CN104630876A - Method for preparing anisotropic photonic crystal - Google Patents

Abstract

A method for preparing an anisotropic photonic crystal relates to the anisotropic photonic crystal. 1) Adding hydrophilic monomers, hydrophobic monomers, and cross-linking agents to the solvent, heating with nitrogen gas to carry out polymerization reaction, then adding initiator solution, and continuing the reaction with nitrogen gas to obtain monodisperse special-shaped polymer microspheres; 2) Disperse the monodisperse special-shaped polymer microspheres prepared in step 1) in water to obtain a polymer microsphere emulsion, put glass flakes into the polymer microsphere emulsion, and obtain anisotropic photonic crystals after the water is completely volatilized. The addition of the cross-linking agent causes cross-linking to occur inside the macromolecular chains, forming anisotropic beads with irregular shapes that are different from the past. The operation process is simple and feasible, and the obtained special-shaped beads are strictly monodisperse. Polymer microspheres with special-shaped core-shell structure are obtained by one-step polymerization without soap emulsion. The operation process is simple and easy, and the product polymer microspheres do not contain impurities such as surfactants and buffers. The product is pure and the particle size can be adjusted. control.

Description

A kind of preparation method of anisotropic photonic crystal

technical field

The invention relates to anisotropic photonic crystals, in particular to a preparation method of anisotropic photonic crystals.

Background technique

In 1987, Yablonovit (Yablonovitch, E.1987.Phys.Rev.Lett.58, 2059-2062.) and John (John, S.1987.Phys.Rev.Lett.58, 2486-2489) respectively proposed photon Crystal (Photonic Crystal) concept. Since the photonic crystal has a periodically adjustable dielectric constant, it can cause Bragg scattering of the propagating light, which can effectively play the role of light concentrating and filtering, and can produce physical phenomena such as super prisms and negative refractive index. Therefore, aroused widespread concern in the scientific community. As an important class of advanced optical materials, photonic crystals have shown great application prospects in photonic crystal reflective devices, photonic crystal filters, light-emitting diodes and photonic crystal fibers, and have become an important material for building photonic devices. The preparation techniques of photonic crystals mainly include complex semiconductor micromachining techniques such as photoetching, electrochemical etching, electron beam and focused ion beam etching. The self-assembly method is widely favored because of its simple process, and van der Waals force, hydrogen bond, electrostatic force and surface tension as its driving force can well realize the orderly arrangement of photonic crystals.

Anisotropic photonic crystals have attracted widespread attention due to their special structural properties. The symmetrical structure of regular spheres causes the polarization mode to generate energy band degeneracy at the W point or U point in the Bury source region. Therefore, for general dielectric spheres , it is very difficult to produce low-refractive-index full-bandgap photonic crystals. As the anisotropic photonic crystal itself does not have symmetry, the assembly unit can effectively avoid the energy band annexation caused by the symmetrical structure, making it possible to prepare a low-refractive-index full-bandgap photonic crystal, and can construct a structure that cannot be formed by spherical particles. , to achieve complete 3D or finer photonic bandgap, thereby expanding the application of photonic crystals. At present, anisotropic photonic crystals have been developed, such as Ian D.Hosein and Chekesha M.Liddell et al. (Langmuir 2007,23,8810-8814) prepared mushroom-shaped monodisperse PS polymer microspheres by suspension polymerization, and A hexagonal long-range ordered structure was obtained by convective self-assembly, resulting in a thin and transparent film. Jin-Gyu Park (JACS2010, 132, 5960–5961) et al produced a dumbbell-shaped (PS-co-TMSPA) polymer through two-step seed emulsion polymerization, and obtained a regularly arranged photonic crystal structure through vertical evaporation deposition. The resulting photonic crystal film exhibits the same thickness and morphology over a large area.

In Chinese patent CN200510011219.2, a full-color colloidal photonic crystal film is prepared by using hard-core-soft-shell polymer latex particles. This method introduces hydrophilic and lipophilic monomers, and the hydrophilic monomers approach during the polymerization process. The shell is formed in the water system, while the lipophilic monomer tends to migrate inside the polymer sphere to form the inner core of the polymer microsphere, and forms regular and smooth microspheres with the action of mechanical force. This method is always a method of preparing regular microspheres. There is no fundamental breakthrough in the method of orderly arranging photonic crystals to produce photonic crystals, which cannot solve the problem that photonic crystals formed by regular smooth balls cannot grow specific photonic band gaps.

Contents of the invention

The purpose of the present invention is to provide a preparation method of anisotropic photonic crystal.

Concrete steps of the present invention are as follows:

1) Adding hydrophilic monomer, hydrophobic monomer and cross-linking agent into the solvent, heating with nitrogen gas to carry out polymerization reaction, then adding initiator solution, continuing nitrogen gas reaction to obtain monodisperse special-shaped polymer microspheres;

2) Disperse the monodisperse special-shaped polymer microspheres prepared in step 1) in water to obtain a polymer microsphere emulsion, put the glass sheet into the polymer microsphere emulsion, and after the water is completely volatilized, anisotropic photon crystals.

In step 1), the content of the hydrophilic monomer, hydrophobic monomer, crosslinking agent, solvent and initiator solution in terms of mass percentage can be: hydrophilic monomer and hydrophobic monomer are 1% to 20%, crosslinking The coupling agent can be 2.5% to 25.4% of the total mass of the hydrophilic monomer and the hydrophobic monomer, the initiator can be 0.1% to 5% of the total mass of the hydrophilic monomer and the hydrophobic monomer, and the rest is a solvent; the hydrophilic The volume ratio of the monomer and the hydrophobic monomer can be 1: (3-20);

The hydrophilic monomer can be selected from at least one of glycidyl methacrylate, hydroxyethyl methacrylate, N-isopropylacrylamide, acrylamide, acrylic acid, etc.;

Described hydrophobic monomer can adopt styrene etc.;

The crosslinking agent can adopt divinylbenzene etc.;

Described solvent can adopt water;

Potassium persulfate can be used as the initiator solution, and the mass percent concentration of the initiator solution can be 0.2% to 2%.

The heating temperature may be 65-85° C., the polymerization reaction may be stirred, and the stirring speed may be 200-600 rpm; the time for continuing the nitrogen gas reaction may be 24 hours.

In step 2), the mass percent concentration of the polymer microsphere emulsion can be 5% to 30%; the glass flakes can be treated with sulfuric acid in advance, and the treatment time can be 12h; the glass flakes can be put into In the polymer microsphere emulsion, it is best to put the glass sheet vertically into the polymer microsphere emulsion. At 60°C, with the evaporation of the solvent, the monodisperse polymer microspheres in the emulsion self-assemble to form a regular structure of regular packing. Anisotropic photonic crystals with widely adjustable colors can be obtained after the water is completely volatilized.

The monodisperse special-shaped core-shell polymer microspheres in the present invention are prepared by a one-step synthesis method of soap-free emulsion, which has the advantages of simple and easy operation and uniform and controllable particle size of the obtained special-shaped microspheres. Since no emulsifier and stabilizer are added, the obtained product is pure, and the subsequent preparation of the polymer photonic crystal can be used without any treatment. The soap-free emulsion one-step polymerization method adopted, the raw materials are two kinds of monomers and crosslinking agent which are hydrophilic and lipophilic. During the polymerization process, the hydrophilic part tends to form a shell layer in the water solvent system, while the lipophilic component tends to polymerize The internal migration of the object sphere forms the inner core of the polymer microsphere, and at the same time, the cross-linking agent makes the macromolecules link together, and under the joint action of the mechanical stirring force, a monodisperse polymer microsphere with a special-shaped core-shell structure is formed. Its particle size can be controlled by changing the concentration of hydrophilic and lipophilic monomers, changing the amount of initiator used, and changing the polymerization temperature and stirring speed according to the needs.

In the present invention, special-shaped monodisperse core-shell polymer microspheres are used to form a uniform emulsion after being dissolved in a water solvent at a certain ratio, and the pre-treated glass sheet is vertically placed in the solution, and heated at a certain temperature Under the environment, with the volatilization of water, the method of self-assembly of special-shaped polymer microspheres forms polymer photonic crystals. The color of the obtained photonic crystal can be adjusted according to the diameter of the anisotropic sphere; the thickness of the photonic crystal film depends on the concentration of the formulated special-shaped polymer microsphere emulsion and the amount of smearing. Since the obtained special-shaped polymer microspheres are strictly monodisperse, the special-shaped balls are easy to be arranged regularly under force during the volatilization process of the solution. At the same time, the special-shaped spheres obtained by soap-free emulsion polymerization have no impurities on the surface, and will not be disturbed by impurities during the stacking and arrangement process, which is conducive to the formation of an ordered structure.

The invention breaks the traditional method of forming photonic crystals by arranging regular balls with uniform particle diameters, and broadens the production field of polymer photonic crystals. At the same time, a photonic band gap that cannot be formed by regular smooth microspheres due to symmetry and size is formed, and a narrower photonic band gap is obtained, which expands the application range of photonic crystals. Due to its special structure and unique optical properties, the special-shaped polymer photonic crystal made according to this method has quite broad application prospects in application fields such as many decorative materials, coatings, films and solar concentrators; and because the present invention uses The special-shaped polymeric microspheres are strictly monodisperse and pure, and have unique advantages in the fields with strict requirements such as environmental protection materials and cosmetics.

In the invention, special-shaped polymer microspheres are prepared through soap-free emulsion polymerization, and an anisotropic photonic crystal is synthesized by a vertical deposition method. This method introduces a cross-linking agent. During the polymerization process, the hydrophilic monomer tends to approach the water system to form a shell, while the lipophilic monomer tends to migrate inside the polymer sphere to form the inner core of the polymer microsphere. The cross-linking agent acts on the monomer The internal polymerization of the monomer can be achieved by using the body, and with the action of mechanical stirring, anisotropic polymer microspheres different from the previous ones can be prepared. And because the soap-free emulsion polymerization is adopted, no impurities such as emulsifiers, buffers, etc. are introduced, and the obtained special-shaped microspheres are pure, and the regular arrangement of the special-shaped microspheres is not affected during the self-assembly process. The anisotropic photonic crystal prepared by this method can form a finer photonic band gap that cannot be obtained in the past photonic crystal, which greatly expands the application of photonic crystal.

The invention provides a method for preparing monodisperse polymer microspheres with special-shaped core-shell structure. In particular, the addition of the cross-linking agent makes the inside of the macromolecular chains cross-linked, forming anisotropic beads with irregular shapes that are different from the past. The operation process is simple and feasible, and the obtained special-shaped beads are strictly monodisperse. Due to the irregular shape of special-shaped spheres, they do not have the attenuation of light waves that hinder the formation of low photonic band gaps. After being packed closely, regular smooth microspheres can form photonic band gaps that cannot be formed due to symmetrical structures, and the obtained photonic band gaps are narrower, thus The scope of application of photonic crystals has been expanded. At the same time, it also broadens the production field of photonic crystals, so that the production of photonic crystals is not limited to regular smooth microspheres, but can also be obtained through the orderly arrangement of special-shaped microspheres. Polymer microspheres with special-shaped core-shell structure are obtained by one-step polymerization without soap emulsion. The operation process is simple and easy, and the product polymer microspheres do not contain impurities such as surfactants and buffers. The product is pure and the particle size can be adjusted. control. Because the prepared special-shaped polymer microspheres and photonic crystals are pure, their applications in the fields of coatings, dyes or pigments, and films are expanded.

Description of drawings

FIG. 1 is a SEM image and a partial enlarged view of the special-shaped polymer microspheres obtained in Example 1.

Fig. 2 is the SEM picture and partial enlarged picture of the special-shaped polymer microspheres obtained in Example 12.

Fig. 3 is a SEM image and a partially enlarged image of the special-shaped polymer microsphere obtained in Example 13.

FIG. 4 is a SEM image and a partially enlarged image of the special-shaped polymer microspheres obtained in Example 14.

FIG. 5 is a SEM image of the special-shaped polymer microspheres obtained in Example 2.

FIG. 6 is a SEM image of the special-shaped polymer microspheres obtained in Example 5.

Fig. 7 is a photo obtained by depositing the anisotropic photonic crystal obtained in the embodiment on the substrate. Wherein a, b, c, d, e figure are embodiment 1～3, 4～5, 6, 7～8, 9～11 respectively.

Detailed ways

The following embodiments will further illustrate the present invention in conjunction with the accompanying drawings.

Example 1:

Add 0.2mL of the hydrophilic monomer glycidyl methacrylate, 2mL of the hydrophobic monomer styrene and 0.05mL of divinylbenzene into a three-necked bottle containing 30mL of deionized water, stir with nitrogen for 30-60min, and heat up to 75°C, and then add an aqueous solution in which 0.04 g of potassium persulfate initiator is dissolved. After reacting for 24 hours, a monodisperse styrene-divinylbenzene-glycidyl methacrylate (PS-DVB-PGMA) special-shaped copolymer microsphere emulsion was obtained. The SEM images and partial enlarged images of the special-shaped polymer microspheres are shown in Fig. 1 .

Under normal pressure, the microspheres and aqueous solution obtained above were configured into a dilute solution at a volume ratio of 1:30. A glass piece soaked in concentrated sulfuric acid for 12 hours was vertically placed in the solution, and placed in a constant temperature drying oven at 60°C for 24 hours. The microspheres in the solution are arranged vertically on the glass sheet in an orderly manner by the surface tension of the solution on the vertical glass sheet during evaporation. The obtained heteromorphic photonic crystal deposited on the substrate is shown in a in Fig. 7 .

Embodiment 2～11: Same as the processing condition of embodiment 1, change the add-on of water, synthesize the monodisperse styrene-divinylbenzene-glycidyl methacrylate (PS-DVB-PGMA) profile of different particle size Copolymer microsphere emulsion, the results are shown in Table 1.

At room temperature, mix the monodisperse PS-DVB-PGMA special-shaped polymer microsphere emulsion water obtained in Examples 2-11 at a volume ratio of 1:30, and put the glass sheet pre-soaked in concentrated sulfuric acid for 12 hours into it vertically. In an environment of 60°C under normal pressure, photonic crystals with regular structures and unique colors can be obtained. The obtained special-shaped photonic crystals deposited on the substrate are shown in b-e in Fig. 7 . The SEM image of the special-shaped polymer microspheres obtained in Example 2 is shown in FIG. 5 , and the SEM image of the special-shaped polymer microspheres obtained in Example 5 is shown in FIG. 6 .

Table 1

With the processing condition of embodiment 1, change hydrophilic monomer to be acrylic acid, hydroxyethyl methacrylate, acrylamide, synthesize the monodisperse styrene-divinylbenzene-acrylic acid (PS-DVB-PAA) of different components , Styrene-divinylbenzene-hydroxyethyl methacrylate (PS-DVB-PHEMA), styrene-divinylbenzene-acrylamide (PS-DVB-PAM) shaped copolymer microsphere emulsion. The results are shown in Table 2. The SEM images and partial enlarged images of the special-shaped polymer microspheres are shown in Figures 2-4.

At room temperature, mix the monodisperse above-mentioned special-shaped microspheres obtained in Examples 12 to 14 with water at a volume ratio of 1:30, and place the glass sheet pre-soaked in concentrated sulfuric acid for 12 h vertically in it. Under the environment, after the water volatilizes, the photonic crystal with regular structure and unique color can be obtained.

Table 2

The invention adopts a soap-free emulsion polymerization method, and prepares a monodisperse special-shaped core-shell structure polymer microsphere emulsion by adding a crosslinking agent. And the emulsion is mixed with water according to a certain ratio, and the pre-treated glass piece is vertically put into the solution under normal pressure and a certain temperature. Ordered polymer photonic crystals. Due to its unique structure and excellent optical properties, the formed photonic crystal film has broad application prospects in many decorative materials, coatings, thin films, and solar concentrators.

Claims (10)

1. a preparation method of anisotropic photonic crystal, is characterized in that its concrete steps are as follows: 1) Adding hydrophilic monomer, hydrophobic monomer and cross-linking agent into the solvent, heating with nitrogen gas to carry out polymerization reaction, then adding initiator solution, continuing nitrogen gas reaction to obtain monodisperse special-shaped polymer microspheres; 2) Disperse the monodisperse special-shaped polymer microspheres prepared in step 1) in water to obtain a polymer microsphere emulsion, put the glass sheet into the polymer microsphere emulsion, and after the water is completely volatilized, anisotropic photon crystals. 2. the preparation method of a kind of anisotropic photonic crystal as claimed in claim 1 is characterized in that in step 1), described hydrophilic monomer, hydrophobic monomer, linking agent, solvent and initiator solution are by mass The percentage content is: hydrophilic monomers and hydrophobic monomers are 1% to 20%, crosslinking agents are 2.5% to 25.4% of the total mass of hydrophilic monomers and hydrophobic monomers, and initiators are hydrophilic monomers and hydrophobic monomers. 0.1%-5% of the total mass of the monomer, and the rest is solvent; the volume ratio of the hydrophilic monomer to the hydrophobic monomer is 1: (3-20). 3. the preparation method of a kind of anisotropic photonic crystal as claimed in claim 1 is characterized in that in step 1), described hydrophilic monomer is selected from glycidyl methacrylate, hydroxyethyl methacrylate, At least one of N-isopropylacrylamide, acrylamide, and acrylic acid. 4. A kind of preparation method of anisotropic photonic crystal as claimed in claim 1, is characterized in that in step 1), described hydrophobic monomer adopts styrene. 5. The preparation method of anisotropic photonic crystal as claimed in claim 1, characterized in that in step 1), the crosslinking agent adopts divinylbenzene. 6. A kind of preparation method of anisotropic photonic crystal as claimed in claim 1, is characterized in that in step 1), described solvent adopts water. 7. the preparation method of a kind of anisotropic photonic crystal as claimed in claim 1 is characterized in that in step 1), described initiator solution adopts potassium persulfate, and the mass percentage concentration of initiator solution can be 0.2%～ 2%. 8. A kind of preparation method of anisotropic photonic crystal as claimed in claim 1, it is characterized in that in step 1), the temperature of described heating is 65～85 ℃, during described polymerization reaction, stir, stirring speed is 200-600rpm; the time for continuing the reaction with nitrogen gas can be 24h. 9. A method for preparing anisotropic photonic crystals according to claim 1, characterized in that in step 2), the mass percent concentration of the polymer microsphere emulsion is 5% to 30%. 10. the preparation method of a kind of anisotropic photonic crystal as claimed in claim 1 is characterized in that in step 2), described glass sheet is treated with sulfuric acid in advance, and the time of processing is 12h; Described glass sheet is put into In the polymer microsphere emulsion, it is best to put the glass sheet vertically into the polymer microsphere emulsion. At 60°C, with the evaporation of the solvent, the monodisperse polymer microspheres in the emulsion self-assemble to form a regular structure of regular packing. Anisotropic photonic crystals with widely adjustable colors can be obtained after the water is completely volatilized.