Temperature and near-infrared light double-response structural color pigment and preparation method thereof

Abstract

The invention discloses a preparation method of a temperature and near-infrared light dual-response structural color pigment, which comprises the following steps: dispersing silicon dioxide nano-microspheres in a buffer solution, adjusting the pH value to 7-9, adding a phenolic compound and metal ions into the buffer solution, mixing, reacting, dispersing and centrifuging to obtain nano-microspheres; dispersing the nano microspheres into a dispersion liquid, and adding an accelerator into the dispersion liquid to obtain a gel pre-polymerization liquid; the dispersion liquid contains a thermo-sensitive polymer monomer, a cross-linking agent and an initiator; taking the gel pre-polymerized liquid as an internal water phase, taking chloroform containing polylactic acid and a surfactant as an oil phase, mixing, and preparing a water-in-oil emulsion by adopting vortex oscillation; placing the water-in-oil emulsion at the bottom of a PVA-containing solution, and preparing a water-in-oil-in-water double emulsion by adopting vortex oscillation again; and transferring the oil-in-water-in-oil-in-water double emulsion into a PVA (Polyvinyl Alcohol) solution, and standing to obtain the temperature and near-infrared light double-response structural color pigment.

Description

Technical Field

[0001] The invention relates to the technical field of structural color pigments, and in particular to a method for preparing a structural color pigment having response characteristics to temperature and near-infrared light, and a structural color pigment prepared by the preparation method. Background Art

[0002] Structural color is a color phenomenon caused by the microstructure of a material rather than chemical pigments, and its color comes from the interference, scattering and diffraction of light.

[0003] In recent years, in order to achieve dynamic control of structural color, periodic photonic structures are usually embedded or encapsulated into polymer elastomers (such as polyurethane PU, polydimethylsiloxane PDMS) or responsive hydrogels (such as poly (N-isopropylacrylamide) PNIPAM, polyacrylamide PAm), etc. When these polymer matrices are stimulated by the external environment, they will expand or contract, causing changes in the lattice constant or the geometric shape of the scatterer, and ultimately showing changes in the corresponding optical properties.

[0004] In the past 10 years, this periodic photonic structure embedded in hydrogel has enabled structural chromogenic materials to develop from static materials to smart responsive materials that can adapt to various stimuli (such as pH, temperature, chemistry, electricity or light). However, existing structural color microspheres can usually only respond to a single external stimulus (such as temperature, humidity or light), which limits their application in complex environments.

[0005] For example, patent CN114989347B, thermosensitive photonic crystal gel microspheres with a wide response range and a high response rate and a preparation method thereof, the prepared gel microspheres only have response characteristics to the external temperature, and the prepared photonic crystal embedded hydrogel microspheres are usually prone to rupture, which seriously affects their actual use.

[0006] The disclosure of the above background technology content is only used to assist in understanding the inventive concept and technical solution of the present invention. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above content has been disclosed before the filing date of this patent application, the above background technology should not be used to evaluate the novelty and creativity of the present application. Summary of the invention

[0007] In view of this, in order to overcome the defects of the prior art, the purpose of the present invention is to provide a method for preparing a structural color pigment that is dual-responsive to temperature and near-infrared light, which has response characteristics to both temperature and near-infrared light.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A method for preparing a temperature and near-infrared light dual-responsive structural color pigment comprises the following steps:

[0010] The silicon dioxide nanospheres are dispersed in a buffer solution, the pH value is adjusted to 7-9, and a phenolic compound and a metal ion are added to the buffer solution, mixed and reacted, and then ultrasonically dispersed and centrifuged to obtain nanospheres;

[0011] Dispersing the nano-microspheres into a dispersion liquid, and adding an accelerator to the dispersion liquid to obtain a gel prepolymer liquid; the dispersion liquid contains a thermosensitive polymer monomer, a cross-linking agent and an initiator;

[0012] The gel prepolymer solution is used as an inner water phase, and chloroform containing polylactic acid and a surfactant is used as an oil phase, and after mixing, a water-in-oil emulsion is prepared by vortex oscillation;

[0013] The water-in-oil emulsion is placed on the bottom of the PVA solution, and vortex oscillation is used again to prepare a water-in-oil-in-water double emulsion;

[0014] The water-in-oil-in-water double emulsion is transferred into a PVA solution, and after standing, a temperature- and near-infrared-light-dual-responsive structural color pigment is obtained.

[0015] According to some preferred embodiments of the present invention, the steps include purification: centrifuging the structural color pigment that responds to both temperature and near-infrared light, decanting the supernatant and redispersing it in deionized water to obtain a purified structural color pigment that responds to both temperature and near-infrared light.

[0016] According to some preferred embodiments of the present invention, the buffer solution is a 8-12 mmol / L Tris buffer solution.

[0017] According to some preferred embodiments of the present invention, the reaction is carried out at 20-60° C. for 50-70 min.

[0018] According to some preferred embodiments of the present invention, the concentration of the silica nanoparticles in the buffer solution is 10-20 g / L; the diameter of the silica nanoparticles is 150-300 nm, the sphericity is good, and the monodispersity index is less than 0.1. Preferably, the silica nanoparticles include microparticles of various diameters, such as 170-190 nm, 200-210 nm, and 250-270 nm, to form structural color pigments with different colors in the initial state.

[0019] According to some preferred implementation aspects of the present invention, the phenolic compound is one or more of dopamine, tannic acid and caffeic acid; and the concentration of the phenolic compound in the buffer solution is 0.01-20 g / L.

[0020] According to some preferred implementation aspects of the present invention, the metal ions are iron ions and / or copper ions; and the concentration of the metal ions in the buffer solution is 0.01-0.4 g / L.

[0021] According to some preferred embodiments of the present invention, an oxidant is added together with the phenolic compound and the metal ions, and the oxidant is one or more selected from sodium perborate, potassium perborate, hydrogen peroxide, ammonium persulfate and sodium percarbonate; and the concentration of the oxidant in the buffer solution is 0-0.5 g / L.

[0022] According to some preferred implementation aspects of the present invention, the temperature-sensitive polymer monomer is N-isopropylacrylamide; the cross-linking agent is NN-methylenebisacrylamide; the initiator is ammonium persulfate; and the accelerator is N,N,N′,N′-tetramethylethylenediamine.

[0023] According to some preferred embodiments of the present invention, the mass fraction of nanospheres in the dispersion is 40-60wt%; the concentration of the thermosensitive polymer monomer in the dispersion is 50-200g / L; the concentration of the crosslinker in the dispersion is 1.5-6g / L; the concentration of the initiator in the dispersion is 1-5g / L; and the concentration of the accelerator in the gel prepolymer solution is 2-5μL / mL.

[0024] According to some preferred embodiments of the present invention, the volume ratio of the inner water phase to the oil phase is 1:4-10.

[0025] According to some preferred implementation aspects of the present invention, the concentration of polylactic acid in the oil phase is 30-100 g / L; the mass fraction of the surfactant in the oil phase is 1-5 wt %. The preferred surfactant is Span 80.

[0026] According to some preferred embodiments of the present invention, when preparing the water-in-oil emulsion, the vortex oscillation speed is 1000-2000 rpm and the time is 10-60 s.

[0027] According to some preferred embodiments of the present invention, when preparing the water-in-oil-in-water double emulsion, the concentration of the PVA solution is 1%-2%; the volume ratio of the water-in-oil emulsion to the PVA solution is 1:1-5; the vortex oscillation speed is 10000-20000rpm, and the time is 10-60s.

[0028] According to some preferred implementation aspects of the present invention, when preparing the structural color pigment with dual response to temperature and near-infrared light, the concentration of the PVA solution is 1%-2%, and the volume is 200-1000 mL.

[0029] In some embodiments, the method for preparing a structural color pigment having response characteristics to both temperature change and near-infrared light of the present invention comprises the following steps:

[0030] S1. Disperse an appropriate amount of spherical and monodisperse silica nanoparticles in a buffer solution, adjust the pH to 7-9, add phenolic compounds, metal ions and oxidants, stir and react at 20-60° C. for 50-70 min, and after the reaction is completed, disperse by ultrasound and centrifuge to obtain nanoparticles coated with polyphenol polymers and metal-polyphenol complexes;

[0031] S2. Dispersing the prepared core-shell nanospheres at a mass fraction of 40-60 wt % into a dispersion solution containing a thermosensitive polymer monomer N-isopropylacrylamide NIPAM, a crosslinking agent NN-methylenebisacrylamide BIS and an initiator ammonium persulfate APS, and adding an accelerator N,N,N′,N′-tetramethylethylenediamine TEMED to the above dispersion to obtain a gel prepolymer solution;

[0032] S3. The prepared gel prepolymer solution was used as the inner aqueous phase, and chloroform containing polylactic acid and surfactant Span 80 was used as the oil phase. The two were added to a centrifuge tube in a volume ratio of 1:4-10 and then vortexed to prepare an oil-in-water emulsion;

[0033] S4. Quickly transfer a certain amount of the water-in-oil emulsion to the bottom of the centrifuge tube containing the PVA solution, and vortex oscillation is used again to prepare a water-in-oil-in-water double emulsion;

[0034] S5. The obtained water-in-oil-in-water double emulsion is transferred to a large amount of PVA solution and allowed to stand for 22-26 hours. After the double emulsion droplets are "solidified", a core-shell structural color pigment with bright color and responsive characteristics to temperature and near-infrared light can be obtained. The prepared structural color pigment can be purified by centrifuging the solution, decanting the supernatant and redispersing it in deionized water.

[0035] The present invention also provides a structural color pigment prepared according to the preparation method as described above, which has bright colors and has the characteristics of responding to temperature changes and near-infrared light.

[0036] The principle of the present invention is as follows: the structural color pigment prepared by the present invention is composed of a hard PLA (polylactic acid) shell layer and a structural color gel core having both responsive characteristics to temperature changes and near-infrared light. Among them, the nano-microspheres coated with polyphenol polymers and metal-polyphenol complexes are arranged in the form of amorphous colloid arrays in a high molecular polymer PNIPAM matrix having responsive characteristics to temperature changes. The excellent photothermal conversion ability of the polyphenol polymers and metal-polyphenol complexes enables the distance between the core-shell nano-microspheres to be reversibly adjusted by controlling the temperature and near-infrared light, thereby realizing the reversible change of the color of the structural color pigment. When the temperature is increased, when the temperature of the environment is higher than the lowest dissolution temperature of the PNIPAM matrix, the contraction of the PNIPAM matrix will cause the distance between the nano-microspheres to decrease; when the temperature is reduced, when the temperature of the environment is lower than or equal to the lowest dissolution temperature of the PNIPAM matrix, the PNIPAM matrix will expand again, the size will return to the original state, the distance between the nano-microspheres will increase, and it will also return to the original state. In addition, the solid PLA shell protects the soft hydrogel core, which can effectively improve the structural strength of the photon microspheres.

[0037] Compared with the existing traditional technology, the advantages of the present invention are: the preparation method of the structural color pigment with dual response to temperature and near-infrared light of the present invention, the prepared structural color pigment has dual response characteristics of temperature and near-infrared light, and can adapt to a variety of application scenarios; the structural color pigment has a simple structure, and the color change is fast and reversible; the preparation method is easy to operate and easy to achieve large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0039] Figure 1 The scanning electron microscope image (a) and the transmission electron microscope image (b) of the cross section of the structural color pigment having the characteristics of responding to both temperature change and near-infrared light prepared in Example 1 of the present invention;

[0040] Figure 2 It is a total reflection spectrum and an optical image of the structural color pigment having response characteristics to both temperature change and near-infrared light prepared in Example 1 of the present invention;

[0041] Figure 3These are digital photos of the structural color pigment having response characteristics to both temperature change and near-infrared light prepared in Example 1 of the present invention under temperature (a) and near-infrared light (d) stimulation; changes in the reflection spectrum after experiencing thermal stimulation (b) and near-infrared stimulation (e); and reversible changes in the reflection peak position after experiencing thermal stimulation (c) and near-infrared light stimulation (f). DETAILED DESCRIPTION

[0042] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0043] Based on the photothermal conversion capability of polyphenol polymers and metal-polyphenol complexes, the present invention provides a structural color pigment that has response characteristics to both temperature changes and near-infrared light. The pigment has a stable structure and dynamic structural color expression, and can achieve color changes under external temperature changes or near-infrared light irradiation. It is suitable for application scenarios such as sensors, smart displays and photothermal conversion.

[0044] Specifically, the method for preparing a structural color pigment having response characteristics to both temperature change and near-infrared light of the present invention comprises the following steps:

[0045] Step 1: Preparation of nanospheres

[0046] An appropriate amount of silica nanoparticles with good sphericity and monodispersity are dispersed in a Tris buffer solution with a concentration of 8-12 mmol / L, the pH value is adjusted to 7-9, phenolic compounds, metal ions and oxidants are added, and the reaction is carried out at 20-60° C. for 50-70 minutes. After the reaction is completed, ultrasonic dispersion and centrifugation are performed to collect the nanoparticles coated with polyphenol polymers and metal-polyphenol complexes.

[0047] The phenolic compound is one or more of dopamine, tannic acid and caffeic acid; the metal ion is iron ion and / or copper ion; the oxidant is one or more of sodium perborate, potassium perborate, hydrogen peroxide, ammonium persulfate and sodium percarbonate. The concentration of the phenolic compound in the buffer solution is 0.01-20 g / L, the concentration of the metal ion is 0.01-0.4 g / L, and the concentration of the oxidant is 0-0.5 g / L.

[0048] The concentration of the silicon dioxide nano-microspheres in the buffer solution is 10-20 g / L; the diameter of the silicon dioxide nano-microspheres is 150-300 nm, the sphericity is good, and the monodispersity index of the microspheres is less than 0.1.

[0049] Step 2: Prepare gel prepolymer solution

[0050] The prepared core-shell nanospheres are dispersed in a dispersion solution containing a thermosensitive polymer monomer N-isopropylacrylamide NIPAM, a crosslinker NN-methylenebisacrylamide BIS and an initiator ammonium persulfate APS at a mass fraction of 40-60wt%, and an accelerator N,N,N′,N′-tetramethylethylenediamine TEMED is added to the above dispersion to obtain a gel prepolymer solution.

[0051] The concentration of N-isopropylacrylamide NIPAMN in the dispersed solution is 50-200 g / L; the concentration of NN-methylenebisacrylamide BIS is 1.5-6 g / L; the concentration of ammonium persulfate APS is 1-5 g / L; and the concentration of N,N,N′,N′-tetramethylethylenediamine (TEMED) in the gel prepolymer solution is 2-5 μL / mL.

[0052] Step 3: Preparation of water-in-oil emulsion

[0053] The prepared gel prepolymer solution was used as the inner water phase, and chloroform containing polylactic acid and surfactant Span 80 was used as the oil phase. The two were added into a centrifuge tube at a volume ratio of 1:4-10 and then vortexed to prepare a water-in-oil emulsion.

[0054] The concentration of polylactic acid in chloroform is 30-100 g / L, and the mass fraction of Span 80 is 1-5 wt %.

[0055] The vortexing speed is 1000-2000 rpm and the time is 10-60 s.

[0056] Step 4: Preparation of water-in-oil-in-water double emulsion

[0057] Then, the water-in-oil emulsion was quickly transferred to the bottom of the centrifuge tube containing the PVA solution, and vortex oscillation was used again to prepare the water-in-oil-in-water double emulsion.

[0058] The concentration of the PVA solution is 1%-2%, and the volume ratio of the water-in-oil emulsion to the PVA solution is 1:1-1:5.

[0059] The vortexing speed is 10000-20000 rpm, and the time is 10-60 s.

[0060] Step 5: Preparation of core-shell structural color pigments

[0061] The obtained water-in-oil-in-water double emulsion is transferred to a large amount of PVA solution, and after standing for 24 hours, a core-shell structural color pigment with responsive characteristics to temperature and near-infrared light can be obtained.

[0062] The concentration of PVA solution is 1%-2%, and the volume is 200-1000mL.

[0063] Step 6: Purification

[0064] The prepared structural color pigment is purified by centrifuging the solution, decanting the supernatant and re-dispersing it in deionized water to obtain a purified structural color pigment that responds to both temperature and near-infrared light.

[0065] Example 1

[0066] The method for preparing the structural color pigment having the characteristics of responding to both temperature change and near-infrared light in this embodiment comprises the following steps:

[0067] 420 mg of SiO2 nanoparticles with good sphericity and monodispersity were added to 25 mL of 10 mmol / L Tris buffer solution, pH value was adjusted to 8.5, and ultrasonic treatment was performed for 20 minutes. SiO2 nanoparticles with different particle sizes were selected to prepare structural color pigments with different initial state colors.

[0068] 20 mg of dopamine hydrochloride and 8 mg of CuCl2 were added to the above buffer solution. After continuous shaking for 1 hour at room temperature, the obtained SiO2@PDA core-shell nanospheres were repeatedly centrifuged and dispersed for 3 times.

[0069] The washed SiO2@PDA nanospheres were dispersed into a solution containing NIPAM (100 g / L), BIS (4 g / L) and APS (2 g / L) at a mass fraction of 60 wt%. Finally, before preparing the responsive structural chromogenic pigment, an accelerator TEMED (5 μL / mL) was added to the above dispersion to obtain a gel prepolymer solution.

[0070] The prepared gel prepolymer solution was used as the inner aqueous phase, and chloroform containing 50 g / L PLA and 2 wt% Span80 was used as the oil phase. The two were added into a 15 mL centrifuge tube at a volume ratio of 1:5, and then vortexed at an oscillation frequency of 1500 rpm for 60 seconds to prepare an oil-in-water emulsion.

[0071] 200 μL of the water-in-oil emulsion was transferred to the bottom of a centrifuge tube containing 500 μL of a 1% PVA aqueous solution, and the mixture was vortexed again at a high speed of 10,000 rpm for 30 s to obtain a water-in-oil-in-water double emulsion.

[0072] The obtained water-in-oil-in-water double emulsion was transferred into 1000 mL of 1% PVA solution and allowed to stand for 24 hours to obtain solid core / shell microspheres.

[0073] The prepared core / shell particles were purified by centrifuging the solution, decanting the supernatant and re-dispersing in deionized water to obtain purified temperature and near-infrared light dual-responsive structural color pigments.

[0074] The scanning electron microscope image of the structural color pigment prepared in this example is as follows Figure 1 As shown in (a), the cross-sectional transmission electron microscopy image is Figure 1 As shown in (b), it can be seen from the figure that the arrangement of nano-microspheres inside the structural color pigment is short-range ordered but long-range disordered. The total reflection spectrum is shown in Figure 2 As shown, the structural color pigment is bright in color, and the optical photograph of the response characteristics is shown in Figure 3 As shown. Figure 3 As can be seen in Figures ac, when the external environment temperature rises, the temperature of the structural color pigment rises, and the gel core embedded in the SiO2@PDA amorphous colloidal array shrinks rapidly, causing the structural color to blue shift; after removing the external stimulus, the structural color can be restored to its original state. Figure 3 As can be seen in the figure, under near-infrared light irradiation, due to the photothermal conversion ability of polydopamine, the temperature of the structural color pigment will also rise, causing the structural color to blue shift. After removing the near-infrared light, the blue shift of the color disappears immediately. Similar to the temperature cycle, under the alternating irradiation of white light and near-infrared light, the switching of the photon microsphere reflection signal is completely reversible.

[0075] Example 2

[0076] The method for preparing the structural color pigment having the characteristics of responding to both temperature change and near-infrared light in this embodiment comprises the following steps:

[0077] 1 g of SiO2 nanospheres with good sphericity and monodispersity were added to 50 mL of 10 mmol / L Tris buffer solution, the pH value was adjusted to 8.3, and ultrasonic treatment was performed for 20 minutes.

[0078] 18 mg of caffeic acid, 6 mg of CuCl2 and 23 mg of NaBO3·4H2O were added to the above buffer solution. After continuous shaking at 60°C for 1 hour, the obtained SiO2@PCfA core-shell nanospheres were repeatedly centrifuged and dispersed and washed three times.

[0079] The washed SiO2@PCfA nanospheres were dispersed into a solution containing NIPAM (150 g / L), BIS (6 g / L) and APS (3 g / L) at a mass fraction of about 55 wt%. Finally, before preparing the responsive structural chromogenic pigment, an accelerator TEMED (5 μL / mL) was added to the above dispersion to obtain a gel prepolymer solution.

[0080] The prepared gel prepolymer solution was used as the inner water phase, and chloroform containing 75 g / L PLA and 2 wt% Span80 was used as the oil phase. The two were added into a 15 mL centrifuge tube at a volume ratio of 1:4, and then vortexed at a frequency of 2000 rpm for 30 seconds to prepare a water-in-oil emulsion.

[0081] 200 μL of the emulsion was transferred and quickly added to the bottom of a centrifuge tube containing 600 μL of a 1.5% PVA aqueous solution, and the mixture was vortexed again at a high speed of 12,000 rpm for 30 s to obtain a water-in-oil-in-water double emulsion.

[0082] The obtained water-in-oil-in-water double emulsion was transferred into 200 mL of 1.5% PVA solution and allowed to stand for 24 hours to obtain solid core / shell microspheres.

[0083] The prepared core / shell particles were purified by centrifuging the solution, decanting the supernatant and re-dispersing in deionized water to obtain purified temperature and near-infrared light dual-responsive structural color pigments.

[0084] Example 3

[0085] The method for preparing the structural color pigment having the characteristics of responding to both temperature change and near-infrared light in this embodiment comprises the following steps:

[0086] 0.8 g of SiO2 nanospheres with good sphericity and monodispersity were added to 50 mL of 10 mmol / L Tris buffer solution, the pH value was adjusted to 8.3, and ultrasonic treatment was performed for 20 minutes.

[0087] 0.51 mg of tannic acid and 0.5 mg of FeCl3 were added to the above buffer solution. After continuous stirring at 50°C for 1 hour, the obtained SiO2@PDA core-shell nanospheres were repeatedly dispersed and washed by centrifugation for 3 times.

[0088] The washed SiO2@PDA nanospheres were dispersed into a solution containing NIPAM (75 g / mL), BIS (2 g / mL) and APS (1 g / L) at a mass fraction of about 50 wt%. Finally, before preparing the responsive structural chromogenic pigment, an accelerator TEMED (2 μL / mL) was added to the above dispersion to obtain a gel prepolymer solution.

[0089] The prepared gel prepolymer solution was used as the inner aqueous phase, and chloroform containing 60 g / L PLA and 1.5 wt% Span 80 was used as the oil phase. The two were added into a 15 mL centrifuge tube at a volume ratio of 1:9, and then vortexed at an oscillation frequency of 1000 rpm for 60 seconds to prepare an oil-in-water emulsion.

[0090] 200 μL of the emulsion was transferred and quickly added to the bottom of a centrifuge tube containing 1 mL of a 2% PVA aqueous solution, and the mixture was vortexed again at a high speed of 15,000 rpm for 20 s to obtain a water-in-oil-in-water double emulsion.

[0091] The obtained water-in-oil-in-water double emulsion was transferred into 500 mL of 2% PVA solution and allowed to stand for 24 hours to obtain solid core / shell microspheres.

[0092] The prepared core / shell particles were purified by centrifuging the solution, decanting the supernatant and re-dispersing in deionized water to obtain purified temperature and near-infrared light dual-responsive structural color pigments.

[0093] The invention discloses a structural color pigment with responsive characteristics to temperature and near-infrared light, and its preparation method comprises the following steps: S1. dispersing an appropriate amount of silicon dioxide nano-microspheres with good sphericity and monodispersity in a buffer solution with a pH value of 7-9, adding phenolic compounds, metal ions and oxidants, reacting at 20-60°C, and after the reaction is completed, ultrasonically dispersing and centrifuging to obtain nano-microspheres coated with polyphenol polymers and metal-polyphenol complexes; S2. dispersing the core-shell nano-microspheres prepared above in a certain mass fraction into a solution containing a temperature-sensitive polymer monomer N-isopropylacrylamide NIPAM, a crosslinking agent NN-methylenebisacrylamide BIS and an initiator ammonium persulfate APS, and adding an accelerator; S3. using the prepared dispersion as an inner aqueous phase, adding a solution containing polylactic acid and a surfactant Span 80% chloroform is used as the oil phase, and after adding it to a centrifuge tube, a vortex oscillation is used to prepare an oil-in-water emulsion; S4. The oil-in-water emulsion is quickly transferred to the bottom of the centrifuge tube containing the PVA solution, and a water-in-oil-in-water double emulsion is prepared by vortex oscillation again; S5. The obtained water-in-oil-in-water double emulsion is transferred to a large amount of PVA solution, and allowed to stand for 24 hours. After the double emulsion droplets are "solidified", a core-shell structural color pigment with bright color and responsive characteristics to temperature and near-infrared light can be obtained, and the prepared structural color pigment is purified by centrifuging the solution, decanting the supernatant and redispersing it in deionized water. The structural color pigment with responsive characteristics to temperature and near-infrared light of the present invention can realize a visual color response to external temperature changes or near-infrared light irradiation, has a stable structure, and changes in color quickly and reversibly. The preparation method is simple and efficient, and it is easy to realize large-scale production.

[0094] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the contents of the present invention and implement them accordingly. They cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a structural color pigment that responds to both temperature and near-infrared light, characterized in that: The steps include: The silicon dioxide nanoparticles are dispersed in a buffer solution, the pH value is adjusted to 7-9, and a phenolic compound and a metal ion are added to the buffer solution, mixed and reacted, dispersed, and centrifuged to obtain nanoparticles; Dispersing the nano-microspheres into a dispersion liquid, and adding an accelerator to the dispersion liquid to obtain a gel prepolymer liquid; the dispersion liquid contains a thermosensitive polymer monomer, a cross-linking agent and an initiator; The gel prepolymer solution is used as an inner water phase, and chloroform containing polylactic acid and a surfactant is used as an oil phase, and after mixing, a water-in-oil emulsion is prepared by vortex oscillation; The water-in-oil emulsion is placed at the bottom of the PVA solution, and vortex oscillation is used again to prepare a water-in-oil-in-water double emulsion; The water-in-oil-in-water double emulsion is transferred into a PVA solution, and after standing, a temperature- and near-infrared-light-dual-responsive structural color pigment is obtained.

2. The preparation method according to claim 1, characterized in that: The step comprises purification: centrifuging the temperature and near-infrared light dual-responsive structural color pigment, decanting the supernatant and redispersing it in deionized water to obtain a purified temperature and near-infrared light dual-responsive structural color pigment.

3. The preparation method according to claim 1, characterized in that: The concentration of the silicon dioxide nano-microspheres in the buffer solution is 10-20 g / L; the diameter of the silicon dioxide nano-microspheres is 150-300 nm, and the monodispersity index is less than 0.

1.

4. The preparation method according to claim 1, characterized in that: The phenolic compound is one or more of dopamine, tannic acid and caffeic acid; and the concentration of the phenolic compound in the buffer solution is 0.01-20 g / L.

5. The preparation method according to claim 1, characterized in that: The metal ions are iron ions and / or copper ions; the concentration of the metal ions in the buffer solution is 0.01-0.4 g / L.

6. The preparation method according to claim 1, characterized in that: Phenolic compounds and metal ions are added to the buffer solution together with an oxidant, wherein the oxidant is one or more selected from sodium perborate, potassium perborate, hydrogen peroxide, ammonium persulfate and sodium percarbonate; the concentration of the oxidant in the buffer solution is 0-0.5 g / L.

7. The preparation method according to claim 1, characterized in that: The temperature-sensitive polymer monomer is N-isopropyl acrylamide; the cross-linking agent is NN-methylenebisacrylamide; the initiator is ammonium persulfate; and the accelerator is N,N,N′,N′-tetramethylethylenediamine.

8. The preparation method according to any one of claim 1, characterized in that: The mass fraction of nano-microspheres in the dispersion is 40-60wt%; the concentration of the thermosensitive polymer monomer in the dispersion is 50-200g / L; the concentration of the cross-linking agent in the dispersion is 1.5-6g / L; the concentration of the initiator in the dispersion is 1-5g / L; and the concentration of the accelerator in the gel prepolymer solution is 2-5μL / mL.

9. The preparation method according to claim 1, characterized in that: The volume ratio of the inner water phase to the oil phase is 1:4-10.

10. The preparation method according to claim 1, characterized in that: The concentration of polylactic acid in the oil phase is 30-100 g / L; the mass fraction of the surfactant in the oil phase is 1-5 wt %.

11. The preparation method according to claim 1, characterized in that: When preparing the water-in-oil-in-water double emulsion, the volume ratio of the water-in-oil emulsion to the PVA solution is 1:1-5; the concentration of the PVA solution is 1%-2%; when preparing the temperature and near-infrared light dual-responsive structural color pigment, the concentration of the PVA solution is 1%-2%.

12. The preparation method according to claim 1, characterized in that: When preparing water-in-oil emulsion, the vortex oscillation speed is 1000-2000rpm, and the time is 10-60s; when preparing water-in-oil-in-water double emulsion, the vortex oscillation speed is 10000-20000rpm, and the time is 10-60s.

13. A structural color pigment with dual response to temperature and near-infrared light, prepared by the preparation method according to any one of claims 1 to 12.

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