An organic-inorganic hybrid photochromic coating and a method for preparing the same

Abstract

The application discloses an organic-inorganic hybrid photochromic coating and a preparation method thereof, and the preparation method comprises the following steps: (1) monomer A, monomer B and monomer C are randomly copolymerized under the action of a photoinitiated free radical to form a high-molecular polymer with a three-dimensional network structure; wherein the monomer A is an amide compound containing an olefin functional group; the monomer B is a fluorine-containing acrylic ester compound; and the monomer C is an imidazole compound containing an olefin functional group; (2) the high-molecular polymer and polyvinylpyrrolidone are dissolved in an organic solvent, and after being uniformly mixed, tungsten oxide precursors are added into the solution to react at room temperature; and (3) the mixed solution after the reaction is coated on a glass substrate and dried to obtain the photochromic coating. In the coating prepared by the application, amorphous WO3 nano dots are highly dispersed in the polymer network, and the particle size of the amorphous WO3 nano dots is not higher than 1.03 nm. The photochromic coating has high transparency (transparent before and after color changing), instant light response and fast fading effect, a large color changing degree, and good environmental stability.

Description

Technical Field

[0001] This invention relates to an organic-inorganic hybrid photochromic coating, and also to a method for preparing the above-mentioned photochromic coating. Background Technology

[0002] The persistent global heatwave has exacerbated energy consumption in building cooling. Therefore, improving building energy efficiency and reducing carbon emissions is crucial. Adjusting window light transmission and controlling solar energy input into buildings can effectively improve energy efficiency and visible daylight comfort.

[0003] Photochromic (PC) smart windows, with their simple structure and ability to modulate light without external energy input, hold immense development potential. Tungsten oxide undergoes charge transfer under external light, with electrons transitioning from the valence band to the conduction band, forming conductive or non-conductive tungsten oxide, thus causing a color change. Due to its rapid response to light and excellent reversibility, it has become one of the most extensively studied inorganic photochromic materials.

[0004] In the current process of preparing WO3-based organic-inorganic hybrid photochromic coatings, the different properties of the organic polymer and the inorganic photochromic material affect each other's transparency during hybridization or composite processes, resulting in low transparency of the final material. Furthermore, WO3 readily grows into large crystalline structures, leading to problems such as low transparency and a narrow light-modulating range in the prepared photochromic material. Tungsten oxide completes its color change and fading through a redox reaction, which is affected by the organic polymer chains, resulting in insufficient sensitivity to the color change and a long time required for the color transition. The material's low oxygen permeability also contributes to the prolonged fading time. Summary of the Invention

[0005] Objective of the invention: The present invention aims to provide an organic-inorganic hybrid photochromic coating with high transparency (transparent before and after color change), instantaneous photoresponse and rapid fading effect, large degree of color change, and good environmental stability; another objective of the present invention is to provide a method for preparing the above-mentioned photochromic coating.

[0006] Technical solution: The preparation method of the organic-inorganic hybrid photochromic coating of the present invention includes the following steps:

[0007] (1) Monomer A, monomer B and monomer C are randomly copolymerized under the action of photo-initiated free radicals to form a polymer with a three-dimensional network structure; wherein, monomer A is an amide compound containing olefin functional groups; monomer B is a fluorinated acrylate compound; and monomer C is an imidazole compound containing olefin functional groups.

[0008] (2) Dissolve the polymer and polyvinylpyrrolidone in an organic solvent, mix well, add tungsten oxide precursor, and react at room temperature;

[0009] The introduction of polyvinylpyrrolidone can, on the one hand, increase the density of hydrogen bonds between polymer molecules, thereby improving the mechanical strength of the coating; on the other hand, it can increase the nitrogen content in the polymer, promote the transfer rate of electrons and protons under photoexcitation, and significantly improve the photoresponse speed and color change depth of amorphous WO3 nanodots.

[0010] (3) The reaction mixture is coated onto a glass substrate and dried to obtain a photochromic coating.

[0011] In step (1), monomer A is one of acrylamide, N-isopropylacrylamide, N,N-dimethylacrylamide, or acrylmorpholine; monomer B is one of trifluoroethyl acrylate, hexafluoroisopropyl acrylate, hexafluorobutyl acrylate, dodecafluoroheptyl acrylate, trifluoroethyl methacrylate, hexafluoroisopropyl methacrylate, hexafluorobutyl methacrylate, or dodecafluoroheptyl methacrylate; and monomer C is one of N-vinylimidazolium, 1-allylimidazolium, or 1-(3-buten-1-yl)-1H-imidazolium.

[0012] In step (1), the amount of monomer A added is 20% to 30% of the total molar amount of monomer A, monomer B and monomer C; the amount of monomer B added is 40% to 50% of the total molar amount of monomer A, monomer B and monomer C; and the amount of monomer C added is 20% to 30% of the total molar amount of monomer A, monomer B and monomer C.

[0013] In step (1), the photoinitiator is one of 907, TPO, 184, 1173, DETX, ITX, 369 or 2599; the amount of photoinitiator added is 1 to 1.5% of the total molar amount of monomer A, monomer B and monomer C.

[0014] In step (2), the organic solvent is N,N-dimethylformamide.

[0015] In step (2), the average molecular weight of the polyvinylpyrrolidone is 3000-30000; the mass ratio of polyvinylpyrrolidone to the polymer is 0.05-0.2:1.

[0016] In step (2), the mass concentration of the polymer in the solution is 0.4 to 0.6 g / mL.

[0017] In step (2), the tungsten oxide precursor is one of phosphotungstic acid, tungsten chloride, sodium tungsinic acid, sodium calcium tungsinic acid, sodium tungstate, or potassium sodium tungstate; the amount of the tungsten oxide precursor added is 10-20% of the total mass of the polymer and polyvinylpyrrolidone.

[0018] In step (2), the drying temperature is 100-120℃ and the drying time is not less than 24 hours.

[0019] The photochromic coating prepared by the above method has amorphous WO3 nanoparticles highly dispersed in the polymer network, and the particle size of the amorphous WO3 nanoparticles is no higher than 1.03 nm.

[0020] The photochromic coating of this invention is colorless and transparent. Amorphous WO3 nanodots absorb sunlight, triggering electron transitions that cause valence state changes, thus coloring the entire coating. In the dark, it quickly turns back to a colorless and transparent state.

[0021] The photochromic coating of this invention transforms WO3 nanoparticles from an oxidized state to a reduced state under sunlight excitation, coloring the entire coating. This coloring effectively reduces indoor absorption of infrared light, thus achieving energy conservation and emission reduction. Specifically, as the duration of sunlight irradiation increases, the coating changes from light blue to dark blue, absorbing a wider range of infrared light. The absorbed infrared light is converted into heat energy on the coating surface and dissipated into the outside air by natural wind, thereby saving energy consumption required for indoor cooling.

[0022] Beneficial Effects: Compared with the prior art, the present invention has the following significant advantages: On the one hand, the polymer in the coating of the present invention can restrict the growth and aggregation of WO3, and in situ grow amorphous tungsten oxide nanodots with a size of about 1 nm in the polymer network. By highly dispersing the amorphous WO3 nanodots in the polymer network (no crystal structure is formed under high dispersion), the transparency of the coating is greatly improved, and the visible light transmittance of the coating reaches 96% in the transparent state. At the same time, since the amorphous WO3 nanodots have a small size and a large specific surface area, they can greatly enhance the activity and speed of the redox reaction, thereby effectively enhancing the photoresponse speed and the color change depth of the coating. On the other hand, the polymer can also greatly promote the transfer speed of electrons and protons under photoexcitation and the oxygen penetration effect, further enabling the coating to have a large degree of color change while having instantaneous photoresponse and rapid fading effect. The coating of the present invention also has the advantages of good aging resistance and environmental stability. Attached Figure Description

[0023] Figure 1 This is a high-resolution transmission electron microscope image of the photochromic coating in Embodiment 1 of the present invention;

[0024] Figure 2 The XRD pattern of the photochromic coating in Embodiment 1 of the present invention;

[0025] Figure 3 The infrared absorption spectra of the photochromic coating in Example 1 of this invention before and after color change after 20 minutes of sunlight irradiation are shown.

[0026] Figure 4 The images show the effect of the photochromic coating in Embodiment 1 of the present invention before and after color change after 20 minutes of sunlight exposure;

[0027] Figure 5 This is a schematic diagram showing the change in visible light transmittance of the photochromic coating in Embodiment 1 of the present invention during 30 minutes of sunlight irradiation;

[0028] Figure 6 This is a schematic diagram showing the change in visible light transmittance of the photochromic coating in Embodiment 1 of the present invention during the fading process in a dark environment for 4 hours;

[0029] Figure 7 This is a temperature monitoring curve of the surface of blank glass and coated glass under sunlight irradiation in Embodiment 1 of the present invention.

[0030] Figure 8 This is a graph showing the indoor temperature monitoring curves for blank glass and photochromic coated glass under real-world conditions.

[0031] Figure 9 This is a graph showing the data of 50 cycles of coloring and fading of the photochromic coating in Embodiment 1 of the present invention;

[0032] Figure 10 The graph shows the base transmittance and glass transition temperature of coatings with different PVP contents introduced in Examples 1, 8, 9, and 10 of this invention.

[0033] Figure 11 The visible light modulation range diagrams of coatings with different PVP contents introduced in Examples 1, 8, and 9 of the present invention, and the color change process spectrum diagrams of the coating of Example 1 after being irradiated by a 365nm ultraviolet lamp for different time periods.

[0034] Figure 12 This is the polymer network structure of the photochromic coating of the present invention. Detailed Implementation

[0035] Example 1

[0036] The method for preparing the organic-inorganic hybrid photochromic coating of the present invention includes the following steps:

[0037] (1) N-vinylimidazolium (723 μL, 8 mmol), 4-acryloylmorpholine (1509.8 μL, 12 mmol), trifluoroethyl methacrylate (2306.1 μL, 20 mmol) and photoinitiator 1173 (61 μL, 0.4 mmol) were mixed and stirred at room temperature for 20 min to obtain a mixed solution; the mixed solution was poured into a 0.3 mm thick silicone mold and irradiated for 10 min under a 35 W ultraviolet lamp (365 nm) with external dimensions of 180 mm * 140 mm * 120 mm to obtain polymer PVH;

[0038] (2) Dissolve 5g of polymer PVH obtained in step (1) and 0.75g of polyvinylpyrrolidone (PVP) in 12mL of N,N-dimethylformamide (DMF) and stir at room temperature for 20-30min; add 575mg of phosphotungstic acid to the solution and stir thoroughly at room temperature for 1h to obtain a mixture.

[0039] (3) Pour the mixture from step (2) onto the glass substrate on the surface of the coater, set the liquid film thickness to 400 μm, the glass substrate temperature to 40 °C, dry for 2 hours, and then transfer it to a 100 °C oven to dry for 24 hours to obtain an organic-inorganic hybrid photochromic coating with a thickness of 100 μL.

[0040] Example 2

[0041] The preparation method of Example 2 is basically the same as that of Example 1, except that in step (1), the molar ratio of N-vinylimidazolium, 4-acryloylmorpholine and trifluoroethyl methacrylate is 3:2:5.

[0042] Example 3

[0043] The preparation method of Example 3 is basically the same as that of Example 1, except that in step (1), the molar ratio of N-vinylimidazolium-4-acryloylmorpholine to trifluoroethyl methacrylate is 3:3:4.

[0044] Example 4

[0045] The preparation method of Example 4 is basically the same as that of Example 1, except that in step (1), 4-acryloylmorpholine is replaced with one of N,N-dimethylacrylamide, acrylamide or N-isopropylacrylamide.

[0046] Example 5

[0047] The preparation method of Example 5 is basically the same as that of Example 1, except that in step (1), trifluoroethyl methacrylate is replaced with one of trifluoroethyl acrylate, hexafluoroisopropyl acrylate, hexafluorobutyl acrylate, dodecylfluoroheptyl acrylate, hexafluorobutyl methacrylate, hexafluoroisopropyl methacrylate, or dodecylfluoroheptyl methacrylate.

[0048] Example 6

[0049] The preparation method of Example 6 is basically the same as that of Example 1, except that in step (1), N-vinylimidazole is replaced with 1-allylimidazole or 1-(3-buten-1-yl)-1H-imidazole.

[0050] Example 7

[0051] The preparation method of Example 7 is basically the same as that of Example 1, except that in step (2), phosphotungstic acid is replaced with one of tungsten chloride, sodium / calcium tungstic silicate, or sodium / potassium tungstate.

[0052] Example 8

[0053] The preparation method of Example 8 is basically the same as that of Example 1, except that in step (2), the mass ratio of PVP to PVH is 0.05:1, and the tungsten oxide precursor accounts for 10% of the total mass of the polymer.

[0054] Example 9

[0055] The preparation method of Example 9 is basically the same as that of Example 1, except that in step (2), the mass ratio of PVP to PVH is 0.1:1, and the tungsten oxide precursor accounts for 10% of the total mass of the polymer.

[0056] Example 10

[0057] The preparation method of Example 10 is basically the same as that of Example 1, except that in step (2), the mass ratio of PVP to PVH is 0.2:1, and the tungsten oxide precursor accounts for 10% of the total mass of the polymer.

[0058] pass Figure 1 High-resolution transmission electron microscopy images and Figure 2 XRD characterization of the coating revealed the internal microstructure of the polymer. The data showed that WO3 did not form crystals inside the polymer (no WO3 lattice fringes and crystallization characteristic peaks). The particle size of tungsten oxide was measured to be 1.03 nm by high-resolution transmission electron microscopy.

[0059] pass Figure 3This indicates that the color-changing coating has a wider range of infrared light absorption, which is the basis for giving the coating the energy-saving performance of building cooling. The wider range of infrared light absorption of the color-changing coating can reduce the infrared light absorption inside the building, thereby slowing down the rise in indoor temperature.

[0060] pass Figures 5-6 It can be seen that when the photochromic coating of Example 1 is placed under sunlight for 20 minutes, the coating color gradually darkens, the transmittance decreases significantly, the coating absorbs infrared light, and the surface temperature of the coating begins to rise; in the dark, the coating begins to fade spontaneously, and the transparency gradually increases; the visible light (400nm~800nm) transmittance of the photochromic coating can be adjusted in the range of 96%~4.8%.

[0061] Example 1 shows that the coating can achieve instantaneous light response speed, reaching its optimal value in 20 minutes. The degree of color change is characterized by the transmittance of the ultraviolet-visible spectrum. After irradiation under a 365nm ultraviolet lamp for 20 minutes, the visible light transmittance of the coating drops to 4.8% (ultraviolet light excitation causes color change, altering the visible light transmittance of the coating), indicating a deep degree of color change.

[0062] The photochromic coating of Example 1 is used to regulate indoor temperature by adjusting the transmittance of sunlight. A sample room with both glass coated with the photochromic coating of Example 1 and blank glass was placed in a real outdoor environment to monitor the indoor temperature for 80 hours. Figure 8 It is known that the color change of the coating can effectively reduce infrared light entering the room and slow down the rise in indoor temperature. Through... Figure 9 It can be seen that the coating of the present invention has good aging resistance and environmental stability. After 50 cycles, the light transmittance and color change ability of the coating remain basically unchanged.

Claims

1. A method for preparing an organic-inorganic hybrid photochromic coating, characterized in that, Includes the following steps: (1) Monomer A, monomer B, and monomer C are randomly copolymerized under photoinitiated free radical action to form a polymer with a three-dimensional network structure; wherein, monomer A is 4-acryloylmorpholine; monomer B is trifluoroethyl methacrylate; monomer C is N-vinylimidazolium; the amount of monomer A added is 20%~30% of the total molar amount of monomer A, monomer B, and monomer C; the amount of monomer B added is 40%~50% of the total molar amount of monomer A, monomer B, and monomer C; and the amount of monomer C added is 20%~30% of the total molar amount of monomer A, monomer B, and monomer C. (2) Dissolve the polymer and polyvinylpyrrolidone in an organic solvent, mix well, add tungsten oxide precursor to the solution, and react at room temperature; the organic solvent is N,N-dimethylformamide; the tungsten oxide precursor is phosphotungstic acid; (3) The mixture after reaction is applied to the glass substrate by spraying, coating, scraping or inkjet printing, and then dried to obtain a photochromic coating. The drying temperature is 100~120℃ and the drying time is not less than 24h.

2. The method for preparing the photochromic coating according to claim 1, characterized in that: In step (1), the photoinitiator is one of 907, TPO, 184, 1173, DETX, ITX or 369; the amount of photoinitiator added is 1 to 1.5% of the total molar amount of monomer A, monomer B and monomer C.

3. The method for preparing the photochromic coating according to claim 1, characterized in that: In step (2), the average molecular weight of the polyvinylpyrrolidone is 3000~30000; the mass ratio of polyvinylpyrrolidone to the polymer is 0.05~0.2:

1.

4. The method for preparing the photochromic coating according to claim 1, characterized in that: In step (2), the mass concentration of the polymer in the solution is 0.4~0.6 g / mL.

5. The method for preparing the photochromic coating according to claim 1, characterized in that: In step (2), the amount of tungsten oxide precursor added is 10-20% of the total mass of the polymer and polyvinylpyrrolidone.

6. The photochromic coating prepared by the method of claim 1, characterized in that: In the coating, amorphous WO3 nanodots are highly dispersed in the polymer network, and the particle size of the amorphous WO3 nanodots is no higher than 1.03 nm.

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