An azobenzene polymer microsphere cluster, a preparation method and application thereof

Abstract

The application discloses an azobenzene polymer microsphere cluster, a preparation method and application thereof, and can assemble and arrange multiple monodisperse azobenzene polymer microspheres containing reactive end group groups in a preset arrangement mode, then irradiates by light, fusion occurs between two adjacent monodisperse azobenzene polymer microspheres, and the fused part is covalently connected through a chemical cross-linking reaction participated by the reactive end group groups, so that a stable azobenzene polymer microsphere cluster can be obtained, and the azobenzene polymer microsphere cluster also has light response characteristics, and is easy to adjust and realize a configuration, and is beneficial to application in the fields of optical switches, optical information storage materials, biological molecule active light regulation materials, nonlinear optical materials or integrated optical materials and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of functional polymer microspheres, and in particular to an azobenzene polymer microsphere cluster, a preparation method therefor and applications thereof. BACKGROUND

[0002] In recent years, micrometer-sized monodisperse polymer microsphere particles have been the focus of scientists' attention due to their great application potential in the fields of chiral recognition, drug delivery, light-emitting devices and chromatographic packing materials. Compared with inorganic nanoparticles, polymer microspheres have some other special properties and functions in addition to the inherent properties of the polymer itself, for example, azobenzene polymers generally contain azo chromophores in the polymer main chain or side chain to form light-responsive polymers, which can be applied in the fields of reversible optical switches, liquid crystal elastomers, light-responsive materials and biomedical applications.

[0003] At present, when a plurality of polymer microspheres are aggregated together to form a polymer microsphere cluster, the structure is similar to that of a molecule. However, it has been found in practice that the resulting polymer microsphere cluster structure is unstable and difficult to fully exert the role of the cluster structure. SUMMARY

[0004] The purpose of the present application is to overcome one or more of the deficiencies in the prior art and provide an improved preparation method for an azobenzene polymer microsphere cluster that has light-responsive properties, a stable structure and an easily adjustable and implemented configuration.

[0005] The present application also provides an azobenzene polymer microsphere cluster prepared by the above method.

[0006] The present application also provides applications of the above azobenzene polymer microsphere cluster in optical switches, optical information storage materials, biomolecule active light regulation materials, nonlinear optical materials or integrated optical materials.

[0007] To achieve the above purpose, one technical solution adopted by the present application is a preparation method for an azobenzene polymer microsphere cluster, which comprises:

[0008] Assembling and arranging a plurality of monodisperse azobenzene polymer microspheres containing reactive end groups in a predetermined arrangement mode;

[0009] Irradiating with light, fusion occurring between every two adjacent monodisperse azobenzene polymer microspheres, and covalent connection being formed by the chemical cross-linking reaction involving the reactive end groups.

[0010] According to some preferred aspects of the present application, the monodisperse azobenzene polymer microspheres have the structure shown in formula (I):

[0011] a, b are independently selected from 2-15, and R is a reactive end group group other than a double bond.

[0012] In some embodiments of the present application, a, b are independently selected from 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15.

[0013] According to some preferred and specific aspects of the present application, R is hydroxyl or amino.

[0014] In some preferred embodiments of the present application, when R is hydroxyl, the chemical cross-linking reaction is an acetal reaction, or, the chemical cross-linking reaction employs addition of a polyisocyanate to undergo nucleophilic reaction with the hydroxyl group; when R is amino, the chemical cross-linking reaction employs addition of a polyisocyanate or a halogenated hydrocarbon to undergo nucleophilic reaction with the amino group.

[0015] In some embodiments of the present application, the acetal reaction is carried out in the presence of an aldehyde substance, including but not limited to formaldehyde.

[0016] In some embodiments of the present application, the acetal reaction is carried out in a first solvent in the presence of hydrochloric acid and formaldehyde.

[0017] In some embodiments of the present application, the first solvent includes but is not limited to petroleum ether.

[0018] In some embodiments of the present application, the acetal reaction is carried out at a reaction temperature of 10-40℃. According to a specific aspect of the present application, the acetal reaction can be carried out at room temperature.

[0019] In some embodiments of the present application, the acetal reaction is carried out under sealed conditions.

[0020] According to some preferred and specific aspects of the present application, the monodisperse azobenzene polymer microspheres have the following structure shown in formula (I-1): a, b are as defined above.

[0021] In some embodiments of the present application, the monodisperse azobenzene polymer microspheres of the structure shown in formula (I-1) are obtained by polymerization of a monomer represented by a compound shown in formula (II), a, b are as defined above.

[0022] According to some preferred aspects of the present application, the polymerization is carried out at a reaction temperature of 75-85℃.

[0023] In some embodiments of the present application, the polymerization is carried out in an oxygen-free environment. Further, the oxygen-free environment is an inert gas environment, and the inert gas is selected from any one of argon, nitrogen, helium, neon, preferably argon.

[0024] In some embodiments of the present application, the polymerization time is 4-20 hours.

[0025] In some embodiments of the present application, the polymerization is carried out in the presence of an initiator, a dispersant and a second solvent.

[0026] In some embodiments of the present application, the initiator is an azo initiator, which is a combination of one or more selected from azobisisobutyronitrile (AIBN), azobisisoheptyl nitrile and dimethyl azobisisobutyrate.

[0027] In some embodiments of the present application, the dispersant is a non-ionic dispersant, which is a combination of one or more selected from polyvinylpyrrolidone (PVP), poly-4-vinylpyridine (P4VP), polyethylene glycol (PEG) and polyhydroxyethyl methacrylate (PHEMA).

[0028] In some embodiments of the present application, the mass ratio of the monomer, the initiator and the dispersant represented by the compound of formula (II) is 60:(0.2-1.0):(1.0-5.0).

[0029] In some embodiments of the present application, the second solvent is a combination of one or more selected from ethanol, methanol, propanol and butanol. Further, the second solvent is substantially free of water.

[0030] In the present application, at the initial stage of the reaction, the monomers nucleate alone or mutually in the polymerization process and precipitate from the medium, and the relatively small nuclei mutually nucleate to form polymer particles. At the same time, the dispersant present in the system is adsorbed on the surface of the polymer particles to stabilize the particles. During the growth of the particles, the polymer particles continuously capture the surrounding free small nuclei, thereby gradually increasing the particle size. The polymer prepared in the present application has a N=N double bond in its structure, which exhibits a unique reversible cis-trans photoisomerization phenomenon under irradiation of light of different wavelengths. In the cis-trans isomerization of azobenzene, the dipole moment and size of the azobenzene molecule also change, thereby leading to changes in the macroscopic properties of the polymer and making the material exhibit reversible response behavior to light and heat to a certain extent.

[0031] In some embodiments of the present application, the compound of formula (II) is synthesized by the following synthetic route:

[0032]

[0033] wherein m is 2-15, a and b are selected from m, and Y is chlorine or bromine.

[0034] In some embodiments of the present application, the compound of formula (II-3) is a combination of one or more selected from the group consisting of 1-bromo-4-hydroxybutane, 1-bromo-6-hydroxyhexane, 1-bromo-8-hydroxyoctane, 1-bromo-10-hydroxydecane.

[0035] In some embodiments of the present application, the compound of formula (II-5) is prepared by reacting p-hydroxyaniline with an aqueous solution of sodium nitrite in hydrochloric acid solution to obtain a diazonium salt solution of p-hydroxyaniline. Further, the reaction temperature is controlled at 0-5°C.

[0036] In some embodiments of the present application, the compound of formula (II-4) is prepared by reacting the compound of formula (II-5) with phenol. Further, in the preparation process, the phenol is dissolved in an aqueous solution of sodium hydroxide, then added dropwise into the diazonium salt solution of p-hydroxyaniline, reacted, and the reaction temperature is controlled at 0-5°C.

[0037] In some embodiments of the present application, the compound of formula (II-1) is prepared by reacting the compound of formula (II-4) with the compound of formula (II-3) in the presence of a base, in the presence of an alkali metal iodide, in a third solvent.

[0038] Further, in the preparation process of the compound of formula (II-1), the base can be potassium carbonate, sodium carbonate, sodium bicarbonate, sodium hydroxide, etc., the alkali metal iodide can be potassium iodide, sodium iodide, etc., and the third solvent includes but is not limited to N,N-dimethylformamide (DMF).

[0039] Further, in the preparation process of the compound of formula (II-1), the reaction is controlled to be carried out at 75-85°C. According to a specific aspect of the present application, the reaction is controlled to be carried out under stirring reflux conditions.

[0040] In some embodiments of the present application, the compound of formula (II) is prepared by reacting the compound of formula (II-1) with the compound of formula (II-2) in the presence of an alkali metal hydride and an alkali metal iodide, in a fourth solvent.

[0041] Further, in the preparation process of the compound of formula (II), the alkali metal hydride includes but is not limited to sodium hydride, potassium hydride, etc., the alkali metal iodide can be potassium iodide, sodium iodide, etc., and the fourth solvent includes but is not limited to tetrahydrofuran, which can be anhydrous tetrahydrofuran.

[0042] Further, in the preparation process of the compound of formula (II), the reaction is controlled to be carried out at 45-55°C.

[0043] Further, in the process of preparing the compound shown in formula (II), by controlling the amount of raw material added and the separation means (such as column chromatography, etc.) in post-treatment, the compound shown in formula (II) is obtained with as high a yield as possible and is separated to obtain the compound shown in formula (II).

[0044] According to a specific aspect of the present application, the monodisperse azobenzene polymer microspheres are:

[0045]

[0046] According to some preferred and specific aspects of the present application, the monodisperse azobenzene polymer microspheres undergo fusion between the microspheres under ultraviolet light irradiation and return to the initial state under visible light irradiation.

[0047] Further, the wavelength of the ultraviolet light is 360-370 nm and the wavelength of the visible light is 430-440 nm. According to a specific aspect of the present application, the wavelength of the ultraviolet light is 365 nm and the wavelength of the visible light is 435 nm.

[0048] According to some preferred aspects of the present application, the assembly arrangement is achieved by setting a template, so that the monodisperse azobenzene polymer microspheres are assembled and arranged in the template to form the preset arrangement mode.

[0049] According to some preferred and specific aspects of the present application, the embodiment of the preparation method comprises: irradiating the monodisperse azobenzene polymer microspheres forming the preset arrangement mode and located in the template with the light, performing the chemical cross-linking reaction, separating from the template, and obtaining the azobenzene polymer microsphere cluster. The present application introduces the azobenzene group with unique light response properties into the polymer microspheres, and prepares the monodisperse azobenzene polymer microspheres by dispersion polymerization technology. Subsequently, through template arrangement, the polymer microspheres undergo photo-fusion due to the unique light response properties of the azobenzene group, and then the fused parts of the microspheres are covalently cross-linked through the chemical cross-linking reaction, so that the stable polymer microsphere cluster is finally obtained, which overcomes the defect of instability of the polymer microsphere cluster constructed in the prior art.

[0050] The present application provides another technical solution: an azobenzene polymer microsphere cluster prepared by the above-mentioned preparation method.

[0051] The present application provides another technical solution: an azobenzene polymer microsphere cluster prepared by the above-mentioned preparation method.

[0052] Due to the use of the above technical solutions, the present application has the following advantages compared with the prior art:

[0053] The present application innovatively adopts monodisperse azobenzene polymer microspheres containing reactive end groups, and the microspheres are orderly assembled in a preset arrangement mode by means of external force (including but not limited to setting a template), at this time the microspheres can contact each other, then the photo-fusion phenomenon of the azobenzene groups is utilized to make the fusion phenomenon occur between the orderly arranged adjacent two microspheres, the contacted parts are fused with each other to form a microsphere cluster structure, and then the reactive end groups of the monodisperse azobenzene polymer microspheres are utilized to realize the chemical crosslinking between the fusion parts of the microspheres, so that the formed microsphere cluster structure is more stable.

[0054] In addition, the microsphere cluster structure and size of the present application are easy to adjust and realize, and the microsphere cluster structure has light response characteristics, and can be applied in the fields of optical switches, optical information storage materials, biological molecule activity light regulation materials, nonlinear optical materials, integrated optical materials and the like. BRIEF DESCRIPTION OF DRAWINGS

[0055] Figure 1 The nuclear magnetic resonance hydrogen spectrum of the styrene-based azobenzene monomer in Example 1 is shown in the figure;

[0056] Figure 2 The morphology diagrams of the azobenzene polymer microspheres prepared by polymerization under different feeding ratios are shown in the figures;

[0057] Figure 3 The DLS spectrum diagrams of the azobenzene polymer microspheres are shown in the figures;

[0058] Figure 4 The schematic diagram of a circular template is shown in the figure;

[0059] Figure 5 The schematic diagram of a capillary micro-molding method template is shown in the figure;

[0060] Figure 6 The morphology diagrams of the monodisperse azobenzene polymer microspheres after irradiation for different times under 365 nm ultraviolet light are shown in the figures;

[0061] Figure 7 The electron microscope diagrams of the morphology changes of the monodisperse azobenzene polymer microspheres after arrangement, irradiation under 365 nm ultraviolet light and irradiation under 435 nm visible light are shown in the figures;

[0062] Figure 8 The electron microscope diagrams of the connection effects of the azobenzene polymer microspheres before and after the acetal reaction are shown in the figures;

[0063] Figure 9 The XPS spectrum diagrams of the monodisperse azobenzene polymer microspheres before and after the acetal reaction are shown in the figures;

[0064] Figure 10 The crosslinked and fixed azobenzene polymer microsphere clusters with different configurations prepared after the template arrangement, photo-fusion and acetal reaction are shown in the figures. DETAILED DESCRIPTION

[0065] The chemical reagents used in the following examples are:

[0066] 1-Bromo-6-hydroxyhexane, Acros, 95%;

[0067] Polyvinylpyrrolidone, PVP K90, J&K;

[0068] 4-Aminophenol, Sinopec Chemical Reagent Co., Ltd., CP;

[0069] Phenol, Aladdin, AR;

[0070] Dichloromethane, Jiangsu Qiangsheng Functional Chemical Co., Ltd., 99.5%;

[0071] Anhydrous sodium sulfate, Sinopharm Chemical Reagent Co., Ltd., 98%;

[0072] Ethyl acetate, Jiangsu Qiangsheng Functional Chemical Co., Ltd., 99.5%;

[0073] Azobisisobutyronitrile (AIBN), Shanghai Reagent Factory No. 4, chemically pure, recrystallized twice before use;

[0074] Sodium hydride, Aladdin, ≥60%;

[0075] Sodium nitrite, Sinopharm Chemical Reagent Co., Ltd., AR;

[0076] Petroleum ether, Jiangsu Qiangsheng Functional Chemical Co., Ltd., analytical grade;

[0077] p-chloromethylstyrene, Meryer, 99%, purified with a short basic alumina column before use;

[0078] Concentrated hydrochloric acid, Jiangsu Qiangsheng Functional Chemical Co., Ltd., analytical grade;

[0079] Formaldehyde aqueous solution, Sinopharm Chemical Reagent Co., Ltd., analytical grade;

[0080] Test instruments and conditions:

[0081] 1H NMR spectrum ( 1 H-NMR: Measured using a Bruker 300MHz NMR spectrometer, with DMSO-d6 as solvent and TMS as internal standard at room temperature;

[0082] Dynamic laser light scattering (DLS) was measured at 25°C using Brookhaven's NanoBrook 90Plus PALS nanoparticle size analyzer at a test angle of 90°.

[0083] SEM images: tested using a cold field emission HITACHI S-4700, with a working acceleration voltage of 15 kV;

[0084] TEM images: tested using a HITACHI HT7700, with a test acceleration voltage of 120 kV.

[0085] Example 1: Synthesis of styrene-based azo monomer

[0086] In a 1 L round bottom flask, p-hydroxyaniline (10.0 g, 0.09 mol) was dissolved in 1 M hydrochloric acid solution (200 mL) and stirred at 0 °C for 30 min. Sodium nitrite (9.3 g, 0.1 mol) was dissolved in 150 mL of deionized water. The reaction temperature was controlled at 0-5 °C, and the sodium nitrite solution was slowly added to the reaction system. The addition was completed in 30 min. The temperature was maintained at 0 °C and the reaction was continued for 30 min. Then 200 mL of ice methanol was poured into the reaction system, and the stirring reaction was continued for 1 h to obtain a diazonium salt solution of p-hydroxyaniline.

[0087] In a 250 mL beaker, phenol (8.6 g, 0.9 mol) was dissolved with 3 M sodium hydroxide aqueous solution (65 mL). The reaction temperature was controlled at 0 °C, and the above-mentioned phenol solution was slowly added to the diazonium salt solution of p-hydroxyaniline, and mechanically stirred for 30 min. Then it was removed to room temperature and the reaction was continued for 2 h. After the reaction was completed, the excess methanol was removed by rotary evaporation, and the solution was adjusted to pH < 5 using concentrated hydrochloric acid, and purple red particles were precipitated. The resulting turbid liquid was filtered, washed with water, dried, recrystallized with ethanol / water (v / v, 1 / 2), and finally dried in vacuum to obtain a purple red compound 1 (12.4 g, yield: 63.3%).

[0088] In a 500 mL round bottom flask, potassium carbonate (9.7 g, 0.07 mol), compound 1 (5.0 g, 0.02 mol), a small amount of KI, and 60 mL of DMF solvent were added, and the temperature was raised to 80 °C and stirred for 30 min. Then 1-bromo-6-hydroxyhexane (10.6 g, 0.06 mol) dissolved in 30 mL of DMF was slowly added to the reaction system, and the reaction was stopped after stirring at 80 °C for 8 h, and cooled to room temperature. After filtration, the filtrate was poured into a large amount of ice water, extracted with ethyl acetate, and the organic phase was washed with saturated ammonium chloride 3 times, dried over anhydrous sodium sulfate, rotary evaporated, and column chromatographed (v / v, petroleum ether / ethyl acetate = 1 / 1) to obtain a dark yellow solid compound 2 (4.23 g, yield: 43.8%).

[0089] In a 500 mL dry round bottom flask, p-chloromethylstyrene (2.9 mL, 0.02 mol), sodium hydride (1.2 g, 0.03 mol) and 20 mL of anhydrous tetrahydrofuran were added and stirred at room temperature for 30 min. Then compound 2 (4.2 g, 0.01 mol) dissolved in 80 mL of anhydrous tetrahydrofuran was added dropwise into the round bottom flask, and a small amount of KI was added, and the reaction was carried out at 50°C for 24 h. After the reaction was completed, it was cooled to room temperature and filtered, and the filtrate was dried over anhydrous sodium sulfate, rotary evaporated, and separated by column chromatography (v / v, petroleum ether / ethyl acetate = 2 / 1). Finally, the styrene azo-containing monomer (Azo) was obtained, and its proton nuclear magnetic resonance spectrum is shown in Figure 1. Figure 1 .

[0090] The above reaction process is as follows:

[0091]

[0092] Example 2: Preparation of monodisperse styrene azobenzene polymer microspheres (containing reactive end group: hydroxyl) PAzo

[0093] The monomer Azo obtained in Example 1, the initiator azobisisobutyronitrile (AIBN), the dispersant PVP K90 and anhydrous ethanol were added to a 10 mL ampoule, and after the addition was completed, the oxygen was removed by three cycles of freeze-pumping-gassing-thawing with double-tube, and then the bottle opening was sealed. Under argon, the reaction was heated and stirred at 80°C for 6 h, and then the reaction was stopped. The reaction solution was transferred to a 25 mL centrifuge tube, and after centrifugation at 15000 rpm for 10 min, the supernatant was poured out, anhydrous ethanol was added for ultrasonic dispersion, and the polymer microspheres were washed, and the supernatant was separated again by centrifugation, and the operation was repeated 2-3 times until the supernatant was colorless. The azobenzene polymer microspheres were separated.

[0094] The azobenzene microsphere synthesis process is as follows:

[0095]

[0096] The specific feeding ratio is shown in Table 1:

[0097] Table 1

[0098]

[0099] Figure 2 The morphology of azobenzene polymer microspheres prepared by dispersion polymerization under different feeding ratios (polymerization time is 6 hours). From the morphology of the azobenzene polymer microspheres prepared by dispersion polymerization under different feeding ratios (polymerization time is 6 hours), it can be seen that the azobenzene polymer microspheres prepared under the feeding ratio of Azo:AIBN:PVP K90 = 60:0.35:1.5 have the best particle size dispersion coefficient. Figure 2

[0100] Figure 3 ​DLS spectra of azobenzene polymer microspheres prepared by dispersion polymerization at different feeding ratios.

[0101] Example 3: Construction of cross-linked fixed different configuration azobenzene polymer microsphere clusters

[0102] The monodisperse azobenzene polymer microspheres prepared in Example 2 were arranged through a circular template (an example of the template can be shown as Figure 4 , and the circular holes in the figure can accommodate different numbers of microspheres at the same time). Due to the different numbers of microspheres filled in the circular holes of the template, two or three connected azobenzene polymer microsphere clusters can be obtained. Subsequently, irradiation was carried out by 365 nm ultraviolet light to make the adjacent azobenzene polymer microspheres fuse. Finally, the template was placed in the steam atmosphere of hydrochloric acid and formaldehyde for acetalization reaction. After the reaction was completed, water washing was carried out and ultrasonic treatment was carried out in ethanol solvent, and the azobenzene polymer microsphere clusters were removed from the template to obtain cross-linked fixed azobenzene polymer microsphere clusters.

[0103] The linear microsphere clusters were arranged through a capillary micro-molding method (the template structure can be shown as Figure 5 , and the gap along the up-down direction in the figure can accommodate multiple microspheres arranged in a linear manner). Through the above steps, linear azobenzene polymer microsphere clusters can be prepared.

[0104] Figure 6 TEM images of adjacent two monodisperse azobenzene polymer microspheres corresponding to different irradiation times of 365 nm ultraviolet light. It can be seen that the monodisperse azobenzene polymer microspheres prepared by the present application can fuse to a certain extent after irradiation by 365 nm ultraviolet light.

[0105] Figure 7 SEM images corresponding to the arrangement of azobenzene polymer microspheres through a linear template, irradiation by 365 nm ultraviolet light and 435 nm visible light to the photo-stable state. It can be seen that the photo-induced fusion-de-fusion has no effect on the arrangement of the polymer microspheres.

[0106] Figure 8 Comparison diagram of the connection effect of azobenzene polymer microspheres after photo-induced fusion and covalent cross-linking and without cross-linking. Figure 8 In a), the electron microscope image after irradiation by 365 nm wavelength ultraviolet light, Figure 8 In b), the electron microscope image corresponding to the ultrasonic treatment of the polymer microspheres after irradiation and without cross-linking, Figure 8 In c), the electron microscope image corresponding to the ultrasonic treatment of the polymer microspheres after irradiation and cross-linking. It can be seen that the cross-linking reaction plays a very obvious role in the fixation of the polymer microspheres.

[0107] Figure 9 XPS spectra of azobenzene polymer microspheres before and after cross-linking. Peak fitting was carried out on the XPS narrow scan spectrum, Figure 9XPS spectrum of O before cross-linking reaction 1s The main peak in the spectrum can be divided into two sub-peaks at 532.2 eV and 533.9 eV, corresponding to oxygen atoms in C-O and O-H respectively, Figure 7 XPS spectrum of C after cross-linking reaction 1s The spectrum can be divided into four different types of carbon atoms, C-C / C-H (284.8 eV), C-OH (285.7 eV), C-N (286.2 eV) and O-C-O (287.7 eV). In the XPS spectrum after acetal reaction, Figure 7 XPS spectrum of O after cross-linking reaction 1s The O-H peak in the spectrum and Figure 7 XPS spectrum of C after cross-linking reaction 1s The C-OH peak in the spectrum disappears, indicating that the -OH group therein has been completely consumed by the reaction and converted into O-C-O group.

[0108] Figure 10 A schematic diagram of different configurations of azobenzene polymer microsphere clusters obtained after template arrangement, photo-fusion, cross-linking and fixation by acetal reaction, and removal of the template.

[0109] The present application overcomes the defect of unstable structure of polymer microsphere clusters constructed by the prior art. Monodisperse azobenzene polymer microspheres are prepared by dispersion polymerization technology. Subsequently, after template arrangement, due to the unique photoresponsive properties of azobenzene groups, the polymer microspheres undergo photo-fusion, and the fused parts of the microspheres are covalently cross-linked by chemical cross-linking reaction, and finally stable polymer microsphere clusters are obtained, which provides a broad prospect for further application. It has great application potential in the fields of optical switch, optical information storage material, photo-regulation of biomolecular activity, nonlinear optical material, nanomaterial, integrated optics, etc.

[0110] The above examples are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made according to the spirit and principle of the present application should be covered within the protection scope of the present application.

[0111] The endpoints of the ranges and any values claimed herein are not to be understood as being limited to the exact values recited as endpoints but rather to also include values which are reasonably close thereto in the light of sound experimentation. For values which are lesser than or greater than the values recited as the stated limits for a given range, new values within that range, between the lower limit and the lesser value, and between the upper limit and the greater value, are considered to be within the range in accordance with the principles of sound experimentation.

Claims

1. A method for preparing a cluster of azobenzene polymer microspheres, characterized by, The preparation method comprises the following steps: a plurality of monodisperse azobenzene polymer microspheres containing reactive end group are assembled according to a preset arrangement mode, the assembly is realized by setting a template, and the monodisperse azobenzene polymer microspheres are assembled in the template; the monodisperse azobenzene polymer microspheres in the preset arrangement mode and located in the template are irradiated with light together with the template, and a chemical cross-linking reaction is carried out, the template is separated, and azobenzene polymer microsphere clusters are obtained; the irradiation with light is carried out by using light, fusion occurs between every two adjacent monodisperse azobenzene polymer microspheres, and the fused parts are formed into covalent connections through a chemical cross-linking reaction in which the reactive end group participates; the chemical cross-linking reaction is an acetal reaction, or the chemical cross-linking reaction is carried out by adding a polyisocyanate to carry out a nucleophilic reaction with a hydroxyl group, or the chemical cross-linking reaction is carried out by adding a polyisocyanate or a halogenated hydrocarbon to carry out a nucleophilic reaction with an amino group.

2. The method for preparing azobenzene polymer microsphere clusters according to claim 1, characterized in that, the monodisperse azobenzene polymer microspheres have a structure shown in formula (I): , formula (I), a, b are independently selected from 2-15, R is hydroxyl or amino.

3. The method for preparing azobenzene polymer microsphere clusters according to claim 1, characterized in that, when R is a hydroxyl group, the chemical cross-linking reaction is an acetal reaction, or the chemical cross-linking reaction is carried out by adding a polyisocyanate to carry out a nucleophilic reaction with a hydroxyl group; when R is an amino group, the chemical cross-linking reaction is carried out by adding a polyisocyanate or a halogenated hydrocarbon to carry out a nucleophilic reaction with an amino group.

4. The method for preparing azobenzene polymer microsphere clusters according to claim 1, characterized in that, the monodisperse azobenzene polymer microspheres are fused between the microspheres under irradiation with ultraviolet light, and are restored to the initial state under irradiation with visible light.

5. The method for preparing azobenzene polymer microsphere clusters according to claim 4, characterized in that, the wavelength of the ultraviolet light is 360-370 nm, and the wavelength of the visible light is 430-440 nm.

6. An azobenzene polymer microsphere cluster prepared by the preparation method in any one of claims 1-5.

7. Application of the azobenzene polymer microsphere cluster in claim 6 to optical switches, optical information storage materials, biomolecule active light regulation materials, nonlinear optical materials or integrated optical materials.

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