CN115616686A - Photonic crystal film and preparation method and application thereof - Google Patents

Abstract

The invention discloses a preparation method and application of a photonic crystal self-supporting film, and belongs to the technical field of nano materials and functional polymer materials. The invention ingeniously utilizes the high refractive index of the polystyrene in the core of the polystyrene @ silicon dioxide photonic crystal and the solvent resistance of the shell silicon dioxide, and combines with the proper viscosity, wettability and volatilization rate of polymer solutions such as cellulose acetate and the like to successfully prepare various polymer photonic crystal films. The method is applicable to various polymer solutions, and can prepare complex patterns through injection printing, and the prepared photonic crystal film has excellent self-supporting property. The anti-counterfeiting pattern prepared by the method is bright in color and wide in coverage, and the application of the photonic crystal film in the fields of anti-counterfeiting, detection, intelligent windows, color-changing coatings and the like can be expanded.

Description

Photonic crystal film and preparation method and application thereof

Technical Field

The invention belongs to the technical field of nano materials and functional polymer materials, and particularly relates to a preparation method and application of a photonic crystal self-supporting film.

Background

The photonic crystal has bright structural color, and the color reflected by the internal periodic micro-nano structure can change along with the incident light angle, so that the photonic crystal is concerned in the fields of anti-counterfeiting, detection, color-changing coatings and the like. However, the traditional photonic crystal preparation relates to the self-assembly of solid nano microspheres, and the nano microspheres tightly arranged by Van der Waals force lack the interaction, so that the prepared photonic crystal is fragile and cannot be self-supported. The solid sphere-based photonic crystal is soaked by the polymer solution, and the composite film formed after the solvent is volatilized has certain toughness due to the addition of the polymer, so that the problems that the photonic crystal film is difficult to support by itself and the like are hopefully solved. However, inorganic materials such as silica, which have a refractive index similar to that of polymers, cause structural color to disappear due to refractive index matching; organic materials such as polystyrene have poor solvent resistance, and the regular structure is destroyed after being soaked by solvents such as ethanol, acetone and the like, so that the structural color disappears. For the above reasons, it is very difficult to prepare a photonic crystal film having a self-supporting property, and no research on this point has been reported.

The polystyrene @ silicon dioxide core-shell nano particles have a silicon dioxide shell, so that the inner core can be protected from being soaked by a solvent, and the polystyrene inner core can provide refractive index difference, so that the polystyrene @ silicon dioxide photonic crystal can still keep the structural color after being soaked by a polymer. The photonic crystal film can be rapidly prepared by using a roll coating method, and can be formed at room temperature or slightly increased temperature, so that the film forming time and cost are reduced. However, when the particle size of the polystyrene particles in the core is too large (more than 220 nm), the reflection band of the composite film is located in the near infrared region due to the larger refractive index of the polystyrene, and the preparation of the composite film with photon color is limited due to the invisible structural color of the polystyrene; and the small-size polystyrene can display broad-spectrum colors, and is expected to be directly used for preparing the photon composite membrane with the broad-spectrum colors. For injection printing of polymer inks, it is required that the inks have a certain viscosity and the solvent is volatilized quickly to make the printed boundary clear. The preparation method of the photonic crystal film has great application value in the fields of anti-counterfeiting, detection, color-changing coatings and the like.

Disclosure of Invention

The invention discloses a photonic crystal film and a preparation method thereof, wherein polystyrene @ silicon dioxide core-shell nano particles are prepared by using small-size polystyrene nano particles, the nano particles with different core-shell sizes are assembled to obtain photonic crystals with different structural colors, then polymer solution is coated on the photonic crystals, and the solvent is volatilized at room temperature to prepare the polymer photonic crystal film. The photon film prepared by the method has self-supporting property, solves the problems of poor self-supporting property and low light transmittance in the prior art, and can be used in the fields of anti-counterfeiting patterns, detection, color-changing coatings and the like.

The photonic crystal film is realized by the following preparation method:

(1) Preparing polystyrene @ silicon dioxide core-shell nanoparticles by using small-size polystyrene nanoparticles, and growing polystyrene @ silicon dioxide photonic crystals on a substrate through vertical deposition;

(2) And (2) coating a polymer solution on the photonic crystal film obtained in the step (1), evaporating the solvent, and preparing the photonic crystal film with self-supporting performance at room temperature.

The coating is a coating method commonly used in the field, and can be roller coating, injection printing, spin coating and the like. The substrate is made of glass, polyurethane, polyethylene terephthalate and the like.

The small-size polystyrene nano particles refer to polystyrene nanospheres with the diameter of 150-220 nm.

The preparation method of the polystyrene @ silicon dioxide core-shell nano particle comprises the following steps: a, adding styrene, polyvinylpyrrolidone, 2' -azobisisobutylamidine dihydrochloride and water into a three-neck flask, and reacting for a period of time at a certain temperature. Centrifugally washing and purifying to obtain small polystyrene nanospheres with the diameter of 150-220 nm; and B, dispersing the polystyrene nanospheres in ethanol, adding tetraethyl orthosilicate and ammonia water into the diluted dispersion under stirring, reacting for a period of time at a certain temperature, and centrifugally washing and purifying to finally obtain the polystyrene @ silicon dioxide core-shell nanoparticles (colloid).

The (small size) polystyrene nanospheres in step a are conventional methods in the art. And B, when the styrene @ silicon dioxide nano particles are prepared, the mass ratio of the polystyrene to the tetraethyl orthosilicate is 1: 4-5.

The preparation process of the polystyrene @ silicon dioxide photonic crystal in the step (1) is as follows:

the substrate is vertically placed in polystyrene @ silicon dioxide core-shell nano particles (colloid), and water in the colloid is evaporated till the water is completely evaporated under the environment of 50 +/-2 ℃ and 60 +/-2% of humidity, so that the photonic crystal with the microsphere structure can be formed on the surface of the substrate.

The mass fraction concentration of the polystyrene @ silica core-shell nanoparticles is not too high, generally 0.5-2wt%, preferably 1.0wt%. The polystyrene @ silicon dioxide photonic crystals with different structural colors are prepared by changing the size of the core shell of the polystyrene @ silicon dioxide nano particles in the colloid.

In one embodiment of the present invention, the polystyrene @ silica photonic crystal of step (1) has a vertical deposition temperature of 45 to 60 ℃.

In one embodiment of the invention, the temperature for coating and preparing the photonic crystal film in the step (2) is 25-50 ℃.

In one embodiment of the present invention, the polymer solution in step (2), wherein the polymer comprises one or more of cellulose acetate, polydimethylsiloxane, or polyethylene glycol.

In one embodiment of the present invention, the polymer solution in the step (2) contains 7 to 15% by mass of a polymer.

In one embodiment of the present invention, the polymer solution in step (2), wherein the solvent comprises one of acetone, ethanol or dichloromethane.

The second purpose of the invention is to apply the photonic crystal film with self-supporting property in the field of color-changing coating.

The third purpose of the invention is to apply the photonic crystal film with self-supporting property to the preparation of anti-counterfeiting patterns.

Has the advantages that:

the preparation method provided by the invention can be used for preparing the photonic crystal film at room temperature, and the prepared photonic crystal film has excellent self-supporting property, high light transmittance and bright structural color. The method is suitable for various polymers and solutions, and photonic crystal patterns can be prepared at room temperature through coating modes such as injection printing and the like. The anti-counterfeiting pattern prepared by the method has bright color and wide coverage, and can be used in the fields of anti-counterfeiting, information encryption, color pattern printing and the like.

Drawings

FIG. 1 is a graph showing transmittance curves of photonic crystal films prepared from different polystyrene @ silica core-shell particles;

FIG. 2 shows the reflectance spectra of photonic crystal films prepared from different polystyrene @ silica core-shell particles;

FIG. 3 is an optical photograph of photonic crystal patterns with different structural colors and shapes prepared by the spray coating method;

FIG. 4 is an optical photograph of a polystyrene photonic crystal prepared photonic crystal film;

FIG. 5 optical photograph of silica photonic crystal prepared photonic crystal film.

Detailed Description

The present invention will be described in detail with reference to the accompanying drawings and examples.

Example 1 preparation of polystyrene @ silica colloid

(1) Preparation of small-size polystyrene colloid:

4.5g of styrene, 5.0g of polyvinylpyrrolidone, 0.26g of 2,2' -azobisisobutylamidine dihydrochloride and 100g of water were charged into a 250mL three-necked flask and reacted at 70 ℃ for 24 hours. Centrifugally washing and purifying to finally obtain polystyrene microspheres with the diameter of 200 nm;

under the same conditions, when the addition amounts of styrene were 4.0g and 5.0g, respectively, polystyrene nanoparticles were successfully prepared, and the particle diameters of the finally prepared polystyrene nanoparticles were 185nm and 220nm, respectively.

(2) Preparation of polystyrene @ silica colloid

5g of polystyrene microspheres (polystyrene particle size 160 nm) with a solids content of 12% were diluted with 120mL of absolute ethanol. Then, stirring at 400rpm and adding 1.5mL tetraethyl orthosilicate to the reaction solution, raising the temperature of the reaction solution to 50 ℃, and then adding 8mL ammonia water dropwise to the reaction solution to react for 3h to obtain polystyrene @ silica colloidal suspension.

It should be noted that, under the same conditions, when the particle diameters of the polystyrene nanoparticles are 185nm and 220nm, the polystyrene @ silica nanoparticles can be successfully prepared, and the particle diameters of the finally prepared polystyrene @ silica nanoparticles are 215nm and 270nm respectively; under the same condition, when the addition amount of tetraethyl orthosilicate is 2.0mL, polystyrene @ silica nanoparticles can be successfully prepared, and the particle size of the finally prepared polystyrene @ silica nanoparticles is 180nm.

Example 2 preparation of polystyrene @ silica Photonic Crystal film by vertical deposition

By vertical deposition of polystyrene @ silica colloidal photonic crystals on a substrate: placing the clean glass vertically in a polystyrene @ silica colloidal suspension at a concentration of 1.0 wt%; and reacting for a period of time at 50 ℃ and 60% humidity, namely forming the photonic crystal with the microsphere structure on the surface of the glass.

It should be noted that, under the same conditions, when the vertical deposition temperature of the polystyrene @ silica photonic crystal is changed to 45 ℃ and 60 ℃, the polystyrene @ silica photonic crystal can be successfully prepared; when the size of the core-shell of the polystyrene @ silicon dioxide core-shell nano particle is changed, the polystyrene @ silicon dioxide photonic crystal can be successfully prepared.

Example 3 preparation of Polymer Photonic Crystal film by roll coating method

Coating a 10wt% acetone solution of cellulose acetate on the polystyrene @ silicon dioxide photonic crystal film by a roll coating method, and drying at 25 ℃ to form a film, thereby preparing the photonic crystal film with self-supporting performance.

It is noted that under the same conditions, when the polymer is replaced by polydimethylsiloxane and polyethylene glycol, the photonic crystal film with self-supporting property can be prepared successfully; under the same conditions, when the concentration (wt%) of the polymer is 7% and 15%, the photonic crystal film with the self-supporting property can be successfully prepared; under the same condition, when the solvent is replaced by ethanol and dichloromethane, the photonic crystal film with self-supporting performance can be successfully prepared; under the same conditions, the photonic crystal film with self-supporting performance can be successfully prepared at the film forming temperature of 35 ℃, 45 ℃ and 50 ℃.

The transmittance curve of the photonic crystal film prepared from different polystyrene @ silica core-shell particles is shown in fig. 1, and the transmittance of the photonic crystal film prepared from different polystyrene @ silica core-shell particles in a visible light region is greater than 60%, so that the film is transparent; the reflection spectrum of the photonic crystal film prepared from the polystyrene @ silicon dioxide core-shell particles is shown in fig. 2, different photonic crystal films have different maximum reflection wavelengths, namely, different structural colors can be presented under illumination, and the color rendering property is excellent.

Example 4 injection printing preparation of Photonic Crystal patterns with different shapes and colors

The polymer solution was printed on different polystyrene @ silica photonic crystals by adding 10wt% cellulose acetate in acetone solution into a syringe, allowing the polymer to have different shapes, and volatilizing the acetone at 25 ℃ to produce the photonic crystal film. Then different photonic crystal films are combined to form a photonic pattern, and the optical photo of the manufactured photonic crystal pattern is shown in figure 3, so that the prepared pattern is rich in color and obvious in area, and the method has rich assembling property.

Comparative example 1 preparation of Photonic Crystal film from polystyrene Photonic Crystal

By vertical deposition of polystyrene colloidal photonic crystals on a substrate: vertically placing a clean substrate in a polystyrene colloidal suspension with a concentration of 1.0 wt%; and reacting for a period of time at 50 ℃ and 60% humidity, namely forming the photonic crystal with the microsphere structure on the surface of the substrate. An acetone solution of cellulose acetate was coated on the polystyrene photonic crystal film by a roll coating method and dried at 25 ℃ to form a film. As shown in FIG. 4, the prepared photonic crystal film has no structural color.

Comparative example 2 preparation of Photonic Crystal film from silica Photonic Crystal

By depositing silica colloidal photonic crystals vertically on a substrate: vertically placing a clean substrate in a silica colloid suspension with a concentration of 1.0 wt%; and reacting for a period of time at 50 ℃ and 60% humidity, namely forming the photonic crystal with the microsphere structure on the surface of the substrate. An acetone solution of cellulose acetate was coated on the silica photonic crystal film by roll coating, and dried at 25 ℃ to form a film. As shown in fig. 5, the prepared photonic crystal film had no structural color.

Comparative example 3 preparation of Photonic Crystal film from Large-size polystyrene @ silica Photonic Crystal

By vertically depositing polystyrene @ silica colloidal photonic crystals on a substrate: the cleaned substrate was placed vertically in a 1.0wt% polystyrene @ silica (core size 255nm, shell thickness 55 nm) colloidal suspension; and reacting for a period of time at 50 ℃ and 60% humidity, namely forming the photonic crystal with the microsphere structure on the surface of the substrate. An acetone solution of cellulose acetate was coated on the silica photonic crystal film by a roll coating method and dried at 25 ℃ to form a film.

TABLE 1 Properties of Photonic Crystal films made with cellulose acetate

Sample (I) 1	Structural color	Transmittance of light	Self-supporting performance
				C 160 S 5	Purple pigment	75％	Is excellent in
C 160 S 10	Purple pigment	75％	Is excellent in
				C 185 S 15	Blue (B)	75％	Is excellent in
C 185 S 25	Light green	75％	Is excellent in
				C 220 S 25	Green	75％	Is excellent in
C 220 S 35	Red wine	75％	Is excellent in
				Polystyrene microsphere	Is free of	75％	Is excellent in
Silica microspheres	Is free of	75％	Is excellent in
				C 255 S 55	Is composed of	75％	Is excellent in

1 samples were prepared from cellulose acetate acetone solutions, the c subscripts representing the core size of the HSPCs and the S subscripts representing the shell thickness of the HSPCs.

Claims (9)

1. A photonic crystal film is characterized by being prepared by the following method:

(1) Preparing polystyrene @ silicon dioxide core-shell nano particles by using small-size polystyrene nano particles, and growing polystyrene @ silicon dioxide photonic crystals on a substrate through vertical deposition;

(2) And (2) coating a polymer solution on the photonic crystal film obtained in the step (1), evaporating the solvent, and preparing the photonic crystal film with self-supporting performance at room temperature.

2. The photonic crystal film according to claim 1, wherein the coating in the preparation method is roll coating, injection printing, spin coating; the substrate is made of glass, polyurethane and polyethylene terephthalate.

3. The photonic crystal film of claim 1, wherein the polystyrene @ silica core-shell nanoparticles prepared in step (1) of the preparation method are prepared as follows:

reacting styrene, polyvinylpyrrolidone, 2' -azobisisobutylamidine dihydrochloride and water, and then centrifugally washing and purifying to obtain polystyrene nano microspheres;

and B, dispersing the polystyrene nano-microspheres in ethanol, adding tetraethyl orthosilicate and ammonia water into the diluted dispersion body under stirring for reaction, and then centrifugally washing and purifying to finally obtain the polystyrene @ silicon dioxide core-shell nano-particles.

4. The photonic crystal film of claim 3, wherein the mass ratio of polystyrene to tetraethyl orthosilicate in the preparation of styrene @ silica nanoparticles in the preparation method step B is 1: 4-5.

5. The photonic crystal film of claim 1, wherein the temperature for coating the prepared photonic crystal film in the step (2) is 25-50 ℃; the polymer is one or more of cellulose acetate, polydimethylsiloxane or polyethylene glycol.

6. The photonic crystal film of claim 1, wherein the polymer solution of step (2) is prepared, wherein the mass fraction of the polymer is 7-15%; the solvent in the polymer solution comprises one of acetone, ethanol or dichloromethane.

7. A method for preparing a photonic crystal film according to claim 1, comprising the steps of:

(1) Preparing polystyrene @ silicon dioxide core-shell nano particles by using small-size polystyrene nano particles, and growing polystyrene @ silicon dioxide photonic crystals on a substrate through vertical deposition;

(2) And (2) coating a polymer solution on the photonic crystal film obtained in the step (1), evaporating the solvent, and preparing the photonic crystal film with self-supporting performance at room temperature.

8. Use of a photonic crystal film according to claim 1, characterized in that the use of the photonic crystal film is in the field of color shifting coatings.

9. The use of the photonic crystal film according to claim 8, wherein the photonic crystal film is used for preparing an anti-counterfeiting pattern.

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