A SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film, its preparation method and application

Abstract

This invention discloses a SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film, its preparation method, and its applications, belonging to the field of colloidal photonic crystal materials technology. First, SiO2 nanoparticles are used as templates. Then, SiO2@phenolic resin core-shell structured microspheres are prepared by thermal polymerization. The SiO2@phenolic resin core-shell structured microspheres are then assembled using a liquid colloidal crystal conversion method to obtain a SiO2@phenolic resin photonic crystal film. Finally, thermoplastic polyurethane is introduced into the interparticle gaps to prepare the SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film. The entire preparation method is simple and highly reproducible. The SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film exhibits good mechanical strength and produces a significant color change upon stretching. Compared with traditional stretchable color-changing photonic crystal films based on inverse opal photonic crystals, it has higher tensile strength and can be practically applied in fields such as structural color sensing, showing broad application prospects.

Description

Technical Field

[0001] This invention belongs to the field of colloidal photonic crystal materials technology, specifically relating to a SiO2-phenolic resin-polyurethane composite photonic crystal deformation and color-changing film, its preparation method, and its application. Background Technology

[0002] Photonic crystal structural colors originate from the interaction between periodically arranged photonic crystal structures and light, possessing the advantages of vibrant colors that never fade. Deformation-sensitive photonic crystal thin films refer to a type of non-close-packed photonic crystal structure that can undergo changes in lattice constant under external forces, thereby inducing changes in structural color. These films can be used in fields such as structural color physical sensors.

[0003] Currently, the main methods for preparing non-closely packed photonic crystal structures include direct solution polymerization of colloidal particles, which involves introducing polymer monomers into a colloidal solution and then polymerizing them to directly fill the gaps between the particles. This method is suitable for hydrogel polymers, resulting in films with relatively weak mechanical strength. The second method involves directly preparing polymer microspheres with hard-core and soft-core structures by controlling the reactants in the polymerization reaction. Then, the low-melting-point outer shells of the particles are melted using a pressure roller method, deformed under extrusion pressure, and fused together to directly assemble into a film. This method has more stringent particle preparation conditions, and the film material depends on the outer shell material of the core-shell structured microspheres. Since many materials cannot be directly polymerized to prepare hard-core-soft-shell structured microspheres, this method severely limits the range of materials that can be selected for core-shell structured microspheres and responsive films.

[0004] Existing methods for fabricating non-closely packed photonic crystal structures suffer from technical challenges, such as weak thin film mechanical strength, stringent fabrication conditions, and the thin film material's dependence on the shell material of the core-shell microspheres. Therefore, there is an urgent need to develop a more practical non-closely packed photonic crystal thin film for use in mechanical force sensors. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a SiO2-phenolic resin-polyurethane composite photonic crystal deformation and color-changing film, its preparation method and application, so as to solve the technical problems of weak mechanical strength of the film in the existing non-closely packed photonic crystal structure, harsh preparation conditions, and limited material selection range due to the dependence of the film material on the shell material of the core-shell structure microspheres.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] This invention discloses a SiO2-phenolic resin-polyurethane composite photonic crystal deformation and color-changing film, comprising SiO2@phenolic resin core-shell structured microspheres, wherein polyurethane is filled between the SiO2@phenolic resin core-shell structured microspheres, and the SiO2@phenolic resin core-shell structured microspheres are composed of SiO2 particles coated with phenolic resin layers.

[0008] Preferably, during stretching, the spacing between SiO2 particles in the SiO2-phenolic resin-polyurethane composite photonic crystal deformable color-changing film changes, and the corresponding structural color also changes. The amount of change is related to the thickness of the phenolic resin layer.

[0009] This invention also discloses a method for preparing the above-mentioned SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film, comprising the following steps:

[0010] 1) SiO2 nanoparticles were dispersed in an aqueous solution to obtain a SiO2 dispersion. A surfactant was added and stirred to react. The mixture was then centrifuged and redispersed in water to obtain a SiO2 colloidal dispersion. Resorcinol, formaldehyde, and ammonia were added and stirred until homogeneous. The mixture was then heated to carry out a polymerization reaction. After the reaction was completed, SiO2@phenolic resin core-shell structured microspheres were obtained. After centrifugation and washing, the microspheres were redispersed in water and coated onto the surface of a substrate to obtain a SiO2@phenolic resin photonic crystal film.

[0011] 2) Dissolve polyurethane in DMF to obtain a polyurethane-DMF solution, and add it to the SiO2@phenolic resin photonic crystal film prepared in step 1). After the polyurethane solution gradually penetrates into the gaps between the particles of the SiO2@phenolic resin photonic crystal film, heat until the solvent is completely evaporated to obtain a SiO2-phenolic resin-polyurethane composite photonic crystal deformation and color-changing film.

[0012] Preferably, in step 1), the size of the SiO2 nanoparticles is 160~300 nm; the concentration of the SiO2 dispersion is 10~25 mg / mL; and the concentration of the SiO2 colloidal dispersion is 2~10 mg / mL.

[0013] Preferably, in step 1), the surfactant is polyvinylpyrrolidone, and the concentration of polyvinylpyrrolidone in the SiO2 particle dispersion is 3~8 mg / mL.

[0014] Preferably, in step 1), the stirring reaction time is 4 to 10 hours.

[0015] Preferably, in step 1), the ratio of polyvinylpyrrolidone: resorcinol: formaldehyde: ammonia is (3~8) mg: (1~3) μL: (1~3) μL: (5~10) μL.

[0016] Preferably, in step 1), the polymerization reaction temperature is 60~100 ℃ and the polymerization reaction time is 2~8 h.

[0017] Preferably, in step 2), the concentration of the polyurethane solution is 0.05~0.15 g / mL, the heating temperature is 60~100 ℃, and the heating time is 3~8 h.

[0018] The present invention also discloses the application of the above-mentioned SiO2-phenolic resin-polyurethane composite photonic crystal deformation color-changing film in photonic crystal mechanical force sensors.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] This invention discloses a SiO2-phenolic resin-polyurethane composite photonic crystal deformation-modifying film. In this film, the SiO2 particles have a non-close-packed structure, achieved by using SiO2 particles as templates, coating them with a polyurethane shell, and then assembling the film. The deformation-modifying effect is achieved by pre-coating the surface of SiO2 nanoparticles with a phenolic resin layer, resulting in a SiO2 nanoparticle film with a core-shell structure. Using O2@phenolic resin core-shell structured microspheres as assembly units, a non-closely packed SiO2 particle structure is achieved. Polyurethane is then filled between the SiO2 particles to obtain a continuous SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film with self-supporting properties. When this film deforms, the lattice spacing changes with external forces due to the elastomer-polyurethane and phenolic resin components between the SiO2 particles, causing a change in structural color and resulting in deformation-changing color effects. It exhibits a bright structural color, produces a noticeable color change upon stretching, and has a stable structure that is not easily damaged. It also possesses good mechanical strength, which can be achieved by filling the gaps between the film particles with any high-strength polymer. It can be used as a photonic crystal sensor, offering advantages such as simple fabrication, low cost, and high repeatability.

[0021] This invention also discloses a method for preparing the aforementioned SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film. By pre-coating a layer of phenolic resin onto the surface of SiO2 nanoparticles using a simple thermal polymerization method, SiO2@phenolic resin core-shell structured microspheres are obtained. These microspheres can be used as photonic crystal assembly units to directly obtain a non-closely packed SiO2@phenolic resin photonic crystal film structure. Introducing polyurethane into the gaps between the SiO2@phenolic resin core-shell structured microspheres effectively improves the bonding strength between SiO2 particles in the SiO2@phenolic resin photonic crystal film. This two-step method for preparing a non-closely packed SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film structure allows for the arbitrary selection of materials filling the gaps between SiO2 particles, providing more material options for the design and fabrication of deformation-changing photonic crystal films. By filling with high-strength polymer polyurethane, the prepared SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film exhibits better mechanical strength. Compared with previous methods, the method disclosed in this invention is simple to operate and highly repeatable. The resulting SiO2-phenolic resin-polyurethane composite photonic crystal deformation and color-changing film can be peeled off from the substrate to obtain a composite film with self-supporting effect.

[0022] This invention also discloses the application of SiO2-phenolic resin-polyurethane composite photonic crystal deformation-color-changing film in photonic crystal mechanical force sensors. When the SiO2-phenolic resin-polyurethane composite photonic crystal deformation-color-changing film is made into a photonic crystal sensor, when the sensor is subjected to mechanical force, the spacing between the particles in its non-closely packed structure will change with the mechanical force, thereby causing a change in structural color. Therefore, it is possible to realize the visual sensing of mechanical force. Attached Figure Description

[0023] Figure 1 This invention discloses the preparation process of SiO2@phenolic resin core-shell structured microspheres, the preparation process of SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film, and a schematic diagram of the changes in the internal structure of the film during deformation-changing.

[0024] Figure 2 The images show TEM images of the SiO2@phenolic resin core-shell structured microspheres, which are the assembly building blocks of the SiO2-phenolic resin-polyurethane composite photonic crystal deformation and color-changing films prepared in Examples 1 and 2 of this invention; wherein, a) the phenolic resin layer has a thickness of 10 nm; and b) the phenolic resin layer has a thickness of 26 nm.

[0025] Figure 3These are morphological and optical performance characterization images of the SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing films obtained by assembling SiO2@phenolic resin core-shell structured microspheres in Examples 1 and 2 of this invention; wherein, a), c), and e) are SEM images, digital photographs, and reflection spectra of the SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing films formed by assembling SiO2@phenolic resin core-shell structured microspheres with a diameter of 210 nm; b), d), and f) are SEM images, digital photographs, and reflection spectra of the SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing films formed by assembling SiO2@phenolic resin core-shell structured microspheres with a diameter of 242 nm.

[0026] Figure 4 Digital photographs and reflection spectra of the SiO2 photonic crystal thin film, SiO2@phenolic resin photonic crystal thin film, and SiO2-phenolic resin-polyurethane composite photonic crystal deformation and color-changing thin film prepared in Examples 1 and 2 of the present invention; wherein, a) corresponds to SiO2@phenolic resin particles with a phenolic resin layer thickness of 10 nm; b) corresponds to SiO2@phenolic resin particles with a phenolic resin layer thickness of 26 nm.

[0027] Figure 5 The figures show the dynamic changes in the reflection spectrum of the SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing films prepared in Examples 1 and 2 of this invention during stretching; wherein, a) is a green SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film prepared using SiO2@phenolic resin core-shell structured microspheres with a size of 211 nm as the basic unit; b) is a red SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film prepared using SiO2@phenolic resin core-shell structured microspheres with a size of 245 nm as the basic unit.

[0028] Figure 6 The images show cross-sectional SEM images of the SiO2-phenolic resin-polyurethane composite photonic crystal deformation and color-changing film prepared in Example 3 of the present invention before and after polyurethane filling; wherein, a) is a cross-sectional SEM image of the SiO2@phenolic resin photonic crystal film before polyurethane filling, and b) is a cross-sectional SEM image of the SiO2-phenolic resin-polyurethane composite photonic crystal deformation and color-changing film after polyurethane filling. Detailed Implementation

[0029] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0030] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0031] The present invention will now be described in further detail with reference to the accompanying drawings:

[0032] This invention discloses a method for preparing a SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film, comprising the following steps:

[0033] 1) Using uniformly sized SiO2 nanoparticles as templates, they were dispersed in deionized water to obtain a SiO2 dispersion. The surface of the SiO2 nanoparticles was modified with the surfactant polyvinylpyrrolidone to obtain surface-modified SiO2 nanoparticles.

[0034] 2) The surface-modified SiO2 nanoparticles obtained in step 1) are redispersed in water to obtain a SiO2 colloidal dispersion. Resorcinol, formaldehyde and ammonia are added to the system and stirred until homogeneous.

[0035] 3) The above reaction system is heated and maintained for a period of time to initiate the polymerization reaction. After the reaction is completed, SiO2@phenolic resin core-shell structured microspheres are obtained.

[0036] 4) After repeatedly centrifuging and washing the SiO2@phenolic resin core-shell structured microspheres obtained in step 3), they are redispersed in deionized water to obtain a mixed solution. The mixed solution is then coated onto the surface of the substrate to obtain a SiO2@phenolic resin photonic crystal film.

[0037] 5) Dissolve polyurethane in DMF to obtain a polyurethane-DMF solution, and drop it onto the SiO2@phenolic resin photonic crystal film prepared in step 4). After the solvent is completely evaporated under heating conditions, a SiO2-phenolic resin-polyurethane composite photonic crystal deformation and color-changing film is obtained.

[0038] In step 1), the size of the SiO2 nanoparticles is 160~300 nm, preferably 200 nm.

[0039] In step 1), the concentration of the SiO2 dispersion is 10~25 mg / mL, preferably 20 mg / mL.

[0040] In step 1), the surfactant is polyvinylpyrrolidone, with a concentration of 3~8 mg / mL, preferably 5 mg / mL.

[0041] In step 1), the surfactant modification time is 4 to 10 hours, preferably 6 hours.

[0042] In step 2), the concentration of the SiO2 colloidal dispersion is 2~10 mg / mL, preferably 5 mg / mL.

[0043] In step 2), the concentration of resorcinol is 1~3 μL / mL, preferably 2 μL / mL.

[0044] In step 2), the concentration of formaldehyde is 1~3 μL / mL, preferably 2 μL / mL.

[0045] In step 2), the concentration of the ammonia water is 5~10 μL / mL, preferably 8 μL / mL.

[0046] In step 2), the volume ratio of resorcinol:formaldehyde:ammonia is (1~3):(1~3):(5~10).

[0047] In step 3), the polymerization reaction temperature is 60~100 ℃, preferably 70 ℃.

[0048] In step 3), the polymerization reaction takes 2 to 8 hours, preferably 6 hours.

[0049] In step 4), the volume percentage of the mixed solution is 15% to 30%, preferably 20%.

[0050] In step 4), the substrate is glass, black PET, or transparent PET.

[0051] In step 5), the heating temperature is 60~100 ℃, preferably 90 ℃.

[0052] In step 5), the heating time is 3 to 8 hours, preferably 5 hours.

[0053] In step 5), the concentration of the polyurethane solution is 0.05~0.15 g / mL, preferably 0.1 g / mL.

[0054] Example 1

[0055] A method for preparing a SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film includes the following steps:

[0056] 1) Using 190 nm SiO2 nanoparticles as templates, they were dispersed in deionized water to obtain a SiO2 dispersion with a concentration of 20 mg / mL. The SiO2 nanoparticles were then surface-modified with polyvinylpyrrolidone (PVP) at a concentration of 5 mg / mL under magnetic stirring. After 6 h of reaction, the surface-modified SiO2 nanoparticles were obtained.

[0057] 2) After centrifuging the surface-modified SiO2 nanoparticles obtained in step 1), redisperse them in deionized water to obtain a SiO2 particle dispersion with a concentration of 5 mg / mL. Add resorcinol, formaldehyde and ammonia to the system, keeping the concentration of resorcinol at 1 μL / mL, the concentration of formaldehyde at 1 μL / mL and the concentration of ammonia at 5 μL / mL, and stir to mix evenly.

[0058] 3) After reacting the above reaction system at 90 °C for 6 h, SiO2@phenolic resin core-shell structured microspheres were obtained;

[0059] 4) After repeatedly centrifuging and washing the SiO2@phenolic resin core-shell structured microspheres obtained in step 3), they were redispersed in water to obtain a mixed solution with a volume percentage of 20%. This solution was then coated onto the surface of a glass substrate and dried at 60 °C for 9 h to obtain a SiO2@phenolic resin photonic crystal film.

[0060] 5) Dissolve polyurethane in DMF at 90 °C to obtain a 0.1 g / mL polyurethane-DMF solution, and fill it into the interparticle gaps of the SiO2@phenolic resin photonic crystal film prepared in step 4). Heat and dry at 100 °C for 3 h. After the solvent has completely evaporated, a SiO2-phenolic resin-polyurethane composite photonic crystal deformation and color-changing film is obtained.

[0061] See Figure 1This invention discloses the preparation process of SiO2@phenolic resin core-shell structured microspheres, the preparation process of SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing films, and the changes in the internal structure of the films during deformation-changing. As shown in the figures, this method successfully induces the polymerization of phenolic resin on the surface of SiO2 nanoparticles to obtain SiO2@phenolic resin core-shell structured microspheres. Using SiO2 nanoparticles as assembly units, the assembled SiO2@phenolic resin photonic crystal film has a non-closely packed structure with phenolic resin as spacers between SiO2 particles. Further introducing polyurethane into the gaps between SiO2 particles results in a SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film with significant deformation-changing characteristics. This is because the spacing between SiO2 particles changes and the lattice constant changes during stretching, ultimately leading to a change in structural color.

[0062] Example 2

[0063] A method for preparing a SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film includes the following steps:

[0064] 1) Using 190 nm SiO2 nanoparticles as templates, they were dispersed in deionized water to obtain a SiO2 dispersion concentration of 10 mg / mL. The SiO2 nanoparticles were then surface-modified with polyvinylpyrrolidone (PVP) at a concentration of 5 mg / mL under magnetic stirring for 6 h to obtain surface-modified SiO2 nanoparticles.

[0065] 2) After centrifuging the surface-modified SiO2 nanoparticles obtained in step 1), they were redispersed in deionized water to obtain a SiO2 particle dispersion with a concentration of 2 mg / mL. Resorcinol, formaldehyde and ammonia were added to the system to maintain the concentration of resorcinol at 2 μL / mL, the concentration of formaldehyde at 2 μL / mL and the concentration of ammonia at 8 μL / mL. The mixture was stirred and mixed evenly.

[0066] 3) After reacting the above reaction system at 90 °C for 4 h, SiO2@phenolic resin core-shell structured microspheres were obtained;

[0067] 4) After repeatedly centrifuging and washing the SiO2@phenolic resin core-shell structured microspheres obtained in step 3), they were redispersed in water to obtain a mixed solution with a volume percentage of 30%. The mixed solution was coated onto the surface of a black PET substrate and dried at 60 °C for 9 h to obtain a SiO2@phenolic resin photonic crystal film.

[0068] 5) Dissolve polyurethane in DMF at 90 °C to obtain a polyurethane-DMF solution with a concentration of 0.15 g / mL, and fill it into the interparticle gaps of the SiO2@phenolic resin photonic crystal film prepared in step 4). Heat at 90 °C for 4 h until the solvent is completely evaporated to obtain a SiO2-phenolic resin-polyurethane composite photonic crystal deformation and color-changing film.

[0069] See Figure 2 The images show TEM images of the SiO2@phenolic resin core-shell structured microspheres, the assembly building blocks of the SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing films prepared in Examples 1 and 2 of this invention. In a), the shell thickness is 10 nm; in b), the shell thickness is 26 nm. As can be seen from the images, the shell thickness of the SiO2@phenolic resin core-shell structured microspheres can be controlled by changing the concentrations of resorcinol and formaldehyde. Using 190 nm SiO2 nanoparticles as templates, when the concentrations of resorcinol and formaldehyde are 1 μL / mL and 2 μL / mL, respectively, the shell thicknesses of the prepared SiO2@phenolic resin core-shell structured microspheres are 10 nm and 26 nm, respectively. Therefore, the shell thickness of the SiO2@phenolic resin core-shell structured microspheres can be controlled by changing the amount of raw materials.

[0070] See Figure 3 These figures depict the morphology and optical properties of the SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing films obtained by assembling SiO2@phenolic resin core-shell structured microspheres according to Examples 1 and 2 of this invention. Specifically, a), c), and e) are SEM images, digital photographs, and reflection spectra of the SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing films formed by assembling SiO2@phenolic resin core-shell structured microspheres with a diameter of 210 nm; b), d), and f) are SEM images, digital photographs, and reflection spectra of the SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing films formed by assembling SiO2@phenolic resin core-shell structured microspheres with a diameter of 242 nm. As can be seen from the figures, the SiO2@phenolic resin particles prepared by this method have uniform particle size and good monodispersity, and after assembly, they are arranged in a highly face-centered cubic packing structure. After being assembled into a SiO2-phenolic resin-polyurethane composite photonic crystal deformation color-changing film, the digital photograph shows that its structural colors are green and orange, with corresponding reflection wavelengths at 510 nm and 575 nm.

[0071] See Figure 4Digital photographs and reflection spectra of the SiO2 photonic crystal thin film, SiO2@phenolic resin photonic crystal thin film, and SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film prepared in Examples 1 and 2 of this invention; wherein, a) corresponds to SiO2@phenolic resin particles with a phenolic resin layer thickness of 10 nm; b) corresponds to SiO2@phenolic resin particles with a phenolic resin layer thickness of 26 nm; as can be seen from the figures, after SiO2 nanoparticles with a size of 190 nm are coated with phenolic resin, when the phenolic resin layer thickness is 10 nm, the size of the corresponding SiO2@phenolic resin particles increases to 210 nm. The assembled SiO2@phenolic resin photonic crystal thin film is blue-green, and after further filling with polyurethane, the film eventually turns green, and the reflection spectrum shifts from 500 nm to 555 nm. When the coating layer thickness is 26 nm, the size of the corresponding SiO2@phenolic resin particles is 242 nm. The resulting SiO2@phenolic resin photonic crystal film is orange. Upon further filling with polyurethane, the film turns red, and the reflection spectrum shifts from 575 nm to 620 nm.

[0072] See Figure 5 The figures show the dynamic changes in the reflection spectra of the SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing films prepared in Examples 1 and 2 of this invention under tensile stress. a) shows a green SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film prepared using SiO2@phenolic resin core-shell microspheres with a size of 210 nm as the basic unit; b) shows a red SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film prepared using SiO2@phenolic resin core-shell microspheres with a size of 242 nm as the basic unit. As can be seen from the figures, the initial wavelengths of the SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing films, located at 555 nm and 620 nm respectively, blue-shift to 425 nm and 450 nm under tensile stress, with wavelength changes as high as 130 nm and 170 nm respectively. These results demonstrate that the SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film prepared in this invention possesses excellent deformation-changing properties.

[0073] Example 3

[0074] A method for preparing a SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film includes the following steps:

[0075] 1) Using 190 nm SiO2 nanoparticles as templates, they were dispersed in an aqueous solution to obtain a SiO2 dispersion concentration of 25 mg / mL. The SiO2 nanoparticles were then surface-modified with polyvinylpyrrolidone (PVP) at a concentration of 8 mg / mL under magnetic stirring. After reacting for 10 h, surface-modified SiO2 nanoparticles were obtained.

[0076] 2) After centrifuging the surface-modified SiO2 nanoparticles obtained in step 1), redisperse them in water to obtain a SiO2 particle dispersion with a concentration of 10 mg / mL. Add resorcinol, formaldehyde and ammonia to the system, keeping the concentration of resorcinol at 3 μL / mL, the concentration of formaldehyde at 3 μL / mL and the concentration of ammonia at 10 μL / mL, and stir to mix evenly.

[0077] 3) After reacting the above reaction system at 100 °C for 6 h, SiO2@phenolic resin core-shell structured microspheres were obtained;

[0078] 4) After repeatedly centrifuging and washing the SiO2@phenolic resin core-shell structured microspheres obtained in step 3), they were redispersed in water to obtain a mixed solution with a volume percentage of 15%. The mixed solution was coated onto the surface of a transparent PET substrate and dried at 60 °C for 9 h to obtain a SiO2@phenolic resin photonic crystal film.

[0079] 5) Dissolve polyurethane in DMF at 90 °C to obtain a 0.1 g / mL polyurethane-DMF solution, and fill it into the interparticle gaps of the SiO2@phenolic resin photonic crystal film prepared in step 4). Heat and dry at 80 °C for 6 h. After the solvent has completely evaporated, a SiO2-phenolic resin-polyurethane composite photonic crystal deformation and color-changing film is obtained.

[0080] Preparation of SiO2 photonic crystal thin films

[0081] 60 μL of SiO2 nanoparticles were dispersed in a mixed solvent of 1 mL ethanol and 140 μL ethylene glycol to obtain a SiO2 dispersion. The solution was heated at 90 °C until the volume decreased to 200 μL to obtain a concentrated SiO2 photonic crystal solution. 50 μL of the concentrated SiO2 photonic crystal solution was evenly spread on a black plastic substrate by a scraping method. After the solvent evaporated completely, a SiO2 photonic crystal film was obtained.

[0082] Characterization and deformation / color change properties of SiO2@phenolic resin-polyurethane composite film

[0083] Using SiO2 particles as templates, SiO2@phenolic resin core-shell structured microspheres were prepared by coating them with a phenolic resin layer. These microspheres were then used as assembly units to prepare SiO2@phenolic resin photonic crystal films. Finally, polyurethane was filled into the gaps between the particles in this film to prepare the SiO2-phenolic resin-polyurethane composite photonic crystal film, which is the objective of this invention.

[0084] See Figure 6 The images show cross-sectional SEM images of the SiO2-phenolic resin-polyurethane composite photonic crystal deformable and color-changing film prepared in Example 3 of this invention before and after polyurethane filling; where a) is a cross-sectional SEM image of the SiO2@phenolic resin photonic crystal film before polyurethane filling, and b) is a cross-sectional SEM image of the SiO2-phenolic resin-polyurethane photonic crystal film after polyurethane filling. As can be seen from the images, the structure of the SiO2@phenolic resin photonic crystal film remains highly ordered before and after polyurethane filling. This indicates that coating with phenolic resin followed by filling with a high-strength polymer does not disrupt the arrangement order of the particles in the photonic crystal film. This is also verified by the corresponding reflection spectrum and the color change of the film.

[0085] Example 4

[0086] A method for preparing a SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film includes the following steps:

[0087] 1) Using 250 nm SiO2 nanoparticles as templates, they were dispersed in deionized water to obtain a SiO2 dispersion with a concentration of 25 mg / mL. The SiO2 nanoparticles were then surface-modified with polyvinylpyrrolidone (PVP) at a concentration of 8 mg / mL under magnetic stirring for 10 h to obtain surface-modified SiO2 nanoparticles.

[0088] 2) After centrifuging the surface-modified SiO2 nanoparticles obtained in step 1), redisperse them in deionized water to obtain a SiO2 particle dispersion with a concentration of 10 mg / mL. Add resorcinol, formaldehyde and ammonia to the system, keeping the concentration of resorcinol at 3 μL / mL, the concentration of formaldehyde at 3 μL / mL and the concentration of ammonia at 10 μL / mL, and stir to mix evenly.

[0089] 3) After reacting the above reaction system at 100 °C for 8 h, SiO2@phenolic resin core-shell structured microspheres were obtained;

[0090] 4) After repeatedly centrifuging and washing the SiO2@phenolic resin core-shell structured microspheres obtained in step 3), they were redispersed in water to obtain a mixed solution with a volume percentage of 15%. The mixed solution was coated onto the surface of a transparent PET substrate and dried at 60 °C for 9 h to obtain a SiO2@phenolic resin photonic crystal film.

[0091] 5) Dissolve polyurethane in DMF at 90 °C to obtain a 0.1 g / mL polyurethane-DMF solution, and fill it into the interparticle gaps of the SiO2@phenolic resin photonic crystal film prepared in step 4). Heat at 80 °C for 6 h until the solvent is completely evaporated to obtain a SiO2-phenolic resin-polyurethane composite photonic crystal deformation and color-changing film.

[0092] Example 5

[0093] A method for preparing a SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film includes the following steps:

[0094] 1) Using 160 nm SiO2 nanoparticles as templates, they were dispersed in deionized water to obtain a SiO2 dispersion concentration of 10 mg / mL. The SiO2 nanoparticles were then surface-modified with polyvinylpyrrolidone (PVP) at a concentration of 3 mg / mL under magnetic stirring for 4 h to obtain surface-modified SiO2 nanoparticles.

[0095] 2) After centrifuging the surface-modified SiO2 nanoparticles obtained in step 1), they were redispersed in deionized water to obtain a SiO2 particle dispersion with a concentration of 2 mg / mL. Resorcinol, formaldehyde and ammonia were added to the system to maintain the concentration of resorcinol at 1 μL / mL, the concentration of formaldehyde at 1 μL / mL and the concentration of ammonia at 7 μL / mL. The mixture was stirred and mixed evenly.

[0096] 3) After reacting the above reaction system at 60 °C for 2 h, SiO2@phenolic resin core-shell structured microspheres were obtained;

[0097] 4) After repeatedly centrifuging and washing the SiO2@phenolic resin core-shell structured microspheres obtained in step 3), they were redispersed in water to obtain a mixed solution with a volume percentage of 15%. The mixed solution was coated onto the surface of a glass substrate and dried at 60 °C for 9 h to obtain a SiO2@phenolic resin photonic crystal film.

[0098] 5) Dissolve polyurethane in DMF at 60 °C to obtain a polyurethane-DMF solution of 0.05 g / mL, and fill it into the interparticle gaps of the SiO2@phenolic resin photonic crystal film prepared in step 4). Heat it at 60 °C for 8 h until the solvent is completely evaporated to obtain a SiO2-phenolic resin-polyurethane composite photonic crystal deformation and color-changing film.

[0099] Example 6

[0100] A method for preparing a SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film includes the following steps:

[0101] 1) Using 300 nm SiO2 nanoparticles as templates, they were dispersed in deionized water to obtain a SiO2 dispersion concentration of 25 mg / mL. The SiO2 nanoparticles were then surface-modified with polyvinylpyrrolidone (PVP) at a concentration of 8 mg / mL for 10 h under magnetic stirring to obtain the modified SiO2 nanoparticles.

[0102] 2) After centrifuging the surface-modified SiO2 nanoparticles obtained in step 1), they were redispersed in deionized water to obtain a SiO2 particle dispersion with a concentration of 10 mg / mL. Resorcinol, formaldehyde and ammonia were added to the system to maintain the concentration of resorcinol at 3 μL / mL, the concentration of formaldehyde at 3 μL / mL and the concentration of ammonia at 5 μL / mL. The mixture was stirred and mixed evenly.

[0103] 3) After reacting the above reaction system at 100 °C for 8 h, SiO2@phenolic resin core-shell structured microspheres were obtained;

[0104] 4) After repeatedly centrifuging and washing the SiO2@phenolic resin core-shell structured microspheres obtained in step 3), they were redispersed in water to obtain a 30% volume percentage mixed solution. The mixed solution was coated onto the surface of a black PET substrate and dried at 60 ℃ for 9 h to obtain a SiO2@phenolic resin photonic crystal film.

[0105] 5) Dissolve polyurethane in DMF at 100 °C to obtain a polyurethane-DMF solution of 0.15 g / mL, and fill it into the interparticle gaps of the SiO2@phenolic resin photonic crystal film prepared in step 4). Heat at 100 °C for 6 h until the solvent is completely evaporated to obtain a SiO2-phenolic resin-polyurethane composite photonic crystal deformation and color-changing film.

[0106] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film, characterized in that, The microspheres include SiO2@phenolic resin core-shell structured microspheres, wherein polyurethane is filled between the SiO2@phenolic resin core-shell structured microspheres, and the SiO2@phenolic resin core-shell structured microspheres are composed of SiO2 particles coated with a phenolic resin layer. The method for preparing the SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film includes the following steps: 1) SiO2 nanoparticles were dispersed in an aqueous solution to obtain a SiO2 dispersion. Polyvinylpyrrolidone was added and stirred to react. After centrifugation, the dispersion was redispersed in water to obtain a SiO2 colloidal dispersion. Resorcinol, formaldehyde, and ammonia were then added and stirred until homogeneous. The mixture was then heated to carry out a polymerization reaction. After the reaction was completed, SiO2@phenolic resin core-shell structured microspheres were obtained. After centrifugation and washing, the microspheres were redispersed in water and coated onto the surface of a substrate to obtain a SiO2@phenolic resin photonic crystal film. 2) Dissolve polyurethane in DMF to obtain a polyurethane-DMF solution, and add it to the SiO2@phenolic resin photonic crystal film prepared in step 1). After the polyurethane solution gradually penetrates into the gaps between the particles of the SiO2@phenolic resin photonic crystal film, heat until the solvent is completely evaporated to obtain a SiO2-phenolic resin-polyurethane composite photonic crystal deformation and color-changing film.

2. The method for preparing the SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film according to claim 1, characterized in that, Includes the following steps: 1) SiO2 nanoparticles were dispersed in an aqueous solution to obtain a SiO2 dispersion. Polyvinylpyrrolidone was added and stirred to react. After centrifugation, the dispersion was redispersed in water to obtain a SiO2 colloidal dispersion. Resorcinol, formaldehyde, and ammonia were then added and stirred until homogeneous. The mixture was then heated to carry out a polymerization reaction. After the reaction was completed, SiO2@phenolic resin core-shell structured microspheres were obtained. After centrifugation and washing, the microspheres were redispersed in water and coated onto the surface of a substrate to obtain a SiO2@phenolic resin photonic crystal film. 2) Dissolve polyurethane in DMF to obtain a polyurethane-DMF solution, and add it to the SiO2@phenolic resin photonic crystal film prepared in step 1). After the polyurethane solution gradually penetrates into the gaps between the particles of the SiO2@phenolic resin photonic crystal film, heat until the solvent is completely evaporated to obtain a SiO2-phenolic resin-polyurethane composite photonic crystal deformation and color-changing film.

3. The method for preparing the SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film according to claim 2, characterized in that, In step 1), the size of the SiO2 nanoparticles is 160~300 nm; the concentration of the SiO2 dispersion is 10~25 mg / mL; and the concentration of the SiO2 colloidal dispersion is 2~10 mg / mL.

4. The method for preparing the SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film according to claim 2, characterized in that, In step 1), the concentration of polyvinylpyrrolidone in the SiO2 particle dispersion is 3~8 mg / mL.

5. The method for preparing the SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film according to claim 2, characterized in that, In step 1), the stirring reaction time is 4 to 10 hours.

6. The method for preparing the SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film according to claim 2, characterized in that, In step 1), the ratio of polyvinylpyrrolidone: resorcinol: formaldehyde: ammonia is (3~8) mg: (1~3) μL: (1~3) μL: (5~10) μL.

7. The method for preparing the SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film according to claim 2, characterized in that, In step 1), the polymerization reaction temperature is 60~100 ℃ and the polymerization reaction time is 2~8 h.

8. The method for preparing the SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film according to claim 2, characterized in that, In step 2), the concentration of the polyurethane solution is 0.05~0.15 g / mL, the heating temperature is 60~100 ℃, and the heating time is 3~8 h.

9. The application of the SiO2-phenolic resin-polyurethane composite photonic crystal deformation-changing film according to claim 1 in a photonic crystal mechanical force sensor.

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