A magnetically responsive photonic crystal structured color microcapsule

Abstract

The invention relates to a magnetic responsive photonic crystal structural color microcapsule, wherein the magnetic colloid dispersion is obtained by dispersing Fe3O4@SiO2 magnetic nanoparticles in deionized water; the magnetic colloid dispersion is then added to a PLA solution containing a lipophilic emulsifier for emulsification and shearing to obtain W / O emulsion droplets; the W / O emulsion droplets are added to water containing a hydrophilic emulsifier for emulsification and shearing to obtain W / O / W double emulsion droplets; and finally the W / O / W double emulsion droplets are placed in an oven for drying, so that the solvent in the oil phase evaporates and PLA is cross-linked to form a solid shell layer that wraps the magnetic colloid aqueous dispersion. The invention prepares the W / O / W double emulsion droplets by a double emulsion shearing method, encapsulates the magnetic photonic crystal colloid droplets inside the PLA polymer shell layer, and realizes the preparation of the magnetic responsive photonic crystal structural color microcapsules.

Description

Technical Field

[0001] The invention relates to the technical field of structural color microcapsules, in particular to a magnetic response photonic crystal structural color microcapsule. Background Art

[0002] Photonic crystals are a type of periodic dielectric structure with a photonic band gap, usually composed of two or more media with different dielectric constants. The most basic feature of photonic crystals is that they have a photonic band gap, and light of a specific frequency is prohibited from propagating within the band gap. These prohibited lights will be selectively reflected by the crystal structure, forming coherent diffraction on the surface of the periodic structure. When the light of these frequencies falls within the visible light range, it can be perceived by the human eye, thus forming a gorgeous structural color. Magnetic responsive photonic crystals are a special photonic crystal color-forming structure formed by assembling magnetic nanoparticles as assembly primitives under the action of a magnetic field. Under the action of a magnetic field, the magnetic nanoparticles in the colloid form a regular and orderly one-dimensional chain structure through the balance of magnetic field force and electrostatic repulsion between each other. By changing the applied magnetic field strength, the distance between particles in the one-dimensional chain structure can be regulated, thereby realizing the response change of the presented structural color to the applied magnetic field. It has the advantages of fast response rate and high sensitivity, and has broad application prospects in the fields of photonic printing, intelligent anti-counterfeiting and display.

[0003] However, the assembly and regulation of photonic crystal structures by magnetic fields currently only exist in liquid colloidal systems. In practical applications, they are mostly magnetically assembled in liquid state and then stably fixed in solid polymer matrix, thus presenting stable structural color. However, this ultimately leads to the loss of the ability to respond to magnetic fields and change color. Therefore, the realization of magnetic response assembly regulation in solid form is of great significance to the development and practical application of photonic crystals in the fields of intelligent anti-counterfeiting and display. Summary of the invention

[0004] The present invention provides a magnetic responsive photonic crystal structural color microcapsule and a preparation method thereof. The preparation method of the present invention is to design and prepare a double emulsion droplet with ferroferric oxide@silicon dioxide (Fe3O4@SiO2) magnetic colloidal dispersion as an inner aqueous phase, a polylactic acid (PLA) solution as an oil phase, and water-in-oil-in-water (W / O / W) as an outer aqueous phase by a double-step emulsification shearing method, and the PLA shell is solidified and cross-linked by evaporating the solvent in the oil phase to obtain a solid magnetic responsive photonic crystal structural color microcapsule.

[0005] A method for preparing a magnetically responsive photonic crystal structured color microcapsule comprises the following steps:

[0006] Step 1: Disperse Fe3O4@SiO2 magnetic nanoparticles in deionized water and perform ultrasonic treatment to obtain Fe3O4@SiO2 magnetic colloidal dispersion as the aqueous phase in the microcapsule;

[0007] Step 2: Add the lipophilic emulsifier and polylactic acid (PLA) to the oil phase solvent, stir, and prepare an oil phase solution; add the Fe3O4@SiO2 magnetic colloidal dispersion to the oil phase solution, stir again, and perform the first step of emulsification shearing to obtain a W / O emulsion;

[0008] Step 3: adding a hydrophilic emulsifier into water and stirring to prepare an external aqueous phase of the microcapsules; adding W / O emulsion droplets into the external aqueous phase of the microcapsules, stirring again, and performing a second step of emulsification and shearing to obtain a W / O / W double emulsion;

[0009] Step 4: drying the W / O / W double emulsion droplets in an oven to volatilize the solvent in the oil phase and cross-link the polylactic acid to form a solid shell layer, thereby obtaining photonic crystal structure color microcapsules encapsulating the magnetic colloid aqueous dispersion.

[0010] In the step 1, the particle size of the Fe3O4@SiO2 magnetic nanoparticles is 100-200 nm; in the Fe3O4@SiO2 colloidal dispersion, the mass fraction of the Fe3O4@SiO2 nanoparticles in deionized water is 0.1-5 wt%; and the monodispersity index of the Fe3O4@SiO2 nanoparticles is less than 0.2.

[0011] In the step 2, the lipophilic emulsifier is selected from one of EM90, Span 80, and KF-6017; the concentration of the lipophilic emulsifier in the oil phase solvent is 0.5-2.0 wt%; the solvent of the oil phase solvent is selected from one or more of dichloromethane, chloroform, and ethyl acetate; the mass concentration of PLA in the oil phase solvent is 5-15 wt%.

[0012] In the step 2, the volume ratio of the Fe3O4@SiO2 magnetic colloid dispersion to the oil phase solution is 1:20-1:5.

[0013] The shearing speed of the first step of emulsification shearing is 250-2500 rpm.

[0014] In the step 3, the hydrophilic emulsifier is selected from one or more of polyvinyl alcohol (PVA), AEO-9, and Tween-80; the concentration of the hydrophilic emulsifier in the external aqueous phase is 0.5-2.0 wt%.

[0015] In the step 3, the volume ratio of the W / O emulsion droplets to the external water phase is 1:10-1:2.5.

[0016] In the step three, the shearing speed of the second emulsification shearing step is 250-2500 rpm.

[0017] In the step 4, the drying temperature is 25-50°C.

[0018] A magnetic response photonic crystal structure color microcapsule is prepared by the above preparation method.

[0019] Application of magnetically responsive photonic crystal structural color microcapsules in magnetochromic materials.

[0020] The magnetic response range of the magnetochromic material is 100-3000 Gs. Beneficial Effects

[0021] The present invention realizes the application of the solid form of magnetically responsive photonic crystals by sealing the magnetically responsive photonic crystal droplets inside the polymer shell layer, and has the advantages of simple operation, low cost, and large-scale preparation.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] (1) The double emulsion shear method is used to prepare W / O / W double emulsion droplets. Compared with the existing oil film emulsification method and microfluidic method, it does not require complex equipment, is simple to operate, and is suitable for large-scale preparation.

[0024] (2) PLA is used as the shell layer of structural color microcapsules, which has the characteristics of good biocompatibility and biodegradability.

[0025] (3) The magnetically responsive photonic crystal colloidal dispersion is encapsulated in the form of droplets inside a polymer shell, thus achieving magnetic response regulation of the photonic crystal structural color in a solid state. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 : Optical photographs of W / O emulsion and W / O / W double emulsion droplets prepared in Example 1 of the present invention.

[0027] Figure 2 : SEM photograph of the magnetically responsive photonic crystal microcapsule prepared in Example 2 of the present invention.

[0028] Figure 3 : Optical photographs of the magnetically responsive photonic crystal microcapsules prepared in Example 1 of the present invention with and without a magnetic field applied.

[0029] Figure 4 : The color change of the magnetically responsive photonic crystal microcapsule prepared in Example 3 of the present invention when different magnetic fields are applied. DETAILED DESCRIPTION

[0030] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention. Example 1

[0031] This embodiment provides a magnetic responsive photonic crystal structured color microcapsule and a preparation method thereof, the specific steps of the method are:

[0032] (1) Fe3O4@SiO2 magnetic nanoparticles with a particle size of 130 nm were ultrasonically dispersed in deionized water at a mass fraction of 1 wt%.

[0033] (2) PLA and EM90 were added to dichloromethane in a mass ratio of 8 wt% and 1 wt%, respectively, and mechanically stirred to fully dissolve them to form an oil phase; the Fe3O4@SiO2 colloidal dispersion in step (1) was added to the oil phase as an inner water phase, and emulsified at a mechanical stirring speed of 2000 rpm to form W / O emulsion droplets, in which the volume ratio of the inner water phase to the oil phase was 1:10.

[0034] (3) PVA was added to deionized water at a mass ratio of 1 wt%, and mechanically stirred to fully dissolve it to form an external aqueous phase; the W / O emulsion droplets obtained in step (2) were added to the external aqueous phase, and secondary emulsification was performed at a mechanical stirring speed of 2000 rpm to form W / O / W double emulsion droplets, wherein the volume ratio of the W / O emulsion to the external aqueous phase was 1:5. Optical photographs of the W / O emulsion and the W / O / W double emulsion droplets, as shown in FIG. Figure 1 shown.

[0035] (4) The W / O / W double emulsion droplets obtained above are placed in an oven at a temperature of 37°C to dry to obtain magnetically responsive photonic crystal structured color microcapsules. Example 2

[0036] The difference between this embodiment and embodiment 1 is that the particle size and mass fraction of the Fe3O4@SiO2 magnetic nanoparticles added are different, and the other operation steps are the same. The SEM photo of the magnetic responsive photonic crystal microcapsule prepared in this embodiment is as follows: Figure 2 shown.

[0037] (1) Fe3O4@SiO2 magnetic nanoparticles with a particle size of 150 nm were ultrasonically dispersed in deionized water at a mass fraction of 0.5 wt%.

[0038] (2) PLA and EM90 were added to dichloromethane in a mass ratio of 8 wt % and 1 wt %, respectively, and mechanically stirred to fully dissolve them to form an oil phase; the Fe3O4@SiO2 colloidal dispersion in step (1) was added to the oil phase as an inner water phase, and emulsified at a mechanical stirring speed of 1000 rpm to form W / O emulsion droplets, wherein the volume ratio of the inner water phase to the oil phase was 1:10.

[0039] (3) Same as Example 1.

[0040] (4) Same as Example 1. Example 3

[0041] (1) Fe3O4@SiO2 magnetic nanoparticles with a particle size of 150 nm were ultrasonically dispersed in deionized water at a mass fraction of 1 wt%.

[0042] (2) PLA and Siban 80 were added to dichloromethane in a mass ratio of 6 wt % and 1 wt %, respectively, and mechanically stirred to fully dissolve them to form an oil phase; the Fe3O4@SiO2 colloidal dispersion in step (1) was added to the oil phase as the inner water phase, and emulsified at a mechanical stirring speed of 500 rpm to form W / O emulsion droplets, in which the volume ratio of the inner water phase to the oil phase was 1:5.

[0043] (3) Same as Example 1.

[0044] (4) Same as Example 1. Example 4

[0045] This embodiment provides a magnetic responsive photonic crystal structured color microcapsule and a preparation method thereof, the specific steps of the method are:

[0046] (1) Same as Example 1.

[0047] (2) Same as Example 1.

[0048] (3) AEO-9 was added into deionized water at a mass ratio of 2 wt%, and the mixture was fully dissolved after mechanical stirring to form an external aqueous phase; the W / O emulsion droplets obtained in step (2) were added into the external aqueous phase, and secondary emulsification was performed at a mechanical stirring speed of 1000 rpm to form W / O / W double emulsion droplets, wherein the volume ratio of the W / O emulsion to the external aqueous phase was 1:10.

[0049] (4) The W / O / W double emulsion droplets obtained above are placed in an oven at a temperature of 37°C to dry to obtain magnetically responsive photonic crystal structured color microcapsules. Example 5

[0050] This embodiment provides a magnetic responsive photonic crystal structured color microcapsule and a preparation method thereof, the specific steps of the method are:

[0051] (1) Fe3O4@SiO2 magnetic nanoparticles with a particle size of 130 nm were ultrasonically dispersed in deionized water at a mass fraction of 5 wt%.

[0052] (2) PLA and KF-6017 were added to dichloromethane in a mass ratio of 8 wt% and 2 wt%, respectively, and mechanically stirred to fully dissolve them to form an oil phase; the Fe3O4@SiO2 colloidal dispersion in step (1) was added to the oil phase as an inner water phase, and emulsified at a mechanical stirring speed of 2000 rpm to form W / O emulsion droplets, wherein the volume ratio of the inner water phase to the oil phase was 1:10.

[0053] (3) Tween-80 was added to deionized water at a mass ratio of 2 wt%, and the mixture was fully dissolved after mechanical stirring to form an external aqueous phase; the W / O emulsion droplets obtained in step (2) were added to the external aqueous phase, and secondary emulsification was performed at a mechanical stirring speed of 1000 rpm to form W / O / W double emulsion droplets, wherein the volume ratio of the W / O emulsion to the external aqueous phase was 1:2.5.

[0054] (4) The W / O / W double emulsion droplets obtained above are placed in an oven at a temperature of 25°C to dry to obtain magnetically responsive photonic crystal structured color microcapsules.

[0055] Figure 1 1 is an optical photograph of the W / O emulsion and W / O / W double emulsion droplets prepared in Example 1. It can be seen from the figure that the morphology of the emulsion droplets is relatively regular; Figure 2 is a SEM photograph of the magnetically responsive photonic crystal microcapsule prepared in Example 2. It can be seen from the figure that the microcapsule has a relatively good regular morphology; Figure 3 are optical photographs of the magnetically responsive photonic crystal microcapsules prepared in Example 1 with and without a magnetic field applied; Figure 4 : The color changes of the magnetically responsive photonic crystal microcapsules prepared in Example 3 of the present invention when different magnetic fields are applied show that the microcapsules can show different color changes as the magnetic field strength changes, and can be applied in different application scenarios of magnetochromic materials.

[0056] Obviously, the above embodiments are merely examples for the purpose of clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. And the obvious changes or modifications derived therefrom.

Claims

1. A method for preparing a magnetically responsive photonic crystal structured color microcapsule, comprising the following steps: Step 1: Disperse Fe3O4@SiO2 magnetic nanoparticles in deionized water and perform ultrasonic treatment to obtain Fe3O4@SiO2 magnetic colloidal dispersion as the aqueous phase in the microcapsule; Step 2: adding a lipophilic emulsifier and polylactic acid to an oil phase solvent, stirring to prepare an oil phase solution; adding a Fe3O4@SiO2 magnetic colloidal dispersion to the oil phase solution, stirring again, and performing the first step of emulsification shearing to obtain a W / O emulsion; the lipophilic emulsifier is selected from one of EM90, Span 80, and KF-6017; the solvent of the oil phase solvent is selected from one or more of dichloromethane, chloroform, and ethyl acetate; Step 3: adding a hydrophilic emulsifier into water and stirring to prepare an external aqueous phase of the microcapsule; adding W / O emulsion droplets into the external aqueous phase of the microcapsule, stirring again, and performing a second step of emulsification and shearing to obtain a W / O / W double emulsion; the hydrophilic emulsifier is selected from one or more of polyvinyl alcohol (PVA), AEO-9, and Tween-80; Step 4: drying the W / O / W double emulsion droplets in an oven to volatilize the solvent in the oil phase and cross-link the polylactic acid to form a solid shell layer, thereby obtaining photonic crystal structure color microcapsules encapsulating the magnetic colloid aqueous dispersion.

2. The preparation method according to claim 1, characterized in that: In the step 1, the particle size of the Fe3O4@SiO2 magnetic nanoparticles is 100-200nm; in the Fe3O4@SiO2 colloidal dispersion, the mass fraction of the Fe3O4@SiO2 nanoparticles in deionized water is 0.1-5wt%; and the monodispersity index of the Fe3O4@SiO2 nanoparticles is less than 0.

2.

3. The preparation method according to claim 1, characterized in that: In the step 2, the concentration of the lipophilic emulsifier in the oil phase solvent is 0.5-2.0 wt %; the mass concentration of PLA in the oil phase solvent is 5-15 wt %.

4. The preparation method according to claim 1, characterized in that: In the step 2, the volume ratio of the Fe3O4@SiO2 magnetic colloid dispersion to the oil phase solution is 1:20 to 1:

5.

5. The preparation method according to claim 1, characterized in that: The shearing speed of the first step of emulsification shearing is 250-2500rpm.

6. The preparation method according to claim 1, characterized in that: In the step 3, the concentration of the hydrophilic emulsifier in the external water phase is 0.5-2.0 wt %.

7. The preparation method according to claim 1, characterized in that: In the step three, the volume ratio of the W / O emulsion droplets to the external water phase is 1:10-1:2.5, and the shear rate of the second emulsification shearing step is 250-2500rpm.

8. A magnetically responsive photonic crystal structured color microcapsule obtained by the preparation method according to any one of claims 1 to 7.

9. Use of the magnetically responsive photonic crystal structured color microcapsules according to claim 8 in magnetochromic materials.

10. The use according to claim 9, characterized in that The magnetic response range of the magnetochromic material is 100-3000Gs.

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