Structural color adhesive, preparation method and application

Abstract

The present application relates to a kind of structural color adhesive, preparation method and application, it is related to photonic crystal composite material and adhesive service failure monitoring technical field.Magnetic colloidal particles are dispersed in polymer monomer, or magnetic colloidal particles and polymer monomer are dispersed in solvent to obtain precursor dispersion liquid, under the action of external magnetic field, by radiation curing to obtain structural color adhesive with stress color change ability;Non-magnetic colloidal particles and polymer monomer are dispersed in solvent, and precursor dispersion liquid is obtained by solvent evaporation method, and structural color adhesive with stress color change ability is obtained by radiation curing.Under the action of external force (tension, compression or shear), adhesive material can change color, and color can be restored when external force is removed.The introduction of structural color in the present application gives adhesive the ability of stress-induced color change, and realizes the visual indication function of adhesive bonding strength in service process.

Description

A structural color adhesive, its preparation method and application Technical Field

[0001] This invention relates to the field of photonic crystal composite materials and adhesive service failure monitoring technology, and more specifically, to a structural color adhesive, its preparation method, and its application. The invention relates to a method for preparing a structural color adhesive, including a method for preparing a structural color adhesive with mechanochromic capabilities, the design and preparation of coloring for adhesive materials, and the use of mechanochromic adhesive materials for stress detection and early warning of material service failure. Background Technology

[0002] In numerous fields such as automobiles, electronic equipment, mechanical parts, building materials, and office supplies, the use of adhesives to replace mechanical bonding is increasingly prevalent. Acrylic resins possess excellent weather resistance, acid and alkali resistance, and lightfastness, and are primarily used in coatings, fabric treatment, and adhesives. Polyacrylate adhesives, characterized by rapid curing, low energy consumption, high transparency, and limited emissions of volatile organic compounds, are widely used in glass, ceramics, wood, leather, and printing. Structural color is a physical color-generating method, produced by the interaction of specific wavelengths of light with the microscopic nanostructures within a material. Unlike colors produced by traditional dyes and pigments, structural colors offer advantages such as high brightness, high color saturation, and insensitivity to ultraviolet light. The development of nanocomposites with structural colors by embedding photonic crystal arrays into soft and highly transparent polymers has been extensive, showing great application potential in sensing, biodetection, and flexible display devices. Meeting diverse human needs for color, the application of structural colors in the field of color coatings holds significant research value.

[0003] Currently, most industrially produced adhesives are colorless. However, with the increasing demand for diverse adhesive colors and functions, some companies have produced colored adhesives, such as colored solid adhesives and color-changing solid adhesives. Existing methods all involve adding pigments or dyes during the production process. For example, CN1055944A describes obtaining solid adhesives of various colors by adding food coloring or dyes. Color-changing adhesives mainly contain phenolphthalein solid adhesives. CN101608103A discloses a highly stable phenolphthalein-based color-changing solid adhesive; after being coated on a substrate, the adhesive's alkalinity decreases upon contact with air, and the purple color disappears when the pH is below 8.2. Existing colored adhesives all face the problem of colorant (dye, pigment) degradation and discoloration after long-term exposure to air. Color-changing adhesives lack the ability to indicate color changes caused by substrate deformation or decreased adhesion of the joints. Summary of the Invention

[0004] To address the shortcomings of existing color adhesives and the needs of specific application scenarios, this invention provides a rapid, large-scale method for preparing structural color adhesives. This method primarily selects polymer monomers used in existing industrially mass-produced adhesives and adds colloidal particles capable of generating structural colors. Furthermore, it optimizes the preparation process, solvent selection, component ratios, and assembly parameters based on the characteristics of different colloidal particles, thereby achieving large-scale preparation of structural color adhesives and color-changing adhesives. This technology improves the optical stability of color adhesives and enhances the functionality of structural color adhesives, enabling visualized monitoring and early warning of bonding performance, thus promoting the industrial development of structural color adhesives.

[0005] To achieve the above objectives, this invention provides a method for preparing an adhesive with structural color, thereby achieving coloring of the adhesive. The structural color adhesive prepared by this invention has color-changing ability, and the adhesive properties of the adhesive can be visually indicated based on the color change.

[0006] According to a first aspect of the present invention, a method for preparing a structural color adhesive is provided, comprising the following steps:

[0007] (1) Magnetic colloidal particles and photoinitiator are dispersed in polymer monomers to obtain a precursor dispersion; or magnetic colloidal particles, polymer monomers and photoinitiator are dispersed in a solvent to obtain a precursor dispersion.

[0008] (2) Apply a magnetic field to the precursor dispersion obtained in step (1). The magnetic colloidal particles are arranged in an orderly manner under the action of the magnetic field to generate structural color. Then, radiation curing is performed to obtain structural color binder.

[0009] Preferably, the mass fraction of magnetic colloidal particles in the precursor dispersion ranges from 1% to 10%.

[0010] Preferably, the magnetic colloidal particles are iron oxide colloidal particles or iron oxide paramagnetic colloidal particles with a coated shell.

[0011] Preferably, the paramagnetic colloidal particles of iron oxide coated with the shell are iron oxide colloidal particles coated with a silica shell or iron oxide colloidal particles coated with polyvinylpyrrolidone.

[0012] Preferably, the size distribution of the magnetic colloidal particles is 100-400 nm.

[0013] According to another aspect of the present invention, a method for preparing a structural color adhesive is provided, comprising the following steps:

[0014] (1) Disperse non-magnetic colloidal particles, polymer monomers and photoinitiators in a solvent to obtain a dispersion; evaporate the solvent in a thermal field placed in a dark environment to obtain a precursor dispersion with structural color.

[0015] (2) Radiation curing is performed on the precursor dispersion with structural color obtained in step (1) to obtain structural color binder.

[0016] Preferably, the volume fraction of non-magnetic colloidal particles in the dispersion ranges from 30% to 80%.

[0017] Preferably, the non-magnetic colloidal particles are zirconium dioxide colloidal particles, silica colloidal particles, titanium dioxide colloidal particles, cerium oxide colloidal particles, zinc sulfide colloidal particles, cellulose nanocrystals, or polymer colloidal particles.

[0018] Preferably, the polymer colloidal particles are polystyrene colloidal particles, polydopamine colloidal particles, or polymethyl methacrylate colloidal particles;

[0019] Preferably, the size distribution of the non-magnetic colloidal particles is 100-400 nm.

[0020] Preferably, the polymer monomer is an acrylate monomer and / or a methacrylate monomer.

[0021] According to another aspect of the present invention, a structural color adhesive prepared by any one of the methods is provided, wherein the color of the structural color adhesive can change under the action of external force, and the color can be restored when the external force is removed.

[0022] Preferably, the external force is tension, compression, or shear.

[0023] According to another aspect of the invention, the structural color adhesive is provided for use in monitoring changes in bond strength or stress detection under load.

[0024] In summary, compared with the prior art, the above-described technical solutions conceived by this invention mainly possess the following technical advantages:

[0025] (1) The coloring of the adhesive by the present invention has the advantages of being stable and not easy to fade compared with traditional colorants (dyes, pigments); and has the ability to indicate the responsive color change of the substrate or adhesive to deformation.

[0026] (2) The introduction of structural color in this invention endows the adhesive with the ability to change color due to force, realizing the function of visually indicating the bonding strength of the adhesive during its service life. For example, during the service life of the adhesive, the bonding ability of the adhesive decreases due to the influence of environmental temperature, humidity, radiation, etc., and creep is prone to occur under load, causing misalignment or detachment of the adhesive joint. In response to the creep failure process of the adhesive, the structural color can respond and produce a color change. This color change can be intuitively perceived by the naked eye and is also easily captured by optical devices such as monitors, digital cameras, and smartphones.

[0027] (3) The method of the present invention is simple. It is based on the existing adhesive production process and improves it. By adding colloidal particles that can generate structural color, structural color adhesive can be prepared. It is low in cost and easy to scale up.

[0028] (4) The present invention can obtain structural color binders with different hydrophilicity, glass transition temperature and functionality by selecting polymer monomers.

[0029] (5) This invention provides a new solution for early warning of adhesive failure during service, which is of great significance to production and daily life safety. For example, a blue structural color adhesive remains blue in a stable state. When the ambient humidity is too high, the cohesive energy of the adhesive decreases, and the adhesive gradually deforms under the action of the load. This deformation process causes the structural color to change from blue to green, yellow, or red. The color change of the adhesive can inform the user that the adhesive performance has deteriorated and the adhesive should be replaced in time to prevent potential adhesion failure. Attached Figure Description

[0030] Figure 1 is a schematic diagram of the preparation and structure of the structural color adhesive of the present invention.

[0031] Figure 2 is a schematic diagram of the preparation and structure of the structural color binder doped with magnetic colloidal particles in Examples 1-5.

[0032] Figure 3 is a schematic diagram of the preparation and structure of the structural color binder doped with non-magnetic colloidal particles in Examples 6-8.

[0033] Figure 4 is a scanning electron microscope image of the magnetic tetroxide colloidal particles used in the preparation of structural color binders in Examples 1-5.

[0034] Figure 5 is a scanning electron microscope image of the non-magnetic silica particles used to prepare the structural color binder in Examples 6-8.

[0035] Figure 6 is a schematic diagram of the color change response mechanism of the structural color binder doped with magnetic colloidal particles under the action of shear force in implementation 1-5.

[0036] Figure 7 shows the structural color adhesive prepared in Example 2 used for bonding glass and bearing heavy objects.

[0037] Figure 8 shows the red shift in color caused by the decrease in bonding strength of the structural color adhesive prepared in Implementation Case 2 when it is used in a high humidity environment.

[0038] Figure 9 shows the service life of the structural color binder prepared in Example 3 in an underwater environment.

[0039] Figure 10 shows the structural color adhesive prepared in Implementation Case 4 failing at high temperature, changing from blue to brownish-yellow.

[0040] Figure 11 is a schematic diagram of the color change response mechanism of the structural color adhesives prepared in Examples 1-8 under tension or compression.

[0041] Figure 12 shows the shear color change effect of the structure color binder doped with non-magnetic colloidal particles prepared in Example 8. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0043] This invention discloses a rapid and large-scale method for preparing structural color adhesives, relating to the fields of photonic crystal composite materials and adhesive service failure monitoring technology. The preparation method involves dispersing monodisperse colloidal particles in polymer monomers, or dispersing monodisperse colloidal particles and polymer monomers in a solvent to obtain a precursor dispersion; the colloidal particles self-assemble and arrange themselves in an ordered manner within a polymer matrix to form a photonic crystal structure, and then curing under radiation to obtain an adhesive with structural color; the structural color adhesive has a vibrant color and is characterized by its stimulus-responsive color-changing ability, whereby the adhesive can change color under external force (tension, compression, or shear), enabling monitoring of changes in adhesive strength during service and providing warnings of adhesive failure. Figure 1 is a schematic diagram of the preparation and structure of the structural color adhesive of this invention.

[0044] Colloidal particles can be divided into magnetic colloidal particles and non-magnetic colloidal particles. The self-assembly of magnetic colloidal particles can be carried out by magnetic field induction. Magnetic colloidal particles can arrange themselves into chain-like structures and generate structural colors under magnetic field. The magnetic field strength ranges from 20 to 4000 Gs. The self-assembly of non-magnetic colloidal particles can be carried out by solvent evaporation. The characteristic of this method is that the temperature can be controlled between 0 and 100℃.

[0045] Preferably, the magnetic nanoparticles are iron(III) oxide; the non-magnetic nanoparticles are zirconium dioxide, silicon dioxide, titanium dioxide, cerium oxide, or zinc sulfide colloidal particles, cellulose nanocrystals, or polymer colloidal particles, such as polystyrene, polydopamine, polymethyl methacrylate, etc.; the colloidal particles may be one or a mixture of the above.

[0046] In some embodiments, the colloidal particle size distribution used is 100-400 nm.

[0047] In some embodiments, the polymer monomers are acrylate monomers and / or methacrylate monomers.

[0048] In some embodiments, the difference in refractive index between the colloidal particles and the polymer formed by the monomer is ≥0.01. If the difference in refractive index between the colloidal particles and the polymer formed by the monomer is too small, an optical bandgap cannot be formed, i.e., structural color cannot be generated.

[0049] In some embodiments, the acrylate and / or methacrylate monomers are selected from acrylate and / or methacrylate units having C1-20 alkyl groups, C3-8 cycloalkyl groups, C6-14 aryl groups, or ethylene glycol and its oligomeric derivative groups as ester groups.

[0050] In some embodiments, the radiation type includes UV light, visible light, electron beams, etc.

[0051] In some embodiments, the photoinitiator comprises 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxycyclohexylphenyl ketone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 1-hydroxycyclohexylphenyl ketone, 2-benzyl-2-dimethylamino-1-(4-morpholinylphenyl)butane-1-one-1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one, benzoin alkyl ethers (e.g., benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, n-butyl benzoin ether, etc.), 2-hydroxy Examples of benzoyl-2-methyl-1-phenylpropane-1-one, p-tert-butyltrichloroacetophenone, p-tert-butyldichloroacetophenone, benzoyl, acetophenone, benzophenone, 2,4-diisopropylthioxanthone, dibenzocycloheptanone, 4,4'-dichlorobenzophenone, 4,4'-bis(dimethylamino)benzophenone, benzenemethylacetone, diacetyl, benzoyl peroxide, 3,3'-dimethyl-4-methoxybenzophenone, 2,2-diethoxyacetophenone, chlorinated acetophenone, hydroxyacetophenone, acetophenone diethyl ketal, 4'-isopropyl-2-hydroxy-2-methylacetophenone, etc.

[0052] Preparation of structure-color binders doped with magnetic colloidal particles:

[0053] (1) A precursor dispersion is obtained by ultrasonic dispersion of polymer monomers, magnetic colloidal particles and photoinitiator, wherein the mass fraction of magnetic colloidal particles is between 1% and 10%.

[0054] (2) Inject the precursor dispersion into the mold, apply a magnetic field below the mold (preferably a transparent mold), and after the magnetic colloidal particles are arranged in an orderly manner under the action of the magnetic field to generate structural color, radiation curing is performed to obtain structural color adhesive sheet; or inject the precursor dispersion into the joint of the joint, apply a magnetic field below the joint, and after the magnetic colloidal particles are arranged in an orderly manner under the action of the magnetic field to generate structural color, radiation curing is performed.

[0055] Preferably, the polymer monomer is liquid at room temperature; the polymer monomer is an acrylate and / or methacrylate monomer. An incomplete list of specific preferred examples includes, but is not limited to, ethyl acrylate, ethyl methacrylate, n-butyl acrylate, n-butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, hexyl acrylate, hexyl methacrylate, n-octyl acrylate, n-octyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isoamyl acrylate, isooctyl acrylate, isononyl acrylate, decyl acrylate, isodecyl acrylate, decyl methacrylate, lauryl acrylate, lauryl methacrylate, tridecyl acrylate, tridecyl methacrylate, tetradecyl acrylate, tetradecyl methacrylate, hexadecyl acrylate, hexadecyl methacrylate. 2-Methylbutyl acrylate, 4-methyl-2-pentyl acrylate, 4-tert-butylcyclohexyl methacrylate, cyclohexyl methacrylate, isobornyl acrylate, N,N-dimethylaminoethyl acrylate, N,N-dimethylaminoethyl methacrylate, N,N-diethylaminoethyl methacrylate, N,N-dimethylaminoethyl methacrylate, N,N-dimethylaminoethyl acrylamide, N,N-dimethylaminoethyl methacrylamide, N,N-dimethylaminopropyl acrylamide, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl acrylate, N-(2-hydroxyethyl)acrylamide, 2-hydroxybutyl methacrylate, and 4-hydroxybutyl acrylate. 2-Acryloyloxyethyl isocyanate, 2-methacryloyloxyethyl isocyanate, 1,1-bis(acryloyloxymethyl)ethyl isocyanate, polyethylene glycol acrylate, polyethylene glycol methacrylate, polyethylene glycol methyl ether methacrylate, poly(ethylene glycol) phenyl ether acrylate, 2-phenoxyethyl acrylate, benzyl methacrylate, 2,2,3,4,4,4-hexafluorobutyl acrylate, 2-(butamino-carbonyl)oxoethyl acrylate, 2-[2-(2-methoxyethoxy)ethoxy]ethyl acrylate, 2-methyl-2-acrylate-2-(2-methoxyethoxy)ethyl acrylate, ethoxyethoxyethyl acrylate, 2-methoxyethyl acrylate, and mixtures thereof.

[0056] Preparation of structure-colored binders doped with non-magnetic colloidal particles:

[0057] Polymer monomers, non-magnetic colloidal particles, and photoinitiators are dispersed in a solvent by ultrasonication, wherein the volume fraction of polymer monomers and non-magnetic colloidal particles is between 30% and 80%.

[0058] (1) The dispersion of polymer monomers, non-magnetic colloidal particles and photoinitiator is evaporated in a thermal field placed in a dark environment to remove the solvent and obtain a colored solution containing non-magnetic colloidal particles, polymer monomers and a small amount of solvent precursor.

[0059] (2) The obtained colored precursor solution is injected into a clamping mold (preferably a transparent mold), and then cured by radiation to obtain a structural color adhesive material. Alternatively, the colored precursor dispersion is injected into the joint of the joint and then cured by radiation.

[0060] Preferably, the polymer monomer is liquid at room temperature; the polymer monomer is an acrylate and / or a methacrylate monomer. An incomplete list of specific preferred examples includes, but is not limited to, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl acrylate, N-(2-hydroxyethyl)acrylamide, 2-hydroxybutyl methacrylate and 4-hydroxybutyl acrylate, polyethylene glycol acrylate, polyethylene glycol methacrylate, polyethylene glycol methyl ether methacrylate, poly(ethylene glycol) phenyl ether acrylate, 2-phenoxyethyl acrylate, benzyl methacrylate, 2-(butamino-carbonyl)oxoethyl acrylate, 2-[2-(2-methoxyethoxy)ethoxy]ethyl acrylate, 2-methyl-2-acrylate-2-(2-methoxyethoxy)ethyl acrylate, ethoxyethoxyethyl acrylate, 2-methoxyethyl acrylate, and mixtures thereof.

[0061] Preferably, the solvent is one or more of water, tetrahydrofuran, 2-phenoxyethanol, N,N-dimethylformamide, ethylene glycol phenyl ether acetate, n-hexane, diethylene glycol diacetate, cyclohexane, methanol, ethanol, isopropanol, 1-phenoxy-2-propanol, dimethyl sulfoxide, and N,N-dimethylacetamide.

[0062] Preferably, the solvent in the precursor dispersion has an evaporation temperature of 30–100°C.

[0063] Preferably, the non-colloidal particles have a mass fraction of 0.1-8% in the solvent; and the polymer monomer has a concentration of 0.1-10% in the solvent.

[0064] The structural color adhesive prepared by this invention is a polymer adhesive. During service, environmental factors such as temperature, humidity, radiation, and oxygen can easily cause it to age and affect its bonding strength. Aging of the structural color adhesive during service leads to a decrease in bonding strength. The creep behavior of the polymer matrix causes deformation of the structural color adhesive and a red shift in the structural color, such as changing from purple or blue to green, yellow, or red. This allows for the monitoring of bonding strength and the warning of service failure.

[0065] The following are specific embodiments.

[0066] Figure 2 shows the preparation and structure of the structural color binder doped with magnetic colloidal particles in Examples 1-5.

[0067] Figure 4 is a scanning electron microscope image of the magnetic tetroxide colloidal particles used in the preparation of structural color binders in Examples 1-5.

[0068] Example 1

[0069] A method for rapid large-scale preparation of structural color adhesives, comprising a mechanotropic structural color adhesive, includes the following steps:

[0070] (1) Monodisperse iron oxide colloidal particles with a diameter of 180 nm and a photoinitiator (2-hydroxy-2-methyl-1-phenylpropanone) were ultrasonically dispersed in polyethylene glycol methyl ether methacrylate monomer (Mw480) to obtain a precursor dispersion. The mass ratio of polyethylene glycol methyl ether methacrylate, iron oxide colloidal particles and photoinitiator was 997:3:1.

[0071] (2) The precursor dispersion is injected into the mold or joint, a magnetic field is applied below the mold or joint, and the mixture is cured by irradiation under 365nm wavelength UV light for 5 minutes to obtain the structural color adhesive, as shown in Figure 6. Under the action of shear force, the reflection spectrum of the structural color adhesive will red shift, and it has the function of force-induced color change.

[0072] Example 2

[0073] (1) A precursor dispersion was obtained by ultrasonically dispersing monodisperse iron oxide colloidal particles with a diameter of 180 nm and a photoinitiator (2-hydroxy-2-methyl-1-phenylpropanone) in a mixture of polyethylene glycol methyl ether methacrylate (Mw480) and N-(2-hydroxyethyl)acrylamide monomers. The mass ratio of polyethylene glycol methyl ether methacrylate, N-(2-hydroxyethyl)acrylamide, iron oxide colloidal particles, and photoinitiator was 490:507:3:1.

[0074] (2) The precursor dispersion is injected into the mold or joint, a magnetic field is applied below the mold or joint, and the mixture is cured under 365nm UV light for 5 minutes to obtain a hydrophilic structural color adhesive, which can firmly bond two glass plates together. The addition of N-(2-hydroxyethyl)acrylamide significantly improves the cohesive energy of the polymer and enhances the elastic modulus of the structural color adhesive. As shown in Figure 7, the obtained high cohesive energy structural color adhesive can withstand a weight of 12kg without debonding.

[0075] (3) As shown in Figure 8, it can be seen that the connectors bonded with structural color adhesive are used to support heavy objects such as 3kg weights and are placed in an environment with 70% relative humidity. Due to the plasticizing effect of water molecules on the adhesive, the creep behavior of the adhesive under the shear force of the heavy object causes the structural color to change from blue to yellow, indicating that the adhesive strength has decreased, deformation has occurred, and it can no longer support the current heavy object, and it is about to fail in service.

[0076] Example 3

[0077] (1) Monodisperse iron oxide colloidal particles with a diameter of 180 nm and a photoinitiator (2-hydroxy-2-methyl-1-phenylpropanone) were ultrasonically dispersed in 2-acrylate-2-(butanoamino-carbonyl)oxoethyl ester monomer to obtain a precursor dispersion. The mass ratio of 2-acrylate-2-(butanoamino-carbonyl)oxoethyl ester, iron oxide colloidal particles and photoinitiator was 997:3:1.

[0078] (2) The precursor dispersion is injected into the mold or joint, a magnetic field is applied below the mold or joint, and the mixture is cured under UV light at a wavelength of 365nm for 5 minutes to obtain a hydrophobic structural color adhesive with mechanochromic function.

[0079] (3) As shown in Figure 9, the prepared hydrophobic structural color adhesive still maintains its color and bonding properties underwater.

[0080] Example 4

[0081] (1) Monodisperse iron oxide colloidal particles with a diameter of 180 nm and a photoinitiator (2-hydroxy-2-methyl-1-phenylpropanone) were ultrasonically dispersed in a mixture of n-butyl acrylate and isobornyl acrylate monomers to obtain a precursor dispersion, wherein the mass ratio of n-butyl acrylate, isobornyl acrylate, iron oxide colloidal particles and photoinitiator was 700:297:3:1.

[0082] (2) The precursor dispersion is injected into the mold or joint, a magnetic field is applied below the mold or joint, and the mixture is cured under UV light at a wavelength of 365nm for 5 minutes to obtain a hydrophobic structural color adhesive with mechanochromic function.

[0083] (3) As shown in Figure 10, the prepared structural color adhesive softens at high temperature and changes from blue to brownish-yellow under the shear force brought by the load.

[0084] Example 5

[0085] (1) Monodisperse iron oxide colloidal particles with a diameter of 180 nm and a photoinitiator (2-hydroxy-2-methyl-1-phenylpropanone) were ultrasonically dispersed in a mixture of n-butyl acrylate and 2-acryloyloxyethyl isocyanate to obtain a precursor dispersion. The mass ratio of n-butyl acrylate, 2-acryloyloxyethyl isocyanate, iron oxide colloidal particles and photoinitiator was 800:197:3:1.

[0086] (2) The precursor dispersion is injected into the mold or joint, a magnetic field is applied below the mold or joint, and the mixture is cured by irradiation under 365nm wavelength UV light for 5 minutes to obtain a structural color adhesive with mechanochromic function.

[0087] Figure 3 shows the preparation and structure of the structural color binder doped with non-magnetic colloidal particles in Examples 6-8.

[0088] Figure 5 is a scanning electron microscope image of the non-magnetic silica particles used to prepare the structural color binder in Examples 6-8.

[0089] Example 6

[0090] (1) Monodisperse silica particles with a diameter of 180 nm, a photoinitiator (2-hydroxy-2-methyl-1-phenylpropanone), and polyethylene glycol methyl ether methacrylate monomer (Mw 480) were ultrasonically dispersed in an ethanol solution, and the ethanol solvent was evaporated at 80°C in the dark to obtain a colored precursor solution. The volume ratio of polyethylene glycol methyl ether methacrylate, silica particles, and photoinitiator was 500:500:1.

[0091] (2) The obtained colored precursor solution is injected into a transparent splice mold or joint, and cured under 365nm wavelength UV light for 5 minutes to obtain a structural color adhesive with mechanochromic function. As shown in the reflectance spectrum of Figure 11, the color of the structural color adhesive undergoes a blue shift when stretched or compressed.

[0092] Example 7

[0093] (1) Monodisperse silica particles with a diameter of 180 nm, photoinitiator (2-hydroxy-2-methyl-1-phenylpropanone), and 2-methyl-2-acrylate-2-(2-methoxyethoxy)ethyl ester were ultrasonically dispersed in an ethanol solution, and the ethanol solvent was evaporated at 80 °C in the dark to obtain a colored precursor solution. The volume ratio of 2-methyl-2-acrylate-2-(2-methoxyethoxy)ethyl ester, silica particles, and photoinitiator was 500:500:1.

[0094] (2) The obtained colored precursor solution is injected into the transparent splice mold or joint and cured under UV light at a wavelength of 365nm for 5 minutes to obtain a structural color adhesive with mechanochromic function.

[0095] Example 8

[0096] (1) Monodisperse silica particles with a diameter of 180 nm, a photoinitiator (2-hydroxy-2-methyl-1-phenylpropanone), and 2-(butanoamino-carbonyl)oxoethyl ester of 2-acrylate were ultrasonically dispersed in an ethanol solution, and the ethanol solvent was evaporated at 80 °C in the dark to obtain a colored precursor solution. The volume ratio of 2-(butanoamino-carbonyl)oxoethyl ester of 2-acrylate, silica particles, and photoinitiator was 500:500:1.

[0097] (2) The obtained colored precursor solution is injected into a transparent splice mold or joint, and cured under 365nm wavelength UV light for 5 minutes to obtain a structural color adhesive with mechanochromic function. As shown in Figure 12, the structural color adhesive changes from blue to orange under shear force.

[0098] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a structural color adhesive, characterized in that, The process includes the following steps: (1) dispersing magnetic colloidal particles and photoinitiator in polymer monomers to obtain a precursor dispersion; or dispersing magnetic colloidal particles, polymer monomers, and photoinitiator in a solvent to obtain a precursor dispersion; (2) applying a magnetic field to the precursor dispersion obtained in step (1), wherein the magnetic colloidal particles are arranged in an orderly manner under the action of the magnetic field to generate structural color, and then undergoing radiation curing to obtain a structural color binder; wherein the magnetic colloidal particles are iron oxide colloidal particles or paramagnetic iron oxide colloidal particles with a shell layer; wherein the paramagnetic iron oxide colloidal particles with a shell layer are iron oxide colloidal particles with a silica shell layer or The polymer monomers are acrylate monomers and / or methacrylate monomers; the photoinitiator is 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxycyclohexylphenyl ketone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, p-tert-butyltrichloroacetophenone, benzophenone, 2,4-diisopropylthioxanthone, 4,4'-dichlorobenzophenone, 4,4'-bis(dimethylamino)benzophenone, 3,3'-dimethyl-4-methoxybenzophenone, 2,2-diethoxyacetophenone, acetophenone diethyl ketal, or 4'-isopropyl-2-hydroxy-2-methylacetophenone.

2. The method for preparing the structural color adhesive as described in claim 1, characterized in that, The mass fraction of magnetic colloidal particles in the precursor dispersion ranges from 1% to 10%.

3. The method for preparing the structural color adhesive as described in claim 1, characterized in that, The magnetic colloidal particles are sized in the range of 100-400 nm.

4. A method for preparing a structural color adhesive, characterized in that, The process includes the following steps: (1) dispersing non-magnetic colloidal particles, polymer monomers, and photoinitiators in a solvent to obtain a dispersion; evaporating the solvent in a thermal field placed in a dark environment to obtain a precursor dispersion with structural color; (2) subjecting the precursor dispersion with structural color obtained in step (1) to radiation curing to obtain a structural color binder; wherein the non-magnetic colloidal particles are zirconium dioxide colloidal particles, silica colloidal particles, titanium dioxide colloidal particles, or cerium oxide colloidal particles; and the polymer monomers are acrylate monomers and / or methyl acrylate monomers. The photoinitiator is a basic acrylate monomer; the photoinitiator is 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxycyclohexylphenyl ketone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, p-tert-butyltrichloroacetophenone, benzophenone, 2,4-diisopropylthioxanthone, 4,4'-dichlorobenzophenone, 4,4'-bis(dimethylamino)benzophenone, 3,3'-dimethyl-4-methoxybenzophenone, 2,2-diethoxyacetophenone, acetophenone diethyl ketal, or 4'-isopropyl-2-hydroxy-2-methylphenylpropanone.

5. The method for preparing the structural color adhesive as described in claim 4, characterized in that, The volume fraction of non-magnetic colloidal particles in the dispersion ranges from 30% to 80%.

6. The method for preparing the structural color adhesive as described in claim 4, characterized in that, The size distribution of the non-magnetic colloidal particles is 100-400 nm.

7. The structural color adhesive prepared by any one of claims 1-5, characterized in that, The structural color adhesive can change color under external force, and the color can be restored when the external force is removed.

8. The structural color adhesive as described in claim 7, characterized in that, The external force is tension, compression, or shear.

9. The structural color adhesive as described in claim 7 or 8 is used for monitoring changes in bond strength or for stress detection under load.

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