Preparation method of snowman-shaped Janus particles, snowman-shaped Janus particles prepared by method and application of snowman-shaped Janus particles

Abstract

The invention provides a preparation method of snowman-shaped Janus particles, the snowman-shaped Janus particles prepared by the method and application of the snowman-shaped Janus particles. The preparation method comprises the following steps: 1, preparing solid microspheres by using a stepped asymmetric T-shaped tube with a micro-channel; 2, silicon oxide is prepared on the surfaces of the solid microspheres through a polymerization reaction and a sol-gel reaction; wherein the snowman-shaped Janus particles comprise a microsphere part and a convex part in contact with the microsphere part, the microsphere part is a solid microsphere containing a cross-linked polymer, the convex part contains silicon oxide, and the average particle size of the snowman-shaped Janus particles is 0.5-60 [mu] m. The snowman-shaped Janus particle disclosed by the invention is adjustable in particle size, uniform in distribution and high in particle size stability, and has the characteristics of good biocompatibility and excellent stability and mechanical strength.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for preparing snowman-like Janus particles, the snowman-like Janus particles prepared by the method and uses thereof, and belongs to the field of composite materials. BACKGROUND

[0002] With the development of microfluidic technology, the preparation method of micro-nano scale particles has been widely used in the fields of biological medicine, chemical sensing, environmental detection, etc. In these applications, polymer microspheres have become a research hotspot due to their good biocompatibility, controllable physical and chemical properties, and unique advantages in drug delivery, cell culture, chemical reaction, etc. The preparation of monodisperse polymer microspheres is the basis for many experimental and industrial applications. However, traditional preparation methods such as emulsion polymerization, suspension polymerization, dispersion polymerization and precipitation polymerization often face problems such as uneven particle size and irregular particle morphology. In order to solve this problem, the application of microfluidic technology has become an effective solution.

[0003] In microfluidic technology, the stepped T-shaped microchannel structure has become an ideal platform for preparing monodisperse polymer microspheres due to its ability to precisely control fluid flow and particle size. The stepped T-shaped microchannel can efficiently prepare polymer microspheres with narrow particle size distribution and uniform morphology by precisely controlling factors such as fluid flow rate, fluid interaction and interfacial tension. The technical background aims to explore the principles, advantages and current research status of the preparation of monodisperse polymer microspheres by stepped T-shaped microchannels.

[0004] Currently, significant progress has been made in the preparation of monodisperse polymer microspheres by microfluidic technology. Many studies have shown that the stepped T-shaped microchannel can achieve highly uniform microsphere preparation, with a narrower particle size distribution than traditional methods and a particle size that can be precisely controlled between tens to hundreds of microns. In addition, the structural design of the stepped T-shaped microchannel is flexible and can meet different application requirements.

[0005] However, there are still some challenges in practical applications. First, the design and manufacturing cost of microfluidic systems is relatively high, especially in large-scale production, how to maintain cost-effectiveness and high precision is a problem that needs to be solved urgently. Second, the influence of changes in physical parameters such as fluid viscosity and surface tension on microsphere preparation is still a complex research problem, how to accurately control these parameters to improve the uniformity of microspheres still needs further exploration. However, there are few reports on the preparation of snowman-like Janus particles using microfluidic systems.

[0006] Reference document 1 discloses a kind of magnetic snowman-shaped asymmetric Janus particles, which includes hydrophilic part and oleophilic part respectively constituting two spheres of snowman-shaped particles, wherein the hydrophilic part includes hydrophilically modified polymer composite microspheres and magnetic nanoparticles attached to the surface of the polymer composite microspheres, and the oleophilic part includes hydrophobically modified silica. However, the particle size of the magnetic snowman-shaped asymmetric Janus particles cannot effectively control the particle size of the microspheres.

[0007] Reference document 2 discloses a snowman-shaped Janus particle and a preparation method thereof. The snowman-shaped Janus particle is an organic / inorganic composite snowman-shaped Janus particle, and the hydrophilic end of the organic / inorganic composite snowman-shaped Janus particle is silica, and the hydrophobic end is dimethyl acrylate / polybutyl acrylate. However, the preparation method of the snowman-shaped particle is too complex.

[0008] Reference document:

[0009] Reference document 1: CN114736322A

[0010] Reference document 2: CN111763292A SUMMARY

[0011] Problems to be solved by the invention

[0012] In view of the technical problems existing in the prior art, the present application first provides a preparation method of a snowman-shaped Janus particle, which solves the problems of too small particle size or uneven particle size obtained by the microsphere preparation method in the prior art, and the problems of too large particle size of the polymer microspheres and difficulty in controlling the particle size. The present application can effectively control the particle size, structure and morphology of the microspheres while ensuring high monodispersity of the microspheres. And by subsequent promoting the phase separation between silica and polymer microspheres, a snowman-shaped Janus particle is prepared.

[0013] Further, the present application also provides a snowman-shaped Janus particle, and the particle size and crosslinking degree of the snowman-shaped Janus particle of the present application are adjustable, and the biocompatibility is good, which can be used as a production material in the application fields of drug delivery, environmental protection, catalysis, etc.

[0014] Solution for solving the problem

[0015] [1] A preparation method of a snowman-shaped Janus particle, comprising the following steps:

[0016] Step one: preparing solid microspheres by using a stepped asymmetric T-shaped tube with microchannels;

[0017] Step two: preparing silica on the surface of the solid microspheres by using a polymerization reaction and a sol-gel reaction; wherein,

[0018] The snowman-like Janus particle has a microsphere portion and a protruding portion in contact with the microsphere portion, wherein

[0019] The microsphere portion is a solid microsphere containing a crosslinked polymer, the protruding portion contains silicon oxide, and

[0020] The average particle size of the snowman-like Janus particle is 0.5-60 μm.

[0021] [2] The preparation method according to the above [1], wherein the process one comprises the following steps:

[0022] The stabilizer is dissolved in water to obtain a continuous phase;

[0023] The monomer, the crosslinking agent and the first initiator are mixed to obtain a dispersed phase;

[0024] The continuous phase and the dispersed phase are sequentially introduced into a stepped asymmetric T-shaped tube with microchannels, and an oil-water mixed droplet is formed;

[0025] The oil-water mixed droplet is solidified to obtain a solid microsphere.

[0026] [3] The preparation method according to the above [2], wherein, in the continuous phase, the content of the stabilizer is 5-20% by mass based on the total mass of the continuous phase; and / or,

[0027] In the dispersed phase, the content of the monomer is 70-90% by mass, the content of the first initiator is 1-15% by mass, and the content of the crosslinking agent is 9-28% by mass based on the total mass of the dispersed phase; and / or,

[0028] The mass ratio of the continuous phase to the dispersed phase is 2:1-6:1; and / or,

[0029] The solidification comprises performing under light; preferably, the wavelength of the light is 350-450 nm, and the time of the light is 30 min-4 h.

[0030] [4] The preparation method according to any one of the above [1]-[3], wherein the process two comprises the following steps:

[0031] The solid microsphere, the silicon oxide precursor, the emulsifier, the second initiator and water are mixed to obtain a microsphere-precursor emulsion;

[0032] The microsphere-precursor emulsion is subjected to seed swelling polymerization under polymerization conditions and the pH value is adjusted by using an alkaline substance to obtain a snowman-like Janus particle;

[0033] Preferably, the pH is 7.0 to 8.5.

[0034] [5] The production method according to the above [4], wherein the content of the solid microspheres is 1 to 3 mass%, the content of the silica precursor is 0.06 to 5 mass%, the content of the second initiator is 0.02 to 2 mass%, the content of the emulsifier is 0.05 to 5%, and the content of the water is 85 to 98.87%, based on the total mass of the microsphere-precursor emulsion as 100%.

[0035] [6] The production method according to any one of the above [1] to [5], wherein the production method further includes a process three, the process three including functionalizing the snowman-like Janus particles to have a functional group.

[0036] [7] A snowman-like Janus particle produced by the production method according to any one of the above [1] to [6];

[0037] The snowman-like Janus particle has a microsphere portion and a protrusion portion in contact with the microsphere portion, wherein,

[0038] The microsphere portion is a solid microsphere including a crosslinked polymer, and the protrusion portion includes silica, and,

[0039] The snowman-like Janus particle has an average particle diameter of 0.5 to 60 μm.

[0040] [8] The snowman-like Janus particle according to the above [7], wherein the crosslinked polymer has a unit based on a monomer including a styrene-based monomer and / or a (meth)acrylate-based monomer and a unit based on a crosslinking agent including one or two or more kinds selected from a di-functional or more vinyl aromatic hydrocarbon and a di-functional or more (meth)acrylate.

[0041] [9] The snowman-like Janus particle according to the above [7] or [8], wherein the coefficient of variation of the particle diameter of the snowman-like Janus particle is 5% or less; and / or,

[0042] The snowman-like Janus particle has a silicon content of 1 to 50 atom%; and / or,

[0043] The crosslinking degree of the crosslinked polymer is 1 to 80%.

[0044]

[10] The snowman-like Janus particle according to any one of the above [7] to [9], wherein the protruding portion is formed by a polymerization reaction and a sol-gel reaction of a silicon oxide precursor including a monomer having an alkoxysilane structure; preferably, the monomer having an alkoxysilane structure has a (meth)acryloyloxy group and an alkoxysilane group.

[0045]

[11] The snowman-like Janus particle according to any one of the above [7] to

[10] , wherein the surface of the snowman-like Janus particle further has a functional group including one or a combination of two or more of a carboxyl group, a mercapto group, a (meth)acryloyl group, and an amino group.

[0046]

[12] Use of the snowman-like Janus particle according to any one of claims [7] to

[11] in drug delivery, a catalyst.

[0047] Effects of the Invention

[0048] The snowman-like Janus particle of the present invention has a particle size that is adjustable and uniformly distributed, high particle size stability, good biocompatibility, and excellent stability and mechanical strength. Snowman-like Janus particles of different particle sizes can meet the needs of drug loading, environmental protection, adsorption, catalysis, and the like.

[0049] The snowman-like Janus particle of the present invention is simple to prepare, and the raw materials are readily available, making it easy to produce in large quantities. BRIEF DESCRIPTION OF DRAWINGS

[0050] Figure 1 A schematic diagram showing the stepped asymmetric T-shaped tube of the microchannel of the present invention;

[0051] Figure 2 A partial enlarged view showing the stepped asymmetric T-shaped tube of the microchannel of the present invention.

[0052] Figure 3 A scanning electron microscope (SEM) photograph showing the snowman-like Janus particle obtained in Example 2. DETAILED DESCRIPTION

[0053] Various exemplary embodiments, features, and aspects of the present invention will be explained in detail in the following. The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any implementation described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations.

[0054] In addition, for a better understanding of the present application, numerous specific details are set forth in the following detailed description. One skilled in the art will understand, however, that the application can be practiced without certain specific details. In other instances, well-known methods, apparatuses, equipment and procedures have not been described in detail so as not to obscure the application.

[0055] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Unless otherwise indicated, the numerical values, numerical ranges, and other values expressed herein are to be rounded to the nearest whole number. Unless otherwise indicated, all measurements are understood to be made at standard conditions, e.g., room temperature (about 25 °C), and under an atmosphere of air, unless otherwise specifically noted.

[0056] In the present specification, the meaning indicated by "may" includes both the meaning that a certain process is performed and the meaning that a certain process is not performed.

[0057] In the present specification, the expressions "some embodiments", "other embodiments", "exemplary embodiments", etc. mean that specific elements described in the embodiments include at least one of the embodiments described herein and can exist in other embodiments or can not exist in other embodiments. In addition, it should be understood that the elements can be combined in various embodiments in any suitable manner.

[0058] In the present specification, the numerical range indicated by "numerical value A ~ numerical value B" means a range including the end point values A and B.

[0059] In the present specification, the term "snowman shape" means a three-dimensional structure in which two spheres (or approximately spherical bodies) having the same size or different sizes are stacked in a partially overlapping manner.

[0060] In the present specification, the "coefficient of variability (CV)" means a statistical quantity indicating the degree of variation in the particle size of the prepared microspheres, and is a percentage of the standard deviation to the average value. The greater the coefficient of variability, the wider the particle size distribution of the microspheres, and the more non-uniform the particle size. The smaller the coefficient of variability, the narrower the particle size distribution of the microspheres, and the more uniform the particle size.

[0061] In the present specification, the numerical range indicated by "more than" or "less than" means a numerical range including the number.

[0062] In the present specification, the meaning indicated by "may" includes both the meaning that a certain process is performed and the meaning that a certain process is not performed.

[0063] In the present specification, the use or non-use of "any" or "any" means the use or non-use of certain components, execution steps, applied conditions, etc.

[0064] In the present specification, the unit names used are international standard unit names, and " % " used indicates mass percent content unless otherwise specified.

[0065] In the present specification, the "particle diameter" used can be measured by a third party software such as ImageJ and an electron scanning microscope photograph, and a laser particle size meter can also be used to measure the particle diameter and distribution of the microspheres.

[0066] The "particle diameter" described for the microsphere portion refers to the longest dimension between two points on the boundary of the microsphere portion in the snowman-like Janus particle, and can be measured by an electron scanning microscope photograph. The average particle diameter is the average value of the particle diameters of all the microspheres.

[0067] The "particle diameter" described for the protrusion portion refers to the longest dimension between two points on the boundary of the protrusion portion in the snowman-like Janus particle, and can be measured by an electron scanning microscope photograph. The average particle diameter is the average value of the particle diameters of all the protrusions.

[0068] The "particle diameter" described for the snowman-like Janus particle refers to the sum of the particle diameters of the microsphere portion and the protrusion portion in the snowman-like Janus particle. The average particle diameter is the average value of the particle diameters of all the snowman-like Janus particles.

[0069] In the present specification, the repeating units directly formed by polymerization of monomers, and units formed by chemically converting part or all of the substituents of the repeating units formed by polymerization of monomers into other substituents are collectively referred to as "units".

[0070] In the present specification, the "(meth)acrylate" used includes the meanings of "methacrylate" and "acrylate"; the "(meth)acrylic acid" used includes the meanings of "methacrylic acid" and "acrylic acid".

[0071] In the present specification, "room temperature" refers to 25°C (± 2°C).

[0072] <First aspect>

[0073] The first aspect of the present application provides a snowman-like Janus particle having a microsphere portion and a protrusion portion on the surface of the microsphere portion, wherein,

[0074] the microsphere portion is a solid microsphere containing a crosslinked polymer, the protrusion portion contains silicon oxide, and

[0075] The average particle diameter of the snowman-like Janus particle is 0.5 to 60 μm.

[0076] The snowman-like Janus particles of the present application have adjustable and uniformly distributed particle sizes, high particle size stability, good biocompatibility, and excellent stability and mechanical strength.

[0077] In the present application, the average particle size of the snowman-like Janus particles is 0.5-60 μm, for example, 0.5-20 μm, 20-55 μm, 30-50 μm, etc.

[0078] In some specific embodiments, the coefficient of variation of the particle size of the snowman-like Janus particles is 5% or less, having excellent monodispersity, for example, 4% or less, 3% or less, 2% or less, etc.

[0079] Generally, when synthesizing micrometer-sized polymer particles, longer monomer diffusion and polymerization reaction time is required, and thus the particle size is difficult to be uniformized, resulting in a large coefficient of variation of the particle size. For example, the coefficient of variation of the size of micrometer-sized polymer particles synthesized by a suspension polymerization method is usually 20-50% or even higher; although the coefficient of variation of nanometer-sized polymer particles synthesized by an emulsion polymerization method is relatively low due to their small size (usually tens to hundreds of nanometers), the emulsion polymerization method is difficult to synthesize micrometer-sized particles. However, the snowman-like Janus particles of the present application are micrometer-sized and have a small coefficient of variation of the particle size.

[0080] In the present application, the coefficient of variation of the particle size can be determined by the following method: observing the particles to be measured by an electron scanning microscope at a magnification of 100-1000 times, randomly selecting 30 particles and measuring the size of each of the 30 particles, and then calculating the average value and the standard deviation of the particle size of the 30 particles as the average value and the standard deviation of the particle size of the particles to be measured, and calculating the coefficient of variation of the particle size of the particles to be measured by the following formula: coefficient of variation of the particle size = (standard deviation of the particle size / average value of the particle size) x 100%; alternatively, the particle size distribution and the corresponding coefficient of variation can be obtained by analyzing the water dispersion of the particles by a laser particle size analyzer.

[0081] In some specific embodiments, the snowman-like Janus particles have a silicon content of 1-50 atom%, for example, 5-40 atom%, 10-30 atom%, etc. Specifically, snowman-like Janus particles with different crosslinking degrees can be obtained by adjusting the amount of the silica precursor.

[0082] In the present application, the silicon content can be determined by the following method: loading the particles to be measured on a copper conductive adhesive substrate, observing the particles under a scanning electron microscope to obtain an image at an accelerating voltage of 15 kV and a magnification of 2000 times, selecting the elements Si, C, and O to be measured, and performing energy dispersive spectrometer (EDS) measurement, thereby determining the atomic percentages of Si, C, and O elements, and calculating the silicon content by the following formula: silicon content = Si atomic percentage / (Si atomic percentage + C atomic percentage + O atomic percentage) x 100%.

[0083] In some specific embodiments, the cross-linking degree of the cross-linked polymer is 1-80%, for example: 5-60%, 10-40%, etc. Specifically, different cross-linking degrees of snowman-shaped Janus particles can be obtained by adjusting the amount of cross-linking agent.

[0084] The cross-linking degree described for the cross-linked polymer can be calculated by the following formula: the number of moles of double bonds of the cross-linking agent used in the preparation of the cross-linked polymer / (the number of moles of double bonds of the cross-linking agent used in the preparation of the cross-linked polymer + the number of moles of double bonds of the monomer B used in the preparation of the cross-linked polymer) x 100%.

[0085] Microsphere portion

[0086] In the snowman-shaped Janus particles of the present application, the microsphere portion is spherical. In this specification, "spherical" includes true spherical and approximately spherical shapes with a coefficient of variation of 5% or less, preferably 3% or less.

[0087] Based on the mass of the snowman-shaped Janus particles, the content of the microsphere portion is 50-90%, for example: 60-80%, etc.

[0088] In the present application, the microsphere portion is a solid microsphere containing a cross-linked polymer. The present application does not particularly limit the specific type of cross-linked polymer.

[0089] wherein the cross-linked polymer has monomer-based units and cross-linking agent-based units, the monomer includes a styrene-based monomer and / or a (meth)acrylate-based monomer, and the cross-linking agent includes one or more than two selected from a di-functional or more vinyl aromatic hydrocarbon and a di-functional or more (meth)acrylate. In the present application, unless otherwise specified, the term "monomer" refers to a compound that can undergo polymerization and has only one polymerizable structure in the structure.

[0090] In some preferred embodiments, from the viewpoint of more easily obtaining the snowman-shaped Janus particles of the present application and reducing costs, the monomer for forming the cross-linked polymer preferably includes a styrene-based monomer.

[0091] For the styrene-based monomer, it can include styrene, substituted styrene, and the like. For the substituted styrene, the substituent group can include alkyl group, alkenyl group, alkoxy group, halogen, and the like, the number of carbon atoms of the alkyl group, alkenyl group, alkoxy group is preferably 1 to 5, and the alkyl group, alkenyl group, alkoxy group can further include the above-mentioned substituent group, for example, halogen, and the like. Specifically, the styrene-based monomer of the present application can include one or a combination of two or more of styrene, methylstyrene, p-methylstyrene, ethylstyrene, chloromethylstyrene, and the like.

[0092] The (meth)acrylate-based monomer refers to (meth)acrylate and its derivatives, including but not limited to alkyl (meth)acrylate, and the like.

[0093] For the alkyl (meth)acrylate, for example, C1-C12 alkyl (meth)acrylate, specific examples include but are not limited to methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, t-butyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, 2-methyl-2-propenoic acid-2-(2-methoxyethoxy)ethyl ester, cyanoethyl acrylate, and the like.

[0094] In the present specification, the structural unit derived from a monomer also encompasses a structural unit having the same structure as that directly derived from the above-described monomer, although not directly derived from the above-described monomer.

[0095] In some preferred embodiments, from the viewpoint of more easily obtaining the snowman-like Janus particles of the present application and reducing the cost, the crosslinking agent includes one or a combination of two or more selected from the group consisting of di-functional or more vinyl aromatic hydrocarbons and di-functional or more (meth)acrylates, more preferably includes a vinyl aromatic hydrocarbon. Specifically, examples of the di-functional or more vinyl aromatic hydrocarbons include divinylbenzene, p-(3-butenyl)styrene, trivinylbenzene, divinyl naphthalene, and the like.

[0096] Examples of the (meth)acrylate having two or more functionalities are not particularly limited, but are preferably di- to hexafunctional (meth)acrylates, for example, di-functional (meth)acrylates such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, pentanediol di(meth)acrylate, and the like; tri-functional (meth)acrylates such as pentaerythritol tri(meth)acrylate, trihydroxymethane tri(meth)acrylate, and glycerol tri(meth)acrylate, and the like; tetra-functional (meth)acrylates such as pentaerythritol tetra(meth)acrylate; penta-functional (meth)acrylates such as dipentaerythritol penta(meth)acrylate; hexa-functional (meth)acrylates such as dipentaerythritol hexa(meth)acrylate, and the like.

[0097] The polymer chain formed from the monomer of the present application and the molecular chain of the crosslinking agent are interpenetrated, thereby forming a network structure of the polymer. Further, in the present application, the average particle diameter of the microsphere portion is 0.1 to 50 μm, for example, 0.1 to 10 μm, 15 to 45 μm, 20 to 40 μm, and the like.

[0098] Protrusion portion

[0099] The snowman-like Janus particle of the present application has a protruding portion, wherein the protruding portion contains silicon oxide. The silicon oxide is a substance having a silicon-oxygen bond, for example, which can be formed by a polymerization reaction and a sol-gel reaction from a silicon oxide precursor including a monomer having an alkoxysilane structure; preferably, the monomer having an alkoxysilane structure has a (meth)acryloyloxy group and an alkoxysilane group.

[0100] Specifically, in a certain pH environment, the radical polymerization rate of the double bond in the silicon oxide precursor is slower than the sol-gel reaction rate, resulting in a change in the compatibility of the silicon-containing portion and the microsphere portion, phase separation, and finally the aggregation of the silicon-containing portion on the surface of the microsphere portion as a protruding portion.

[0101] In some specific embodiments, the content of the microsphere portion is 10 to 50%, for example, 20 to 40%, and the like, based on the mass of the snowman-like Janus particle.

[0102] Preferably, the monomer having an alkoxysilane structure is an alkoxysilane having a (meth)acryloxyalkyl group, including a dialkoxysilane, a trialkoxysilane, and the like. Specifically, γ-(meth)acryloxypropyltrimethoxysilane, γ-(meth)acryloxypropyltriethoxysilane, γ-(meth)acryloxypropyltripropoxysilane, γ-(meth)acryloxypropylmethyldimethoxysilane, γ-(meth)acryloxypropylmethyldiethoxysilane, and the like can be exemplified.

[0103] The protruding portion is a portion protruding from the surface of the microsphere portion. The shape of the protruding portion is not particularly limited in the present application, and the projection thereof on the surface of the microsphere portion can be, for example, a circular shape or any other shape.

[0104] Further, in the present application, the average particle diameter of the protruding portion is 0.05 to 30 μm, for example, 0.05 to 2 μm, 5 to 25 μm, 10 to 20 μm, or the like.

[0105] In some specific embodiments, the ratio of the average particle diameter of the microsphere portion to the average particle diameter of the protruding portion of the snowman-shaped Janus particle is 1:0.2 to 1:0.75, for example, 1:0.3 to 1:0.6, 1:0.4 to 1:0.5, or the like.

[0106] Functional group

[0107] In the present application, the surface of the snowman-shaped Janus particle also has a functional group, and the functional group includes one or a combination of two or more of a carboxyl group, a mercapto group, a (meth)acryloyl group, and an amino group. Specifically, the compound providing the functional group can be, for example, one or a combination of two or more of 3-aminopropyltriethoxysilane, mercaptopropyltrimethoxysilane, 4-triethoxysilylbutyric acid, and the like.

[0108] The snowman-shaped Janus particle of the present application has an adjustable particle diameter and crosslinking degree, and good biocompatibility, and can be used as a production material in the fields of drug delivery, environmental protection, catalysis, and the like.

[0109] <Second aspect>

[0110] The second aspect of the present application provides a method for producing the snowman-shaped Janus particle according to the first aspect of the present application, which includes the following steps:

[0111] Step 1: producing a solid microsphere using a stepped asymmetric T-tube having a microchannel;

[0112] Step 2: producing silica on the surface of the solid microsphere using a polymerization reaction and a sol-gel reaction.

[0113] Process one

[0114] The present application utilizes a stepped asymmetric T-junction with microchannels to prepare solid microspheres. Specifically, the stepped asymmetric T-junction can be purchased commercially or prepared in the laboratory. Further, the stepped asymmetric T-junction can be designed in advance and manufactured on a computer numerical control machine with a milling cutter.

[0115] By Figure 1 and Figure 2 As can be seen, the stepped asymmetric T-junction with microchannels includes a stepped main channel and a bypass channel intersecting perpendicularly with the main channel, and a cylindrical quartz capillary is embedded in the bypass channel. The stepped asymmetric T-junction is machined on a PMMA substrate by a numerical control milling machine. The depth and width of the main channel are both 300-500 μm (for example, 400 μm), the depth and width of the bypass channel are both 400-500 μm (for example, 460 μm), and the outer diameter and inner diameter of the embedded cylindrical quartz capillary are 400-500 μm (for example, 460 μm) and 200-400 μm (for example, 300 μm), respectively. The height of the necking formed by the capillary and the microchannel is about 50-150 μm (for example, 90 μm).

[0116] Snowman-like Janus particles are a kind of heterogeneous structure particles with unique physical and chemical properties, which have a double spherical structure similar to the shape of a snowman, and are usually composed of two different materials or chemical properties. Benefiting from its special structure and function, such particles have shown important application potential in drug delivery, oil-water separation, optical devices and catalysis, etc. Compared with traditional monodisperse microspheres, the structure of Janus particles endows them with stronger interfacial activity, higher surface interfacial tension responsiveness, and the ability to simultaneously regulate the properties of two materials.

[0117] Among the many preparation methods, microfluidic technology has become an important tool for preparing snowman-like Janus particles due to its high efficiency, accuracy and good repeatability. In particular, based on the stepped T-junction, by designing a unique microchannel geometry, the shear force between the continuous phase and the dispersed phase can be greatly improved, and by embedding a capillary with a smaller inner diameter, a small-particle-size microchannel structure can be obtained at low cost and portability. The stepped design can effectively realize an asymmetric flow field, control the interfacial instability, and at the same time realize the focusing of the continuous phase fluid, providing a larger shear force on the interface. Thus, microspheres with smaller size and better dispersity than traditional suspension polymerization can be prepared, thereby realizing precise control of the particle size, shape and composition of the particles.

[0118] The snowman-like Janus particles prepared by the stepped T-shaped microchannel have important significance in practical applications. For example, in the field of drug delivery, the heterogeneous double-sphere structure can realize the improvement of drug loading and the dual-mode regulation of drug release; in emulsion stabilization, the two parts of the particle can provide hydrophobic and hydrophilic surfaces, respectively, significantly improving the interfacial stability, and if the particle is also endowed with magnetism, the effect of oil-water separation can be achieved. In addition, by introducing optical, magnetic or conductive materials, the particle can also be endowed with more corresponding properties, which has broad prospects in the field of flexible electronics and photocatalysis.

[0119] In some specific embodiments, the step one comprises the following steps:

[0120] dissolving the stabilizer in water to obtain a continuous phase;

[0121] mixing the monomer, the crosslinking agent and the first initiator to obtain a dispersed phase;

[0122] sequentially introducing the continuous phase and the dispersed phase into the stepped asymmetric T-shaped tube with a microchannel to form oil-water mixed droplets;

[0123] solidifying the oil-water mixed droplets to obtain solid microspheres.

[0124] Specifically, the dispersed phase and the continuous phase are injected into the stepped asymmetric T-shaped tube by two micro-injection pumps respectively. The continuous phase is injected into the main channel by the micro-injection pump, and the dispersed phase is injected into the bypass channel containing the embedded capillary by the micro-injection pump. At the intersection of the main channel and the bypass channel, the dispersed phase fluid is broken to form droplets under the shearing force of the continuous phase fluid. The generation process of the droplets is recorded by a high-speed microscopy system. By changing the flow rates of the dispersed phase and the continuous phase, droplets with different particle sizes can be obtained. The oil-water mixed droplets are received by a receiving bottle on the other side of the microchannel.

[0125] The present application dissolves the stabilizer in water to obtain a continuous phase after uniform dissolution. By using the stabilizer, oil-water mixed droplets with uniformly dispersed oil droplets in the continuous phase can be obtained.

[0126] Specifically, the type of stabilizer is not particularly limited in the present application, and can be a stabilizer commonly used in suspension polymerization in the art. Specifically, the stabilizer includes but is not limited to one or a combination of two or more of polyvinyl alcohol, gelatin, starch, polyacrylic acid, sulfonated polystyrene, etc.

[0127] In some specific embodiments, the content of the stabilizer in the continuous phase is 5-20% by mass based on 100% of the total mass of the continuous phase, for example: 8-15% by mass, 9-12% by mass, etc.

[0128] Further, the monomer, the crosslinking agent and the first initiator are mixed to obtain a dispersed phase.

[0129] The kind of the first initiator is not particularly limited in the present application, and can be an initiator commonly used in the art. Specifically, the first initiator is a photoinitiator, and specifically, the photoinitiator includes one or a combination of two or more of benzoin dimethyl ether, diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, or benzophenone.

[0130] The kind of the monomer and the crosslinking agent that can be used in the present application is as described above. Preferably, the monomer includes a styrene-based monomer and / or a (meth)acrylate-based monomer, and the crosslinking agent includes one or a combination of two or more selected from a di-functional or higher vinyl aromatic hydrocarbon and a di-functional or higher (meth)acrylate.

[0131] In some specific embodiments, the content of the monomer in the dispersed phase is 70-90% by mass, for example 75-85% by mass, 78-82% by mass, etc., based on the total mass of the dispersed phase being 100%; the content of the first initiator is 1-15% by mass, for example 3-12% by mass, 5-10% by mass, etc.; and the content of the crosslinking agent is 9-28% by mass, for example 10-25% by mass, 12-20% by mass, etc.

[0132] In some specific embodiments, the mass ratio of the continuous phase to the dispersed phase is 2:1-6:1, for example 2.5:1-5:1, 3.5:1-4.5:1, etc.

[0133] In some specific embodiments, the curing includes being performed under light; specifically, the curing of the present application can be performed under irradiation of visible light or ultraviolet light. Preferably, the wavelength of the light is 350-450 nm, for example 365-405 nm, etc.; and the irradiation time is 30 min-4 h, for example 1-3 h, etc. The time of curing, i.e. the time of polymerization, is 30 min-4 h, for example 1-3 h, etc.

[0134] In the present application, by adjusting the concentration of the dispersant in the continuous phase, the viscosity of the continuous phase, the flow rate of the two phases, the viscosity and interfacial tension of the two phases, the injection pump flow rate of the dispersed phase and the continuous phase, the content of the crosslinking agent, etc., the particle size of the snowman-like Janus particles can be adjusted in the range of 0.5-60 μm, the crosslinking degree can be adjusted in the range of 1-80%, and the silicon content can be adjusted in the range of 1-50 atom%.

[0135] In some specific embodiments, the continuous phase flow rate is 900-3000 μL / min, for example, 1200-2500 μL / min, 1500-2200 μL / min, 2500-3000 μL / min, etc., and the dispersed phase flow rate is 4-300 μL / min, for example, 60-250 μL / min, 100-200 μL / min, etc. It should be noted that the flow rate of the stepped asymmetric T-tube is affected by the size of the cylindrical quartz capillary port, the syringe tube diameter of the continuous phase and the dispersed phase, and the gas bubbles in the liquid, and the size of the droplets extruded at the same injection pump injection rate fluctuates. Therefore, the change in the size of the droplets in the tube (i.e., the change in the flow rate at the meeting point of the continuous phase and the dispersed phase) needs to be monitored during the experiment, and the flow rate of the continuous phase or the dispersed phase injection pump needs to be adjusted to ensure the size of the droplets. Therefore, the injection pump flow rate is still a range in the specific experiment, and cannot be fixed as a point value.

[0136] Process two

[0137] The process two of the present application utilizes a polymerization reaction and a sol-gel reaction to prepare silicon oxide on the surface of the solid microspheres.

[0138] Specifically, the process two can include the following steps:

[0139] The solid microspheres, the silicon oxide precursor, the emulsifier, the second initiator, and water are mixed to obtain a microsphere-precursor emulsion;

[0140] The microsphere-precursor emulsion is subjected to seed swelling polymerization under polymerization conditions and the pH value is adjusted by using an alkaline substance to obtain a snowman-like Janus particle.

[0141] The present application mixes the solid microspheres, the silicon oxide precursor, the emulsifier, the second initiator, and water to obtain a microsphere-precursor emulsion. Specifically, the emulsifier and water can be mixed first to prepare an emulsifier solution, and then the emulsifier solution is mixed with the solid microspheres, the silicon oxide precursor, and the second initiator to obtain the microsphere-precursor emulsion.

[0142] Specifically, the second initiator can include an oil-soluble initiator. Examples of the oil-soluble initiator can include: azo-based initiators such as azobisisobutyronitrile, azobisisoamyl nitrile, azobisisoheptyl nitrile, and the like; organic peroxide-based initiators such as dibenzoyl peroxide, dicumyl peroxide, dilauryl peroxide, di-tert-butyl peroxide, tert-butyl peroxyneohexanoate, tert-butyl peroxyneodecanoate, di-sec-butyl peroxydicarbonate, di-(hexadecyl) peroxydicarbonate, tert-amyl peroxyneodecanoate, tert-butyl peroxyneopentanoate, di-(4-tert-butylcyclohexyl) peroxydicarbonate, dicyclohexyl peroxydicarbonate, diisopropyl peroxydicarbonate, dibutyl peroxydicarbonate, di-(2-ethylhexyl) peroxydicarbonate, tert-butyl 2-ethylhexyl peroxy-2-ethylhexanoate. These initiators can be used alone or in combination of two or more.

[0143] The emulsifier in the present application is an oil-in-water emulsifier, preferably the emulsifier is one or a combination of two or more selected from sodium dodecyl sulfonate, sodium dodecyl sulfate, sodium dodecyl benzene sulfonate.

[0144] The type of silicon oxide precursor that can be used in the present application is as described above. The silicon oxide precursor includes a monomer having an alkoxysilane structure; preferably, the monomer having an alkoxysilane structure has a (meth)acryloyloxy group and an alkoxysilane group.

[0145] In some specific embodiments, the content of the solid microspheres is 1-3% by mass, for example: 1.8-2.8% by mass, 1.5-2.5% by mass, based on the total mass of the microsphere-precursor emulsion; the content of the silicon oxide precursor is 0.06-5.0% by mass, for example: 0.1-4% by mass, 0.5-3% by mass; the content of the second initiator is 0.02-2.00% by mass, for example: 0.05-1.5% by mass, 0.1-1% by mass; the content of the emulsifier is 0.05-5%, for example: 0.1-4% by mass, 0.5-3% by mass, etc.; the content of the water is 85-98.87%, for example: 90-98%, 92-96%, etc.

[0146] The microsphere-precursor emulsion is subjected to a seed swelling polymerization reaction under polymerization conditions and the pH value is adjusted using a basic substance; specifically, the microsphere-precursor emulsion can be emulsified under polymerization conditions for 0.5-2 hours first, then subjected to a seed swelling polymerization reaction, while the pH value is adjusted using a basic substance. The obtained solid microspheres are dispersed in water as seeds for the reaction. During the reaction, the original solid microspheres and the silicon oxide precursor undergo phase separation, thereby forming a microsphere part and a protruding part on the surface of the microsphere part, thereby obtaining a snowman-like Janus particle.

[0147] In the present application, the pH value after the pH value is adjusted by the alkaline substance is 7.0-8.5. By adjusting the pH value, the polymerization rate of silicon oxide and the sol-gel degree can be adjusted. The alkaline substance in the present application is not particularly limited and can be the alkaline substance commonly used in the art, and specifically can be one or a combination of two or more of ammonia water (NH3·H2O), sodium hydroxide, potassium hydroxide, sodium carbonate, and sodium bicarbonate. As preferred, the alkaline substance can be an ammonia water solution. Specifically, considering that the reaction can be more effectively carried out, the concentration of the ammonia water solution can be 20-35%, for example, 22-32%, 25-30%, etc.

[0148] In some specific embodiments, the temperature of the seed swelling polymerization reaction is 60-80°C, for example, 70°C, and the reaction time of the seed swelling polymerization reaction is 8-36 h, preferably 12-24 h.

[0149] By the preparation method of the present application, the particle size, crosslinking degree, and silicon content of the snowman-like Janus particles obtained can be adjusted. The preparation method of the present application is simple, and the structure of the product is clear, and batch production can be realized.

[0150] Further, the preparation method of the present application optionally further comprises a post-treatment step, for example, a step of separating, washing, and drying the obtained solid microspheres or snowman-like Janus particles after process one and / or process two.

[0151] Process three

[0152] In the present application, the snowman-like Janus particles can be subjected to functionalization treatment so as to have a functional group.

[0153] In some specific embodiments, the snowman-like Janus particles can be subjected to functionalization treatment by using a compound providing a functional group. Specifically, the compound providing a functional group can be one or a combination of two or more of 3-aminopropyl triethoxysilane, mercaptopropyl trimethoxysilane, and 4-triethoxysilyl butyric acid.

[0154] In some specific embodiments, the snowman-like Janus particles are placed in an alcohol solvent, and an alkaline substance or an acidic substance and a compound providing a functional group are added for functionalization treatment, so as to obtain functionalized snowman-like Janus particles. Generally, when the functionalization group is a carboxyl group, an acidic substance can be used; when the functionalization group is an amino group, an acidic substance can be used.

[0155] Further, in the present application, the mass ratio of the snowman-like Janus particle to the compound providing the functional group is 0.25:1 to 10:1, for example, 0.5:1 to 8:1, 1:1 to 5:1, etc.

[0156] The present application does not make a special limitation on the temperature and time for the functionalization treatment, which can be specifically 12 to 36 hours of functionalization treatment at room temperature.

[0157] The present application does not make a special limitation on the amount of the basic substance, which can be generally kept at pH 7 to 8.5. The present application does not make a special limitation on the basic substance, which can be the above-mentioned basic substance involved in the present application. The present application does not make a special limitation on the amount of the acidic substance, which can be used as long as the reaction can be carried out. The present application does not make a special limitation on the basic substance, which can be some acidic substances commonly used in the art, for example, acetic acid, etc.

[0158] <Third aspect>

[0159] The third aspect of the present application also provides a use of the snowman-like Janus particle according to the first aspect of the present application in drug delivery, catalyst, etc.

[0160] Examples

[0161] The embodiments of the present application will be described in detail below with reference to the examples, but those skilled in the art will understand that the following examples are only used to illustrate the present application and should not be regarded as limiting the scope of the present application. The specific conditions not mentioned in the examples are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not marked with the manufacturer, which are all conventional products that can be obtained by market purchase.

[0162] As shown in Figs. 1 and 2, the stepped asymmetric T-shaped tube with microchannels is composed of a stepped main channel and a bypass channel which is perpendicular to the main channel and in which a cylindrical quartz capillary is embedded. The stepped asymmetric T-shaped tube is processed on a PMMA substrate by a numerical control milling machine. The depth and width of the main channel are both 400 μm, the depth and width of the bypass channel are both 460 μm, and the outer diameter and inner diameter of the embedded cylindrical quartz capillary are 460 μm and 300 μm, respectively. The height of the necking formed by the capillary and the microchannel is about 90 μm. Figure 1 Figure 2 As shown in Figs. 1 and 2, the stepped asymmetric T-shaped tube with microchannels is composed of a stepped main channel and a bypass channel which is perpendicular to the main channel and in which a cylindrical quartz capillary is embedded. The stepped asymmetric T-shaped tube is processed on a PMMA substrate by a numerical control milling machine. The depth and width of the main channel are both 400 μm, the depth and width of the bypass channel are both 460 μm, and the outer diameter and inner diameter of the embedded cylindrical quartz capillary are 460 μm and 300 μm, respectively. The height of the necking formed by the capillary and the microchannel is about 90 μm.

[0163] Example 1

[0164] Styrene 8.0 g, divinylbenzene 1.0 g, and diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide 1.0 g were mixed to obtain a dispersed phase; polyvinyl alcohol (type 1788) was dissolved in water to obtain 40 mL of a 10 wt% polyvinyl alcohol (type 1788) aqueous solution, which was a continuous phase.​

[0165] The continuous phase was injected into the main channel of the stepped asymmetric T-junction by a microsyringe pump, and the dispersed phase was injected into the bypass channel of the stepped asymmetric T-junction containing the embedded capillary by a microsyringe pump. The flow rates of the dispersed phase and the continuous phase were adjusted by adjusting the microsyringe pumps, wherein the flow rate of the continuous phase was 2000-2400 μL / min, and the flow rate of the dispersed phase was 180-580 μL / min. Uniform droplets were prepared by the stepped T-junction device, and a glass dish was used as a collection container to receive the droplets. The droplets were irradiated under ultraviolet light at 365 nm for 3 h to initiate curing. A microsphere dispersion was obtained. The average particle size of the microspheres was 0.8 μm, the crosslinking degree was 17%, and the coefficient of variation was 0.9%. The microspheres were separated by centrifugation at 3000 rpm, washed with deionized water three times, and vacuum dried to obtain solid microspheres.

[0166] The above solid microspheres 1 g, 3-(methacryloyloxy)propyl trimethoxysilane 0.6 g, azobisisobutyronitrile 0.02 g, 50 mL of a 1 wt% aqueous solution of sodium dodecyl sulfate, were ultrasonically emulsified for 2 min, and then reacted at 70 °C for 1 h. Then 50 mL of a 1 wt% aqueous solution of sodium dodecyl sulfate was added, and the reaction was continued at 70 °C for 1 h. Finally, 50 mL of a 1 wt% aqueous solution of sodium dodecyl sulfate was added, and the reaction was continued at 70 °C for 1 h. The reaction solution was cooled to room temperature, and the product was collected by centrifugation at 3000 rpm. The microspheres were washed with deionized water three times, and vacuum dried to obtain the solid microspheres. L of ammonia water (28 wt%) was added to adjust the pH value to 7.5, and the reaction was continued for 24 h. Finally, crosslinked polystyrene / silica snowman Janus particles with a silicon content of 5 atom%, an average particle size of the microsphere part of 0.8 μm, and an average particle size of the protruding part of 0.35 μm were obtained. The coefficient of variation of the snowman Janus particles was 2%, and the average particle size of the snowman Janus particles was 1.15 μm.

[0167] Example 2

[0168] Styrene 12 g, divinylbenzene 2 g, and diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide 0.8 g were mixed to obtain the dispersed phase; polyvinyl alcohol (type 1788) was dissolved in water to obtain a 10 wt% polyvinyl alcohol (type 1788) aqueous solution of 40 mL, which was the continuous phase.

[0169] The continuous phase was injected into the main channel of a stepped asymmetric T-tube using a micro-injection pump, while the dispersed phase was injected into the bypass channel containing an embedded capillary tube within the same tube. The flow rates of the continuous and dispersed phases were adjusted by regulating the micro-injection pumps, with the continuous phase flow rate at 1500-1900 μL / min and the dispersed phase flow rate at 80-400 μL / min. Uniform droplets were prepared using the stepped T-tube apparatus and collected in a glass dish. Curing was initiated under 365 nm UV light for 3 h, yielding a microsphere dispersion. The microspheres had an average particle size of 40 μm, a crosslinking degree of 21%, and a coefficient of variation of 2%. The microspheres were centrifuged at 3000 rpm, washed with deionized water three times, and then vacuum-dried to obtain solid microspheres.

[0170] Take 1 g of the above solid microspheres, 0.6 g of 3-(methacryloyloxy)propyltrimethoxysilane, 0.02 g of azobisisobutyronitrile, and 50 mL of a 1 wt% sodium dodecyl sulfate aqueous solution. Sonicate the mixture for 2 min, react at 70 °C for 1 h, and then add 50 mL of sodium dodecyl sulfate aqueous solution. L of ammonia water (28 wt%) was added, the pH was adjusted to 7.5, and the reaction was carried out for another 24 hours. The final product was cross-linked polystyrene / silica snowman-shaped Janus particles with a silicon content of 5 atomic%, an average particle size of 40 μm for the microspheres, and an average particle size of 18 μm for the protrusions. The coefficient of variation for these snowman-shaped Janus particles was 3%, and the average particle size was 58 μm.

[0171] Example 3

[0172] 9 g of styrene, 2.5 g of divinylbenzene, and 0.8 g of diphenyl (2,4,6-trimethylbenzoyl)phosphine oxide were mixed to obtain the dispersed phase; polyvinyl alcohol (type 1788) was dissolved in water to obtain 40 mL of a 10 wt% aqueous solution of polyvinyl alcohol (type 1788), which is the continuous phase.

[0173] The continuous phase was injected into the main channel of a stepped asymmetric T-tube using a micro-injection pump, while the dispersed phase was injected into the bypass channel containing an embedded capillary within the same tube. The flow rates of the continuous and dispersed phases were adjusted by regulating the micro-injection pumps, with the continuous phase flow rate at 1580-2400 μL / min and the dispersed phase flow rate at 180-300 μL / min. Uniform droplets were prepared using a flow-focusing microcapillary device and collected in a glass dish. The droplets were then irradiated with 365 nm UV light for 3.5 h to obtain a microsphere dispersion. The microspheres had an average particle size of 30 μm, a crosslinking degree of 31%, and a coefficient of variation of 1%. The microspheres were centrifuged at 3000 rpm, washed with deionized water three times, and then vacuum-dried to obtain solid microspheres.

[0174] Take 1 g of the above solid microspheres, 2.0 g of 3-(methacryloyloxy)propyltrimethoxysilane, 0.02 g of azobisisobutyronitrile, 50 mL of a 1 wt% aqueous solution of sodium dodecyl sulfate, ultrasonic emulsification for 2 min, and after reaction at 70 °C for 1 h, 100 L ammonia (28 wt%), adjust the pH value to 8.0 and react for 24 h. Finally, cross-linked polystyrene / silica snowman Janus particles with a silicon content of 40 atom% and an average particle size of the microsphere part of 30 μm and an average particle size of the protruding part of 21 μm are obtained. The coefficient of variation of the snowman Janus particles is 2%, and the average particle size of the snowman Janus particles is 51 μm.

[0175] Example 4

[0176] Take 0.1 g of the above snowman Janus particles after drying in Example 3, place them in 20 g of ethanol, add 2 μL of glacial acetic acid, then add 0.4 g of 4-triethoxysilyl butyric acid, and stir at room temperature for 24 h. Finally, centrifugal separation at 3000 rpm, and washing of the particles with deionized water and ethanol, respectively, vacuum drying, and finally obtaining snowman Janus particles with carboxyl functionalization. Example 5

[0177] Take 0.1 g of the above snowman Janus particles in Example 3, place them in 20 g of ethanol, add 2 μL of glacial acetic acid, then add 0.4 g of 4-triethoxysilyl butyric acid, and stir at room temperature for 24 h. Finally, centrifugal separation at 3000 rpm, and washing of the particles with deionized water and ethanol, respectively, vacuum drying, and finally obtaining snowman Janus particles with carboxyl functionalization.

[0178] Comparative Example

[0179] Comparative Example

[0180] A 1 g of lyophilized polystyrene hollow sphere (commercially available, size 30 μm, cross-linking degree 10%, shell thickness 2 μm) powder was placed in 40 mL of a sodium dodecyl sulfate solution (0.25 wt%), 90 μL of ammonia water (ammonia concentration 28 mass%) was added to make the pH value of the system 8, and the system was dispersed under ultrasonic for 3 min to obtain a polystyrene dispersion. 2 g of 3-(methacryloyloxy)propyltrimethoxysilane and 0.02 g of azobisisobutyronitrile were uniformly dispersed in another container, 10 mL of deionized water was added, and the solution was slowly added dropwise to the above polystyrene dispersion. The system was stirred at 100 rpm at room temperature for 30 min, and ultrasonic was used to assist the dispersion of the oil phase into the water phase. Then, the system was transferred to an oil bath and reacted at 70°C for 6 h. Finally, cross-linked polystyrene / silica snowman-like Janus particles with a silicon content of 18 atom%, an average particle size of the organic polymer part of 30 μm, and an average particle size of the silicon-containing material part of 18 μm were obtained. The average particle size of the snowman-like Janus particles was 48 μm. The coefficient of variation of the particles of the snowman-like Janus particles was 16%.

[0181] The snowman-like Janus particles were placed in 20 g of ethanol, 2 μL of glacial acetic acid was added, 0.4 g of 4-triethoxysilyl butyric acid was added, and the system was stirred at room temperature for 24 h. Finally, the system was centrifuged at 3000 rpm, the particles were washed with deionized water and ethanol, respectively, and vacuum dried to obtain carboxyl-functionalized snowman-like Janus particles.

[0182] Solvent resistance test

[0183] 0.5 g of the snowman-like Janus particles of Example 3 were immersed in the following three solvents, respectively (25°C, 24 h): ethanol ② acetone ③ toluene. The solvent absorption rate was determined by thermogravimetric analysis (TGA), and the results are shown in Table 1.

[0184] Table 1

[0185]

[0186] As can be seen from Table 1, the snowman-like Janus particles have excellent particle size stability (swelling rate <0.5%) in polar / non-polar solvents, which meets the application requirements in complex solvent environments.

[0187] <Zeta potential analysis>

[0188] The absolute value of the Zeta potential of the snowman-like particles of Example 5 and the snowman-like Janus particles of the comparative example was measured to evaluate the surface charge stability.

[0189] The snowman-like Janus particles with carboxyl functionalization of Example 5 and Comparative Example were dispersed in 5 mL deionized water (concentration 0.01 wt%) respectively, and ultrasonic treatment was performed for 10 min to ensure uniform dispersion of the particles. 1 mL of the suspension was taken by a syringe, and was injected into a Zeta potential sample cell (the injection process should be slow to avoid the generation of bubbles), and automatic measurement was started, and the Zeta potential value and electrophoretic mobility were recorded. The results are shown in Table 2.

[0190] The pH value of the dispersion was adjusted to 4.0-9.0 by using HCl or NaOH, and the above measurement process was repeated, and the influence of the pH value on the surface charge stability was evaluated. The results are shown in Tables 3 and 4.

[0191] Table 2

[0192]

[0193] The results show that the absolute value of the Zeta potential of Example 5 is 48% higher than that of Comparative Example, indicating that the surface charge density is higher, the electrostatic repulsion between particles is stronger, and the dispersion stability is more excellent.

[0194] Table 3

[0195]

[0196] Table 4 Zeta potential under different ionic strength (pH = 7.0)

[0197]

[0198] The results of Tables 3 and 4 show that the snowman-like Janus particles with carboxyl functionalization of Example 5 have smaller potential fluctuations in acidic, alkaline conditions and high salt environments, indicating that the surface charge stability is significantly better than that of the hollow particles (Comparative Example). The snowman-like Janus particles with carboxyl functionalization of Comparative Example have a hollow structure, and the shell is thin and the internal cavity is easily penetrated by the medium, resulting in intensified charge shielding effect and decreased stability.

[0199] Industrial applicability

[0200] The snowman-like Janus particles of the present application can be used as drug delivery, catalysis and other products.

[0201] It should be noted that although the technical solutions of the present application are described with specific examples, those skilled in the art can understand that the present application should not be limited thereto.

[0202] Having described various embodiments of the application, it is to be understood that the above description is meant not to limit and not to encompass all of the possible embodiments covered by the claims. Many modifications and variations of this application can be apparent to those of ordinary skill in the art without departing from the spirit and scope of the described embodiments. It is intended that the scope of the application should only be limited by the appended claims.

Claims

1. A method for preparing snowman-shaped Janus particles, characterized in that, The process includes the following steps: Step 1: Solid microspheres are prepared using a stepped asymmetric T-tube with microchannels; Step 2: Silica is prepared on the surface of the solid microspheres using polymerization and sol-gel reactions; wherein, The snowman-shaped Janus particles have microsphere portions and protrusions in contact with the microsphere portions, wherein, The microsphere portion is a solid microsphere containing a cross-linked polymer, and the protruding portion contains silicon oxide. The average particle size of the snowman-shaped Janus particles is 0.5~60μm.

2. The preparation method according to claim 1, characterized in that, The first process includes the following steps: The stabilizer was dissolved in water to obtain a continuous phase; The monomer, crosslinking agent, and first initiator are mixed to obtain a dispersed phase; The continuous phase and the dispersed phase are sequentially introduced into a stepped asymmetric T-tube with microchannels, forming an oil-water mixed droplet; The oil-water mixture droplets were solidified to obtain solid microspheres.

3. The preparation method according to claim 2, characterized in that, In the continuous phase, based on the total mass of the continuous phase as 100%, the content of the stabilizer is 5-20% by mass; and / or, In the dispersed phase, based on the total mass of the dispersed phase (100%), the content of the monomer is 70-90% by mass, the content of the first initiator is 1-15% by mass, and the content of the crosslinking agent is 9-28% by mass; and / or, The mass ratio of the continuous phase to the dispersed phase is 2:1 to 6:1; and / or, The curing is carried out under light irradiation; preferably, the wavelength of the light irradiation is 350~450 nm, and the irradiation time is 30 min~4 h.

4. The preparation method according to any one of claims 1-3, characterized in that, The second process includes the following steps: Solid microspheres, silica precursor, emulsifier, second initiator and water are mixed to obtain microsphere-precursor emulsion; The microsphere-precursor emulsion was subjected to seed swelling polymerization under polymerization conditions, and the pH value was adjusted using an alkaline substance to obtain snowman-shaped Janus particles. Preferably, the pH value is 7.0 to 8.

5.

5. The preparation method according to claim 4, characterized in that, Based on the total mass of the microsphere-precursor emulsion as 100%, the content of the solid microspheres is 1-3% by mass, the content of the silica precursor is 0.06-5% by mass, the content of the second initiator is 0.02-2% by mass, the content of the emulsifier is 0.05-5%, and the content of water is 85-98.87%.

6. The preparation method according to any one of claims 1-5, characterized in that, The preparation method further includes a third step, which involves functionalizing the snowman-shaped Janus particles to give the snowman-shaped Janus particles functional groups.

7. A snowman-shaped Janus particle, characterized in that, It is prepared by the preparation method according to any one of claims 1-6; The snowman-shaped Janus particles have microsphere portions and protrusions in contact with the microsphere portions, wherein, The microsphere portion is a solid microsphere containing a cross-linked polymer, and the protruding portion contains silicon oxide. The average particle size of the snowman-shaped Janus particles is 0.5~60μm.

8. The snowman-shaped Janus particles according to claim 7, characterized in that, The crosslinked polymer has monomer-based units and crosslinker-based units, wherein the monomers include styrene monomers and / or (meth)acrylate monomers, and the crosslinker includes one or more combinations selected from difunctional or higher vinyl aromatic hydrocarbons and difunctional or higher (meth)acrylates.

9. The snowman-shaped Janus particles according to claim 7 or 8, characterized in that, The coefficient of variation of the particle size of the snowman-shaped Janus particles is less than 5%; and / or, The silicon content of the snowman-shaped Janus particles is 1-50 atomic%; and / or, The degree of crosslinking of the crosslinked polymer is 1 to 80%.

10. The snowman-shaped Janus particles according to any one of claims 7-9, characterized in that, The protrusion is formed by polymerization and sol-gel reaction of a silica precursor, wherein the silica precursor comprises a monomer having an alkoxysilane structure; preferably, the monomer having an alkoxysilane structure has (meth)acryloyloxy and alkoxysilyl groups.

11. The snowman-shaped Janus particles according to any one of claims 7-10, characterized in that, The surface of the snowman-shaped Janus particles also has functional groups, which include one or more combinations of carboxyl, mercapto, (meth)acryloyl and amino groups.

12. Use of the snowman-shaped Janus particles according to any one of claims 7-11 in drug delivery and as a catalyst.

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