A nanocomposite film with photochromic properties and preparation method thereof

Abstract

The present invention belongs to the technical field of photochromic materials and relates to a nanocomposite film with photochromic properties and a preparation method thereof. During preparation, a pretreated nanoinorganic material and a dispersant are first added to an organic dye solution and stirred to obtain a mixed solution. A polymer matrix is ​​then added to the mixed solution and ultrasonically mixed to form a precursor solution. Finally, under the condition of applying an electric field, the precursor solution is evenly coated on the matrix material and cured to obtain a nanocomposite film with photochromic properties. The product has a thickness of 50 to 500 nm, a surface roughness of less than 10 nm, a color change response time of less than 10 seconds in the visible light range, and a fading recovery time of less than 30 seconds. The method of the present invention achieves synergistic efficiency between the materials by adopting a dual-dye synergistic system, surface modification of the nanoinorganic material, and an electric field-assisted directional film formation process. The product has significantly improved mechanical properties, photochromic performance, and cyclic stability.

Description

Technical Field

[0001] The invention belongs to the technical field of photochromic materials and relates to a nano composite film with photochromic properties and a preparation method thereof. Background Art

[0002] As a key branch of the smart materials field, photochromic materials have demonstrated tremendous potential for application in numerous cutting-edge scientific fields. In optical devices, they can be used to create adaptive light filters that automatically adjust transmittance based on ambient light intensity, protecting the eyes and enhancing visual comfort. In the field of information storage, their photochromic properties can be leveraged to write, read, and erase data, potentially significantly increasing storage density and data processing speed.

[0003] Traditional photochromic films typically use a single organic dye as the photochromic component, such as common spiropyran or fulgide dyes. During the preparation process, these organic dyes are simply dissolved in a polymer matrix, such as polymethyl methacrylate (PMMA), and then formed into a thin film on the substrate using conventional coating methods such as spin coating and doctor blade coating. In the application of nanoinorganic materials, untreated nanoparticles, such as nano-titanium dioxide and nano-zinc oxide, are often simply mixed directly into a mixed solution of the polymer matrix and the organic dye. During film coating, no special measures are generally taken to control the arrangement and distribution of the nanoparticles. The curing process also often uses a single thermal curing method, cross-linking the polymer matrix at a certain temperature to form a shape.

[0004] In terms of photochromic performance, traditional single dye systems cannot achieve multi-wavelength response or color gradient changes, are difficult to adapt to complex lighting environments, and have long color change response times and slow fading recovery times, which cannot meet the demand for fast light response.

[0005] Existing multi-dye systems suffer from signal interference caused by spectral overlap between dyes (e.g., fluorescence leakage requires complex compensation and adjustment), low excitation efficiency caused by energy level mismatch (e.g., traditional TADF molecular sensitizers have weak visible light absorption and difficult energy level adjustment), and aggregate fluorescence quenching (ACQ) and photobleaching due to poor dispersion (e.g., organic dyes are easily damaged by water molecule penetration in aqueous media).

[0006] In the utilization of inorganic nanomaterials, nanoparticles without surface treatment and specialized dispersion processes tend to agglomerate, failing to fully realize their enhanced mechanical properties, stability, and photocatalytic properties, resulting in limited improvements in the overall performance of the film. Conventional preparation processes lack precise control over the film's microstructure, making it difficult to create anisotropic photoresponsive behavior, limiting the film's application in specialized optical fields.

[0007] To address these issues, Reference 1 (Biodegradable polymers for food packaging: areview[J]. Advanced Functional Materials, 2008, 19(12): 634-643.) reported a thin film fabricated by loading a photochromic molecule, spiropyran, into a hydrogen-bonded organic framework. The pattern changed completely from yellow-green to red after 2.5 minutes of UV irradiation. The image could be stored for at least 3 hours without fading and could be restored to its original state at 70°C. This cycle could be repeated for at least 30 times without noticeable fatigue. However, the film's color change time and cyclic stability still need to be improved.

[0008] Reference 2 (Angewandte Chemie International Edition, 2024, 63(23):e202404066.) discloses a preferred mopsa-1 molecule in a thermoplastic polyurethane (TPU) film. The film fades in just 6 seconds under 550nm light and recovers color in just 17 seconds when heated to 60°C. Furthermore, the film maintains 67% absorbance after 500 cycles of fading and recovery. This film meets the requirement of a fading time of less than 30 seconds and exhibits good fatigue resistance. However, the absorbance after 500 cycles is only 67% of the initial value (significant attenuation), and the color change response time is not disclosed (only the fading time is mentioned).

[0009] Therefore, it is of great significance to study a nanocomposite film with photochromic properties and a preparation method thereof to solve the problems existing in the prior art. Summary of the Invention

[0010] The purpose of the present invention is to solve the problems existing in the prior art and provide a nanocomposite film with photochromic properties and a preparation method thereof.

[0011] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0012] The preparation method of the nanocomposite film with photochromic properties comprises the following steps: first, adding the pretreated nano-inorganic material and dispersant to the organic dye solution, stirring and mixing to obtain a mixed solution; then, adding the polymer matrix to the mixed solution, ultrasonically mixing to obtain a precursor solution; finally, applying an electric field to uniformly coat the precursor solution on the matrix material, and curing the resulting nanocomposite film with photochromic properties; the detailed preparation process is as follows: Figure 2 As shown;

[0013] The particle size of nano-inorganic materials is 10~100nm;

[0014] Pretreatment refers to calcination in a muffle furnace to remove surface impurities and adsorbents, thereby enhancing their activity and dispersibility;

[0015] The organic dye is a composition of spiropyran and azobenzene, and the mass ratio of spiropyran to azobenzene is 1:1~4:1; this ratio range is determined based on the energy level matching characteristics of the two and the synergistic effect of light response. When the mass ratio of spiropyran to azobenzene is 1:1~4:1, the molecular energy level difference between the two can form an effective charge transfer channel, and the ring-opening / ring-closing isomerization of spiropyran and the cis-trans isomerization of azobenzene produce wavelength response superposition in the visible light range, realizing multi-color scale changes in a wide spectral range of 360~700nm; if the proportion of spiropyran is lower than If the ratio of spiropyrans to spiropyrans exceeds 50%, the cis-trans isomerization dominated by azobenzenes will result in a single color gradient and a narrowed response wavelength range of 450-600 nm, failing to cover the full UV-visible spectrum. If the ratio of spiropyrans to spiropyrans exceeds 80%, the photostability defects of spiropyrans will be amplified, causing the fading recovery time after 1000 cycles to be extended to more than 40 seconds. In addition, the steric hindrance effect of the two dyes will intensify the aggregation of nanoparticles and increase the surface roughness to more than 15 nm. Therefore, strictly limiting the mass ratio range is the key to achieving multi-wavelength response, rapid color change, and long cycle life.

[0016] The polymer matrix is ​​polymethyl methacrylate (PMMA) or polyvinyl alcohol (PVA), and the number average molecular weight of the polymer matrix is ​​50,000 to 100,000;

[0017] The mass ratio of the pretreated nano-inorganic material, organic dye, and polymer matrix is ​​5-20:0.5-10:70-94.5;

[0018] The matrix material is rectangular in shape, and the direction of the electric field is parallel to the length direction of the matrix material.

[0019] Using a single organic dye alone cannot achieve multi-wavelength response and the color change response time is long. The untreated nano-inorganic material has poor dispersibility and limited improvement in mechanical properties. Without electric field assistance, the nanoparticles are disordered and the light signal transmission efficiency is low. Using a single curing method alone cannot balance the mechanical strength and the freedom of movement of dye molecules. The dual-dye system, treated nano-inorganic materials, electric field-assisted film-forming technology and staged curing process are used together to achieve significant improvements in the film's photochromic properties (color change response time <10 seconds, fading recovery time <30 seconds, stable performance after 1,000 cycles) and mechanical properties (significantly improved tensile strength and hardness), far exceeding the simple superposition of the effects of each technical means used alone.

[0020] As the preferred technical solution:

[0021] In the above-mentioned method for preparing the nanocomposite film with photochromic properties, the nano inorganic material is nano titanium dioxide or nano zinc oxide.

[0022] The method for preparing the nanocomposite film having photochromic properties as described above comprises the following steps: calcining in a muffle furnace is carried out in a nitrogen or argon atmosphere, the gas flow rate is controlled at 50-100 ml / min, the calcining temperature is 400-600°C, and the calcining time is 2-4 hours;

[0023] The nano inorganic material is subjected to surface coating or doping treatment after being calcined in a muffle furnace.

[0024] In the photochromic nanocomposite film system of this invention, the nanoinorganic material, organic dye, and polymer matrix form a complex, interconnected and mutually influential system. The nanoinorganic material, organic dye, and polymer matrix work together to enhance film performance. The nanoinorganic material is selected from nano-titanium dioxide or nano-zinc oxide, with a strictly controlled particle size of 10-100 nm. It undergoes a pretreatment by calcining in an inert gas atmosphere (nitrogen or argon, flow rate 50-100 ml / min) at 400-600°C for 2-4 hours, followed by surface coating or doping. This treatment not only removes surface impurities and adsorbates, enhances its activity and dispersibility, inhibits photocorrosion, but also strengthens charge transfer with the organic dye. The organic dye is a combination of spiropyran and azobenzene. By matching their energy levels, they achieve multi-wavelength response or color gradients, exhibiting unique optical changes under complex lighting conditions. The polymer matrix, made of polymethyl methacrylate (PMMA) or polyvinyl alcohol (PVA), has a molecular weight controlled between 50,000 and 100,000, providing stable support for the entire system and balancing comprehensive film properties such as flexibility and film-forming properties. During the preparation process, the nano-inorganic material is treated to uniformly disperse within the polymer matrix, effectively enhancing the film's mechanical properties and stability. Its energy level matches that of the organic dye, resulting in a film with a color change response time of less than 10 seconds and a fading recovery time of less than 30 seconds. The film also exhibits excellent cyclic stability, maintaining its photochromic properties even after 1,000 cycles, significantly improving its photochromic performance. These closely intertwined approaches work together to overcome the shortcomings of conventional films, achieving a comprehensive improvement in the film's performance and demonstrating the unique advantages of the optimized material combination of this invention.

[0025] In the above-mentioned method for preparing the nanocomposite film with photochromic properties, the dispersant is oleic acid or sodium dodecylbenzenesulfonate, and the amount of the dispersant added is 1-5% of the mass of the nano-inorganic material.

[0026] In the above-mentioned method for preparing the nanocomposite film with photochromic properties, the concentration of the organic dye solution is 0.01-0.1 mol / L.

[0027] The preparation method of the nanocomposite film with photochromic properties as described above is coated by spin coating, blade coating or spray coating.

[0028] The preparation method of the nanocomposite film having photochromic properties as described above is as follows: Figure 1 As shown in the figure, the intensity of the applied electric field is 50~200V / cm. This electric field intensity range has been verified by experiments to be able to effectively act on the charged nanoparticles and guide their directional arrangement without negatively affecting the stability of the precursor solution and other properties of the film; the two electrodes used to form the electric field are installed on both sides of the substrate material, and the electrode spacing is 2~5cm. According to the size of the substrate material and the size of the coating equipment, the electrode spacing is controlled in an appropriate range, generally 2-5cm; the appropriate electrode spacing helps to form a more uniform electric field in the coating area, ensuring that the nanoparticles can be subjected to a more consistent electric field force in the entire coating area.

[0029] Electrode materials are usually inert metal electrodes, such as platinum electrodes. Platinum electrodes are chemically stable and are not prone to chemical reactions under the action of electric fields, and will not introduce impurities that affect film quality.

[0030] In the method for preparing a nanocomposite film with photochromic properties described above, the curing process includes sequential UV curing and thermal curing. UV curing refers to irradiation with ultraviolet light at a wavelength of 254-365 nm for 5-15 minutes, and thermal curing refers to drying at 80-120°C for 1-3 hours. A single thermal curing method cannot balance the mechanical strength of the film with the freedom of movement of the dye molecules, which will affect the film's overall performance and long-term stability. A staged control method combining UV curing and thermal curing is adopted. First, UV curing is performed for initial cross-linking to maintain the freedom of movement of the dye molecules, and then thermal curing is performed to cross-link the polymer matrix to the desired density. This balances the mechanical strength of the film with the freedom of movement of the dye molecules, ensuring the photochromic properties and overall stability.

[0031] The present invention also provides a nanocomposite film with photochromic properties prepared by any of the preparation methods described above. The nanocomposite film with photochromic properties has a thickness of 50 to 500 nm, a flat and smooth surface, and a roughness of less than 10 nm. The surface roughness is controlled to be less than 10 nm by strictly controlling the particle size of the raw materials (e.g., a particle size of 10 to 100 nm for the nano-inorganic material), optimizing the mixing and dispersion process (e.g., ultrasonic mixing, addition of a dispersant, etc.), precisely controlling the coating parameters (e.g., spin coating speed, scraping angle, spraying pressure, etc.), and balancing the film properties by using a step-by-step curing method.

[0032] The nanocomposite film with photochromic properties can stably exhibit photochromic properties under different environmental conditions. In the visible light range, the color change response time is less than 10 seconds, and the fading recovery time is less than 30 seconds. After 1000 cycles, the color change response time is still less than 10 seconds, and the fading recovery time is still less than 30 seconds. The absorption peak position and intensity change law of the light absorption spectrum are basically maintained, but the intensity is slightly weakened.

[0033] Principle of the invention:

[0034] The present invention achieves a comprehensive improvement in the overall performance of the film through optimized material combination and preparation. In terms of material selection, spiropyran and azobenzene dyes are paired, and energy level matching is used to achieve multi-wavelength response or color gradient changes, enriching the photochromic expression. Nano-inorganic materials such as nano-titanium dioxide and nano-zinc oxide are strictly controlled to have a particle size of 10 to 100 nanometers, and are surface coated or doped and calcined in an inert gas atmosphere, which enhances activity and dispersibility, inhibits photocorrosion, and improves mechanical properties, stability, and photocatalytic properties. The polymer matrix is ​​selected from polymethyl methacrylate or polyvinyl alcohol, and the number average molecular weight is ensured to be between 50,000 and 100,000 by gel permeation chromatography testing. This provides stable support for organic dyes and nano-inorganic materials, and balances the overall performance of the film, such as flexibility and film-forming properties. In terms of preparation technology, electric field-assisted film formation technology precisely sets the electric field strength, selects inert metal electrodes and appropriate electrode spacing, induces the directional alignment of nanoparticles, constructs anisotropic photoresponse behavior, and improves the functionality of the film. These optimization methods are interrelated. The enhanced photocatalytic properties of nano-inorganic materials combined with the optimized preparation process facilitate the transmission of light signals inside the film, significantly shortening the color change response time and fading recovery time; the stable polymer matrix support system and nano-inorganic materials synergistically improve the mechanical properties of the film; the anisotropic light response behavior and the photochromic performance promote each other, comprehensively improving the photochromic performance, stability and mechanical properties of the film.

[0035] Beneficial effects:

[0036] (1) The present invention provides a method for preparing a nanocomposite film with photochromic properties, wherein spiropyran and azobenzene organic dyes are used to construct a dual dye system, and multi-wavelength response or color gradient change is achieved through energy level matching. This innovative combination breaks through the limitations of traditional single dyes and greatly enriches the expression of photochromism in thin films. By complementing each other with the sensitivity of different dyes to light of different wavelengths, the film can exhibit unique and diverse optical changes under complex lighting environments, meeting the special needs of high-end application scenarios for light-responsive materials.

[0037] (2) The present invention provides a method for preparing a nanocomposite film with photochromic properties. In the coating process, electric field-assisted film-forming technology is introduced. By precisely setting the electric field strength (50-200 V / cm), selecting inert metal electrodes (such as platinum electrodes) and a suitable electrode spacing (2-5 cm), the nanoparticles are induced to arrange in a directional manner, anisotropic photoresponse behavior is constructed, and the distribution state of the nanoparticles in the film is changed. This gives the film unique optical and electrical properties, and effectively improves the functionality of the film.

[0038] (3) The method for preparing a nanocomposite film with photochromic properties of the present invention adopts a staged control method combining UV curing and thermal curing, which balances the mechanical strength of the film and the freedom of movement of the dye molecules, and plays a key role in ensuring the photochromic performance and overall stability of the film.

[0039] (4) The present invention provides a method for preparing a nanocomposite film with photochromic properties. Through precise energy level matching of a dual-dye collaborative system (such as the formation of a charge transfer channel by a mass ratio of spiropyran to azobenzene of 1 to 4:1), surface coating treatment of nano-inorganic materials (such as the construction of a hydrophobic cage structure by a silane coupling agent to inhibit agglomeration), and electric field-assisted film-forming technology (such as the optimization of light signal transmission by the directional arrangement of nanoparticles under a specific electric field intensity), the synergistic enhancement of multi-wavelength response (360 to 700 nm), rapid color change (response time < 10 seconds), and long cycle life (stable performance after 1000 cycles) is achieved.

[0040] (5) The nanocomposite film of the present invention has photochromic properties. The film has a uniform overall thickness and a smooth surface. This fine microstructure not only ensures the beauty of the film, but more importantly, lays a solid foundation for its application in the fields of optics, electronics, etc.; and it can stably exhibit photochromic properties under different environmental conditions. While meeting high-end needs, it expands its application potential in more complex scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Schematic diagram of the principle and operation of electric field assisted film formation;

[0042] Figure 2 Flow chart for raw material pretreatment and mixed solution preparation. DETAILED DESCRIPTION

[0043] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0044] The test methods involved in the performance indicators in the embodiments and comparative examples of the present invention are as follows:

[0045] Roughness: The surface was measured using an atomic force microscope (AFM, model: Bruker Innova) with a scanning range of 10 μm × 10 μm and a tip radius of <10 nm. The average value of the measured values ​​from five different areas was taken.

[0046] Color change response time and fading recovery time: Under illumination from a xenon lamp (light intensity 100mW / cm², model: Newport Oriel94023A), the time it takes for the film to change from its initial state to its maximum color change state is recorded by a high-speed camera (shooting frequency 1000 frames / second). The color change response time is defined as the color change response time. After the illumination is removed, the time it takes for the film to recover from its maximum color change state to its initial state is defined as the fading recovery time.

[0047] 1000-cycle test: Use a xenon lamp for cyclic testing, with each light exposure period lasting 15 seconds and each light fading period lasting 30 seconds. After 1000 cycles, test the color change response time and fading recovery time using the above method.

[0048] Tensile strength: According to GB / T 1040.3-2018, the tensile test was carried out using a universal material testing machine (model: Instron5967) at a tensile speed of 50 mm / min.

[0049] Hardness: Hardness testing was performed using a nanoindenter (MTS Nano Indenter G200) in accordance with ISO 14577-4:2016, with a load of 10 mN and a hold time of 5 seconds.

[0050] Wear: Wear resistance testing was completed in accordance with ASTM D4060-18 using a Taber 5135 tribometer (model: Taber 5135) to simulate actual friction scenarios. A CS-10 grinding wheel was used, with a load of 100 g and a rotation speed of 60 rpm. The mass loss after 500 cycles was measured.

[0051] Example 1

[0052] A method for preparing a nanocomposite film with photochromic properties, comprising the following steps:

[0053] (1) Preparation of raw materials:

[0054] Nano inorganic materials: nano titanium dioxide, with an average particle size of 20nm;

[0055] Dispersant: oleic acid;

[0056] Organic dye: a composition of methyl spiropyran (purity 98%) and p-nitroazobenzene (purity 98%) in a mass ratio of 1:1;

[0057] Organic solvent: acetone;

[0058] Polymer matrix: polymethyl methacrylate, number average molecular weight 50,000;

[0059] Base material: glass sheet;

[0060] (2) In a nitrogen atmosphere, the nano-inorganic material was pre-treated by calcining in a muffle furnace at 400 °C for 4 hours, and then the surface was coated with a SiO2 shell;

[0061] The nitrogen flow rate was controlled at 50 ml / min; the mass ratio of SiO2 to nano-inorganic material was 1:10;

[0062] (3) Dissolve the organic dye in an organic solvent in a constant temperature water bath at 25°C and stir at 300 rpm for 2 hours to obtain an organic dye solution with a concentration of 0.01 mol / L;

[0063] (4) adding the nano-inorganic material and dispersant treated in step (2) to the organic dye solution, continuing to stir for 5 hours, and mixing uniformly to obtain a mixed solution;

[0064] The mass ratio of the pretreated nano-inorganic material, organic dye and polymer matrix is ​​5:0.5:94.5; the amount of dispersant added is 1% of the mass of the nano-inorganic material;

[0065] (5) adding the polymer matrix to the mixed solution and ultrasonically mixing at a frequency of 20 kHz for 2 hours to form a precursor solution;

[0066] (6) In the coating equipment, two platinum electrodes are installed on both sides of the substrate material, ensuring that the electrodes are parallel to the length direction of the substrate material and the electrode spacing is 2 cm;

[0067] (7) Under the condition of applying an electric field, the precursor solution of step (5) is evenly coated on the substrate material by spin coating;

[0068] The intensity of the applied electric field was 100 V / cm; the spin coating speed was 1000 rpm, and the spin coating time was 60 seconds;

[0069] (8) subjecting the product of step (7) to UV curing and thermal curing treatment in sequence to obtain a nanocomposite film having photochromic properties;

[0070] Among them, UV curing refers to irradiation under ultraviolet light with a wavelength of 254nm for 5 minutes, and thermal curing refers to drying at 80°C for 3 hours.

[0071] The final nanocomposite film with photochromic properties has a thickness of 50nm and a surface roughness of 5nm; the nanocomposite film with photochromic properties has a color change response time of 8 seconds and a fading recovery time of 25 seconds in the visible light range; after 1000 cycles, the color change response time is 9 seconds and the fading recovery time is 28 seconds; the nanocomposite film with photochromic properties has a tensile strength of 80MPa, a hardness of 2.5GPa, and a wear loss of 4mg.

[0072] Comparative Example 1

[0073] A method for preparing a nanocomposite film is basically the same as that of Example 1, except that the organic dye is a single organic dye, namely, methyl spiropyran.

[0074] The surface roughness of the final nanocomposite film is 12nm; in the visible light range, the color change response time of the nanocomposite film is 15 seconds, and the fading recovery time is 40 seconds. After 500 cycles, the color change response time is 18 seconds and the fading recovery time is 45 seconds; the tensile strength of the nanocomposite film is 60MPa, the hardness is 1.8GPa, and the wear loss is 12mg.

[0075] Comparing Comparative Example 1 with Example 1, it can be found that in Comparative Example 1, the tensile strength and hardness decrease, the wear is aggravated, the color change response time is prolonged, and the fading recovery time is prolonged. This is because a single organic dye cannot form energy level matching and synergistic effects with other dyes, and can neither achieve multi-wavelength response and color gradient changes, nor optimize the nanoparticle dispersibility and interfacial bonding strength through charge transfer between the two dyes, resulting in a simultaneous decrease in photochromic efficiency and mechanical properties.

[0076] Comparative Example 2

[0077] A method for preparing a nanocomposite film is basically the same as that in Example 1, except that step (2) is omitted.

[0078] The surface roughness of the final nanocomposite film is 15nm; in the visible light range, the color change response time of the nanocomposite film is 15 seconds, and the fading recovery time is 40 seconds. After 500 cycles, the color change response time is 18 seconds and the fading recovery time is 45 seconds; the tensile strength of the nanocomposite film is 50MPa, the hardness is 1.5GPa, and the wear loss is 18mg.

[0079] Comparing Comparative Example 2 with Example 1, it can be found that the cyclic stability, tensile strength and hardness of Comparative Example 2 are reduced, the discoloration and fading time are increased, the wear is aggravated, and the photocatalytic properties are weakened, affecting the photochromic effect. This is because the nano-inorganic materials are not calcined and surface-coated, resulting in residual impurities on the surface of the nanoparticles, reduced activity and dispersibility, easy agglomeration and weakened photocatalytic properties, and the inability to effectively enhance the interfacial bonding force and light signal transmission efficiency, thereby affecting the photochromic performance and mechanical properties.

[0080] Comparative Example 3

[0081] A method for preparing a nanocomposite film is basically the same as that of Example 1, except that steps (6) and (7) are omitted.

[0082] The surface roughness of the final nanocomposite film is 12nm; in the visible light range, the color change response time of the nanocomposite film is 15 seconds, and the fading recovery time is 35 seconds. After 500 cycles, the color change response time is 18 seconds and the fading recovery time is 40 seconds; the tensile strength of the nanocomposite film is 70MPa, the hardness is 2.2GPa, and the wear loss is 8mg.

[0083] Comparing Comparative Example 3 with Example 1, it can be found that the color change response time and fading recovery time of Comparative Example 3 are prolonged, the performance fluctuates greatly during the cycle, the tensile strength and hardness decrease, and the wear is aggravated. This is because the electric field is not applied to assist the film formation, and the nanoparticles cannot be arranged in a directional manner, resulting in obstruction of the optical signal transmission path and weakening of the interface bonding force, which not only affects the energy transfer efficiency in the photochromic process, but also reduces the density of the film structure, thereby reducing the light response speed, cycle stability and mechanical properties.

[0084] Comparative Example 4

[0085] A method for preparing a nanocomposite film is basically the same as that in Example 1, except that step (8) only performs UV curing treatment.

[0086] The surface roughness of the final nanocomposite film is 11nm; in the visible light range, the color change response time of the nanocomposite film is 15 seconds, and the fading recovery time is 40 seconds. After 500 cycles, the color change response time is 18 seconds and the fading recovery time is 45 seconds; the tensile strength of the nanocomposite film is 70MPa, the hardness is 2.0GPa, and the wear loss is 10mg.

[0087] Comparing Comparative Example 4 with Example 1, it can be found that the mechanical properties (tensile strength, hardness) of the nanocomposite film are reduced and the fading recovery time is prolonged. This is because only UV curing without thermal curing results in insufficient cross-linking density of the polymer matrix, which cannot balance the mechanical strength and the freedom of movement of the dye molecules.

[0088] Example 2

[0089] A method for preparing a nanocomposite film with photochromic properties, comprising the following steps:

[0090] (1) Preparation of raw materials:

[0091] Nano inorganic materials: nano zinc oxide, with an average particle size of 30nm;

[0092] Dispersant: sodium dodecylbenzenesulfonate;

[0093] Organic dye: a composition of ethyl spiropyran (purity 98%) and p-methoxyazobenzene (purity 98%) in a mass ratio of 1:1;

[0094] Organic solvent: anhydrous ethanol;

[0095] Polymer matrix: polyvinyl alcohol, number average molecular weight 60,000;

[0096] Substrate material: silicon wafer;

[0097] (2) In an argon atmosphere, the nano-inorganic material was pre-treated by calcination in a muffle furnace at 500 °C for 3 hours, and then nitrogen doping was performed;

[0098] The argon flow rate was controlled at 60 ml / min; the nitrogen-containing substance doped was ammonia water with a concentration of 25 wt%; the mass ratio of ammonia water to nano-inorganic material was 1:10;

[0099] (3) Dissolve the organic dye in an organic solvent in a constant temperature water bath at 28°C and stir at 400 rpm for 1.5 hours to obtain an organic dye solution with a concentration of 0.03 mol / L;

[0100] (4) adding the nano-inorganic material and dispersant treated in step (2) to the organic dye solution, continuing to stir for 4 hours, and mixing uniformly to obtain a mixed solution;

[0101] The mass ratio of the pretreated nano-inorganic material, organic dye and polymer matrix is ​​10:5:85; the amount of dispersant added is 2% of the mass of the nano-inorganic material;

[0102] (5) adding the polymer matrix to the mixed solution and ultrasonically mixing at a frequency of 30 kHz for 1.5 hours to form a precursor solution;

[0103] (6) In the coating equipment, two platinum electrodes are installed on both sides of the substrate material, ensuring that the electrodes are parallel to the length direction of the substrate material and the electrode spacing is 3 cm;

[0104] (7) Under the condition of applying an electric field, the precursor solution of step (5) is evenly coated on the substrate material by a doctor blade method;

[0105] The intensity of the applied electric field was 150 V / cm; the angle between the scraper and the substrate was 15 degrees, and the scraping speed was 3 mm / s.

[0106] (8) subjecting the product of step (7) to UV curing and thermal curing treatment in sequence to obtain a nanocomposite film having photochromic properties;

[0107] Among them, UV curing refers to irradiation under ultraviolet light with a wavelength of 365nm for 8 minutes, and thermal curing refers to drying at 100°C for 2 hours.

[0108] The final nanocomposite film with photochromic properties has a thickness of 100nm and a surface roughness of 6nm; the nanocomposite film with photochromic properties has a color change response time of 7 seconds and a fading recovery time of 20 seconds in the visible light range; after 1000 cycles, the color change response time is 8 seconds and the fading recovery time is 25 seconds; the nanocomposite film with photochromic properties has a tensile strength of 85MPa, a hardness of 2.8GPa, and a wear loss of 5mg.

[0109] Example 3

[0110] A method for preparing a nanocomposite film with photochromic properties, comprising the following steps:

[0111] (1) Preparation of raw materials:

[0112] Nano inorganic materials: nano titanium dioxide, with an average particle size of 50nm;

[0113] Dispersant: oleic acid;

[0114] Organic dye: a composition of propylspiropyran (purity 98%) and p-chloroazobenzene (purity 98%) in a mass ratio of 2:1;

[0115] Organic solvent: acetone;

[0116] Polymer matrix: polymethyl methacrylate, number average molecular weight 70,000;

[0117] Base material: glass sheet;

[0118] (2) In a nitrogen atmosphere, the nano-inorganic material was pre-treated by calcination in a muffle furnace at 600 °C for 2 hours, and then the surface was coated with a SiO2 shell;

[0119] The nitrogen flow rate was controlled at 70 ml / min; the mass ratio of SiO2 to nano-inorganic material was 1:10;

[0120] (3) Dissolve the organic dye in an organic solvent in a constant temperature water bath at 30°C and stir at 500 rpm for 1 hour to obtain a 0.05 mol / L organic dye solution;

[0121] (4) adding the nano-inorganic material and dispersant treated in step (2) to the organic dye solution, continuing to stir for 3 hours, and mixing uniformly to obtain a mixed solution;

[0122] The mass ratio of the pretreated nano-inorganic material, organic dye and polymer matrix is ​​20:10:70; the amount of dispersant added is 3% of the mass of the nano-inorganic material;

[0123] (5) adding the polymer matrix to the mixed solution and ultrasonically mixing at a frequency of 40 kHz for 1 hour to form a precursor solution;

[0124] (6) In the coating equipment, two platinum electrodes are installed on both sides of the substrate material, ensuring that the electrodes are parallel to the length direction of the substrate material and the electrode spacing is 4 cm;

[0125] (7) Under the condition of applying an electric field, the precursor solution of step (5) is evenly coated on the base material by spraying;

[0126] The intensity of the applied electric field was 200 V / cm; the distance between the spray gun and the substrate was 10 cm, and the spraying pressure was 0.5 MPa;

[0127] (8) subjecting the product of step (7) to UV curing and thermal curing treatment in sequence to obtain a nanocomposite film having photochromic properties;

[0128] Among them, UV curing refers to irradiation with ultraviolet light with a wavelength of 300nm for 10 minutes, and thermal curing refers to drying at 120℃ for 1 hour.

[0129] The final nanocomposite film with photochromic properties has a thickness of 200nm and a surface roughness of 7nm; the nanocomposite film with photochromic properties has a color change response time of 6 seconds and a fading recovery time of 28 seconds in the visible light range; after 1000 cycles, the color change response time is 7 seconds and the fading recovery time is 29 seconds; the nanocomposite film with photochromic properties has a tensile strength of 90MPa, a hardness of 3GPa, and a wear loss of 6mg.

[0130] Example 4

[0131] A method for preparing a nanocomposite film with photochromic properties, comprising the following steps:

[0132] (1) Preparation of raw materials:

[0133] Nano inorganic materials: nano zinc oxide, with an average particle size of 80nm;

[0134] Dispersant: sodium dodecylbenzenesulfonate;

[0135] Organic dye: a composition of butylspiropyran (98% purity) and p-bromoazobenzene (98% purity) in a mass ratio of 3:1;

[0136] Organic solvent: anhydrous ethanol;

[0137] Polymer matrix: polyvinyl alcohol, number average molecular weight of 80,000;

[0138] Substrate material: silicon wafer;

[0139] (2) In an argon atmosphere, the nano-inorganic material was calcined in a muffle furnace at 450 °C for 3.5 hours and then nitrogen doped;

[0140] The argon flow rate was controlled at 80 ml / min; the nitrogen-containing substance doped was ammonia water with a concentration of 25 wt%; the mass ratio of ammonia water to nano-inorganic material was 1:10;

[0141] (3) Dissolve the organic dye in an organic solvent in a constant temperature water bath at 32°C and stir at 350 rpm for 1.75 hours to obtain a 0.08 mol / L organic dye solution;

[0142] (4) adding the nano-inorganic material and dispersant treated in step (2) to the organic dye solution, continuing to stir for 4.5 hours, and mixing uniformly to obtain a mixed solution;

[0143] The mass ratio of the pretreated nano-inorganic material, organic dye and polymer matrix is ​​15:8:77; the amount of dispersant added is 4% of the mass of the nano-inorganic material;

[0144] (5) adding the polymer matrix to the mixed solution and ultrasonically mixing at a frequency of 25 kHz for 1.75 hours to form a precursor solution;

[0145] (6) In the coating equipment, two platinum electrodes are installed on both sides of the substrate material, ensuring that the electrodes are parallel to the length direction of the substrate material and the electrode spacing is 5 cm;

[0146] (7) Under the condition of applying an electric field, the precursor solution of step (5) is evenly coated on the substrate material by spin coating;

[0147] The intensity of the applied electric field was 120 V / cm; the spin coating speed was 3000 rpm, and the spin coating time was 30 seconds;

[0148] (8) subjecting the product of step (7) to UV curing and thermal curing treatment in sequence to obtain a nanocomposite film having photochromic properties;

[0149] Among them, UV curing refers to irradiation under ultraviolet light with a wavelength of 320nm for 12 minutes, and thermal curing refers to drying at 90°C for 2.5 hours.

[0150] The final nanocomposite film with photochromic properties has a thickness of 300nm and a surface roughness of 8nm; the nanocomposite film with photochromic properties has a color change response time of 9 seconds and a fading recovery time of 15 seconds in the visible light range; after 1000 cycles, the color change response time is 8 seconds and the fading recovery time is 20 seconds; the nanocomposite film with photochromic properties has a tensile strength of 75MPa, a hardness of 2.6GPa, and a wear loss of 3mg.

[0151] Example 5

[0152] A method for preparing a nanocomposite film with photochromic properties, comprising the following steps:

[0153] (1) Preparation of raw materials:

[0154] Nano inorganic materials: nano titanium dioxide, with an average particle size of 100nm;

[0155] Dispersant: sodium dodecylbenzenesulfonate;

[0156] Organic dye: a composition of amylspiropyran (purity 98%) and p-iodoazobenzene (purity 98%) in a mass ratio of 4:1;

[0157] Organic solvent: acetone;

[0158] Polymer matrix: polymethyl methacrylate, number average molecular weight of 100,000;

[0159] Base material: glass sheet;

[0160] (2) In a nitrogen atmosphere, the nano-inorganic material was pre-treated by calcination in a muffle furnace at 550 °C for 2.5 hours, and then the surface was coated with a SiO2 shell;

[0161] The nitrogen flow rate was controlled at 100 ml / min; the mass ratio between SiO2 and nano-inorganic material was 1:10;

[0162] (3) Dissolve the organic dye in an organic solvent in a constant temperature water bath at 35°C and stir at 450 rpm for 1.25 hours to obtain a 0.1 mol / L organic dye solution;

[0163] (4) adding the nano-inorganic material and dispersant treated in step (2) to the organic dye solution, continuing to stir for 3.5 hours, and mixing uniformly to obtain a mixed solution;

[0164] The mass ratio of the pretreated nano-inorganic material, organic dye and polymer matrix is ​​12:3:85; the amount of dispersant added is 5% of the mass of the nano-inorganic material;

[0165] (5) adding the polymer matrix to the mixed solution and ultrasonically mixing at a frequency of 35 kHz for 1.25 hours to form a precursor solution;

[0166] (6) In the coating equipment, two platinum electrodes are installed on both sides of the substrate material, ensuring that the electrodes are parallel to the length direction of the substrate material and the electrode spacing is 2 cm;

[0167] (7) Under the condition of applying an electric field, the precursor solution of step (5) is evenly coated on the substrate material by a doctor blade method;

[0168] The intensity of the applied electric field was 180 V / cm; the angle between the scraper and the substrate was 30 degrees, and the scraping speed was 1 mm / s.

[0169] (8) subjecting the product of step (7) to UV curing and thermal curing treatment in sequence to obtain a nanocomposite film having photochromic properties;

[0170] Among them, UV curing refers to irradiation under ultraviolet light with a wavelength of 350nm for 15 minutes, and thermal curing refers to drying at 110°C for 1.5 hours.

[0171] The final nanocomposite film with photochromic properties has a thickness of 500nm and a surface roughness of 9nm; the nanocomposite film with photochromic properties has a color change response time of 5 seconds and a fading recovery time of 22 seconds in the visible light range. After 1000 cycles, the color change response time is 6 seconds and the fading recovery time is 23 seconds; the nanocomposite film with photochromic properties has a tensile strength of 95MPa, a hardness of 2.9GPa, and a wear loss of 7mg.

Claims

1. A method for preparing a nanocomposite film having photochromic properties, characterized in that: First, the pretreated nano-inorganic material and dispersant are added to an organic dye solution and stirred to obtain a mixed solution. Then, a polymer matrix is ​​added to the mixed solution and ultrasonically mixed to obtain a precursor solution. Finally, the precursor solution is evenly coated on the matrix material under the condition of applying an electric field and cured to obtain a nano-composite film with photochromic properties. The particle size of nano-inorganic materials is 10~100nm; Pretreatment refers to muffle furnace calcination; The organic dye is a combination of spiropyran and azobenzene, with the mass ratio of spiropyran to azobenzene being 1-4:1; the polymer matrix is ​​polymethyl methacrylate or polyvinyl alcohol, and the number average molecular weight of the polymer matrix is ​​50,000-100,000; The mass ratio of the pretreated nano-inorganic material, organic dye, and polymer matrix is ​​5-20:0.5-10:70-94.5; The direction of the electric field is parallel to the length direction of the matrix material; The curing treatment includes UV curing and thermal curing performed in sequence. UV curing refers to irradiation with ultraviolet light of a wavelength of 254 to 365 nm for 5 to 15 minutes, and thermal curing refers to drying at 80 to 120°C for 1 to 3 hours.

2. The method for preparing a nanocomposite film having photochromic properties according to claim 1, wherein: The nano inorganic material is nano titanium dioxide or nano zinc oxide.

3. The method for preparing a nanocomposite film having photochromic properties according to claim 1, wherein: Muffle furnace calcination is carried out in a nitrogen or argon atmosphere, with the gas flow rate controlled at 50-100 ml / min, the calcination temperature at 400-600°C, and the calcination time at 2-4 hours; The nano inorganic material is subjected to surface coating or doping treatment after being calcined in a muffle furnace.

4. The method for preparing a nanocomposite film having photochromic properties according to claim 1, wherein: The dispersant is oleic acid or sodium dodecylbenzenesulfonate, and the added amount of the dispersant is 1-5% of the mass of the nano-inorganic material.

5. The method for preparing a nanocomposite film having photochromic properties according to claim 1, wherein: The concentration of the organic dye solution is 0.01~0.1mol / L.

6. The method for preparing a nanocomposite film having photochromic properties according to claim 1, wherein: The coating method is spin coating, knife coating or spray coating.

7. The method for preparing a nanocomposite film having photochromic properties according to claim 1, wherein: The intensity of the applied electric field is 50~200V / cm; two electrodes for forming the electric field are respectively installed on both sides of the base material, and the electrode spacing is 2~5cm.

8. A nanocomposite film having photochromic properties obtained by the preparation method according to any one of claims 1 to 7, characterized in that: The thickness of the nanocomposite film with photochromic properties is 50-500 nm, and the surface roughness is less than 10 nm; The nano-composite film with photochromic properties has a color change response time of less than 10 seconds and a fading recovery time of less than 30 seconds within the visible light range. After 1,000 cycles, the color change response time is still less than 10 seconds and the fading recovery time is still less than 30 seconds.

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