Photoinduced multicolor self-repairing polyurethane material and synthesis method thereof

Abstract

The invention relates to a photoinduced multi-color self-repairing polyurethane material and a synthesis method thereof, the photoinduced multi-color self-repairing polyurethane material has the following structural formula: # imgabs0 #, R1 and R3 are independently selected from any one of H, F, Cl, Br, CH3 and OCH3, n is selected from an integer of 25-500, R2 is selected from one of long-chain diol substances (tetrahydrofuran), diamine substances and lipid substances, and n is an integer of 1-5. And R4 is selected from one or more of a spiropyran compound, an azobenzene compound, a diarylethene compound and a donor-acceptor Steinporus adduct. According to the invention, the self-repairing elastomer material and the color-changeable substance are copolymerized, so that the synthesis of the multicolor self-repairing polyurethane material is realized, the utilization rate of the coating is increased, the protection effect is effectively achieved, the color is changed, the energy consumption is reduced, and the color-changeable self-repairing polyurethane material has great value for establishing a resource-saving and environment-friendly society.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and particularly relates to a photo-induced multicolor self-healing polyurethane material and a synthesis method thereof. Background Art

[0002] Polymer material products will generate cracks due to external stimuli such as temperature, external force, and pH during use, which will have a great impact on the performance of the materials. Small cracks are prone to develop into large cracks, ultimately leading to material failure, thus posing potential safety hazards and even causing safety accidents. This problem is particularly prominent in the fields of construction, aerospace, deep-sea exploration, regenerative medicine, and aerial operations. Precise repair of tiny scars on the material surface requires high costs, and internal damage cannot be repaired. Inspired by the fact that animal and plant tissues in nature can rely on their own abilities to complete internal and external healing after being damaged, the concept of self-healing materials was proposed.

[0003] Polymer elastomers are a type of material that has been developed earlier, widely used, and has a large market demand. Self-healing elastomer materials are intelligent materials that have the advantages of traditional elastomer materials, can be competent in more application scenarios, and have more excellent performance. Compared with traditional elastomer materials, the self-healing function brings many advantages to the materials, which can eliminate potential safety hazards, extend the service life of the materials, enhance the strength of the materials, and ensure the full play of the material performance. The definition of self-healing elastomers can be summarized as: elastomer materials that can rely on the properties of the materials themselves for self-healing when damaged, thereby delaying or even avoiding performance degradation. After decades of development, self-healing elastomers have now developed into a mature field. According to different preparation methods, they can be divided into two categories: external aid type and intrinsic type.

[0004] At present, certain research progress has been made in the intrinsic self-healing system. Among them, hydrogen bonds have low bond energy, which gives them excellent reversibility. Hydrogen bonds are also relatively common and exist between many different atoms. Currently, many polymer elastomer materials already contain a large number of hydrogen bonds. For example, polyurea, polyurethane, etc. that have achieved industrial production. These polymers containing hydrogen bonds are common, easily available, and have low costs. These characteristics of hydrogen bonds give multiple hydrogen bond self-healing elastomers excellent application prospects and development conditions. The development time of the multiple hydrogen bond self-healing structure is only more than ten years, but hydrogen bonds have a development history of more than one hundred years from discovery to now. Multiple hydrogen bond self-healing polyurethane elastomer materials still have problems such as low repair efficiency, slow speed, and specific conditions required for repair. In the current field of color-changing materials, there are still problems such as single color-changing types and small color density. Summary of the Invention

[0005] In order to solve one or several of the technical problems existing in the prior art, the present invention provides a photo-induced multicolor self-healing polyurethane material and a synthesis method thereof.

[0006] The technical solution of the present invention to solve the above technical problems is as follows: A photoinduced multicolor self-healing polyurethane material has the following structural formula:

[0007]

[0008] Wherein, R1 and R3 are independently selected from any one of H, F, Cl, Br, CH3, and OCH3, n is an integer selected from 25 to 500, R2 is selected from one or more of long-chain diol substances, diamine substances, and lipid substances, and R4 is selected from one or more of spiropyran compounds, azobenzene compounds, diarylethene compounds, and donor-acceptor Stenhouse adducts.

[0009] The beneficial effects of the present invention are: The photoinduced multicolor self-healing polyurethane material of the present invention copolymerizes a self-healing elastomer material with a color-changing substance to realize the synthesis of a multicolor self-healing polyurethane material, which is beneficial to improving the utilization rate of coatings, effectively playing a protective role and changing colors, reducing energy consumption, and has great value for building a resource-saving and environment-friendly society.

[0010] On the basis of the above technical solution, the present invention can also be further improved as follows.

[0011] Further, the tensile strength of the spiropyran compound is 4 to 50 Mpa, the elongation at break is 5 to 600%, the photochromic response speed is less than 90 s, and the cycle stability is greater than 100 times.

[0012] Further, the Young's modulus of the photoinduced multicolor self-healing polyurethane material is 80 to 90 MPa, the elongation at break is 600 to 650%, and the breaking strength is 19 to 20 Mpa;

[0013] The photoinduced multicolor self-healing polyurethane material presents red under ultraviolet light illumination of 298 to 400 nm and / or green light of 500 to 560 nm, and then changes from red to yellow under light irradiation of 420 to 450 nm.

[0014] A synthesis method of the above photoinduced multicolor self-healing polyurethane material includes the following steps:

[0015] S1, mixing and reacting a first mixed reaction system containing a diamine substance, a cyanate ester substance, a diol substance, and a first solvent at 70 to 120 °C for 20 to 30 h to obtain a chain extender;

[0016] S2, reacting a second mixed system containing a dicyanate ester substance, polytetrahydrofuran, and a second solvent at 50 to 100 °C for 2 to 6 h to obtain a prepolymer;

[0017] S3. React the third mixed reaction system containing a chain extender, a prepolymer, and a third solvent at 50 - 100 °C for 2 - 6 h to obtain a self-healing polyurethane material;

[0018] S4. Carry out a copolymerization reaction on the self-healing polyurethane material containing S3 with one or more of a spiropyran compound, an azobenzene compound, a diarylethene compound, and a donor-acceptor Stenhouse adduct to obtain a photoinduced multicolor self-healing polyurethane material.

[0019] The beneficial effects of the present invention are as follows: The self-healing elastomer material (self-healing polyurethane material) is an intelligent material with the advantages of traditional elastomer materials, capable of being competent in more application scenarios and having better performance. Compared with traditional elastomer materials, the self-healing function brings many advantages to the material, which can eliminate potential safety hazards, extend the service life of the material, enhance the strength of the material, and ensure the full play of the material's performance.

[0020] In the present invention, a copolymerization operation is carried out on a variety of color-changing factors and a polyurethane elastomer, improving the color-changing efficiency and color density of the self-healing material. Adopting the intrinsic self-healing idea of multiple hydrogen bonds, aiming at the problems of low repair efficiency, slow speed, and the need for specific conditions during repair of the existing multiple hydrogen bond self-healing polyurethane elastomer materials, through the design of the polyurethane molecular structure, a structure capable of forming high-density multiple hydrogen bonds is synthesized, and a class of multiple hydrogen bond polyurethane elastomer materials that can self-heal quickly and efficiently at room temperature and have good mechanical properties is prepared.

[0021] Furthermore, the diamine substances include any one or a combination of two or more of 2,6-diaminopyridine, ethylenediamine, 1,2-propanediamine, p-phenylenediamine, diaminomaleonitrile, and 1,6-diaminohexane.

[0022] Furthermore, the 2,6-diaminopyridine is purified by the following method: Dissolve 2,6-diaminopyridine in an alcohol substance, then add an adsorbent for adsorption, and after filtration, evaporate the filtrate to obtain pure 2,6-diaminopyridine;

[0023] The alcohol substance includes one of methanol, ethanol, and n-propanol, and the adsorbent includes at least one of activated carbon, molecular sieve, silica gel, and alumina.

[0024] Furthermore, the diol substances include any one or a combination of two or more of ethylene glycol, propylene glycol, polyethylene glycol, and 1,4-butanediol.

[0025] Furthermore, the diisocyanate substances include any one or a combination of two or more of isophorone diisocyanate (IPDI), toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI), and lysine diisocyanate (LDI).

[0026] Further, the first solvent, the second solvent, and the third solvent each include at least one of water, DMF, and THF;

[0027] The molar ratio of the polytetrahydrofuran to the dicyanate ester substance is 1:(2 - 2.5);

[0028] The molar ratio of the diamine substance to the diol substance is 1:(0 - 10).

[0029] Application of the above-mentioned photoinduced multicolor self-healing polyurethane material in a car wrap coating.

[0030] The present invention can protect the car body shell and cause color change. Specific embodiments

[0031] In view of the defects of the prior art, the inventors of this case have, through long-term research and a large number of practices, been able to propose the technical solution of the present invention. It mainly introduces 2,6-bis(hydroxyacetamido)pyridine as a chain extender into the polyurethane elastomer, enabling it to have both excellent mechanical properties and excellent self-healing properties. Then, the spiropyran compound and the azobenzene compound are copolymerized with the self-healing polyurethane material to finally form a multicolor self-healing film.

[0032] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention.

[0033] The spiropyran compound and the azobenzene compound used in the present invention can be synthesized by the following methods:

[0034] A method for synthesizing a spiropyran diol SP-2OH: Weigh methyl indole ring (1.00 g, 4.9 mmol) and 3-hydroxymethyl-5-nitro salicylaldehyde (0.81 g, 4.1 mmol) into a 100 mL three-necked flask. Add 14 mL of ethanol and 14 mL of water, install a reflux device, protect with nitrogen, and stir and reflux for 5 h (80 °C). Post-treatment: After removing the solvent from the reaction liquid in a rotary evaporator, recrystallize it 3 times in acetonitrile:water = 7:3, and dry it under reduced pressure in a vacuum oven to obtain a brick-red powder.

[0035] Synthesis method of M-Azo-3: Weigh 1.00 g (2.0 mmol) of M-Azo-2, 1.84 g (6.1 mmol) of triethylamine, and 0.05 g (0.4 mmol) of 4-dimethylaminopyridine into a 100 mL three-necked flask. Measure 30 mL of THF in a fume hood and add it to the flask. Stir at 0 °C for 2 h to obtain a homogeneous solution. Dilute 0.84 g (8.0 mmol) of methacryloyl chloride with 5 mL of THF, and add it dropwise to the above solution. Slowly return to room temperature and react overnight. Filter out the insoluble substances, and add the filtrate dropwise to 100 mL of deionized water. After suction filtration, the crude product is obtained. Recrystallize the crude product from ethanol to obtain 0.79 g of orange-yellow solid M-Azo-3, with a yield of 53.1%. At the end of the experiment, the three are copolymerized to prepare a color-changing self-healing polyurethane thin film material.

[0036] Synthesis method of 2,3,3-trimethyl-N-hydroxyethylindole: Weigh 2,3,3-trimethyl-3H-indole (2.61 g, 16 mmol) and 2-bromoethanol (2.46 g, 20 mmol) and add them to a 100 mL three-necked flask. Then add the solvent acetonitrile (20 mL), install a reflux device, protect with nitrogen, stir and reflux for 24 h (oil bath at 80 °C), and rotary evaporate to remove acetonitrile. Wash with n-hexane three times, dry in a vacuum oven and weigh to obtain a purple-red solid powder.

[0037] Synthesis method of methyl indole ring: Weigh 2,3,3-trimethyl-N-hydroxyethylindole (2.93 g, 10 mmol) and KOH (0.92 g, 16 mmol) into a 100 mL beaker, then add water (50 mL), stir at room temperature for 15 min, and a yellow oily substance is formed. Extract the yellow oily substance with ether (20 mL × 3), rotary evaporate to remove ether, and dry under reduced pressure to obtain a yellow oily substance.

[0038] Synthesis method of 3-hydroxymethyl-5-nitrosalicylaldehyde: Weigh 3-chloromethyl-5-nitrosalicylaldehyde (2.00 g, 9.27 mmol) and the solvent acetone (11 mL) into a 100 mL three-necked flask, install a reflux device, protect with nitrogen throughout the process, stir and reflux for 20 min (oil bath at 80 °C), then measure 3 M NaOH solution (3 mL) and water (2 mL) into a constant pressure dropping funnel, and add them dropwise to the three-necked flask. The dropping time exceeds 20 min, and then stir and reflux for 3 h. Post-treatment: After rotary evaporating the solvent from the reaction liquid, recrystallize three times in water and dry under reduced pressure to obtain a light green powder.

[0039] Synthesis method of M-Azo-1: Weigh 3.00 g (0.028 mol) of p-aminophenol and 7.80 g of distilled water into a 100 mL three-necked flask. While stirring in an ice bath, gradually add 7.8 mL of concentrated HCl dropwise to the three-necked flask using a constant-pressure dropping funnel. After the addition is complete, react for about 30 min. Weigh 2.28 g of NaNO2 (0.033 mol), prepare a 27% NaNO2 solution, and gradually add it dropwise to the three-necked flask. The solution gradually turns reddish-brown, and the temperature is maintained at 0 - 5 °C throughout the process. After the addition is complete, stir for about 2 h, and the solution changes from reddish-brown to orange-red transparent. Weigh 2.75 g (0.069 mol) of NaOH into a 100 mL small beaker, and prepare a 25% NaOH solution. Weigh 2.97 g (0.028 mol) of o-cresol into another 100 mL small beaker, and add the NaOH solution to the o-cresol to prepare a sodium o-cresolate solution. While stirring in an ice-water bath, gradually add the diazonium salt solution prepared in the previous stage dropwise to the sodium o-cresolate solution to obtain a dark red-brown solution. After the addition of the diazonium salt solution is complete, restore the temperature to room temperature and stir overnight. Gradually add the reaction solution dropwise to 150 mL of 1 mol / L hydrochloric acid for acidification, stir for 30 min, and then filter by suction. Add the filter cake to 150 mL of distilled water for washing, stir for 30 min, and then filter by suction. Repeat the washing until the filtrate is neutral. The washed product is dried in an oven at 50 °C to obtain 5.04 g of brown-black M-Azo-1.

[0040] Synthesis method of M-Azo-2, the specific operation is as follows: Weigh 2.00 g (8.8 mmol) of M-Azo-1, 3.54 g (21.0 mmol) of 2-chloroethoxy-2-ethoxy diethanol, 2.90 g (21.0 mmol) of K2CO3, 0.20 g of KI, and 50 mL of DMF into a three-necked flask, add a magnetic stirrer, and reflux with condensation at 120 °C for 48 h to obtain a reddish-brown liquid. Drop the reaction solution into 100 mL of deionized water and then filter by suction. The filter cake is repeatedly washed until the filtrate is golden yellow. The washed product is dried in an oven at 50 °C to obtain 1.49 g of dark yellow M-Azo-2, and the yield is 34.5%.

[0041] Example 1

[0042] (1) Take 0.224 g of 2,6-bis(hydroxyacetamido)pyridine (diamine substance), 1,4-butanediol and 0.261 g of tert-butyl isocyanate into a 50 ml schlenk flask. The molar ratio of 1,4-butanediol to 2,6-bis(hydroxyacetamido)pyridine is 1:9. After adding 5 ml of anhydrous DMF, react at 80 °C for 24 h. During this period, it can be observed that the white solid raw materials dissolve, and finally a light yellow solution is obtained.

[0043] (2) Cool the obtained solution to room temperature, perform suction filtration, wash the obtained white solid with water, and after rotary evaporation of the solvent, 0.452 g of the model compound small molecule B is obtained, presenting as a white powder. After recrystallization with ethanol, 0.12 g of the purified product is obtained, which is the chain extender.

[0044] (3) Take 1.3 g (2 mmol) of polytetrahydrofuran (Mn = 650) and add it to a 100 ml three-necked round-bottom flask. Heat it under vacuum (pressure less than 100 Pa) at 120 °C for 2 h to remove the small amount of water contained in the polytetrahydrofuran and make it molten.

[0045] (4) Then cool it to room temperature, install a mechanical stirring device and a condensing reflux device under an argon atmosphere, add 3 ml of anhydrous N,N-dimethylformamide (DMF) as the reaction solvent, add 0.889 g (4 mmol) of isophorone diisocyanate (IPDI) according to the molar ratio of polytetrahydrofuran to isophorone diisocyanate of 1:2, and then add 1 - 2 drops of dibutyltin dilaurate (DBTDL) as a catalyst; heat it to 70 °C under mechanical stirring and react for 3 h. The whole reaction process is carried out under argon protection to obtain a polyurethane prepolymer.

[0046] (5) After the polyurethane prepolymer is prepared, maintain the argon protection atmosphere and the mechanical stirring device. Mix the chain extender at a certain ratio (the molar ratio of the chain extender to polytetrahydrofuran is 1:1) at 70 °C.

[0047] (6) Replace the air in the mechanical stirring device with argon, heat and dissolve the chain extender with 3 ml of anhydrous N,N-dimethylformamide (DMF) and then add it to the reaction system. Continue to react for 3 h, add 3 ml of methanol to quench the unreacted isocyanate groups, stir for 30 min, then turn off the stirring, cool down to room temperature, and obtain a polyurethane solution.

[0048] (7) Wash and purify the prepared polyurethane solution with acetonitrile, remove the supernatant after sedimentation and centrifugation, and repeat three times. Then air-dry the solid at the bottom for 12 h, treat it at 60 °C in a blast drying oven for 6 h, and then put it in a vacuum drying oven and treat it at 80 °C for 8 h to obtain a self-healing polyurethane material extended by 2,6-bis(hydroxyacetamido)pyridine, that is, a polyurethane elastomer film.

[0049] Example 2

[0050] On the basis of Example 1, set the molar ratio of 1,4-butanediol to 2,6-bis(hydroxyacetamido)pyridine to 2:8. The rest is the same as in Example 1.

[0051] Example 3

[0052] On the basis of Example 1, the molar ratio of 1,4-butanediol to 2,6-bis(hydroxyacetamido)pyridine was set to 3:7. The rest was the same as in Example 1.

[0053] Example 4

[0054] On the basis of Example 1, the molar ratio of 1,4-butanediol to 2,6-bis(hydroxyacetamido)pyridine was set to 4:6. The rest was the same as in Example 1.

[0055] Example 5

[0056] On the basis of Example 1, the molar ratio of 1,4-butanediol to 2,6-bis(hydroxyacetamido)pyridine was set to 5:5. The rest was the same as in Example 1.

[0057] Example 6

[0058] On the basis of Example 1, the molar ratio of 1,4-butanediol to 2,6-bis(hydroxyacetamido)pyridine was set to 6:4. The rest was the same as in Example 1.

[0059] Example 7

[0060] On the basis of Example 1, the molar ratio of 1,4-butanediol to 2,6-bis(hydroxyacetamido)pyridine was set to 7:3. The rest was the same as in Example 1.

[0061] Example 8

[0062] On the basis of Example 1, the molar ratio of 1,4-butanediol to 2,6-bis(hydroxyacetamido)pyridine was set to 8:2. The rest was the same as in Example 1.

[0063] Example 9

[0064] On the basis of Example 1, the molar ratio of 1,4-butanediol to 2,6-bis(hydroxyacetamido)pyridine was set to 9:1. The rest was the same as in Example 1.

[0065] Example 10

[0066] On the basis of Example 1, the molar ratio of 1,4-butanediol to 2,6-bis(hydroxyacetamido)pyridine was set to 10:0. The rest was the same as in Example 1.

[0067] Example 11

[0068] On the basis of Example 4, isophorone diisocyanate was replaced with toluene diisocyanate (TDI). The rest was the same as in Example 4.

[0069] Example 12

[0070] Based on Example 4, isophorone diisocyanate was replaced with lysine diisocyanate (LDI). The rest was the same as in Example 4.

[0071] Example 13

[0072] Based on Example 4, isophorone diisocyanate was replaced with hexamethylene diisocyanate (HDI). The rest was the same as in Example 4.

[0073] Example 14

[0074] The polyurethane solution obtained in Example 4 was washed and purified with acetonitrile. After sedimentation and centrifugation, the supernatant was removed, and this was repeated three times. Then, the prepared spiropyran diol SP-2OH was copolymerized with the polyurethane solution. Then, the solid at the bottom layer was air-dried for 12 h, placed in a forced-air drying oven at 60 °C for 6 h, and then placed in a vacuum drying oven at 80 °C for 8 h to obtain a color-changing polyurethane elastomer film. The obtained material had color-changing properties. Under ultraviolet light irradiation, the spiropyran spiro ring structure would open, and the molecular color would usually change from colorless or light color to dark color, such as red, purple, or blue.

[0075] Example 15

[0076] The polyurethane solution obtained in Example 4 was washed and purified with acetonitrile. After sedimentation and centrifugation, the supernatant was removed, and this was repeated three times. Then, the prepared orange solid M-Azo-3 was copolymerized with the polyurethane solution. Then, the solid at the bottom layer was air-dried for 12 h, placed in a forced-air drying oven at 60 °C for 6 h, and then placed in a vacuum drying oven at 80 °C for 8 h to obtain a color-changing polyurethane elastomer film. The obtained material had color-changing properties. Under ultraviolet light irradiation, azobenzene compounds would change from trans to cis, and the material color would change from colorless or light yellow to orange or red.

[0077] Example 16

[0078] The polyurethane solution obtained in Example 4 was washed and purified with acetonitrile. After sedimentation and centrifugation, the supernatant was removed, and this was repeated three times. Then, the prepared orange solid M-Azo-3 and spiropyran diol SP-2OH were copolymerized with the polyurethane solution. Then, the solid at the bottom layer was air-dried for 12 h, placed in a forced-air drying oven at 60 °C for 6 h, and then placed in a vacuum drying oven at 80 °C for 8 h to obtain a color-changing polyurethane elastomer film. The obtained material had color-changing properties. Under ultraviolet light irradiation, azobenzene compounds would change from trans to cis, and the material color would change from colorless or light yellow to orange or red. Under ultraviolet light irradiation, the spiropyran spiro ring structure would open, and the molecular color would usually change from colorless or light color to dark color, such as red, purple, or blue, with a wide range of color changes.

[0079] Test Example

[0080] The performance parameters of the polyurethane elastomer film prepared in the above examples and the photo-induced multicolor self-healing polyurethane material prepared in the comparative example are tested.

[0081] The DMA, mechanical properties and self-healing properties are tested using the prepared standard polyurethane elastomer specimens; gel permeation chromatography and DSC are tested using small pieces of samples cut after film formation; the microscope and the profilometer both use the dust-free samples cast on the glass plate after being treated with a needle filter.

[0082] The test methods are as follows:

[0083] Dynamic thermomechanical analysis (DMA): The dynamic thermomechanical analysis of the standard polyurethane elastomer specimens is carried out using a DMA Q800 dynamic thermomechanical analyzer from TA Instruments, USA. The test temperature range is -120 °C - 150 °C, the frequency is 1 Hz, the amplitude is 15 μm, and the heating rate is 2 °C / min. The size of the test specimens is 20 mm in length, 5 mm in width and 0.25 mm in thickness. The specimens are fixed and clamped using a tensile mold and tested in a nitrogen atmosphere to obtain the elongation at break of the specimens.

[0084] Differential scanning calorimeter (DSC): Differential scanning calorimetric analysis of the polyurethane elastomer specimens is carried out using a DSC 2500 differential scanning calorimeter from TA Instruments, USA. The amount of sample used for each test is 10 - 15 mg, which is placed in a sealed aluminum crucible, and the test is carried out in a nitrogen atmosphere. The temperature setting program is as follows: starting from -90 °C, it is heated to 150 °C at a rate of 30 K / min, held for 3 min, then cooled from 150 °C to -90 °C at a rate of 30 K / min and held for 3 min, and the second heating starts from -90 °C and is heated to 150 °C to end. The second heating is carried out to remove the thermal history, and the heating curves of the second heating process are used for the DSC tests of all samples to obtain the glass transition temperature of the samples.

[0085] Mechanical property test: The mechanical properties of the samples are tested using an Instron 5943 1SET instrument from the USA. A tensile fixture is used during the test, and the tensile speed is set to 2.5 mm / mm / min. The test samples are all rectangular specimens. The length and width of the samples are measured using a vernier caliper, and the thickness is measured using a thickness gauge. The number of cycles for the cyclic tensile test is 5 times for all. At least three specimens are tested for each group of samples, and the poor test results caused by internal defects of the material or adverse factors during the sample preparation process are discarded to obtain the toughness value of the samples.

[0086] Self-healing performance test: The method for the self-healing test of mechanical properties is as follows: Cut the prepared rectangular specimen in half with scissors, and use tweezers to fit the two separated parts along the cutting interface on a glass plate. Squeeze the spline from both sides until the fracture surface is completely fitted and keep in full contact for a period of time. Then use an Instron 5943 1SET instrument from the United States to conduct a tensile fracture test on the sample. Compare the obtained stress-strain curve with the original data to draw a conclusion, and record the temperature at that time under constant temperature conditions. Obtain the fracture strength of the sample.

[0087] The method for apparent cut self-healing is as follows: Place a polyurethane elastomer film with a smooth and dust-free surface on a clean glass slide, and use a scalpel to make incisions with a width not exceeding 100 μm on the surface. Align the scratched incisions and let it stand still to observe its change over time. Use a CX40M model metallurgical microscope from Suzhou Jingtong Instrument Co., Ltd. for shooting and observation, and use a white light lamp for illumination during shooting. The scratch depth is tested using a Dektak XT model step profiler (probe-type surface profiler) from Bruker Corporation in the United States. During the test, mark the sample surface, and record the distance from the deepest point of the scratch to the marked point over time. Take the decrease in the distance as the basis for the scratch to become shallower. Obtain the repair rate of the sample.

[0088] The experimental results of Examples 1 to 13 and Comparative Examples 1 to 3 are shown in Table 1:

[0089] Table 1 Experimental results of Examples 1 to 13 and Comparative Examples 1 to 3

[0090]

[0091] As can be seen from Table 1, as the molar ratio of the chain extender 2,6-bis(hydroxyacetamido)pyridine introduced increases, the elastic modulus and fracture strength of the series of samples both show a trend of first increasing and then decreasing, while the elongation at break of the samples generally shows a trend of first decreasing and then increasing.

[0092] When the introduction amount of 2,6-bis(hydroxyacetamido)pyridine reaches 60%, the toughness of polyurethane can be improved. After the introduction amount reaches 70%, the toughness of the polyurethane elastomer can increase significantly. Therefore, introducing 2,6-bis(hydroxyacetamido)pyridine into the polyurethane elastomer can significantly improve the toughness of the material.

[0093] 2,6-bis(hydroxyacetamido)pyridine as the main chain component of polyurethane can effectively promote the formation of multiple hydrogen bonds. And in Example 4, setting the molar ratio of 1,4-butanediol to 2,6-bis(hydroxyacetamido)pyridine to 4:6 is beneficial to the formation of multiple hydrogen bonds, thereby improving the toughness and repair rate.

[0094] In addition, with reference to the foregoing embodiments, the inventors of the present case also conducted tests using other raw materials, process operations, and process conditions described in this specification, and all obtained relatively ideal results.

[0095] All aspects, embodiments, features, and examples of the present invention should be considered illustrative in all respects and are not intended to limit the present invention, the scope of which is defined only by the claims. Without departing from the spirit and scope of the claimed invention, those skilled in the art will appreciate other embodiments, modifications, and uses.

[0096] The use of headings and sections in the present invention is not meant to limit the invention; each section can apply to any aspect, embodiment, or feature of the invention.

[0097] Throughout the present invention, where a composition is described as having, comprising, or including a particular component or where a process is described as having, comprising, or including a particular process step, it is contemplated that the compositions of the present invention teachings also consist essentially of or consist of the recited components, and the processes of the present invention teachings also consist essentially of or consist of the recited process steps.

[0098] It should be understood that the order of the steps or the order of performing a particular action is not of great importance so long as the teachings of the present invention remain operable. In addition, two or more steps or actions can be carried out simultaneously.

[0099] Although the present invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions, and / or additions can be made and elements of the embodiments can be substituted with substantial equivalents without departing from the spirit and scope of the present invention. Additionally, many modifications can be made to adapt a particular situation or material to the teachings of the present invention without departing from the scope of the present invention. Therefore, the present invention is not intended to be limited to the particular embodiments disclosed for carrying out the present invention, but is intended to cover all embodiments falling within the scope of the appended claims. Moreover, unless specifically stated, any use of the terms first, second, etc. does not denote any order or importance, but the terms first, second, etc. are used to distinguish one element from another.

Claims

1. A photoinduced multicolor self-healing polyurethane material, characterized in that, It has the following structural formula: Wherein, R1 and R3 are independently selected from any one of H, F, Cl, Br, CH3, and OCH3, n is an integer selected from 25 to 500, R2 is selected from one or more of long-chain diol substances, diamine substances, and lipid substances, and R4 is selected from one or more of spiropyran compounds, azobenzene compounds, diarylethene compounds, and donor-acceptor Stenhouse adducts.

2. The one kind of photoinduced multi-color self-healing polyurethane material according to claim 1, characterized in that, The tensile strength of the spiropyran compound is 4 to 50 Mpa, the elongation at break is 5 to 600%, the photochromic response speed is less than 90 s, and the cycle stability is greater than 100 times.

3. The one kind of photoinduced multi-color self-healing polyurethane material according to claim 1, characterized in that, The Young's modulus of the photochromic multicolor self-healing polyurethane material is 80 to 100 MPa, the elongation at break is 600 to 700%, and the breaking strength is 18 to 20 Mpa; The photochromic multicolor self-healing polyurethane material appears red under ultraviolet light illumination of 298 to 400 nm and / or green light of 500 to 560 nm, and then turns from red to yellow under light illumination of 420 to 450 nm.

4. A method for synthesizing the photo-induced multi-color self-healing polyurethane material according to any one of claims 1 to 3, characterized in that, It includes the following steps: S1, mixing and reacting a first mixed reaction system containing a diamine substance, a cyanate ester substance, a diol substance, and a first solvent at 70 to 120 °C for 20 to 30 h to obtain a chain extender; S2, reacting a second mixed system containing a dicyanate ester substance, polytetrahydrofuran, and a second solvent at 50 - 100 °C for 2 to 6 h to obtain a prepolymer; S3, reacting a third mixed reaction system containing a chain extender, a prepolymer, and a third solvent at 50 to 100 °C for 2 to 6 h to obtain a self-healing polyurethane material; S4, carrying out a copolymerization reaction of the self-healing polyurethane material obtained in S3 with one or more of spiropyran compounds, azobenzene compounds, diarylethene compounds, and donor-acceptor Stenhouse adducts to obtain a photochromic multicolor self-healing polyurethane material.

5. The synthesis method according to claim 4, wherein, The diamine substance includes any one or a combination of two or more of 2,6-diaminopyridine, ethylenediamine, 1,2-propanediamine, p-phenylenediamine, diaminomaleonitrile, and 1,6-diaminohexane.

6. The synthesis method according to claim 5, wherein The 2,6-diaminopyridine is purified by the following method: dissolving 2,6-diaminopyridine in an alcohol substance, adding an adsorbent for adsorption, and evaporating the filtrate after filtration to obtain pure 2,6-diaminopyridine; The alcohol substance includes one of methanol, ethanol, and n-propanol, and the adsorbent includes at least one of activated carbon, molecular sieve, silica gel, and alumina.

7. The synthesis method according to claim 4, wherein The diol substance includes any one or a combination of two or more of ethylene glycol, propylene glycol, polyethylene glycol, and 1,4-butanediol.

8. The synthesis method according to claim 4, characterized in that, The dicyanate ester substance includes any one or a combination of two or more of isophorone diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, and lysine diisocyanate.

9. The synthesis method according to claim 4, characterized in that, The first solvent, the second solvent, and the third solvent each include at least one of water, DMF, and THF; The molar ratio of polytetrahydrofuran to the dicyanate ester substance is 1:(2 - 2.5); The molar ratio of the diamine substance to the diol substance is 1:(0 - 10).

10. Application of the photo-induced multicolor self-healing polyurethane material according to any one of claims 1 to 3 to a car paint coating.

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