Preparation method of photoresponsive self-cleaning optical coating with dynamic self-repairing function

Abstract

The invention discloses a preparation method of a photoresponsive self-cleaning optical coating with a dynamic self-repairing function. The preparation method comprises the following steps: adding a monomer containing a Diels-Alder reaction bond into a polyurethane prepolymer, and reacting to obtain the polyurethane elastomer with self-repairing capability. An azobenzene derivative is connected to a polyurethane elastomer through a covalent bond, and the photoresponsive self-repairing polymer is obtained. Hydrophobically modified TiO2 nanoparticles are prepared in situ through a sol-gel method. In order to further improve the dispersity of the TiO2 nanoparticles in the polymer, a silane coupling agent is adopted to carry out surface modification on the TiO2 nanoparticles. The preparation method comprises the following steps: mixing a photoresponsive self-repairing polymer and a TiO2 nanoparticle dispersion liquid in proportion, uniformly stirring, coating the mixed liquid on the surface of a base material, forming a uniform coating through a brush coating or spray coating method, and curing the coating at a proper temperature. Due to the excellent characteristics of light response self-repairing, ultraviolet resistance, wear resistance and the like, the coating can keep a long transparent period and good antifouling durability in an outdoor environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of self-cleaning coatings. Specifically, it relates to a photo-responsive self-cleaning optical coating with dynamic self-healing function, its preparation method and application, especially the use of this self-healing photo-responsive self-cleaning coating for the protection of the surface of optical devices. Background Art

[0002] With the rapid development of optical technology, optical devices (such as camera lenses, microscopes, lasers, solar panels, etc.) are increasingly widely used in various fields. However, the problems of surface contamination and damage of optical devices have always been the key factors affecting their performance and service life. Pollutants (such as dust, oil stains, fingerprints, etc.) will reduce the light transmittance and imaging quality of optical devices, while surface scratches and microcracks may cause light scattering, increased reflectivity, and even device failure. Therefore, there is an urgent need to develop an optical coating with both self-cleaning and self-healing functions.

[0003] Traditional optical coatings mainly rely on hydrophobic or superhydrophobic surfaces to achieve self-cleaning functions, but these coatings often lack scratch resistance and anti-aging ability, and are difficult to deal with pollution problems in complex environments. In recent years, self-cleaning coatings based on photocatalytic materials (such as titanium dioxide, TiO 2 ) have received extensive attention due to their ability to efficiently decompose organic pollutants

Chemosphere, 2022, 307, 135951

[0004] To overcome the above problems, researchers have begun to explore introducing dynamic self-healing functions into optical coatings. Self-healing materials can restore their original properties through chemical or physical mechanisms after being damaged, thereby extending the service life of the coatings. For example, microencapsulated self-healing agents can release the healing agent when the coating is mechanically damaged, fill the scratches and restore the integrity and functionality of the coating

Nature Materials, 2007, 6, 581 - 585

Advanced Functional Materials, 2022, 32, 2201290

[0005] Currently, there are still several problems with the transparent anti-fouling and self-cleaning coatings for optical devices on the market: 1. After the coating is scratched by external forces, it is often difficult to achieve self-repair; 2. After organic pollutants and the like adhere, it is difficult to effectively remove them in outdoor environments; 3. It is difficult to balance the transparency and self-cleaning ability of the coating. Summary of the Invention

[0006] The purpose of the present invention is to provide a photo-responsive self-cleaning optical coating with a dynamic self-repair function and a preparation method thereof. This coating can not only decompose pollutants through the photocatalytic action of titanium dioxide (TiO 2 ) nanoparticles in the polymer network, but also achieve rapid self-repair after being damaged, thereby maintaining its long-term performance stability. The introduction of photo-responsive materials enables the coating to dynamically adjust its surface properties according to environmental light conditions, further enhancing its adaptability and functionality. For example, under strong light conditions, the photo-responsive polymer can enhance the hydrophilicity of the coating and promote the removal of pollutants; while under weak light conditions, the coating can restore its hydrophobicity to prevent pollutant attachment. By introducing thermally reversible furan-maleimide covalent bonds into the polyurethane main chain, the dynamic self-repair of the damaged part is achieved through the Diels Alder (DA) reaction and r-DA reaction. The interfacial gradient composite network formed by TiO 2 nanoparticles and amino silicone oil solves the problem of difficult balance between nanoparticle dispersion and light transmittance. The self-repairing transparent composite coating constructed has obvious hydrophobicity on its surface and can achieve the self-cleaning effect of solid pollutants on the surface of optical devices under the flushing of fine rainwater.

[0007] The surface modification technology of inorganic nanoparticles is used to prepare titanium dioxide (TiO 2 ) nanoparticles with controllable sizes through an in-situ sol-gel method, and their surface and interface are chemically grafted and modified to introduce hydrophobic and reactive functional groups, improving their compatibility with the polyurethane matrix and avoiding agglomeration during the curing process. By introducing reversible dynamic covalent bonds and photo-responsive azo units into the polyurethane elastomer, the dynamic reversible repair of the coating is achieved. Finally, a composite coating is prepared through a curing cross-linking reaction. The photo-responsive azo polyurethane prepolymer is adjusted by regulating the dosage of azobenzene derivatives, the polymerization reaction temperature, and time; the anti-ultraviolet, wear-resistant, and hydrophobic properties of the composite coating are regulated by adjusting the dosages of hydrophobic modifiers and TiO 2 ; the cross-linking degree and adhesion of the coating are regulated by adjusting the dosage of amino silicone oil.

[0008] To solve the above technical problems, the following technical solutions are adopted:

[0009] A preparation method of a photo-responsive self-cleaning optical coating with a dynamic self-repair function includes the following steps:

[0010] (1) Preparation of modified TiO 2 nanoparticles

[0011] Preparation of modified TiO 2 nanoparticles includes: mixing tetrabutyl titanate or tetraisopropyl titanate with a modified solvent in proportion, stirring evenly to form a titanium source solution; subsequently, adding a stabilizer and a hydrophobic modifier, mixing the above reactants evenly at a rotation speed of 50 - 1000 rpm, then slowly dropping a mixed solution of deionized water and nitric acid, adjusting the pH range to 2 - 5; adjusting the temperature to 25°C - 40°C, reacting for 0.1 h - 10 h, after forming a transparent sol, allowing the sol to stand for 24 h to form a wet gel; drying the wet gel at a certain temperature for a period of time to obtain a dry gel; calcining the dry gel at a certain temperature for a period of time to obtain hydrophobic modified TiO 2 nanoparticles;

[0012] (2) Preparation of polyurethane prepolymer

[0013] Mix polyester polyol and diisocyanate in proportion, heat to 50°C - 90°C under nitrogen protection, react for 0.5 h - 10 h to generate an isocyanate - terminated polyurethane prepolymer; then obtain two different polyurethane prepolymers through the following two methods:

[0014] a. Add an azobenzene derivative to the polyurethane prepolymer and continue to react for 1 h, so that the azobenzene derivative reacts with the isocyanate group of the polyurethane prepolymer through a hydroxyl group to obtain a photo - responsive polyurethane prepolymer;

[0015] b. Add a furan - maleimide monomer containing a dynamic covalent bond to the polyurethane prepolymer and continue to react for 2 h to obtain a polyurethane prepolymer with a dynamic reversible repair function;

[0016] (3) Preparation of composite coating

[0017] Disperse the modified TiO 2 nanoparticles in a film - forming solvent, add the two polyurethane prepolymers and amino silicone oil prepared in the above step (2), stir evenly to obtain a coating; form a composite coating on a glass substrate by a coating method.

[0018] Preferably, the stabilizer is selected from at least one of the following: acetylacetone, polyvinylpyrrolidone, polyvinyl alcohol, carboxymethyl chitosan.

[0019] Preferably, the hydrophobic modifier is selected from at least one of the following: oleic acid, oleylamine, octyltrimethoxysilane, (3 - mercaptopropyl)trimethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, octadecyltrimethoxysilane, octadecyltriethoxysilane.

[0020] After optimization, the modified solvent is selected from at least one of the following: water, ethanol, isopropanol, ethylene glycol, glycerol, dimethyl sulfoxide, dimethylformamide. Further preferably, isopropanol and dimethyl sulfoxide.

[0021] After optimization, the mass ratio of tetrabutyl titanate to the modified solvent is 5% - 25%; the mass dosage of the stabilizer is 0.1% - 5% of the mass dosage of the modified solvent; the mass dosage of the hydrophobic modifier is 15% - 50% of the mass dosage of the modified solvent.

[0022] After optimization, the drying temperature of the wet gel is 25°C - 80°C, and the drying time is 0.5h - 24h; further preferably, the drying temperature is 50°C - 70°C, and the drying time is 8h - 15h.

[0023] After optimization, the calcination temperature of the dry gel is 300°C - 800°C, and the calcination time is 0.5h - 12h; further preferably, the calcination temperature is 400°C - 600°C, and the calcination time is 5h - 15h.

[0024] After optimization, the average size of TiO 2 nanoparticles is controlled within 10nm - 30nm.

[0025] After optimization, in the step (2), the mass dosage ratio of the polyester polyol to the diisocyanate is 5:1 - 2:1; the mass dosage of the azobenzene derivative is 1% - 5% of the mass dosage of the polyester polyol.

[0026] After optimization, in the step (2), the mass dosage of the furan - maleimide monomer is 10% - 50% of the mass dosage of the polyurethane prepolymer, and the ratio of the furan ring group to the maleimide group is 0.5:1 - 10:1; considering the self - healing performance of the cross - linked polymer, the ratio of the furan ring group to the maleimide group is further preferably 5:1 - 8:1.

[0027] After optimization, in the step (2), the polyester polyol is selected from at least one of the following: polyethylene adipate glycol, polybutylene adipate glycol, polyethylene terephthalate glycol, polypropylene glycol phthalate anhydride, polyethylene sebacate glycol, polyneopentyl adipate glycol, poly(1,6 - hexanediol adipate) glycol, polylactic acid - based polyol.

[0028] After optimization, in the step (2), the diisocyanate is selected from at least one of the following: diphenylmethane diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, naphthalene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, cyclohexane diisocyanate, p-phenylene diisocyanate; considering weather resistance and chemical stability, diphenylmethane diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate are further preferred.

[0029] After optimization, in the step (2), the azobenzene derivative is selected from at least one of the following: 4-hydroxyazobenzene, 4-iodo-azobenzene, 4,4'-bis(2-methoxy-n-propionate-3-yl)azobenzene, 4,4'-bis(2-methoxy-ethyl propionate-3-yl)azobenzene, 4-(2-methoxy-n-propionate-3-yl)-4'-hydroxy-3'-carboxyazobenzene, disodium salt of 4,4'-bis(2-methoxy-n-propionate-3-yl)azobenzene, 2-substituted-4,4'-diaminoazobenzene;

[0030] After optimization, in the step (2), the furan maleimide group is selected from at least one of the following: furfuryl alcohol maleimide, bismaleimide-bisfuran, furan acrylate maleimide, furfuryl ethyl maleimide, furfuryl propyl maleimide, bisfuryl bismaleimide, furfuryl phenyl maleimide, furfuryl cyclohexyl maleimide, furfuryl polyethylene glycol maleimide.

[0031] After optimization, the reaction conditions of the polyurethane prepolymer in the step (2) are further preferably: reacting at 70 °C to 80 °C for 0.5 h to 3 h.

[0032] After optimization, in the step (3), the modified TiO 2 The mass dosage of the nanoparticles is 0.5% to 20% of the sum of the mass dosages of the two polyurethane prepolymers; the sum of the mass dosages of the two polyurethane prepolymers is 30% to 70% of the mass dosage of the film-forming solvent; the mass dosage of the amino silicone oil is 2% to 5% of the mass dosage of the film-forming solvent. The mass ratio of the photo-responsive polyurethane prepolymer to the polyurethane prepolymer with a dynamic reversible repair function is 1:5 to 1:1.

[0033] After optimization, in the step (3), the film-forming solvent is selected from at least one of the following: tetrahydrofuran, acetone, xylene, 1,4-dioxane, N,N-dimethylformamide.

[0034] After optimization, in the step (3), the amino silicone oil is selected from at least one of the following: aminoethylaminopropyl polydimethylsiloxane, aminopropyl polydimethylsiloxane, aminoethyl silicone oil, α-hydro-β-hydroxy-polydimethylsiloxane, AC-211N amino silicone oil, DK-N322 amino silicone oil.

[0035] After optimization, in the step (3), the molecular weight of the amino silicone oil is controlled to be 1000-20000. Considering the self-healing effect of the coating, the molecular weight of the amino silicone oil is further preferably 3000-5000.

[0036] After optimization, in the step (3), the coating process is selected from at least one of the following: spin coating, spraying, roller coating or brush coating; where:

[0037] a. The process parameters of spin coating are: the spin coating speed is 500 rpm - 2000 rpm, and the time is 5 s - 120 s. Pre-cure at 50°C - 180°C for 10 min - 60 min, and then high-temperature cure at 100°C - 180°C for 0.5 h - 24 h;

[0038] b. The process parameters of spraying are: the spraying pressure is 0.3 - 20 MPa, the nozzle diameter is 0.5 - 1.2 mm, the spraying distance is 20 - 30 cm, the spraying speed is 0.5 - 1.5 m / s, pre-cure at 20°C - 180°C for 10 min - 30 min, and high-temperature cure at 100°C - 200°C for 0.5 h - 3 h;

[0039] c. The process parameters of roller coating are: the roller coating speed is 0.5 - 1 m / s, the coating viscosity is 500 - 2000 mPa·s, pre-cure at 20°C - 180°C for 10 min - 30 min, and pre-cure at 100°C - 200°C for 0.5 h - 3 h;

[0040] d. The process parameters of brush coating are: the brush coating speed is 0.2 - 0.5 m / s, the coating viscosity is 1000 - 4000 mPa·s, pre-cure at 20°C - 180°C for 10 min - 30 min, and high-temperature cure at 100°C - 200°C for 0.5 h - 3 h.

[0041] Considering the construction cost and efficiency, spraying and brush coating are further preferred.

[0042] Due to the adoption of the above technical solution, the following beneficial effects are achieved:

[0043] In the present invention, a monomer containing a Diels - Alder reaction bond is added to the polyurethane prepolymer, and after reaction, a polyurethane elastomer with self-healing ability is obtained. An azobenzene derivative is covalently bonded to the polyurethane elastomer to obtain a photo-responsive self-healing polymer. Hydrophobically modified TiO 2 nanoparticles are in-situ prepared by the sol - gel method. In order to further improve its dispersibility in the polymer, the TiO 2 nanoparticles are surface-modified with a silane coupling agent. By combining the photo-responsive self-healing polymer with TiO 2The nanoparticle dispersion is mixed in proportion and stirred evenly. After that, the mixed solution is coated on the surface of the substrate, and a uniform coating is formed by brushing or spraying methods. The coating is cured at an appropriate temperature to form a stable film. The excellent light-responsive self-repairing, ultraviolet resistance, and wear resistance characteristics enable the coating to maintain a long-lasting transparent period and good anti-fouling durability in outdoor environments, showing broad application prospects in the anti-fouling field of the surfaces of optical devices in outdoor environments.

[0044] The present invention's technology proposes a multifunctional optical coating integrating light-responsive, dynamic self-repairing, and self-cleaning functions. This coating is prepared through a three-step composite process based on the synergistic effect of photocatalytic materials (TiO 2 nanoparticles), photo-isomerizable molecules (azobenzene derivatives), and dynamic covalent bond polyurethane elastomers. First, through the copolymerization reaction of a polyurethane prepolymer and a Diels-Alder dynamic covalent bond monomer, a polymer matrix with thermally responsive self-repairing ability is constructed, and azobenzene derivatives are further grafted to endow it with photo-induced structure tunability. Second, TiO 2 nanoparticles modified with surface silanes are prepared by the sol-gel method to enhance their dispersibility and photocatalytic activity in the polymer matrix. Finally, by compounding the above components with a fluorinated polymer solution, coating and curing are carried out to form a composite coating with both hydrophobic surface and photocatalytic self-cleaning functions. This coating can trigger the photocatalytic degradation effect of TiO 2 under ultraviolet light irradiation, and the degradation rate of oleic acid pollutants reaches 95% within 2 hours; the photo-isomerization characteristics of azobenzene groups enable dynamic regulation of the surface energy of the coating, further synergistically realizing the self-shedding of pollutants with the hydrophobic property. At the same time, based on the thermally reversible characteristics of dynamic covalent bonds, after 30 minutes of ultraviolet light irradiation, the scratch depth of the coating is restored from 15 μm to less than 0.5 μm, and the self-repair efficiency exceeds 99%. The cyclic test shows that the coating still maintains more than 90% hydrophobicity and photocatalytic activity after 30 damage-repair cycles. This work provides a new idea for developing long-life and self-adaptive optical coatings through a multi-mechanism coupling strategy and has application potential in fields such as solar panels and optical device protection.

[0045] Compared with the prior art, the technical solution of the present invention has the following technical advantages:

[0046] 1) Synergy of dynamic self-repair and light response: Traditional self-repair coatings mostly rely on a single stimulus (such as heating) to achieve repair, while in this solution, the combination of dynamic covalent bonds (Diels-Alder bonds) and light-responsive azobenzene can trigger repair under light irradiation or mild heating, realizing multiple response mechanisms, reducing energy consumption, and expanding the applicable scenarios. 2) Long-term self-cleaning and durability improvement: Existing photocatalytic coatings (such as pure TiO 2) It is prone to failure due to mechanical damage or photo-corrosion. In this solution, through the composite structure of the polyurethane elastomer matrix and the surface silicone, while photocatalytically degrading pollutants, the hydrophobic surface is used to reduce the attachment of dirt, and the micro-cracks are repaired through the self-healing mechanism, significantly extending the coating life. 3) Multifunctional integrated design: Traditional technologies often need to stack different coatings to achieve self-cleaning, self-healing or light-responsive functions, resulting in poor interfacial compatibility. In this solution, the photo-responsive group (azobenzene), photocatalytic particles (TiO 2 ) and the dynamic polymer network are integrated through chemical bonding to form a uniform and stable composite coating, avoiding delamination problems, and the preparation process is simple and applicable to complex substrates. 4) Enhanced environmental adaptability: The photo-induced isomerization of azobenzene can dynamically adjust the surface wettability. Combining with the photocatalytic activity of TiO 2 , the coating can efficiently degrade pollutants under both ultraviolet / visible light, adapting to the changing environment.

[0047] In summary, the present invention takes into account both functionality and practicality, providing an innovative solution for the intelligentization and long-term effectiveness of optical coatings. Description of the Drawings

[0048] Figure 1 It is the microscopic scanning electron microscope photo of the coating before repair in Example 1.

[0049] Figure 2 It is the microscopic scanning electron microscope photo of the coating after repair in Example 1.

[0050] Figure 3 It is the microscopic scanning electron microscope photo of the coating before repair in Comparative Example 1.

[0051] Figure 4 It is the microscopic scanning electron microscope photo of the coating after repair in Comparative Example 1.

[0052] Figure 5 It is the microscopic scanning electron microscope photo of the coating before repair in Comparative Example 2.

[0053] Figure 6 It is the microscopic scanning electron microscope photo of the coating after repair in Comparative Example 2.

[0054] Figure 7 It is the microscopic scanning electron microscope photo of the coating before repair in Example 2.

[0055] Figure 8 It is the microscopic scanning electron microscope photo of the coating after repair in Example 2.

[0056] Figure 9 It is the microscopic scanning electron microscope photo of the coating before repair in Example 3.

[0057] Figure 10 It is the microscopic scanning electron microscope photo of the coating after repair in Example 3.

[0058] Figure 11 SEM micrograph of the coating before repair in Example 4.

[0059] Figure 12 SEM micrograph of the coating after repair in Example 4.

[0060] Figure 13 SEM micrograph of the coating before repair in Example 5.

[0061] Figure 14 SEM micrograph of the coating after repair in Example 5. Detailed implementation manners

[0062] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the following will further elaborate on the present invention in combination with specific embodiments. The specific examples described herein are only used to explain the present invention and are not used to limit the present invention. The protection scope of the present invention is by no means limited thereto.

[0063] Example 1

[0064] Mix 10 g of tetrabutyl titanate with 100 g of ethanol and stir evenly to form a titanium source solution. Subsequently, add 0.1 g of acetylacetone and 15 g of cetyltrimethoxysilane. After mixing the above reactants evenly at a rotation speed of 500 rpm, slowly dropwise add a mixed solution of deionized water and nitric acid to adjust the pH to 3. Adjust the temperature to 30 °C and react for 6 h. After forming a transparent sol, let the sol stand for 24 h to form a wet gel. Dry the wet gel at 60 °C for 12 h to obtain a dry gel. Calcinate the dry gel at 500 °C for 8 h to obtain hydrophobic modified TiO 2 nanoparticles.

[0065] Mix 20 g of polyethylene glycol adipate polyol and 5 g of diphenylmethane diisocyanate, and heat to 75 °C under nitrogen protection and react for 2 h to generate an isocyanate-terminated polyurethane prepolymer. Add 0.2 g of 4,4'-bis(2-methoxypropyl-3-yl)azobenzene and continue to react for 1 h to allow the azobenzene derivative to react with the isocyanate group of the prepolymer through a hydroxyl group to obtain a photo-responsive polyurethane prepolymer. Subsequently, add 2 g of furan acrylate maleimide monomer (the ratio of the furan ring group to the maleimide group is 4) to 20 g of the polyurethane prepolymer and continue to react for 2 h to obtain a polyurethane prepolymer with a dynamic reversible repair function.

[0066] Mix 5 g of surface-modified TiO 2The nanoparticles were dispersed in 200 g of xylene, and 60 g of a photo-responsive polyurethane prepolymer and 6 g of aminoethylaminopropyl polydimethylsiloxane were added, and then stirred evenly. The prepared coating was sprayed onto a glass substrate to form a composite coating. The spraying pressure was controlled at 5 MPa, the nozzle diameter was 0.8 mm, the spraying distance was 25 cm, the spraying speed was 1.0 m / s, pre-cured at 80 °C for 20 min, and then cured at 150 °C for 2 h to obtain the composite coating.

[0067] The water contact angle of the coating was measured by dynamic video contact angle, the light transmittance of the coating was measured using a UV-visible spectrophotometer in the wavelength range of 300 - 800 nm, and the abrasion resistance of the coating was measured according to ASTM D 4213-2008. The photocatalytic degradation index of the composite coating was tested by photocatalytic nanomaterials oxidizing and decomposing organic substances, referring to GB / T 30452-2013 "Test Method for Photocatalytic Degradation Index of Photocatalytic Nanomaterials". The self-healing performance test method of the coating: The coating was evenly coated on substrates (such as glass, silicon wafers), and after curing, it was cut into standardized sizes (such as 20 mm × 20 mm). Irradiated with light of a specific wavelength (such as ultraviolet light at 365 nm or visible light at 450 nm) for 6 h. The closure of scratches / cracks was observed using an optical microscope. The water contact angle of the prepared composite coating was 120°, the light transmittance after coating on glass was 93.5%, and the photocatalytic degradation index was 23 nmol / (L·min).

[0068] As Figure 1 and Figure 2 shown, they are the microscopic scanning electron microscope photos of the coating before repair and after repair in Example 1 respectively.

[0069] Comparative Example 1

[0070] After mixing 20 g of polyethylene adipate glycol and 5 g of diphenylmethane diisocyanate, it was heated to 75 °C under nitrogen protection and reacted for 2 h to form an isocyanate-terminated polyurethane prepolymer. 0.2 g of 4,4'-bis(2-methoxypropionate-3-yl)azobenzene was added and the reaction was continued for 1 h to make the azobenzene derivative react with the isocyanate group of the prepolymer through the hydroxyl group, obtaining a photo-responsive polyurethane prepolymer. Subsequently, 2 g of furan acrylate maleimide monomer (the ratio of furan ring group to maleimide group is 4) was added to 20 g of the polyurethane prepolymer, and the reaction was continued for 2 h to obtain a polyurethane prepolymer with dynamic reversible repair function.

[0071] Disperse 60 g of photo-responsive polyurethane prepolymer and 6 g of aminoethylaminopropyl polydimethylsiloxane in 200 g of xylene and stir evenly. Form a composite coating on a glass substrate by spraying the prepared coating. Control the spraying pressure at 5 MPa, the nozzle diameter at 0.8 mm, the spraying distance at 25 cm, the spraying speed at 1.0 m / s, pre-cure at 80 °C for 20 min, and cure at 150 °C for 2 h to obtain the composite coating.

[0072] Measure the water contact angle of the coating by dynamic video contact angle, measure the light transmittance of the coating using a UV-visible spectrophotometer in the wavelength range of 300 - 800 nm, and measure the wear resistance of the coating according to ASTM D 4213-2008. Test the photocatalytic index of the composite coating by the oxidation and decomposition of organic substances by photocatalytic nanomaterials, referring to GB / T 30452-2013 "Test Method for Photocatalytic Index of Photocatalytic Nanomaterials". Test method for the self-healing performance of the coating: Uniformly coat the coating on a substrate (such as glass, silicon wafer), and cut it into a standardized size (such as 20 mm × 20 mm) after curing. Irradiate with light of a specific wavelength (such as ultraviolet light at 365 nm or visible light at 450 nm) for 6 h. Observe the closure of scratches / cracks using an optical microscope. The water contact angle of the prepared composite coating is 116°, the light transmittance after coating on glass is 94.3%, and the coating has no photocatalytic performance.

[0073] As Figure 3 and Figure 4 shown, they are respectively the microscopic scanning electron microscope photos of the coating before repair and after repair in Example 1.

[0074] Comparative Example 2

[0075] Mix 10 g of tetrabutyl titanate with 100 g of ethanol and stir evenly to form a titanium source solution. Subsequently, add 0.1 g of acetylacetone and 15 g of cetyltrimethoxysilane. After mixing the above reactants evenly under the condition of a rotation speed of 500 rpm, slowly drop a mixed solution of deionized water and nitric acid to adjust the pH to 3. Adjust the temperature to 30 °C and react for 6 h. After forming a transparent sol, let the sol stand for 24 h to form a wet gel. Dry the wet gel at 60 °C for 12 h to obtain a dry gel. Calcinate the dry gel at 500 °C for 8 h to obtain hydrophobic modified TiO 2 nanoparticles.

[0076] Mix 20 g of polyethylene adipate glycol and 5 g of diphenylmethane diisocyanate, and heat to 75 °C under nitrogen protection and react for 2 h to generate an isocyanate-terminated polyurethane prepolymer. Subsequently, add 2 g of furan acrylate maleimide monomer (the ratio of furan ring group to maleimide group is 4) to 20 g of the polyurethane prepolymer and continue to react for 2 h to obtain a polyurethane prepolymer with dynamic reversible repair function.

[0077] Disperse 5 g of surface-modified TiO 2 nanoparticles in 200 g of xylene, add 6 g of aminoethylaminopropyl polydimethylsiloxane, and stir evenly. Spray the prepared coating on a glass substrate to form a composite coating. Control the spraying pressure at 5 MPa, the nozzle diameter at 0.8 mm, the spraying distance at 25 cm, the spraying speed at 1.0 m / s, pre-cure at 80 °C for 20 min, and cure at 150 °C for 2 h to obtain the composite coating.

[0078] Measure the water contact angle of the coating by dynamic video contact angle, measure the light transmittance of the coating using a UV-visible spectrophotometer in the wavelength range of 300 - 800 nm, and measure the wear resistance of the coating according to ASTM D 4213-2008. Oxidize and decompose organic substances by photocatalytic nanomaterials, and refer to GB / T 30452-2013 "Test Method for Photolysis Index of Photocatalytic Nanomaterials" to test the photolysis index of the composite coating. Test method for the self-healing performance of the coating: Uniformly coat the coating on a substrate (such as glass, silicon wafer), and cut it into standardized dimensions (such as 20 mm × 20 mm) after curing. Irradiate with light of a specific wavelength (such as ultraviolet light at 365 nm or visible light at 450 nm) for 6 h. Observe the closure of scratches / cracks using an optical microscope. The water contact angle of the prepared composite coating is 122°, the light transmittance after coating on glass is 92.8%, and the photolysis index is 22 nmol / (L·min).

[0079] As Figure 5 and Figure 6 shown, they are the microscopic scanning electron microscope photos of the coating before repair and after repair in Example 1 respectively.

[0080] Example 2

[0081] Mix 10 g of tetrabutyl titanate with 150 g of ethanol and stir evenly to form a titanium source solution. Subsequently, add 0.15 g of polyvinyl alcohol and 16.3 g of octadecyltrimethoxysilane. After mixing the above reactants evenly at a rotation speed of 500 rpm, slowly drop a mixed solution of deionized water and nitric acid to adjust the pH to 3. Adjust the temperature to 40 °C and react for 5 h. After forming a transparent sol, let the sol stand for 24 h to form a wet gel. Dry the wet gel at 70 °C for 6 h to obtain a dry gel. Calcinate the dry gel at 600 °C for 5 h to obtain hydrophobic modified TiO 2 nanoparticles.

[0082] After mixing 21 g of polyethylene terephthalate glycol and 7 g of isophorone diisocyanate, it was heated to 75 °C under nitrogen protection and reacted for 2 h to form an isocyanate-terminated polyurethane prepolymer. 0.35 g of 4,4'-bis(2-ethoxycarbonylethyl-3-yl)azobenzene was added and the reaction was continued for 1 h to allow the azobenzene derivative to react with the isocyanate group of the prepolymer through the hydroxyl group, obtaining a photo-responsive polyurethane prepolymer. Subsequently, 2.3 g of bifuryl bismaleimide monomer (the ratio of furan ring group to maleimide group is 6) was added to 25 g of the polyurethane prepolymer and the reaction was continued for 2 h to obtain a polyurethane prepolymer with dynamic reversible repair function.

[0083] 8.3 g of surface-modified TiO 2 nanoparticles were dispersed in 300 g of acetone, 50 g of photo-responsive polyurethane prepolymer and 4.7 g of aminoethylaminopropyl polydimethylsiloxane were added, and stirred evenly. The prepared coating was sprayed on a glass substrate to form a composite coating. The spraying pressure was controlled at 3 MPa, the nozzle diameter was 0.6 mm, the spraying distance was 20 cm, the spraying speed was 1.5 m / s, pre-cured at 60 °C for 30 min, and high-temperature cured at 180 °C for 1.5 h to obtain the composite coating. The water contact angle of the prepared composite coating was 125°, the light transmittance after coating on glass was 90.2%, and the photolysis index was 28 nmol / (L·min).

[0084] As Figure 7 and Figure 8 shown, they are the microscopic scanning electron microscope photos of the coating before repair and after repair in Example 1 respectively.

[0085] Example 3

[0086] 5 g of tetrabutyl titanate was mixed with 80 g of isopropanol and stirred evenly to form a titanium source solution. Subsequently, 0.26 g of polyvinyl alcohol and 21.3 g of octadecyltrimethoxysilane were added. After mixing the above reactants evenly at a rotation speed of 500 rpm, a mixed solution of deionized water and nitric acid was slowly added dropwise to adjust the pH to 3. The temperature was adjusted to 40 °C and reacted for 5 h. After forming a transparent sol, the sol was allowed to stand for 24 h to form a wet gel. The wet gel was dried at 70 °C for 6 h to obtain a dry gel. The dry gel was calcined at 600 °C for 5 h to obtain hydrophobic modified TiO 2 nanoparticles.

[0087] After mixing 26 g of poly(adipic acid-neopentyl glycol) polyol and 6 g of hexamethylene diisocyanate, it was heated to 75 °C under nitrogen protection and reacted for 2 h to form an isocyanate-terminated polyurethane prepolymer. 0.43 g of sodium 4,4'-bis(3-(2-methoxypropionate))azobenzene-2,2'-disulfonate was added and the reaction was continued for 1 h to allow the azobenzene derivative to react with the isocyanate group of the prepolymer through the hydroxyl group, obtaining a photo-responsive polyurethane prepolymer. Subsequently, 2.3 g of difurylbismaleimide monomer (the ratio of furan ring group to maleimide group is 6) was added to 25 g of the polyurethane prepolymer and the reaction was continued for 2 h to obtain a polyurethane prepolymer with dynamic reversible repair function.

[0088] 6.5 g of surface-modified TiO 2 nanoparticles were dispersed in 240 g of tetrahydrofuran. 30 g of the photo-responsive polyurethane prepolymer and 3.7 g of α-hydro-β-hydroxy-polydimethylsiloxane were added and stirred evenly. The prepared coating was sprayed onto a glass substrate to form a composite coating. The spraying pressure was controlled at 6 MPa, the nozzle diameter was 0.6 mm, the spraying distance was 30 cm, the spraying speed was 1.5 m / s, pre-cured at 80 °C for 20 min, and high-temperature cured at 150 °C for 2 h to obtain the composite coating. Using the testing method in Example 1, the water contact angle of the prepared composite coating was measured to be 129°, the light transmittance after coating on glass was 93.6%, and the photolysis index was 25 nmol / (L·min).

[0089] As Figure 9 and Figure 10 shown, they are the microscopic scanning electron microscope photos of the coating before repair and after repair in Example 1 respectively.

[0090] Example 4

[0091] 2.5 g of tetrabutyl titanate was mixed with 50 g of isopropanol and stirred evenly to form a titanium source solution. Subsequently, 0.33 g of polyvinylpyrrolidone and 8.5 g of dodecyltrimethoxysilane were added. After mixing the above reactants evenly at a rotation speed of 500 rpm, a mixed solution of deionized water and nitric acid was slowly added dropwise to adjust the pH range to 3. The temperature was adjusted to 50 °C and the reaction was carried out for 3 h. After forming a transparent sol, the sol was allowed to stand for 24 h to form a wet gel. The wet gel was dried at 80 °C for 3 h to obtain a dry gel. The dry gel was calcined at 550 °C for 8 h to obtain hydrophobic modified TiO 2 nanoparticles.

[0092] After mixing 30 g of poly(adipic acid-neopentyl glycol) polyol and 15 g of diphenylmethane diisocyanate, it was heated to 65 °C under nitrogen protection and reacted for 5 h to form an isocyanate-terminated polyurethane prepolymer. 0.52 g of 4,4'-bis(2-ethoxycarbonylethyl-3-yl)azobenzene was added and the reaction was continued for 1 h to allow the azobenzene derivative to react with the isocyanate group of the prepolymer through the hydroxyl group, obtaining a photo-responsive polyurethane prepolymer. Subsequently, 1.8 g of furan acrylate maleimide monomer (the ratio of furan ring group to maleimide group is 5) was added to 22 g of the polyurethane prepolymer and the reaction was continued for 2 h to obtain a polyurethane prepolymer with dynamic reversible repair function.

[0093] 7.2 g of surface-modified TiO 2 nanoparticles were dispersed in 200 g of 1,4-dioxane, 23 g of the photo-responsive polyurethane prepolymer and 2.5 g of aminoethyl aminopropyl polydimethylsiloxane were added, and stirred evenly. The prepared coating was sprayed on a glass substrate to form a composite coating. The spraying pressure was controlled at 5 MPa, the nozzle diameter was 0.8 mm, the spraying distance was 25 cm, the spraying speed was 1.0 m / s, pre-cured at 80 °C for 20 min, and high-temperature cured at 150 °C for 2 h to obtain the composite coating. Using the testing method in Example 1, the water contact angle of the prepared composite coating was measured to be 112°, the light transmittance after coating on glass was 94.7%, and the photolysis index was 26 nmol / (L·min).

[0094] As Figure 11 and Figure 12 shown, they are the microscopic scanning electron microscope photos of the coating before repair and after repair in Example 1 respectively.

[0095] Example 5

[0096] 50 g of tetrabutyl titanate was mixed with 500 g of ethanol and stirred evenly to form a titanium source solution. Subsequently, 0.48 g of acetylacetone and 12.6 g of octadecyltriethoxysilane were added. After mixing the above reactants evenly at a rotation speed of 500 rpm, a mixed solution of deionized water and nitric acid was slowly added dropwise to adjust the pH range to 3. The temperature was adjusted to 40 °C and reacted for 3 h. After forming a transparent sol, the sol was allowed to stand for 24 h to form a wet gel. The wet gel was dried at 50 °C for 8 h to obtain a dry gel. The dry gel was calcined at 600 °C for 5 h to obtain hydrophobic modified TiO 2 nanoparticles.

[0097] After mixing 26 g of poly(propylene glycol phthalate) polyol and 6.2 g of isophorone diisocyanate, it was heated to 75 °C under nitrogen protection and reacted for 2 h to form an isocyanate-terminated polyurethane prepolymer. 0.33 g of 2-substituted-4,4'-diaminoazobenzene was added and the reaction was continued for 1 h to allow the azobenzene derivative to react with the isocyanate group of the prepolymer through the hydroxyl group, obtaining a photo-responsive polyurethane prepolymer. Subsequently, 2.4 g of furanethyl maleimide monomer (the ratio of the furan ring group to the maleimide group is 5) was added to 33.5 g of the polyurethane prepolymer and the reaction was continued for 2 h to obtain a polyurethane prepolymer with a dynamic reversible repair function.

[0098] Disperse 5 g of surface-modified TiO 2 nanoparticles in 200 g of xylene, add 60 g of the photo-responsive polyurethane prepolymer and 6 g of aminoethylaminopropyl polydimethylsiloxane, and stir evenly. The prepared coating was formed into a composite coating on a glass substrate by brushing, controlling the brushing speed at 0.3 m / s, the brushing speed was 0.2 - 0.5 m / s, the coating viscosity was 2000 mPa·s, pre-cured at 60 °C for 30 min, and high-temperature cured at 120 °C for 2 h to obtain the composite coating. Using the testing method in Example 1, the water contact angle of the prepared composite coating was measured to be 123°, the light transmittance after coating on glass was 94.8%, and the photolysis index was 26 nmol / (L·min).

[0099] As Figure 13 and Figure 14 shown, they are respectively the microscopic scanning electron microscope photos of the coating before repair and after repair in Example 1.

[0100] Table 1

[0101]

[0102] As shown in Table 1, the examples and the comparative examples, the amount of hydrophobically modified titanium dioxide nanoparticles, the amount of photo-responsive polyurethane prepolymer, and the ratio of the furan ring group to the maleimide group in the furan acrylate maleimide monomer are directly related to the contact angle, light transmittance, photocatalytic ability, and self-healing effect of the coating. In Comparative Example 1, since no titanium dioxide nanoparticles were added, the contact angle of the coating decreased. Although the light transmittance of the coating was improved to some extent, the lack of a photocatalytic unit resulted in a photocatalytic index of 0 for the coating, indicating that the coating had no photocatalytic performance. In Comparative Example 2, since no photo-responsive polyurethane prepolymer was added, the self-healing time of the composite coating was significantly prolonged. The photocatalytic index of the coating with added titanium dioxide nanoparticles was 22 nmol / (L·min), showing excellent photocatalytic performance. In Example 5, the ratio of the furan ring group to the maleimide group in the furan acrylate maleimide monomer was 5, which was higher than that in Comparative Example 1. The self-healing time of the composite coating was significantly reduced, and the coating had excellent self-healing performance. To comprehensively consider the photocatalytic and self-healing properties, it can be seen that the dosage and group ratio in Example 5 were the best. Therefore, in Examples 2 and 3, the amount of silica nanoparticles was increased, and the ratio of the furan ring group to the maleimide group in the furan acrylate maleimide monomer was controlled to be 6. The contact angle of the composite coating was significantly increased, and the coating not only had good photocatalytic performance and self-healing effect but also had excellent light transmittance.

[0103] The above are only specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications made based on the present invention to solve substantially the same technical problems and achieve substantially the same technical effects are all covered by the protection scope of the present invention.

Claims

1. A method for preparing a light-responsive self-cleaning optical coating with dynamic self-repairing function, characterized in that: The steps include: Step 1, preparing modified TiO2 nanoparticles; Tetrabutyl titanate or tetraisopropyl titanate is mixed with a modified solvent in proportion and stirred evenly to form a titanium source solution; then, a stabilizer and a hydrophobic modifier are added, and the above reactants are mixed evenly at a rotation speed of 50 to 1000 rpm, and then a mixed solution of deionized water and nitric acid is slowly added dropwise; the temperature is adjusted to 25° C. to 40° C., and the reaction is carried out for 0.1 h to 10 h. After a transparent sol is formed, the sol is allowed to stand for 24 h to form a wet gel; Drying the wet gel at a certain temperature for a period of time to obtain a dry gel; The dry gel is calcined at a certain temperature for a period of time to obtain hydrophobically modified TiO2 nanoparticles; Step 2, preparing a polyurethane prepolymer; The polyester polyol and the diisocyanate are mixed in proportion, heated to 50°C to 90°C under nitrogen protection, and reacted for 0.5h to 10h to generate an isocyanate-terminated polyurethane prepolymer; based on the polyurethane prepolymer, a photoresponsive polyurethane prepolymer and a polyurethane prepolymer with a dynamic reversible repair function are prepared by different methods; Step 3, preparing a composite coating; The modified TiO2 nanoparticles are dispersed in a film-forming solvent, and a photoresponsive polyurethane prepolymer, a polyurethane prepolymer with a dynamic reversible repair function and an amino silicone oil are added, and the mixture is stirred evenly to obtain a coating; the prepared coating is applied on a glass substrate to form a composite coating.

2. The method for preparing a light-responsive self-cleaning optical coating with dynamic self-repairing function according to claim 1, characterized in that: In step 1, after slowly dropping the mixed solution of deionized water and nitric acid, the pH range is adjusted to 2-5.

3. The method for preparing a light-responsive self-cleaning optical coating with dynamic self-repairing function according to claim 1 or 2, characterized in that: The average size of the hydrophobically modified TiO2 nanoparticles prepared in step 1 is controlled to be between 10 nm and 30 nm.

4. The method for preparing a light-responsive self-cleaning optical coating with dynamic self-repairing function according to claim 3, characterized in that: The preparation of the photoresponsive polyurethane prepolymer in step 2 is as follows: An azobenzene derivative is added to the polyurethane prepolymer and the reaction is continued for 1 hour, so that the azobenzene derivative reacts with the isocyanate group of the polyurethane prepolymer through the hydroxyl group to obtain a photoresponsive polyurethane prepolymer.

5. The method for preparing a light-responsive self-cleaning optical coating with dynamic self-repairing function according to claim 4, characterized in that: The preparation of the polyurethane prepolymer with dynamic reversible repair function in step 2 is as follows: A furan-maleimide monomer containing a dynamic covalent bond is added to the polyurethane prepolymer, and the reaction is continued for 2 hours to obtain a polyurethane prepolymer with a dynamic reversible repair function.

6. The method for preparing a light-responsive self-cleaning optical coating with dynamic self-repairing function according to claim 5, characterized in that: In step 2, the mass ratio of polyester polyol to diisocyanate is (5:1) to (2:1); the mass amount of azobenzene derivative is 1% to 5% of the mass amount of polyester polyol; and the mass amount of furan-maleimide monomer is 10% to 50% of the mass amount of polyurethane prepolymer.

7. The method for preparing a light-responsive self-cleaning optical coating with dynamic self-repairing function according to claim 6, characterized in that: The ratio of the furan ring group to the maleimide group in the furan-maleimide monomer described in step 2 is 0.5:1 to 10:

1.

8. The method for preparing a light-responsive self-cleaning optical coating with dynamic self-repairing function according to claim 1, characterized in that: The mass amount of the modified TiO2 nanoparticles in step 3 is 0.5% to 20% of the sum of the mass amounts of the two polyurethane prepolymers; the sum of the mass amounts of the two polyurethane prepolymers is 30% to 70% of the mass amount of the film-forming solvent; the mass amount of the amino silicone oil is 2% to 5% of the mass amount of the film-forming solvent.

9. The method for preparing a light-responsive self-cleaning optical coating with dynamic self-repairing function according to claim 8, characterized in that: In step 3, the mass ratio of the photoresponsive polyurethane prepolymer to the polyurethane prepolymer with dynamic reversible repair function is 1:5 to 1:

1.

10. The method for preparing a light-responsive self-cleaning optical coating with dynamic self-repairing function according to claim 8, characterized in that: The coating process in step 3 is selected from at least one of the following: spraying or brushing; wherein: ① The process parameters of spraying are: spraying pressure of 0.3-20MPa, nozzle diameter of 0.5-1.2mm, spraying distance of 20-30cm, spraying speed of 0.5-1.5m / s, pre-curing at 20℃-180℃ for 10min-30min, high temperature curing at 100℃-200℃ for 0.5h-3h; ② The process parameters of brush coating are: brush coating speed is 0.2~0.5m / s, coating viscosity is 1000~4000mPa·s, pre-curing at 20℃~180℃ for 10min~30min, and high temperature curing at 100℃~200℃ for 0.5h~3h.

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