Microcapsules based on aggregation-induced emission materials, their preparation methods and applications

Abstract

This invention provides an aggregation-induced emission (AIE) material and its preparation method, as well as microcapsules based on the AIE material, their preparation method, and their application in composite material damage detection. By doping the AIE-based microcapsules provided by this invention into the polymer coating of a composite material, high-contrast imaging can be achieved using near-infrared fluorescence. Therefore, it can effectively image internal damage through external materials, making it a potentially valuable damage detection dopant material. It enables imaging of internal damage in composite materials and spontaneously reports the damage location via fluorescence.

Description

Technical Field

[0001] This invention belongs to the field of aggregation-induced emission materials technology, and specifically relates to an aggregation-induced emission material and its preparation method, microcapsules based on the aggregation-induced emission material and their preparation method and applications. Background Technology

[0002] Composite materials play a vital role in various industries, including aerospace, automotive, and shipbuilding. However, harsh working environments expose composite materials to various forms of damage, such as microscopic internal problems like delamination, fiber breakage, and back-side tensile cracking. These issues can become the starting point for broader structural damage. Traditional damage detection methods, such as X-ray inspection, ultrasonic testing, and infrared thermography, all have limitations. X-rays can cause ionization, leading to sample damage; ultrasonic testing is affected by environmental factors such as corrosion; and infrared thermography is limited by ambient temperature and has a large margin of error.

[0003] Therefore, a new solution is needed. Summary of the Invention

[0004] In order to overcome the shortcomings and deficiencies of the prior art, the present invention provides an aggregation-induced emission material and its preparation method, microcapsules based on the aggregation-induced emission material and their preparation method and application.

[0005] According to one aspect of the present invention, an aggregation-induced emission material is provided, the aggregation-induced emission material having the following structure:

[0006]

[0007] Where R is selected from

[0008] According to another aspect of the present invention, a method for preparing the aggregation-induced emission material as described above is also provided, comprising the following steps:

[0009] The first intermediate was obtained by bromination and low-temperature coupling of the first compound.

[0010] The second compound was subjected to the McMurry reaction to give the second intermediate product;

[0011] The first intermediate product and the second intermediate product after low-temperature substitution were respectively subjected to Stille coupling reaction with a third compound to synthesize crude products, which were then separated by column chromatography to obtain the aggregation-induced emission material.

[0012] The structural formula of the first compound is:

[0013]

[0014] The structural formula of the second compound is:

[0015]

[0016] The structural formula of the third compound is:

[0017]

[0018] According to another aspect of the present invention, a method for preparing microcapsules based on the aggregation-induced emission material as described above is also provided, characterized by comprising the following steps:

[0019] The aggregation-induced luminescent material was dissolved in n-hexyl acetate to obtain a first mixture;

[0020] Formaldehyde solution and urea are dissolved in water to form urea-formaldehyde prepolymer;

[0021] The first mixture, the urea-formaldehyde prepolymer, and resorcinol were mixed, and the crude product was washed and air-dried to obtain the microcapsules based on aggregation-induced emission materials.

[0022] According to another aspect of the present invention, a microcapsule based on aggregation-induced emission material prepared by the preparation method described above is also provided.

[0023] In the microcapsules based on aggregation-induced emission materials provided by the present invention, the microcapsules have a double-layered spherical shell structure.

[0024] According to another aspect of the present invention, the application of microcapsules based on aggregation-induced emission materials as described above in the detection of damage in composite materials is also provided.

[0025] The application provided by this invention includes the following steps:

[0026] The microcapsules based on aggregation-induced emission material are added to the cured composite material;

[0027] After degassing in a vacuum oven, the coating is applied to a support plate and cured at room temperature to form a coating on the support plate;

[0028] After the coating was damaged, near-infrared imaging was used to capture images, and near-infrared fluorescence was observed at the damaged area.

[0029] The following beneficial effects can be achieved by implementing this invention:

[0030] This invention provides an aggregation-induced emission (AIE) material and its preparation method, as well as microcapsules based on the AIE material, their preparation method, and their application in composite material damage detection. By doping the AIE-based microcapsules provided by this invention into the polymer coating of a composite material, high-contrast imaging can be achieved using near-infrared fluorescence. Therefore, it can effectively image internal damage through external materials, making it a potentially valuable damage detection dopant material. It enables imaging of internal damage in composite materials and spontaneously reports the damage location via fluorescence. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort:

[0032] Figure 1 The image shown is a scanning electron microscope image of the microcapsules based on aggregation-induced emission materials of the present invention;

[0033] Figure 2 The image shown is a photograph of a composite material containing microcapsules based on aggregation-induced emission materials of the present invention, after being covered with a polyurethane film.

[0034] Figure 3 The image shown is a fluorescence image of a near-infrared imager after the composite material containing microcapsules based on the aggregation-induced emission material of the present invention is covered with a polyurethane film. Detailed Implementation

[0035] To provide a clearer understanding of the technical features, objectives, and effects of this invention, specific embodiments are now described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments described in this specification without inventive effort are within the scope of protection of this invention.

[0036] This invention provides a method for preparing aggregation-induced emission materials, the synthetic route of which is shown below:

[0037]

[0038] The preparation method includes the following steps:

[0039] Step S1: The first compound is subjected to a bromination reaction and a low-temperature coupling reaction to obtain the first intermediate product;

[0040] Specifically, in one embodiment of the present invention, compound a is brominated according to the synthetic route shown above to obtain compound b. Compound a is dissolved in chloroform and acetic acid, then N-bromosuccinimide is added and stirred at room temperature; the mixture is then extracted with dichloromethane, washed with brine, and dried with anhydrous sodium sulfate. The solvent is removed by rotary evaporation, and the crude product is purified by silica gel column chromatography and petroleum ether to obtain compound b.

[0041] Specifically, in one embodiment of the present invention, compound b is coupled at low temperature to obtain compound c. Compound b is dissolved in anhydrous tetrahydrofuran under argon atmosphere, n-butyllithium is added dropwise, followed by the addition of anhydrous ketone chloride. After quenching with water, the mixture is extracted with dichloromethane, washed with brine, and dried over anhydrous sodium sulfate. The solvent is removed by rotary evaporation, and the crude product is purified by silica gel column chromatography and petroleum ether to obtain compound c.

[0042] Step S2: The first intermediate product after low-temperature substitution is combined with the third compound by Stille coupling reaction to synthesize a crude product, which is then separated by column chromatography to obtain the aggregation-induced emission material.

[0043] Specifically, in one embodiment of the present invention, compound c is subjected to low-temperature substitution. Compound c is dissolved in anhydrous tetrahydrofuran under an argon atmosphere. The solution is maintained at low temperature and room temperature for a period of time, respectively. Then, tri-tert-butyltin chloride is added dropwise at low temperature. After quenching, the mixture is extracted with dichloromethane, washed with brine, and dried with anhydrous sodium sulfate. The solvent is removed by rotary evaporation to obtain the low-temperature substituted compound c.

[0044] Specifically, in one embodiment of the present invention, compound c and compound f are subjected to a Stille coupling reaction. Compound c, compound f, cesium fluoride, and tetraphenylphosphine palladium are mixed and stirred overnight at high temperature under argon protection, then extracted with dichloromethane, and the organic solvent is removed under reduced pressure. The crude product is purified by column chromatography to obtain compound g.

[0045] This invention also provides a method for preparing aggregation-induced emission materials, the synthetic route of which is shown below:

[0046]

[0047]

[0048] The preparation method includes the following steps:

[0049] Step S1': The second compound is subjected to the McMurry reaction to obtain the second intermediate product;

[0050] Specifically, in one embodiment of the present invention, compound d is subjected to a McMurry reaction according to the synthetic route shown above to obtain compound e. Zinc powder and compound d are mixed, and anhydrous tetrahydrofuran is added under argon protection. After cooling the mixture, titanium tetrachloride is added. The reaction mixture is heated to room temperature and stirred; then the reaction is heated to a high temperature and stirred, cooled, and quenched with aqueous hydrochloric acid. The mixture is extracted with dichloromethane, washed with brine, and dried with anhydrous sodium sulfate. The solvent is removed by rotary evaporation, and the crude product is purified by silica gel column chromatography and petroleum ether to obtain compound e.

[0051] Step S2': The second intermediate product after low-temperature substitution is combined with the third compound by Stille coupling reaction to synthesize a crude product, which is then separated by column chromatography to obtain the aggregation-induced emission material.

[0052] Specifically, in one embodiment of the present invention, compound e is subjected to low-temperature substitution. Compound e is dissolved in anhydrous tetrahydrofuran under an argon atmosphere. The solution is maintained at low temperature and room temperature for a period of time, respectively. Then, tri-tert-butyltin chloride is added dropwise at low temperature. After quenching, the mixture is extracted with dichloromethane, washed with brine, and dried with anhydrous sodium sulfate. The solvent is removed by rotary evaporation to obtain the low-temperature substituted compound e.

[0053] Specifically, in one embodiment of the present invention, compound e is subjected to a Stille coupling reaction with compound f. Compound e, compound f, cesium fluoride, and tetraphenylphosphine palladium are mixed and stirred overnight at high temperature under argon protection, then extracted with dichloromethane, and the organic solvent is removed under reduced pressure. The crude product is purified by column chromatography to obtain compound h.

[0054] This invention also provides a method for preparing microcapsules based on the above-mentioned aggregation-induced emission material, wherein the compound g or h obtained above is dissolved in n-hexyl acetate, and microcapsules containing the aggregation-induced emission material are prepared by a two-step method based on urea-formaldehyde in-situ polymerization. Specifically, the method includes the following steps:

[0055] Step S10: Dissolve the aggregation-induced luminescence material in n-hexyl acetate to obtain a first mixture.

[0056] Specifically, in one embodiment of the present invention, the above-mentioned compound g or h is dissolved in water to prepare an aqueous solution, and then urea, resorcinol and NH4Cl are added. After adjusting the pH, a hexyl acetate solution is added and dispersed in the aqueous solution, and formaldehyde is added after stirring.

[0057] Step S20: Dissolve formaldehyde solution and urea in water to form urea-formaldehyde prepolymer;

[0058] Specifically, in one embodiment of the present invention, formaldehyde solution, urea and water are reacted at 70°C for 1 hour under conditions of pH 8 to initially form urea-formaldehyde (UF) prepolymer.

[0059] Step S30: Mix the first mixture, the urea-formaldehyde prepolymer and resorcinol, and the crude product obtained is washed and air-dried to obtain the microcapsules based on aggregation-induced emission material.

[0060] Specifically, in one embodiment of the present invention, the UF prepolymer is mixed with the mixture from the first step and resorcinol. After adjusting the pH, the mixture is reacted at high temperature for a period of time to obtain a crude product; then it is thoroughly washed multiple times with deionized water and air-dried overnight to obtain microcapsules containing aggregation-induced emission materials. Figure 1 The image shown is a scanning electron microscope image of the aggregation-induced emission material microcapsules, as shown. Figure 1 As shown, the microcapsule has a spherical structure.

[0061] This invention also provides an application of microcapsules based on aggregation-induced emission materials in composite material damage detection. These microcapsules are doped into the polymer coating of the composite material, and high-contrast imaging is achieved using near-infrared fluorescence. Therefore, imaging of internal damage can be effectively achieved through external materials. Thus, it is a damage detection dopant material with great potential. In use, the microcapsules are added to the cured composite material, degassed in a vacuum oven, coated onto a support plate, and cured at room temperature, forming a coating on the support plate. After the coating is damaged, near-infrared imaging is used, and near-infrared fluorescence is observed at the damaged area. This enables imaging of internal damage in composite materials and spontaneous reporting of the damaged location via fluorescence.

[0062] Example 1: Preparation of Aggregation-Induced Emission Materials

[0063] Compound a was dissolved in chloroform and acetic acid (V:V = 1:1). N-bromosuccinimide was added and the mixture was stirred at room temperature for 3 hours. The mixture was then extracted with dichloromethane, washed with brine, and dried over anhydrous sodium sulfate. The solvent was removed by rotary evaporation, and the crude product was purified by silica gel column chromatography and petroleum ether to give compound b. Compound b was dissolved in 20 mL of anhydrous tetrahydrofuran under argon atmosphere. Butyllithium was added dropwise at -78 °C and maintained for 2 hours, followed by the addition of anhydrous ketone chloride. The reaction mixture was maintained at -78 °C for 2 hours, then heated to -60 °C and maintained for 2 hours, and then slowly heated to room temperature. After quenching with water, the mixture was extracted with dichloromethane, washed with brine, and dried over anhydrous sodium sulfate. The solvent was removed by rotary evaporation, and the crude product was purified by silica gel column chromatography and petroleum ether to give compound c. Compound c was dissolved in 20 mL of anhydrous tetrahydrofuran under argon atmosphere. The mixture was maintained at -78 °C for 30 minutes, then at room temperature for 30 minutes. Tri-tert-butyltin chloride was added dropwise at -78°C, and the reaction mixture was maintained at -78°C for 30 minutes, then slowly heated to room temperature. After quenching with H₂O, the mixture was extracted with dichloromethane, washed with brine, and dried over anhydrous sodium sulfate. The solvent was removed by rotary evaporation, and the crude product was mixed with compound f, cesium fluoride, and tetrakis(triphenylphosphine)palladium, stirred overnight at 120°C under argon protection, and then extracted with dichloromethane, removing the organic solvent under reduced pressure. The crude product was purified by column chromatography to give pure g.

[0064] The following are the names, numbers, physical states, and NMR data of the aggregation-induced emission materials synthesized using the above method.

[0065] Compound g: 56% yield, solid powder. 1 H NMR (400MHz, CDCl3) δ (pmm): 7.56-7.28 (m, 6H), 7.23-6.84 (m, 8H), 4.32-4.07 (s, 4H), 2.15-2.00 (s, 2H), 1.47-1.06 (m, 64H), 0.91-0.73 (s, 12H). 13C NMR (100MHz, CDCl3) δ (pmm): 162.0,149.2,147.8,147.0,145.4,139.2,138.9,137.7,1 37.4,136.1,135.2,133.1,132.2,130.9,130.1,129.8,128.3,127.6,127.4,124.8,12 4.5,124.4,124.0,123.5,119.0,118.9,116.0,114.0,96.1,46.4,35.0,34.9,34.4,33.8,31.9,31.6,31.5,31.4,30.2,30.1,29.7,29.5,29.4,29.2,29.0,26.5,22.7,14.1.

[0066] Example 2: Preparation of Aggregation-Induced Emission Materials

[0067] Zinc powder and compound d were added to a 100 mL double-necked flask. Anhydrous tetrahydrofuran was added under argon protection. The mixture was cooled to -78 °C, and titanium tetrachloride was added dropwise using a syringe. The reaction mixture was heated to room temperature and stirred for 2 hours. The reaction was then heated to 80 °C and stirred for 19 hours, and quenched with hydrochloric acid (10% wt) aqueous solution after cooling. The mixture was extracted with dichloromethane, washed with brine, and dried with anhydrous sodium sulfate. The solvent was removed by rotary evaporation, and the crude product was purified by silica gel column chromatography and petroleum ether to give compound e. Compound e was dissolved in 20 mL of anhydrous tetrahydrofuran under argon protection. The mixture was kept at -78 °C for 30 minutes, and then at room temperature for 30 minutes. Tri-tert-butyltin chloride was added dropwise at -78 °C, and the reaction mixture was kept at -78 °C for 30 minutes, and then slowly heated to room temperature. After quenching with H2O, the mixture was extracted with dichloromethane, washed with brine, and dried with anhydrous sodium sulfate. The solvent was removed by rotary evaporation. The crude product was mixed with compound f, cesium fluoride, and tetraphenylphosphine palladium, and stirred overnight at 120°C under argon protection. The mixture was then extracted with dichloromethane, and the organic solvent was removed under reduced pressure. The crude product was purified by column chromatography to obtain pure h.

[0068] The following are the names, numbers, physical states, and NMR data of the aggregation-induced emission materials synthesized using the above method.

[0069] Compound h: 60% yield, solid powder. 1H NMR (400MHz, CDCl3) δ (pmm): 7.63 (s, 1H), 7.50 (s, 1H), 7.41-7.27 (m, 4H), 7.24-7.00 (m, 8H), 6.89 (s, 2H),6.84-6.67(m,4H),4.35-4.15(m,4H),2.22-1.98(m,2H),1.48-1.14(m,64H),0.91-0.75(m,12H). 13 C NMR (100MHz, CDCl3) δ (pmm): 161.9, 161.8, 149.2, 147.1, 145.5, 144.6, 141.3, 139.3, 139.0, 138.9, 137.9,131.2,131.0,130.9,130.8,130.6,12939,129.2,128.9,128.8,128.2,127.6,127.0,126.9,1 26.3,124.5.124.4.124.0.123.5.119.1,119.0,118.9,115.5,114.1,36.6,35.0,34.9,34.5,33.9,32.0,31.9,31.8,31.5,30.3,30.2,29.7,29.6,29.5,29.4,29.2,29.0,26.8,26.7,26.5,22.7,14.2.

[0070] Example 3: Preparation of microcapsules based on aggregation-induced emission materials

[0071] Prepare 30 mL of a 0.5 wt% aqueous solution of compound g (poly(ethylene-phthalic acid-maleic anhydride)) (EMA, Mw = 100,000-500,000), adding 0.4 g urea, 0.04 g resorcinol, and 0.04 g NH4Cl. After adjusting the pH to 3.5, disperse 4 g of a COTh-NDTA solution in hexyl acetate in the aqueous solution, stirring at 500 rpm for 15 minutes. Subsequently, add 1 g of formaldehyde, maintaining the temperature at 55°C for 4 hours. In the second step, react 2.5 g of formaldehyde solution, 1 g of urea, and 5 g of water at pH 8 at 70°C for 1 hour to initially form a urea-formaldehyde (UF) prepolymer. Then, mix this UF prepolymer with the mixture from the first step and 0.6 g of resorcinol. After adjusting the pH to 3, allow the system to react at 55°C for another 3 hours. The crude product was thoroughly washed multiple times with deionized water and then air-dried overnight to obtain microcapsules containing aggregation-induced emission materials. Figure 1 The microstructure of the prepared microcapsules is shown, exhibiting a spherical structure.

[0072] Example 4: Preparation of a coating containing microcapsules based on aggregation-induced emission materials

[0073] The epoxy resin (E-51) was mixed with its curing agent, and then 10 wt% microcapsules were added. After degassing the mixture in a vacuum oven for 20 minutes, it was applied to a polished glass plate and then fully cured at room temperature.

[0074] Example 5: Near-infrared fluorescence imaging of the internal damaged area of ​​a composite material containing microcapsules based on aggregation-induced emission materials.

[0075] The coating prepared above was cut open with a sharp scalpel, and a layer of polyurethane film was then applied. Figure 2 The internal scratches are not visible under white light. Figure 3 The image shows a clear fluorescence image of the scratch captured by a near-infrared imager. It can be seen that the addition of microcapsules based on aggregation-induced emission materials to the composite material can effectively achieve imaging of internal damage through the external material, making it a damage detection dopant material with great potential.

[0076] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many modifications under the guidance of the present invention without departing from the spirit and scope of the claims. These modifications are all within the scope of protection of the present invention.

Claims

1. An aggregation-induced emission material, characterized in that, The aggregation-induced emission material has a structure as shown in the following formula: wherein R is selected from 2. The preparation method of the aggregation-induced emission material according to claim 1, wherein, The method comprises the following steps: The first compound is subjected to bromination and low-temperature coupling to obtain a first intermediate product; The second compound is subjected to McMurry reaction to obtain a second intermediate product; The first intermediate product after low-temperature substitution and the second intermediate product after low-temperature substitution are respectively subjected to Stille coupling reaction with a third compound to synthesize a crude product, and then the crude product is separated by column chromatography to obtain the aggregation-induced emission material, wherein, The first compound has a structural formula as shown in the following formula: The second compound has a structural formula as shown in the following formula: The third compound has a structural formula as shown in the following formula:

3. A method for producing microcapsules based on the aggregation-induced emission material according to claim 1, characterized in that The method comprises the following steps: The aggregation-induced emission material is dissolved in n-hexyl acetate to obtain a first mixture; Formaldehyde solution and urea are dissolved in water to form a urea-formaldehyde prepolymer; The first mixture, the urea-formaldehyde prepolymer and resorcinol are mixed to obtain a crude product, and the crude product is cleaned and air-dried to obtain the aggregation-induced emission material-based microcapsule.

4. An aggregation-induced emission material-based microcapsule prepared by the preparation method of claim 3.

5. The microcapsule based on an aggregation-induced emission material according to claim 4, wherein the shell is formed from a polymerization reaction of a monomer. The microcapsule has a double-layer spherical shell structure.

6. Application of the aggregation-induced emission material-based microcapsule of claim 4 or 5 in composite material damage detection.

7. Use according to claim 6, wherein The method comprises the following steps: The aggregation-induced emission material-based microcapsule is added to the cured composite material; After degassing in a vacuum oven, the microcapsule is coated on a support plate and cured at room temperature to form a coating layer on the support plate; After the coating layer is damaged, near-infrared imaging is used for shooting, and near-infrared fluorescence is generated at the damaged position.

8. Use according to claim 7, wherein the compound is ###0002### The composite material is epoxy resin, and the support plate is a polished glass plate.

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