobenzeneboronic acid structure into a polyurethane network. The boron-oxygen hexacyclic structure formed by the dehydration condensation of benzeneboronic acid increases the crosslinking density and improves the material's mechanical properties. Simultaneously, the photoresponsive reversible isomerization of the azo structure successfully regulates the reversible fracture and recombination of the boron-oxygen hexacyclic structure, endowing the material with excellent self-healing properties. Through its innovative repair mechanism design, this material successfully resolves the contradiction between high strength and high repair efficiency in existing photoresponsive self-healing materials.

[0007] Secondly, the polyurea material prepared by this invention, in addition to having excellent mechanical properties and self-healing properties, also has excellent light-responsive deformation and humidity-responsive deformation properties, which solves the problem of the single function of existing light-responsive self-healing materials.

[0008] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0009] Figure 1The 1H NMR spectrum of a monophenol containing an azobenzeneboronic acid structure; Figure 2 The infrared spectrum of a monophenol containing an azobenzeneboronic acid structure; Figure 3 The 1H NMR spectrum of a monool containing an azobenzeneboronic acid structure; Figure 4 The infrared spectrum of a monool containing an azophenylboronic acid structure; Figure 5 The UV-Vis absorption spectrum of a monool containing an azophenylboronic acid structure; Figure 6 The infrared spectrum of polyurethane PHBTA-1; Figure 7 Differential scanning calorimetry for polyurethane PHBTA-1; Figure 8 The tensile curves of polyurethane PHBTA-1 before and after visible light response repair are shown. Figure 9 The infrared spectrum of polyurethane PHBTA-2; Figure 10 The image shows the UV-Vis absorption spectrum of polyurethane PHBTA-2. Figure 11 Differential scanning calorimetry for polyurethane PHBTA-2; Figure 12 The tensile curves of polyurethane PHBTA-2 before and after visible light response repair are shown. Figure 13 A water-light response actuation diagram of polyurethane PHBTA-2; Figure 14 Photo-water response animation of polyurethane PHBTA-2. Detailed Implementation

[0010] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0011] Example 1: (1) Preparation of monools containing azophenylboronic acid structure: 5 g of 2-amino-6-methoxybenzothiazole was added to a 500 mL round-bottom flask under ice bath conditions, followed by 125 mL of glacial acetic acid and 100 mL of dilute sulfuric acid (60%). After the system temperature stabilized, 62.5 mL of an aqueous solution containing 2.095 g of sodium nitrite was slowly added dropwise. The reaction was allowed to proceed for 1 h. Subsequently, an ethanol solution containing 3.81 g of 3-hydroxyphenylboronic acid was added dropwise to the system. After the addition was complete, the mixture was stirred for 1 h. The pH of the reaction system was adjusted to 6-7. The mixture was then filtered, washed with water, and dried to obtain a monophenol containing an azophenylboronic acid structure.

[0012] 3 g of azophenylboronic acid-containing monophenol, 1.37 g of chlorohexanol, 3 g of potassium carbonate, and 0.6 g of potassium iodide were added to a 100 mL single-necked flask and dissolved in DMF. The mixture was refluxed at 80 °C for 10 h, followed by extraction with ethyl acetate, washing three times with sodium hydroxide aqueous solution, three times with water, and three times with saturated brine. The organic layer was dried over anhydrous sodium sulfate for 2 h, and the solvent was evaporated to obtain the azophenylboronic acid-containing monophenol. The reaction equation is as follows: ; Figure 1 The proton NMR spectrum of a monophenol containing an azobenzeneboronic acid structure. 1 ¹H NMR (400 MHz, Dimethylsulfoxide-d6) with chemical shifts of 10.68 ppm (Ar-OH), 7.99–6.95 ppm (Ar-H), and 3.87 ppm (-Ar-O-CH3) confirmed its successful preparation.

[0013] Figure 2 The infrared spectrum of a monophenol containing an azophenylboronic acid structure is shown, with infrared absorption peaks at 3284 cm⁻¹. -1 (-OH), 2963 cm -1 2834 cm -1 (-CH3), 1600 cm -1 1563 cm -1 1475 cm -1 (Ar), 1365 cm -1 (BO) proves that it was successfully prepared.

[0014] Figure 3 The proton NMR spectrum of a monool containing an azophenylboronic acid structure 1 ¹H NMR (400 MHz, Chloroform-d) with chemical shifts of 8.07–6.98 ppm (Ar-H), 4.08 ppm (-Ar-O-CH₃), 3.91 ppm (-Ar-O-CH₂), 3.68 ppm (HO-CH₂), and 1.91–1.40 ppm (-CH₂) confirmed successful preparation.

[0015] Figure 4 The infrared spectrum of a monool containing an azophenylboronic acid structure is shown, with infrared absorption peaks at 3319 cm⁻¹. -1 (-OH), 2941 cm -1 2862 cm -1 (-CH3), 1600 cm -1 1579 cm -11494 cm -1 1467 cm -1 (Ar), 1365cm -1 (BO) proves that it was successfully prepared.

[0016] Figure 5 The image shows the UV-Vis absorption spectrum of a monool containing an azobenzylboronic acid structure. Under initial conditions, the trans absorption peak of the azobenzyl benzothiazole structure containing borate groups is observed at approximately 432 nm, while the cis absorption peak is observed at approximately 550 nm. After irradiation with 450 nm blue light for 120 s, the trans structure changes to the cis structure, causing the peak at 432 nm to decrease and the peak at 550 nm to increase. Subsequently, after irradiation with 550 nm green light for 60 s, the cis structure changes back to the trans structure, returning to the initial position, demonstrating the visible light response behavior of this small molecule.

[0017] (2) Preparation of visible light-responsive dynamic covalent crosslinked self-healing polyurethane: Add 1.5 g of anhydrous polyethylene glycol 1000, 0.5046 g of hexamethylene diisocyanate, 0.0675 g of 1,4-butanediol, and 4 mL of anhydrous DMF to a 100 mL round-bottom flask. After stirring at 60 °C for 5 min, add DBTDL and react for 1 h. Then, add 0.03 g of trimethylolpropane dropwise to the reaction system, followed by 6 mL of anhydrous DMF. Continue the reaction for 1 h, then add 0.03 g of a monool containing azophenylboronic acid structure. After reacting for 1 h, pour the mixture into a mold and dry it to form a film, thus obtaining visible light responsive covalently reversibly crosslinked polyurethane PHBTA-1.

[0018] Figure 6 The image shows the infrared spectrum of polyurethane PHBTA-1. The infrared absorption peaks are at 3327 cm⁻¹. -1 (-NH-), 2923cm -1 2864 cm -1 (-CH2), 1697 cm -1 (-C=O), 1566 cm -1 1464 cm -1 (Ar), 1370 cm -1 (BO), 1103 cm -1 (COC), 730 cm -1 (B3-O3) proves the successful preparation of polyurethane PHBTA-1.

[0019] Figure 7 This is a differential scanning calorimetry (DSC) curve of polyurethane PHBTA-1. It can be seen that the melting temperature of PHBTA-1 is 32℃.

[0020] Figure 8 The figures show the tensile curves of polyurethane PHBTA-1 before and after visible light response repair. As can be seen from the figures, the initial tensile stress of the spline was 2.42 MPa, and the elongation at break was 416.4%. After irradiation with 450 nm visible light for 5 minutes and 550 nm visible light for 5 minutes, the tensile stress of the repaired PHBTA-1 was 2.40 MPa, and the elongation at break was 420.9%. Its strength self-healing efficiency was 99.1%, and its strain self-healing efficiency was 101.0%.

[0021] Example 2: The method for preparing monools containing azophenylboronic acid structures is the same as step (1) in Example 1. (2) Preparation of visible light-responsive dynamic covalent crosslinked self-healing polyurethane: Add 1.5 g of anhydrous polyethylene glycol 1000, 0.63 g of hexamethylene diisocyanate, 0.1352 g of 1,4-butanediol, and 4 mL of anhydrous DMF to a 100 mL round-bottom flask. After stirring at 60 °C for 5 min, add DBTDL and react for 1 h. Then, add 0.0604 g of trimethylolpropane dropwise to the reaction system, followed by 6 mL of anhydrous DMF. Continue the reaction for 1 h, then add 0.06 g of a monool containing azophenylboronic acid structure. After reacting for 1 h, pour the mixture into a mold and dry it to form a film, thus obtaining visible light responsive covalently reversibly crosslinked polyurethane PHBTA-2.

[0022] Figure 9 This is the infrared spectrum of polyurethane PHBTA-2. The infrared absorption peaks are at 3322 cm⁻¹. -1 (-NH-), 2930cm -1 2867 cm -1 (-CH2), 1698 cm -1 (-C=O), 1559 cm -1 1461 cm -1 (Ar), 1356 cm -1 (BO), 1107 cm -1 (COC), 736 cm -1 (B3-O3) proves the successful preparation of polyurethane PHBTA-2.

[0023] Figure 10The image shows the UV-Vis absorption spectrum of polyurethane PHBTA-2. Around 432 nm, the trans absorption peak of the azobenzothiazole structure containing borate groups is observed, while around 550 nm, the cis absorption peak is observed. After 60 s of blue light irradiation at 450 nm, the trans structure changes to the cis structure, resulting in a decrease in the peak at 430 nm and an increase in the peak at 550 nm. Subsequently, after 20 s of green light irradiation at 550 nm, the cis structure changes back to the trans structure, with the peak increasing at 430 nm and decreasing at 550 nm, demonstrating the visible light response behavior of this polyurethane.

[0024] Figure 11 The differential scanning calorimetry (DSC) curve of polyurethane PHBTA-2 shows that the melting temperature of PMHA-1 is 21℃, and there is a relatively weak hard segment melting temperature at a higher temperature (94℃).

[0025] Figure 12 The figures show the tensile curves of polyurethane PHBTA-2 before and after visible light response repair. As can be seen from the figures, the initial tensile stress of the sample was 16.47 MPa and the elongation at break was 1106.4%. After being irradiated with 450 nm visible light for 4 h and 550 nm visible light for 4 h, the tensile strength of the repaired PHBTA-2 was 15.79 MPa and the elongation at break was 1016.9%. Its strength self-healing efficiency was 95.8% and its strain self-healing efficiency was 91.9%.

[0026] Figure 13 The actuation diagram of the water-light response of polyurethane PHBTA-2 shows that in the initial state, the film is perpendicular to the foam. After being irradiated with 450 nm blue light, the film bends and lifts the foam. Then, water droplets are added to the center of the bend, causing the film to bend in the opposite direction. After adding 5 drops of water, the foam is lowered.

[0027] Figure 14 The photo-water response actuation diagram of polyurethane PHBTA-2 is shown. In the initial state, the film is perpendicular to the foam. Water droplets are continuously added to one side of the film, causing the film to gradually bend and eventually lift the foam. Then, a 450 nm light source is used to irradiate the center of the bend of the film to induce photo-actuation and release the foam.

[0028] Example 3: The method for preparing monools containing azophenylboronic acid structures is the same as step (1) in Example 1. (2) Preparation of visible light-responsive dynamic covalent crosslinked self-healing polyurethane: Add 1.5 g of anhydrous polyethylene glycol 1000, 0.83 g of isoflurane diisocyanate, 0.1352 g of 1,4-butanediol, and 4 mL of anhydrous DMF to a 100 mL round-bottom flask. After stirring at 60 °C for 5 min, add DBTDL and react for 1 h. Then, add 0.0604 g of trimethylolpropane dropwise to the reaction system, followed by 6 mL of anhydrous DMF. Continue the reaction for 1 h, then add 0.06 g of a monool containing azophenylboronic acid structure. After reacting for 1 h, pour the mixture into a mold and dry it to form a film, thus obtaining a visible light-responsive covalently reversible crosslinked polyurethane.

[0029] Example 4: The method for preparing monools containing azophenylboronic acid structures is the same as step (1) in Example 1. (2) Preparation of visible light-responsive dynamic covalent crosslinked self-healing polyurethane: Add 1.5 g of anhydrous polyethylene glycol 1000, 0.78 g of trimethylhexamethylene diisocyanate, 0.1352 g of 1,4-butanediol, and 4 mL of anhydrous DMF to a 100 mL round-bottom flask. After stirring at 60 °C for 5 min, add DBTDL and react for 1 h. Then add 0.0604 g of trimethylolpropane dropwise to the reaction system, followed by 6 mL of anhydrous DMF. Continue the reaction for 1 h, then add 0.06 g of a monool containing azophenylboronic acid structure. After reacting for 1 h, pour the mixture into a mold and dry it to form a film, thus obtaining a visible light-responsive covalently reversible crosslinked polyurethane.

[0030] Example 5: The method for preparing monools containing azophenylboronic acid structures is the same as step (1) in Example 1. (2) Preparation of visible light-responsive dynamic covalent crosslinked self-healing polyurethane: Add 1.5 g of anhydrous polyethylene glycol 1000, 0.63 g of hexamethylene diisocyanate, 0.1352 g of 1,4-butanediol, and 4 mL of anhydrous DMF to a 100 mL round-bottom flask. After stirring at 60 °C for 5 min, add DBTDL and react for 1 h. Then, add 0.0201 g of trimethylolpropane dropwise to the reaction system, followed by 6 mL of anhydrous DMF. Continue the reaction for 1 h, then add 0.06 g of a monool containing azophenylboronic acid structure. After reacting for 1 h, pour the mixture into a mold and dry it to form a film, thus obtaining a visible light-responsive covalently reversible crosslinked polyurethane.

[0031] Example 6: The method for preparing monools containing azophenylboronic acid structures is the same as step (1) in Example 1. (2) Preparation of visible light-responsive dynamic covalent crosslinked self-healing polyurethane: Add 1.5 g of anhydrous polyethylene glycol 1000, 0.7568 g of hexamethylene diisocyanate, 0.2027 g of 1,4-butanediol, and 4 mL of anhydrous DMF to a 100 mL round-bottom flask. After stirring at 60 °C for 5 min, add DBTDL and react for 1 h. Then, add 0.0604 g of trimethylolpropane dropwise to the reaction system, followed by 6 mL of anhydrous DMF. Continue the reaction for 1 h, then add 0.06 g of a monool containing azophenylboronic acid structure. After reacting for 1 h, pour the mixture into a mold and dry it to form a film, thus obtaining a visible light-responsive covalently reversible crosslinked polyurethane.

[0032] Example 7: The method for preparing monools containing azophenylboronic acid structures is the same as step (1) in Example 1. (2) Preparation of visible light-responsive dynamic covalent crosslinked self-healing polyurethane: Add 1.5 g of anhydrous polyethylene glycol 1000, 0.883 g of hexamethylene diisocyanate, 0.2703 g of 1,4-butanediol, and 4 mL of anhydrous DMF to a 100 mL round-bottom flask. After stirring at 60 °C for 5 min, add DBTDL and react for 1 h. Then, add 0.0604 g of trimethylolpropane dropwise to the reaction system, followed by 6 mL of anhydrous DMF. Continue the reaction for 1 h, then add 0.06 g of a monool containing azophenylboronic acid structure. After reacting for 1 h, pour the mixture into a mold and dry it to form a film, thus obtaining a visible light-responsive covalently reversible crosslinked polyurethane.

[0033] In summary, this invention introduces a photoactive azophenylboronic acid structure into polyurethane and achieves solar-responsive self-healing of high-strength polyurethane materials through reversible metal coordination bonds in response to sunlight, thus solving the problem that existing photoresponsive self-healing materials require irradiation with specific wavelengths of light.

[0034] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A visible light-responsive dynamically covalently crosslinked self-healing polyurethane material, characterized in that, The polyurethane material is obtained by reacting diisocyanate, long-chain diol, butanediol, trimethylolpropane, and a monool containing azophenylboronic acid in a molar ratio of 1:0.2-0.6:0.1-0.6:0.01-0.2:0.02-0.

15. The general structural formula of the polyurethane is: ； In the formula, the value of m ranges from 1 to 6; In the formula, R1 is one or more of the following structural formulas; ； In the formula, R2 is one or more of the following structural formulas; ； In the formula, the value of n ranges from 3 to 40.

2. The visible light-responsive dynamic covalent crosslinked self-healing polyurethane material as described in claim 1, characterized in that, The general structural formula of the monool containing the azophenylboronic acid structure is as follows: ； In the formula, the value of m ranges from 1 to 6.

3. The preparation method of a visible light-responsive dynamic covalent crosslinked self-healing polyurethane material as described in any one of claims 1-2, characterized in that, Includes the following steps: S1. Preparation of monools containing azophenylboronic acid structure: Monophenols containing azophenylboronic acid structure, chlorosubstituted alkyl alcohols, potassium carbonate and potassium iodide were added to a round-bottom flask in a molar ratio of 1:1.2:2.4:0.4, dissolved in N,N-dimethylformamide, and stirred at 80°C for 12 hours. After the reaction was completed, the monools containing azophenylboronic acid structure were obtained by extraction, washing and drying. S2. Preparation of visible light responsive dynamic covalent crosslinked self-healing polyurethane: Under nitrogen protection, diisocyanate, long-chain diol, and butanediol were dissolved in N,N-dimethylformamide, and then the catalyst dibutyltin dilaurate was added. The reaction was carried out at 60°C for 2-4 hours. Then, trimethylolpropane was added dropwise and the reaction was continued for 1-2 hours. Finally, a monool containing azophenylboronic acid structure was added and the reaction was carried out for 1 hour to obtain visible light responsive dynamic covalent crosslinked self-healing polyurethane.

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