Chemically and morphologically anisotropic polymer hemispherical particles, and preparation and visual detection methods thereof

Abstract

The present invention belongs to the field of new material technology, and more specifically, relates to a chemically and morphologically anisotropic polymer hemispherical particle, and a method for its preparation and visualization detection. The preparation method is to use a seed emulsion polymerization method to cause polymerization-induced phase separation of monomers in emulsion droplets, and then selectively wash with a solvent to obtain polymer hemispherical particles with chemical and morphological anisotropy. The hemispherical synthesis method described in the present invention is simple and efficient, and the reaction conditions are mild. The synthesized polymer hemispherical particles have anisotropy with different chemical compositions and morphologies, and the chemical composition is adjustable, and the surface can be modified again. The synthesis of the new anisotropic polymer hemispheres of the present invention expands the types of anisotropic polymer particles and has good application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of new materials, and more specifically, relates to a chemically and morphologically anisotropic polymer hemispherical particle, and a preparation and visual detection method thereof. Background Art

[0002] The study of the synthesis of anisotropic microspheres is of great significance for the development of new materials in the field of colloidal science. These colloids are usually anisotropic in morphology or chemical composition. Non-spherical particles with anisotropic morphology will show different physical properties from spherical particles. Anisotropic microspheres with different chemical compositions in multiple regions can achieve multiple manifestations of different properties on the same microsphere. Anisotropic colloidal particles can have great application prospects in specific recognition, self-assembled colloids, surfactants, displays, catalysts, cell imaging and recognition, drug release and delivery, etc. In particular, hemispherical particles have a natural advantage in assembly. The golf ball-shaped morphology, due to its unique morphology with dimples on the surface, gives this type of microsphere unique tribology and surface activity, and can be used to prepare optical materials with unique crystal structure and light scattering properties.

[0003] Many advanced technologies, including seed polymerization, microfluidics, mechanical stretching, electrohydrodynamic jetting, aggregation, template-assisted methods, and self-assembly, have been developed for the production of non-spherical anisotropic particles. However, the precise preparation of anisotropic microspheres with specific morphologies remains extremely challenging due to the following drawbacks: 1) large-scale production is difficult, reproducibility is low, and the product is not monodisperse; 2) the particles have a single chemical composition or morphology, lacking the ability to express multiple chemical compositions or morphologies; and 3) the need for specialized equipment, difficulty in operation, and complexity of the process. Summary of the Invention

[0004] In response to the shortcomings of the prior art, the purpose of the present invention is to provide a chemically and morphologically anisotropic polymer hemispherical particle, and a method for its preparation and visual detection, so as to solve the technical problems of the prior art such as the extremely challenging process of accurately preparing anisotropic microspheres with a certain special morphology.

[0005] To achieve the above objectives, the present invention provides a method for preparing chemically and morphologically anisotropic polymer hemispherical particles, comprising the following steps:

[0006] (1) dispersing non-crosslinked linear polystyrene microspheres in an aqueous solution containing a surfactant to obtain a first mixed solution; mixing a hydrophilic monomer, a hydrophobic monomer, and a hydrophobic initiator with the aqueous solution containing a surfactant and emulsifying the mixture to obtain a first emulsion; the homopolymer of the hydrophilic monomer, the homopolymer of the hydrophobic monomer, and the copolymer of the hydrophilic monomer and the hydrophobic monomer are not miscible with the non-crosslinked polystyrene;

[0007] (2) mixing the first mixed solution and the first emulsion in step (1) and stirring them sufficiently so that the hydrophobic monomer and the hydrophobic initiator enter the interior of the non-crosslinked linear polystyrene microspheres and swell the non-crosslinked linear polystyrene microspheres, thereby obtaining a second mixture;

[0008] (3) introducing an inert protective gas into the second mixture of step (2), heating to induce a polymerization reaction between the hydrophilic monomer and the hydrophobic monomer, and obtaining a crude product;

[0009] (4) The crude product of step (3) is washed with deionized water and an alcohol solvent in sequence, the washed polymer particles are dispersed in water, and dried to obtain chemically and morphologically anisotropic polymer hemispherical particles.

[0010] Preferably, the particle size of the non-crosslinked linear polystyrene microspheres is 0.1-50 μm, and the concentration of the non-crosslinked linear polystyrene microspheres in the first mixed solution is 1-500 mg / mL; more preferably 1-50 mg / mL.

[0011] Preferably, the surfactant is one or more of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, cetyl ammonium bromide, cetyltrimethylammonium bromide and polyvinyl alcohol, and the concentration of the surfactant in the aqueous solution containing the surfactant is 0.1-50 g / L; more preferably 1-10 g / L.

[0012] Preferably, the hydrophilic monomer is acrylic acid and / or methacrylic acid; the molar concentration of the hydrophilic monomer in the first emulsion is 0.1-10.0 mol / L, more preferably 0.1-1.0 mol / L; the hydrophobic monomer is an acrylate monomer whose homopolymer glass transition temperature is 30-70°C, preferably one or more of ethyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate and glycidyl methacrylate; the molar concentration of the hydrophobic monomer in the first emulsion is 0.1-5.0 mol / L, more preferably 0.5-3.0 mol / L.

[0013] Preferably, the hydrophobic initiator is a hydrophobic thermal initiator, preferably azobisisobutyronitrile; the concentration of the initiator in the first emulsion is 1-5 g / L; the concentration of the surfactant in the first emulsion is 1-5 g / L, more preferably 2-3 g / L.

[0014] Preferably, the stirring in step (2) is performed for 1-24 hours, more preferably for 3-14 hours, and is supplemented by heating at a temperature not higher than 40°C.

[0015] Preferably, the polymerization reaction in step (3) has a reaction time of 1-24 hours, more preferably 10-16 hours; and a reaction temperature of 50-100°C, more preferably 60-70°C.

[0016] Preferably, the alcohol solvent in step (4) is one or more of ethanol, propanol, isopropanol, n-propanol, n-butanol and n-hexanol.

[0017] According to another aspect of the present invention, there are provided polymer hemispherical particles with chemical and morphological anisotropy prepared by the preparation method.

[0018] Preferably, the polymer hemispherical particles have a hemispherical or quasi-hemispherical shape, the spherical surface of the hemisphere or quasi-hemispherical particle has an uneven surface, and the bottom of the hemisphere or quasi-hemispherical particle has a smooth surface; the polymer hemispherical particles are amphiphilic, with a hydrophilic outer side and a hydrophobic inner side, wherein the outer side contains a homopolymer of a hydrophilic monomer and a copolymer of a hydrophilic monomer and a hydrophobic monomer; and the inner side contains a homopolymer of a hydrophobic monomer and non-cross-linked polystyrene.

[0019] Preferably, the particle size of the polymer hemispherical particles is 0.1-50 μm, more preferably 1-10 μm.

[0020] According to another aspect of the present invention, a method for visualizing the aggregation-induced luminescence of the polymer hemispherical particles is provided, wherein the polymer hemispherical particles are dyed with a hydrophilic fluorescent dye and a hydrophobic fluorescent dye having an aggregation-induced luminescence effect, respectively, so that the hydrophilic regions and hydrophobic regions on the polymer hemispherical particles can be observed, respectively, thereby detecting the chemical anisotropy of the polymer hemispherical particles.

[0021] In general, the above technical solutions conceived by the present invention have the following beneficial effects compared with the prior art:

[0022] (1) The present invention provides a method for preparing polymer hemispherical particles, which adopts a seed emulsion polymerization method, wherein the homopolymer of the hydrophilic monomer, the homopolymer of the hydrophobic monomer, and the copolymer of the hydrophilic monomer and the hydrophobic monomer are not miscible with the non-crosslinked polystyrene microsphere seeds used in the present invention, so that the monomers undergo polymerization-induced phase separation in the emulsion droplets, and then selectively washed with a solvent to obtain polymer hemispherical particles with chemical and morphological anisotropy, breaking the limitation of traditional emulsion polymerization that spherical particles are easily formed due to the influence of surface tension.

[0023] (2) The polymer hemispherical particles synthesized in the present invention exhibit both chemical and morphological anisotropy. Morphologically, one side of the microsphere is a golf ball-shaped convex surface with pits, while the other side is a smooth flat surface. Physically, the microsphere is hydrophilic on the outside and hydrophobic on the inside. In other words, the inside and outside of the microsphere have different chemical compositions. The chemical composition and morphology are different in all directions. The chemical composition can be arbitrarily adjusted by changing the type of monomer, and its surface functional groups can also be further modified.

[0024] (3) The polymer hemispherical particles of the present invention have great application prospects in particle surfactants, interface assembly, oil-water separation, photonic crystals, etc.

[0025] (4) The preparation method of the polymer hemispherical particles of the present invention has a simple process, easy-to-control experimental conditions, and a simple and easy post-processing method, and has certain industrial application value.

[0026] (5) The present invention provides a chemically and morphologically anisotropic polymer hemispherical particle having amphiphilic properties. The present invention also provides a method for visualizing the aggregation-induced luminescence of the polymer hemispherical particle. The polymer hemispherical particle is dyed with a hydrophilic fluorescent dye and a hydrophobic fluorescent dye having an aggregation-induced luminescence effect, respectively. The hydrophilic and hydrophobic regions on the polymer hemispherical particle can be observed through fluorescent photography, thereby detecting the chemical anisotropy of the polymer hemispherical particle. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic flow chart of the method for preparing polymer hemispherical particles of the present invention;

[0028] Figure 2 is a scanning electron microscope image of the polymer hemispherical particles synthesized in Example 1 of the present invention;

[0029] Figure 3 Statistical diagram of particle size of the polymer hemispherical particles synthesized in Example 1 of the present invention;

[0030] Figure 4 This is a transmission electron micrograph of the polymer hemispherical particles synthesized in Example 1 of the present invention after being embedded and sectioned;

[0031] Figure 5 This is a fluorescent photograph of the polymer hemispherical particles synthesized in Example 1 of the present invention after being dyed with a hydrophilic fluorescent dye;

[0032] Figure 6 This is a fluorescent photograph of the polymer hemispherical particles synthesized in Example 1 of the present invention after being dyed with a hydrophobic fluorescent dye;

[0033] Figure 7This is an overlay of photos after staining with hydrophilic dye and hydrophobic dye;

[0034] Figure 8 Schematic diagram of the inferred chemical structure of the hemispherical particles prepared in this example;

[0035] Figure 9 This is the NMR spectrum of the polymer hemispherical particles prepared in Example 1;

[0036] Figure 10 This is the Fourier transform infrared spectrum of the polymer hemispherical particles prepared in Example 1;

[0037] Figure 11 Comparison of the morphology of polymer particles obtained at different hydrophobic monomer concentrations;

[0038] Figure 12 This is a comparison of the morphologies of different polymer particles obtained with different types of hydrophobic monomers;

[0039] Figure 13 Comparison of the morphology of polymer particles obtained with different alcohol cleaning agents. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0041] The present invention provides a method for preparing chemically and morphologically anisotropic polymer hemispherical particles, such as Figure 1 As shown, the following steps are included:

[0042] (1) dispersing non-crosslinked linear polystyrene (PSt) microspheres in an aqueous solution containing a surfactant to obtain a first mixed solution; mixing a hydrophilic monomer, a hydrophobic monomer, and a hydrophobic initiator with the aqueous solution containing the surfactant and emulsifying the mixture to obtain a first emulsion; the homopolymer of the hydrophilic monomer, the homopolymer of the hydrophobic monomer, and the copolymer of the hydrophilic monomer and the hydrophobic monomer are not miscible with the non-crosslinked linear polystyrene;

[0043] (2) mixing the first mixed solution and the first emulsion in step (1) and stirring them sufficiently so that the hydrophobic monomer and the initiator enter the interior of the non-crosslinked linear polystyrene microspheres and swell the non-crosslinked linear polystyrene microspheres, thereby obtaining a second mixture;

[0044] (3) introducing an inert protective gas into the second mixture of step (2), heating to induce a polymerization reaction between the hydrophilic monomer and the hydrophobic monomer, and obtaining a crude product; since the homopolymer of the hydrophilic monomer, the homopolymer of the hydrophobic monomer, and the copolymer of the hydrophilic monomer and the hydrophobic monomer are not miscible with the non-crosslinked polystyrene microspheres, as the polymerization reaction occurs, the homopolymer of the hydrophobic monomer, the homopolymer of the hydrophilic monomer, and the copolymer of the hydrophilic monomer and the hydrophobic monomer gradually undergo microphase separation from the polystyrene to form two phases; one phase is a polymer-rich phase (the polymer includes a homopolymer of the hydrophilic monomer, a homopolymer of the hydrophobic monomer, and a copolymer of the hydrophilic monomer and the hydrophobic monomer), and the other phase is a non-crosslinked linear polystyrene-rich phase;

[0045] (4) The crude product of step (3) is washed with deionized water and then with an alcohol solvent, and the washed polymer particles are dispersed in water, and dried to obtain chemically and morphologically anisotropic polymer hemispherical particles. First, deionized water is used to remove the homopolymer of the water-soluble hydrophilic monomer and other hydrophilic molecules, and then an alcohol solvent is used to dissolve the homopolymer of the hydrophobic monomer and the copolymer of the hydrophobic monomer and the hydrophilic monomer, causing the polymer particles to deform and compress to form hemispherical particles.

[0046] The non-crosslinked linear polystyrene (PSt) microspheres described herein can be prepared by the following method: dispersing styrene and sodium chloride in water, then adding ammonium persulfate as an initiator and introducing an inert protective gas of nitrogen or argon, heating to initiate polymerization, washing the mixture alternately with water and ethanol multiple times, and freeze-drying to obtain PSt. In some embodiments, the particle size of the non-crosslinked linear polystyrene (PSt) microspheres is 0.1-50 μm, preferably 1-10 μm; the concentration of the non-crosslinked linear polystyrene microspheres in the first mixed solution is 1-500 mg / mL, preferably 1-50 mg / mL, and more preferably 10-30 mg / mL.

[0047] In some embodiments, the surfactant is one or more of sodium dodecyl sulfate (abbreviated as SDS), sodium dodecylbenzenesulfonate, cetyl ammonium bromide, cetyltrimethylammonium bromide and polyvinyl alcohol, and the concentration of the surfactant in the aqueous solution containing the surfactant is 0.1-50 g / L; preferably 1-10 g / L, and more preferably 2-5 g / L.

[0048] In some embodiments, the hydrophilic monomer is acrylic acid and / or methacrylic acid; the molar concentration of the hydrophilic monomer in the first emulsion is 0.1-10.0 mol / L, preferably 0.1-1.0 mol / L, and more preferably 0.4-0.6 mol / L. The hydrophobic monomer is an acrylate monomer whose homopolymer glass transition temperature is 30-70°C; including but not limited to one or more of ethyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate and glycidyl methacrylate; the molar concentration of the hydrophobic monomer in the first emulsion is 0.1-5.0 mol / L, preferably 0.5-3.0 mol / L, and more preferably 0.8-1.5 mol / L. The present invention has found in experiments that regulating the concentration of the hydrophobic monomer can regulate the morphology of the resulting polymer hemispherical particles.

[0049] The hydrophilic monomer, the hydrophobic monomer, the initiator and the aqueous solution containing the surfactant are mixed and emulsified. The emulsification can be carried out by various conventional emulsification methods, including but not limited to ultrasound, high-speed stirring, etc. In some embodiments, an ultrasonic cell crusher is used for emulsification to obtain a first emulsion.

[0050] In some embodiments, the initiator is a hydrophobic thermal initiator, preferably azobisisobutyronitrile (AIBN). The concentration of the initiator in the first emulsion is 1-5 g / L; the concentration of the surfactant in the first emulsion is 1-5 g / L, preferably 2-3 g / L.

[0051] The present invention mixes and stirs the first mixed liquid and the first emulsion, allowing the hydrophobic monomer and the hydrophobic thermal initiator to enter the interior of the PSt microspheres and cause the PSt microspheres to swell; then, heating is performed to initiate monomer polymerization. Since the homopolymer of the hydrophilic monomer, the homopolymer of the hydrophobic monomer, and the copolymer of the hydrophilic monomer and the hydrophobic monomer used in the present invention are not miscible with the non-crosslinked polystyrene microsphere seeds used in the present invention, as the polymerization reaction occurs, the homopolymer of the hydrophobic monomer, the homopolymer of the hydrophilic monomer, and the copolymer of the hydrophilic monomer and the hydrophobic monomer gradually undergo microphase separation from the polystyrene to form two phases; and experiments have found that the homopolymer of the hydrophilic monomer is located on the surface of the entire obtained particle, while the homopolymer of the hydrophobic monomer and the vast majority of the copolymer of the hydrophilic monomer and the hydrophobic monomer occupy one side (hemisphere) of the microsphere, and the other side (hemisphere) is mainly polystyrene, with a very small amount of the copolymer of the hydrophilic monomer and the hydrophobic monomer located on the end side surface of the polystyrene.

[0052] In some embodiments, the stirring in step (2) is performed for 1-24 hours, preferably 3-14 hours, and is supplemented by heating at a temperature not exceeding 40°C. The polymerization reaction in step (3) is performed for 1-24 hours, preferably 10-16 hours, at a temperature of 50-100°C, preferably 60-70°C.

[0053] In some embodiments, before the polymerization reaction in step (3), a dispersant is added to the second mixture to prevent polymer particles from sticking together during the polymerization reaction; the dispersant includes, but is not limited to, polyvinyl alcohol (PVA). The amount of the dispersant added is 0.02-0.05% of the total mass of the second mixture.

[0054] In some embodiments, the alcohol solvent in step (4) is one or more of ethanol, propanol, isopropanol, n-propanol, n-butanol, and n-hexanol. The protective gas is an inert gas, including but not limited to nitrogen, argon, etc. Experiments have found that in the preparation process of the polymer particles of the present invention, spherical particles are first obtained through swelling and polymerization. The spherical particles are washed with alcohol solvents, and their spherical morphology can be adjusted to a hemispherical or quasi-hemispherical shape. The possible reason is that after the polymerization reaction is completed and the differential phase is completed (one side is a polymer-rich phase and the other side is a polystyrene (PSt)-rich phase), a water solvent is first used to wash and remove the homopolymer of the water-soluble hydrophilic monomer and other hydrophilic molecules. Then, when an alcohol solvent such as ethanol is used for washing, ethanol dissolves the homopolymer of the hydrophobic monomer and the copolymer of the hydrophobic monomer and the hydrophilic monomer, causing the polymer particles to deform and compress. The dissolution of the internal polymer causes an imbalance of force inside and outside the polymer particles. The empty sphere is squeezed by external force and collapses into a hemisphere. At the same time, since a small amount of copolymer on the surface of the PSt-rich hard phase in the polymer particles is partially washed away by ethanol, there are several pits on the convex surface of the polymer hemisphere.

[0055] The present invention provides chemically and morphologically anisotropic polymer hemispherical particles. The polymer hemispherical particles have a hemispherical or quasi-hemispherical morphology, wherein the hemispherical surface has a convex surface similar to the surface of a golf ball, and the hemispherical bottom has a smooth surface. Nuclear magnetic resonance and Fourier transform infrared spectroscopy analysis show that the polymer hemispherical particles are amphiphilic, with a hydrophilic outer side and a hydrophobic inner side, wherein the outer side contains a homopolymer of a hydrophilic monomer and a copolymer of a hydrophilic monomer and a hydrophobic monomer; and the inner side contains a homopolymer of a hydrophobic monomer and non-crosslinked polystyrene.

[0056] In some embodiments, the polymer hemispherical particles have a particle size of 0.1-50 μm, preferably 1-10 μm.

[0057] The present invention provides a chemically and morphologically anisotropic polymer hemispherical particle with amphiphilic properties. The present invention also provides a method for visualizing aggregation-induced luminescence (AIE) of the polymer hemispherical particle. The polymer hemispherical particle is dyed with a hydrophilic fluorescent dye and a hydrophobic fluorescent dye, respectively, each exhibiting AIE. Fluorescent images allow visualization of the hydrophilic and hydrophobic regions on the polymer hemispherical particle, thereby enabling detection of the chemical anisotropy of the polymer hemispherical particle.

[0058] The present invention uses a fluorescent dye with aggregation-induced emission (AIE) effect to perform visual detection of the polymer hemispherical particles. Compared with other common fluorescent dyes with large planar conjugated structures, it can exhibit a better fluorescence effect, especially for the detection of hydrophobic regions. The use of common fluorescent dyes may cause fluorescence quenching due to the aggregation-induced quenching effect. The fluorescent dyes with aggregation-induced emission effect of the present invention, including the hydrophilic AIE fluorescent dye TPA-2OH and the hydrophobic AIE fluorescent dye TPE, generate fluorescence only in an aggregated state, so that not only the hydrophilic region but also the hydrophobic region of the polymer hemispherical particles of the present invention can be clearly observed.

[0059] Patent document CN107383282A discloses a method for synthesizing polymer Janus particles with chemical and topological anisotropy. It directly prepares crescent-shaped anisotropic Janus particles by emulsion interfacial polymerization. It uses a hydrophobic crosslinker. The resulting crescent-shaped microspheres are crosslinked microspheres. The non-crosslinked polystyrene microsphere seeds used are miscible with the monomer polymer, making them unable to phase separate after polymerization. The subsequent treatment only serves as a cleaning function and does not affect the original morphology or properties of the microspheres. The Janus microspheres obtained by this method are crosslinked particles and are not suitable for non-crosslinked systems. No matter how they are adjusted, the microspheres cannot obtain a smooth bottom hemisphere, which limits its application in planar substrate interface assembly. The mechanism of hemisphere formation in the present invention is mainly polymerization-induced phase separation and selective dissolution of alcohol solvents. Microphase separation during the polymerization process causes the hydrophobic region of the polymer to be differentiated into two independent regions. The addition of alcohol solvents causes a portion of the alcohol-soluble polymer to be selectively dissolved, thereby generating hemispheres. The polymer hemispherical particles prepared by the present invention, also known as colloidal particles, are naturally suitable for interfacial assembly, and their amphiphilic and anisotropic morphology can give the microspheres higher interfacial activity and interfacial desorption energy. 2D non-densely packed colloidal crystal patterns are mainly used in structural development or optical materials. For example, non-densely packed colloidal patterns can be used as anti-reflective coatings to improve the solar thermal efficiency of planar and micro-patterned substrates; the optical tunability of colloidal crystal patterns makes it possible to develop printable and erasable substrates based on colloidal crystals. Adjustable colloidal crystal patterns can be formed on periodically micro-patterned substrates, thereby producing novel single-layer crystal structures. These substrates are mostly flat surfaces, such as silicon, glass, graphene, polyethylene terephthalate, and polydimethylsiloxane surfaces. The hemispherical particles of the present invention are very suitable as colloids in the pattern. The smooth bottom plane of the hemisphere provides the most favorable morphological conditions for the good assembly of microspheres on the surface.

[0060] The following are examples:

[0061] In the following examples of the present invention, non-crosslinked linear polystyrene microspheres (referred to as PSt seeds in the examples) were prepared as follows: 0.1 g NaCl, 60 g H₂O, 6.0 mL styrene, and 70 mg ammonium persulfate (APS) were added sequentially to a 100 mL single-necked flask. A condenser was inserted into the flask neck, and nitrogen was removed by double-row pipettes to remove oxygen. The mixture was then placed in an oil bath and reacted at 70°C for 24 hours. After the reaction, stirring was stopped, the reaction solution was removed and centrifuged, and the resulting microspheres were washed three times with water and then ethanol. The sample was observed using an electron microscope to determine the morphology and particle size of the seed microspheres. The product was freeze-dried to obtain a white powder, namely PSt microspheres with an average particle size of 1.6 μm.

[0062] Example 1

[0063] Two 50 mL round-bottom centrifuge tubes were prepared. Tube A was added with 0.2 g of PSt seeds and 20 mL of SDS solution, which was ultrasonically dispersed and set aside. Tube B was added with 10 mL of SDS solution, 2.5 mL of iBMA (isobutyl methacrylate), 40.0 mg of AIBN (azobisisobutyronitrile), and 0.4 mL of AA (acrylic acid) and emulsified using an ultrasonic cell disruptor. Tubes A and B were sequentially poured into a round-bottom flask, and the mixed solution was stirred at 40°C for 5 hours. After adding 5 mL of PVA to the flask, the reaction temperature was raised to 65°C, and after deoxygenation by venting N2 through a double-row pipe, the reaction was allowed to proceed for 14 hours. After completion of the reaction, the reaction solution was centrifuged at 4000 rpm to obtain a first white precipitate. The microsphere morphology was observed using an electron microscope, and the microspheres were rinsed with deionized water.

[0064] Ethanol was added to the washed microspheres. After sonication, the dispersion was centrifuged at 2000 rpm and rinsed again with deionized water to obtain a second white precipitate. The microsphere morphology was observed under an electron microscope. The first and second white precipitates were freeze-dried to obtain a first and second white powders.

[0065] The second white powder obtained by freeze-drying the second white precipitate was subjected to scanning electron microscopy analysis, particle size analysis, transmission electron microscopy analysis,

[0066] The second white powder obtained by freeze-drying the second white precipitate was analyzed by scanning electron microscopy. Figure 2 .Depend on Figure 2 It can be seen that the obtained polymer microspheres are regular hemispherical particles with smooth bottoms and rough convex surfaces. The particle size analysis of the second white powder is shown in the following figure. Figure 3 .Depend on Figure 3 It can be seen that the average diameter of the polymer hemisphere is 1.93 ± 0.06 μm; the second white powder was analyzed by transmission electron microscopy, and the results are shown in Figure 4 ,Depend on Figure 4 It can also be seen that the microspheres have a hemispherical structure. The second white powder is dyed with a hydrophilic fluorescent dye TPA-2OH. Specifically, the microsphere sample is spin-coated on a glass cover slip and then the fluorescent dye is dropped on it. The fluorescent photograph after dyeing is shown in FIG. Figure 5 As shown, the structural formula of the hydrophilic fluorescent dye TPA-2OH is shown in formula (1):

[0067]

[0068] Formula (1)

[0069] Depend on Figure 5It can be seen that after the polymer hemispherical particles are dyed with a hydrophilic fluorescent dye, only the hydrophilic surface has fluorescence, while the hydrophobic surface has no fluorescence; the second white powder is dyed with a hydrophobic fluorescent dye, and the fluorescence photograph after dyeing is as shown in FIG. Figure 6 As shown by Figure 6 It can be seen that after the polymer hemispherical particles are dyed with the hydrophobic AIE fluorescent dye TPE (tetraphenylethylene), only the internal hydrophobic region has fluorescence, while the surface hydrophilic surface has no fluorescence.

[0070] The photos dyed with hydrophilic and hydrophobic dyes are superimposed, and the results are as follows: Figure 7 As shown by Figure 7 It can be seen that the hydrophilic and hydrophobic regions are clearly distinct, indicating that the synthesized particles have anisotropic chemical composition and the microspheres are hydrophilic on the outside and hydrophobic on the inside.

[0071] Figure 8 Schematic diagram of the inferred chemical structure of the hemispherical particles prepared in this example. Figure 9 This is the NMR spectrum of the polymer hemispherical particles prepared in Example 1. Figure 10 Here is its Fourier transform infrared spectrum. Nuclear magnetic resonance (NMR) analysis shows that the peaks at 7.08-6.45 are attributed to the hydrogen at position A in styrene, the peaks at 3.94-3.70 are attributed to the hydrogen at position B on the O-C-C bond in isobutyl methacrylate, and the peaks at 1.95-0.88 are attributed to the hydrogens on the remaining carbon chains. Fourier transform infrared spectroscopy: Comparison of the FT-IR spectra of the PSt seed particles and the hemispherical particles of this example. The hemispherical spectrum contains characteristic peaks for the benzene ring (1601-1368 cm-1) and CH in benzene (730-690 cm-1), as well as peaks for C=O (1729 cm-1) and COC of P(iBMA-co-AA) (1300-1000 cm-1). Fourier transform infrared (FTIR) spectroscopy confirms the successful polymerization of the PSt / P(iBMA-co-AA) polymer colloid.

[0072] Example 2

[0073] The volume of the hydrophobic monomer iBMA in Example 1 was changed from 2.5 mL to a) 1 mL, b) 1.5 mL, c) 2 mL, e) 3 mL, f) 3.5 mL, g) 4 mL, and h) 4.5 mL, respectively. Other conditions were the same as in Example 1. The scanning electron microscopy images of the obtained polymer hemispherical or quasi-hemispherical particles are shown in FIG. Figure 11 Content a), Content b), Content c), Content e), Content f), Content g), and Content h), wherein Content d) is a scanning electron microscope image of the hemispherical polymer particles of Example 1. Content i) is the cross-sectional width data of the hemispherical particles obtained with changes in iBMA concentration.

[0074] from Figure 11 It can be seen that when the concentration of the hydrophobic monomer iBMA in the first emulsion is 1.2 mol / L, the prepared polymer particles have a standard hemispherical morphology. On this basis, when the concentration of the hydrophobic monomer is further reduced, the smooth surface of the polymer particles becomes concave; when the concentration of the hydrophobic monomer is further increased, the smooth surface of the polymer particles becomes convex.

[0075] Example 3

[0076] The hydrophobic monomer in Example 1 was replaced from iBMA to styrene (St) with a homopolymer glass transition temperature of 100°C, methyl methacrylate (MMA) monomer with a temperature of 105°C, ethyl methacrylate (EMA) monomer with a temperature of 65°C, and n-butyl methacrylate (nBMAA) monomer with a temperature of 20°C. Other conditions were the same as in Example 1. The morphology of the prepared polymer particles was as follows: Figure 12 shown.

[0077] Figure 12 The first row shows scanning electron micrographs of the first white powder before washing with ethanol, while the second row shows scanning electron micrographs of the second white powder after washing with ethanol. The different columns correspond to the different hydrophobic monomers used. Different monomers were used in the seeded emulsion polymerization, such as styrene (St), methyl methacrylate (MMA), ethyl methacrylate (EMA), isobutyl methacrylate (iBMA), and n-butyl methacrylate (nBMA). Their homopolymers, PSt, PMMA, PEMA, PiBMA, and PnBMA, have glass transition temperatures of 100°C, 105°C, 65°C, 53°C, and 20°C, respectively. Before washing with ethanol, round polymer microspheres with similar morphology were observed. After washing with ethanol, the morphology of the polymer colloids changed depending on the monomer type. Figure 12In cases a) and f) using St as the hydrophobic monomer, and in cases b) and g) using MMA as the hydrophobic monomer, the resulting polymer particles were spherical, both before and after ethanol washing; no hemispherical particles were obtained. In cases c) and h) using EMA as the hydrophobic monomer, and in cases d) and i) using iBMA as Example 1, standard hemispherical particles were obtained. In cases e) and j) using nBMA as the hydrophobic monomer, deformation also occurred after ethanol washing, but smooth surfaces were not obtained. This is presumably because the morphological changes in the polymer colloids induced by ethanol washing depend on the polymer's glass transition temperature. The glass transition temperatures of PSt and PMMA are well above room temperature, so even if the hydrophilic polymer is partially removed by ethanol, the resulting hard polymer microspheres do not collapse. Polymers with intermediate glass transition temperatures, such as PEMA and PiBMA, are relatively soft, resulting in flexible but collapsible polymer colloids. Therefore, similar hemispherical polymers were obtained using EMA and iBMA. For flexible PnBMA with a glass transition temperature below room temperature, irregular polymer microspheres were observed because the flexible PnBMA polymer flowed around the hemispheres. Therefore, we believe that when the homopolymer has a moderate glass transition temperature (e.g., 30-70°C) and is immiscible with polystyrene as a hydrophobic monomer, polymer hemispheres can form.

[0078] Example 4

[0079] The washing solvent in Example 1 was replaced from ethanol to methanol, isopropanol, n-propanol, n-butanol and n-hexanol respectively, and other conditions were the same as in Example 1. The scanning electron micrograph of the second white powder obtained after washing and freeze-drying is shown in FIG13 .

[0080] Figure 13 The cleaning solvent for content a) is methanol, content b) is ethanol, content c) is isopropanol, content d) is n-propanol, content e) is n-butanol, and content f) is n-hexanol. It can be seen that, except for methanol, which failed to produce hemispherical polymer particles, the other alcohol solvents all produced hemispherical polymer particles. This may be due to the high polarity of methanol, which has poor solubility in the P(iBMA-co-AA) copolymer and is unable to remove the P(iBMA-co-AA).

[0081] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing chemically and morphologically anisotropic polymer hemispherical particles, characterized in that: The steps include: (1) Dispersing non-crosslinked linear polystyrene microspheres in an aqueous solution containing a surfactant to obtain a first mixed solution; mixing a hydrophilic monomer, a hydrophobic monomer, and a hydrophobic initiator with the aqueous solution containing a surfactant and emulsifying the mixture to obtain a first emulsion; the homopolymer of the hydrophilic monomer, the homopolymer of the hydrophobic monomer, and the copolymer of the hydrophilic monomer and the hydrophobic monomer are not miscible with the non-crosslinked linear polystyrene; the hydrophilic monomer is acrylic acid and / or methacrylic acid; the molar concentration of the hydrophilic monomer in the first emulsion is 0.1-10.0 mol / L; the hydrophobic monomer is an acrylate monomer whose homopolymer glass transition temperature is 30-70°C; the molar concentration of the hydrophobic monomer in the first emulsion is 0.1-5.0 mol / L; (2) mixing the first mixed solution and the first emulsion in step (1) and stirring them sufficiently so that the hydrophobic monomer and the hydrophobic initiator enter the interior of the non-crosslinked linear polystyrene microspheres and swell the non-crosslinked linear polystyrene microspheres, thereby obtaining a second mixture; (3) introducing an inert protective gas into the second mixture of step (2), heating to induce a polymerization reaction between the hydrophilic monomer and the hydrophobic monomer, and obtaining a crude product; (4) The crude product of step (3) is washed with deionized water and an alcohol solvent in sequence, the washed polymer particles are dispersed in water, and dried to obtain chemically and morphologically anisotropic polymer hemispherical particles; the alcohol solvent is one or more of ethanol, propanol, isopropanol, n-propanol, n-butanol and n-hexanol.

2. The preparation method according to claim 1, wherein The particle size of the non-crosslinked linear polystyrene microspheres is 0.1-50 μm, and the concentration of the non-crosslinked linear polystyrene microspheres in the first mixed solution is 1-500 mg / mL.

3. The preparation method according to claim 1, wherein The surfactant is one or more of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, cetyl ammonium bromide, cetyltrimethylammonium bromide and polyvinyl alcohol, and the concentration of the surfactant in the aqueous solution containing the surfactant is 0.1-50 g / L.

4. The preparation method according to claim 1, wherein The hydrophobic monomer is one or more of ethyl methacrylate, isopropyl methacrylate, isobutyl methacrylate and glycidyl methacrylate.

5. The preparation method according to claim 1, wherein The hydrophobic initiator is a hydrophobic thermal initiator; the concentration of the initiator in the first emulsion is 1-5 g / L; the concentration of the surfactant in the first emulsion is 1-5 g / L.

6. The preparation method according to claim 1, wherein The stirring in step (2) is performed for 1-24 hours and is supplemented by heating at a temperature not exceeding 40°C; The polymerization reaction in step (3) has a reaction time of 1-24 hours and a reaction temperature of 50-100°C.

7. The chemically and morphologically anisotropic polymer hemispherical particles prepared by the preparation method according to any one of claims 1 to 6.

8. The polymer hemispherical particles according to claim 7, characterized in that The polymer hemispherical particles have a hemispherical or quasi-hemispherical shape, the spherical surface of the hemispherical or quasi-hemispherical particle has an uneven surface, and the bottom of the hemispherical or quasi-hemispherical particle has a smooth surface; the polymer hemispherical particles are amphiphilic, with a hydrophilic outer side and a hydrophobic inner side.

9. The method for visualizing the detection of aggregation-induced luminescence of polymer hemispherical particles according to claim 7 or 8, wherein: The polymer hemispherical particles are dyed with a hydrophilic fluorescent dye and a hydrophobic fluorescent dye having aggregation-induced emission effect, respectively, so that the hydrophilic region and the hydrophobic region on the polymer hemispherical particles can be observed respectively, thereby detecting the chemical anisotropy of the polymer hemispherical particles.

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