A Pomosomes Hollow Shell Structure and Its Preparation Method

Abstract

The present invention discloses a Pomosomes hollow shell structure and a preparation method thereof. The preparation method comprises the following steps: (1) dissolving a positively charged polymer in an oil phase, and dispersing a polyoxometalate and an inorganic salt in an aqueous phase, wherein the polyoxometalate can form an assembly with the positively charged polymer through electrostatic interaction; the inorganic salt is used to reduce the electrostatic repulsion between polyoxometalates; (2) mixing the oil phase and the aqueous phase and then emulsifying, and standing to obtain an emulsion containing a nanoshell structure. The present invention prepares a stable shell structure by using small-sized nanoparticles as raw materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of shell - structured composite materials, and more specifically, relates to a Pomosomes hollow shell structure and a preparation method thereof. Background Art

[0002] Colloidosomes are mainly shell - structured materials made with emulsions as templates. With the development of industry and technology, the application fields of colloidosomes have been continuously expanding. Colloidosomes with different structural components have broad application prospects in various different fields due to their different properties. They can be applied in drug carriers, controlled release of contents, microreactors, as carriers to protect biological macromolecules, catalysts, and various functional materials, etc.

[0003] Colloidosomes are usually prepared by emulsion - templating processing techniques. Target particles are dispersed in a selected solvent, and then the two - phase is emulsified to produce an emulsion. The particles adsorb on the liquid - liquid interface to stabilize the emulsion. After using methods such as sintering, covalent cross - linking, and dispersion - phase gelation to lock the particles, the solvent volatilizes to form colloidosomes. Since methods of locking particles such as sintering and covalent cross - linking are simple and practical and have advantages in maintaining the stability of colloidosomes, the robustness of colloidosomes and the rapid responsiveness of releasing contents on demand are mutually exclusive in nature, which limits the applications in biopharmaceutical carriers and microreactors. One way to solve this problem is to use a dynamic fixation method to lock the particles on the interface instead of permanent locking (sintering or covalent cross - linking). In this way, the assembly and disassembly of particles can be flexibly controlled under the required stimuli. The preparation mechanism of dynamic colloidosomes mainly relies on non - covalent bonding methods of locking particles, including van der Waals forces, host - guest interactions, and electrostatic interactions, etc.

[0004] Guo et al. synthesized colloidosomes by using the electrostatic interaction between the opposite charges of polyethyleneimine - modified silica nanoparticles and carbon quantum dots (Colloidal Assembly Route for Responsive Colloidosomes with Tunable Permeability. Nano letters, 2015, 7, 2876). The carbon quantum dots used therein have pH - sensitive charge reversibility, so this dynamic colloidosomes has pH - regulated disassembly and release capabilities.

[0005] Li et al. prepared stable nanoscale colloidosomes using nitrobenzene diamine-doped SiO2 nanoparticles with opposite charges (Dynamic Hybrid Colloidosomes via Electrostatic Interactions for pH-Balanced Low Premature Leakage and Ultrafast Cargo Release. Nano Letters, 2019, 19, 6065). In this process, the functional groups of the positively charged SiO2 nanoparticles undergo photoisomerization to neutral functional groups, and the positively charged nanoparticles are thus transformed into negatively charged nanoparticles. As a result, the electrostatic interaction between the nanoparticles with opposite charges disappears after illumination, the capsules disintegrate, and the contents are released. A strong colloidosomes shell layer is generated without the addition of an extra crosslinking agent during the process, and its light-controlled release ability is also expected to be applied in fields such as drug delivery. However, the disadvantage of the above two methods is that the particle sizes used are above 20 nm, and the colloidosomes are micron-sized, resulting in relatively large pore sizes between the particles, which is not conducive to the controllable encapsulation of small molecules. Due to the limitation of thermal energy, it is difficult to fix small-sized particles at the interface. Therefore, the preparation of a shell structure that can encapsulate small molecules with nanoscale sizes has not been proposed yet.

[0006] In summary, although a large amount of work has been devoted to the research of colloidosomes, it is still extremely difficult to prepare a stable colloidosomes shell structure using small-sized nanoparticles. Summary of the Invention

[0007] In view of the above defects or improvement requirements of the prior art, the present invention provides a Pomosomes hollow shell structure and a preparation method thereof. The purpose is to prepare a hollow shell structure using polyoxometalate as a raw material, thereby solving the technical problem that it is still extremely difficult to prepare a stable colloidosomes shell structure using small-sized nanoparticles.

[0008] To achieve the above object, according to one aspect of the present invention, a preparation method of a Pomosomes hollow shell structure is provided. The method includes the following steps:

[0009] (1) Dissolve a positively charged polymer in an oil phase, and disperse a polyoxometalate and an inorganic salt in an aqueous phase. The polyoxometalate can form an assembly with the positively charged polymer through electrostatic interaction; the inorganic salt is used to reduce the electrostatic repulsion between polyoxometalates.

[0010] (2) Mix the oil phase and the aqueous phase and then emulsify them. After standing, an emulsion containing the Pomosomes hollow shell structure is obtained.

[0011] In the present invention, the colloidosomes shell prepared from polyoxometalate as the raw material is named POMosomes.

[0012] Preferably, the positively charged polymer is a polymer containing amino and / or pyridine groups; preferably, the positively charged polymer is one of monoaminopropyl-terminated polydimethylsiloxane, diaminopropyl-terminated polydimethylsiloxane, and aminopropylmethylsiloxane-dimethylsiloxane random copolymer, or the positively charged polymer contains both monoaminoterminal polydimethylsiloxane and styrene-(2-vinylpyridine) block copolymer.

[0013] Preferably, the number of amino groups contained in the aminopropylmethylsiloxane-dimethylsiloxane random copolymer is 5-53.

[0014] Preferably, the polyoxometalate is any one of {Mo 72 V 30}, {Mo 72 Fe 30}, {Mo 72 Cr 30}, {Cu 20 P8W 48}, {P4Y9W43}.

[0015] Preferably, the organic solvent is any one of toluene, carbon tetrachloride, chloroform, and dichloromethane.

[0016] Preferably, the inorganic salt is an inorganic salt with a relatively small hydration radius compared to the ionic form of the same group elements, and the inorganic salt is rubidium chloride, sodium chloride, or potassium chloride.

[0017] Preferably, the molar concentration of the positively charged polymer in the oil phase is 0.01-0.046 mM, and the mass concentration of the polyoxometalate in the aqueous phase is 0.05-0.5 mg / mL; the molar ratio of the positively charged polymer to the polyoxometalate is (0.38-17.52):1; the addition amount of the inorganic salt is 8 mM.

[0018] Preferably, the molecular weight of the positively charged polymer is 2000-20000 g / mol, and the average molecular weight between amino groups in the positively charged polymer is 377-3000 g / mol. Preferably, the emulsification is achieved by a water bath ultrasonic instrument and a magnetic stirrer; the dissolution of the positively charged polymer and the polyoxometalate is achieved by a vortex mixer and a water bath ultrasonic instrument.

[0019] According to another aspect of the present invention, a Pomosomes hollow shell structure is provided. The Pomosomes hollow nanoshell structure is spherical with a particle size of 0.2 - 3 μm.

[0020] Generally speaking, compared with the prior art through the above technical solutions conceived by the present invention, at least the following beneficial effects can be achieved.

[0021] (1) The size of the polyoxometalate is at the molecular level, with a size of 1 - 6 nm. A stable nanoshell structure can be obtained through the preparation method of the present invention. Specifically, in the present invention, the interface between the positively charged polymer in the oil phase and the negatively charged polyoxometalate in the water phase undergoes electrostatic interaction, blocking the oil - water interface, thereby improving the mechanical strength of the interface layer and preparing a strong and stable shell structure. When the assembly forms a high - density and highly uniform monolayer film on the interface, it can resist the compressive force during the subsequent drying process, thus obtaining a strong shell. It solves the problem that it is still extremely difficult to prepare a stable colloidosomes shell structure using small - sized nanoparticles as raw materials.

[0022] Moreover, the preparation process provided by the present invention is simple, can be continuously prepared on a large scale, and does not require post - treatment of the obtained emulsion. It provides an effective solution to the problem of Rayleigh instability of small - sized particles at the interface during the preparation of the emulsion shell structure, shows great potential in the field of coating preparation, and has industrialization potential.

[0023] (2) The positively charged polymer in the present invention has a wide selection range. Functionalized polymers can be selected according to the mechanical strength required for the interface to resist compressive force. Either bifunctional functionalized polymers or functionalized polymers with multiple functional groups can be selected; either a random copolymer can be selected as a ligand, or a monofunctional polymer and a block copolymer can be selected as two ligands, providing a broad selection space for the synthesis of the emulsion shell structure. Therefore, this method has strong practicability.

[0024] (3) In the present invention, the emulsion is emulsified by the method of water - bath ultrasonic and magnetic stirring, which is simple and easy to operate. A strong shell structure can be prepared without other auxiliary means to increase the mechanical strength of the shell. By selecting polyoxometalate particles, some of the characteristics of the polyoxometalate can be imparted to the water - oil interface layer, providing a new idea for the preparation of multifunctional shell structures.

[0025] (4) In the present invention, the molar concentration of the selected positively charged polymer is 0.01 - 0.046 mM, and the mass concentration of the polyoxometalate is 0.05 - 0.5 mg / mL. If there is too much positively charged polymer or polyoxometalate, flocculation is likely to occur; if there is too little, the density of the interface assembly is insufficient and the mechanical strength is insufficient.

[0026] The higher the molecular weight of the positively charged polymer, the slower the diffusion rate of the polymer; the lower the average molecular weight between amino groups in the positively charged polymer, the greater the mechanical strength and the lower the elasticity of the nanoshell structure. When preparing Pomosomes, it is required that the polymer has a relatively low molecular weight (2000 - 20000 g / mol). At this time, the polymer has a relatively fast diffusion rate and can self - rearrange to reach a dense assembly density; at the same time, the average molecular weight between amino groups of the polymer should be within a certain range (377 - 3000 g / mol). At this time, the polymer has cross - linking ability, making the interface have higher strength and elasticity. During the solvent evaporation process, it can not only maintain stability but also have a certain space for rebound.

[0027] Among them, the formula for the polymer diffusion coefficient is: D = kT / ξ ∝ 1 / M, where D is the polymer diffusion coefficient, T is the temperature, M is the polymer molecular weight, ξ is the friction coefficient, and the diffusion rate of polymer segments is inversely proportional to the molecular weight; therefore, when other parameters are fixed, the diffusion rate can be controlled to a certain extent by controlling the molecular weight of the polymer, and then the arrangement rate and uniformity of the polymer and polyoxometalate can be controlled, realizing the uniform high - density arrangement of the assembly on the interface shell layer and the preparation of strong Pomosomes. Description of the Drawings

[0028] Figure 1 is the interfacial storage modulus diagram of 0.1 mg / mL {Mo 72 V 30} and different functionalized polymers at 0.0001 mM;

[0029] Figure 2 、 3 are the scanning electron microscope and transmission electron microscope diagrams of Pomosomes prepared by using 0.3 mL of 0.2 mg / mL {Mo 72 V 30} / H2O / 8 mM RbCl / H2O as the aqueous phase, 3 mL of 0.01 mM NH2 - PDMS - NH2 / C7H8 as the oil phase, shaking for 10 s, and ultrasonic emulsification for 5 min;

[0030] Figure 4 、 5 are the scanning electron microscope and transmission electron microscope diagrams of Pomosomes prepared by using 1 mL of 0.2 mg / mL {Mo 72 V 30} / H2O / 8 mM RbCl / H2O as the aqueous phase, 15 mL of 0.01 mM RCPPDMS - 5NH2 / C7H8 as the oil phase, shaking for 10 s, and ultrasonic emulsification for 1 h;

[0031] Figure 6 , 7 are respectively the scanning electron microscope and transmission electron microscope images of POMosomes prepared by using 1 ml of 0.2 mg / mL {Mo 72 V 30} / H2O / 8 mM RbCl / H2O as the aqueous phase, 15 ml of 0.01 mM RCPPDMS-53NH2 / C7H8 as the oil phase, shaking for 10 s, and ultrasonic emulsification for 30 min;

[0032] Figure 8 is the scanning electron microscope image of POMosomes prepared by using 0.8 mL of 0.5 mg / mL {Mo 72 V 30} / H2O / 8 mM RbCl / H2O as the aqueous phase, 12 mL of 0.1 mM PDMS-NH2 / C7H8 as the oil phase, shaking for 10 s, ultrasonic emulsification for 1 h to prepare the emulsion, and then adding 6 mL of 0.1 mg / mL PS-b-P2VP / C7H8 and magnetic stirring for 35 min;

[0033] Figure 9 is the scanning electron microscope image of the emulsion prepared by using 1 mL of 0.2 mg / mL {Mo 72 V 30} / H2O / 8 mM RbCl / H2O solution as the aqueous phase, 15 mL of 0.01 mM PDMS-NH2 / C7H8 as the oil phase, and ultrasonic emulsification for 30 min;

[0034] Figure 10 is the scanning electron microscope image of the emulsion prepared by using 1 mL of 0.2 mg / mL {Mo 72 V 30} / H2O / 8 mM RbCl / H2O solution as the aqueous phase, 15 mL of 0.01 mM RCP PDMS-42NH2 / C7H8 as the oil phase, and ultrasonic emulsification for 30 min;

[0035] Figure 11 is the scanning electron microscope image of the emulsion prepared by using 1 mL of 0.2 mg / mL {Mo 72 V 30} / H2O / 8 mM RbCl / H2O solution as the aqueous phase, 15 mL of 0.1 mg / mL PS-b-P2VP / C7H8 as the oil phase, and ultrasonic emulsification for 1 h;

[0036] Figure 12 is the scanning electron microscope image of the emulsion prepared by using 1 mL of 0.2 mg / mL {Mo 72 V 30The scanning electron microscope image of the emulsion prepared by mixing an aqueous phase of / H2O / 8 mM RbCl / H2O solution and an oil phase of a mixed solution of 0.1 mM PDMS-NH2 / C7H8 and 0.1 mg / mL PS-b-P2VP / C7H8 in volumes of 1 mL and 15 mL respectively, followed by emulsification and ultrasonic emulsification for 1 h. Detailed implementation manners

[0037] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, 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 used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0038] It should be noted that the polyoxometalates {Mo 72 V 30}, {Mo 72 Fe 30}, {Mo 72 Cr 30}, {Cu 20 P8W 48}, {P4Y9W43} in the embodiments of the present invention refer to molecular clusters composed of transition metals and oxygen-containing ligands.

[0039] The monoaminopropyl-terminated polydimethylsiloxane (PDMS-NH2), diaminopropyl-terminated polydimethylsiloxane (NH2-PDMS-NH2), aminopropylmethylsiloxane-dimethylsiloxane random copolymer (RCP PDMS-5NH2, RCP PDMS-53NH2), and styrene-(2-vinylpyridine) block copolymer (PS-b-P2VP) in the embodiments of the present invention are all purchased from the market.

[0040] In the embodiments of the present invention, {Mo 72 V 30} was specifically prepared as follows: Pipette 0.5 mL of concentrated sulfuric acid (18.4 mol / L) and slowly add it to a beaker containing 17.9 mL of water to prepare 0.5 mol / L dilute sulfuric acid. Pipette 8 mL of the dilute sulfuric acid into a 50 mL round-bottom flask, mix with 2.42 g of Na2MoO4·2H2O, and stir magnetically until dissolved. Dissolve 2.53 g of VOSO4·5H2O in 30 mL of water, pour it into the sulfuric acid solution of Na2MoO4·2H2O, stir magnetically for 30 minutes under a nitrogen atmosphere, then add 0.65 g of KCl, stir magnetically for 30 minutes, and seal. Let it stand for one week in a light-proof environment, cool it in a -3°C refrigerator for 1 hour, filter it under a nitrogen atmosphere, and wash it several times with cold water. Finally, place the filter paper in a vacuum drying oven containing discolored silica gel and dry it for 3 days to obtain {Mo 72 V 30} solid, and replace the silica gel several times during this period.

[0041] Example 1

[0042] In this example, the solution containing polyoxometalate and the solution containing positively charged polymer were used to test the shear modulus of the two-phase interface by an interfacial viscoelasticity measuring instrument. Specifically:

[0043] (1) Weigh 0.0039 g of {Mo 72 V 30} into a beaker containing 9.75 ml of deionized water, disperse it evenly using a water bath ultrasonic instrument with a frequency of 40 KHz and a working time of 3 min - 5 min to obtain a dispersion of 0.4 mg / ml {Mo 72 V 30} / H2O, and dilute it to 0.1 mg / mL with deionized water.

[0044] (2) Weigh 0.04 g, 0.06 g, 0.16 g, 1 g, 0.4 g, and 0.1 g of PDMS-NH2 (the molecular weight of this polymer is 2000 g / mol and it has only one amino group, so there is no average molecular weight between amino groups), NH2-PDMS-NH2 (the molecular weight of this polymer is 3000 g / mol and the average molecular weight between amino groups is 3000 g / mol), RCP PDMS-5NH2 (the molecular weight of this polymer is 8000 g / mol and the average molecular weight between amino groups is 1600 g / mol), RCP PDMS-42NH2 (the molecular weight of this polymer is 50000 g / mol and the average molecular weight between amino groups is 1190 g / mol), RCP PDMS-53NH2 (the molecular weight of this polymer is 20000 g / mol and the average molecular weight between amino groups is 377 g / mol), and PS-b-P2VP (the molecular weight of this polymer is 16500 g / mol and the average molecular weight between amino groups is 105 g / mol) into reagent bottles containing 20 ml of toluene. Using a vortex mixer, stir and mix for 5 min at a rotation speed of 800 revolutions per minute to obtain solutions of 1 mM PDMS-NH2 / C7H8, NH2-PDMS-NH2 / C7H8, RCP PDMS-5NH2 / C7H8, RCP PDMS-42NH2 / C7H8, RCP PDMS-53NH2 / C7H8, and PS-b-P2VP / C7H8 respectively, and dilute them to 0.0001 mM with toluene.

[0045] (3) Use an interfacial viscoelasticity measuring instrument to measure the shear modulus of the two-phase interface for the solutions of the 5 different polymers prepared in steps (1) and (2) respectively.

[0046] The shear modulus is as Figure 1 shown. When PDMS-NH2 is selected as the polymer ligand, the storage modulus of 0.2 mg / mL {Mo 72 V 30} / H2O and 0.0001 mM PDMS-NH2 / C7H8 is lower than 10 mN / m, indicating that the assembly strength of the two-phase interface is extremely low. When NH2-PDMS-NH2 or RCP PDMS-5NH2 or RCP PDMS-42NH2 or RCP PDMS-53NH2 is used as the polymer ligand, its storage modulus is about 20 mN / m, indicating that the cross-linked structure generated by the multi-functional group polymer increases the mechanical strength of the interface; when PS-b-P2VP is used as the polymer ligand, its storage modulus is around 100 mN m -1 or so, indicating that its high functional group density significantly increases the mechanical strength of the interface, and due to the rigidity brought by the pyridine group to the chain segment, the relaxation ability of the interface is weakened, resulting in its extremely high storage modulus.

[0047] Example 2

[0048] In this example, a Pomosomes hollow shell structure was prepared, and the specific preparation method was as follows:

[0049] (1) Weigh 0.3 g of RbCl into a beaker containing 10 ml of deionized water, and disperse it evenly using a water bath ultrasonic instrument. The frequency of the water bath ultrasonic instrument is 40 KHz, and the working time is 3 min to 5 min. The resulting dispersion is 250 mM RbCl / H2O, which is diluted to 16 mM using deionized water.

[0050] Add the 0.4 mg / mL {Mo 72 V 30} / H2O obtained in Example 1 above, add the same volume of 16 mM RbCl / H2O, and use a vortex mixer to stir and mix for 5 min under the condition of a rotation speed of 800 revolutions per minute. The resulting solution is 0.2 mg / mL {Mo 72 V 30} / H2O / 8 mM RbCl / H2O.

[0051] (2) Dilute the 1 mM NH2-PDMS-NH2 obtained in Example 1 above to 0.01 mM using toluene to obtain 0.01 mM NH2-PDMS-NH2 / C7H8.

[0052] (3) Load the 0.2 mg / mL {Mo 72 V 30} / H2O / 8 mM RbCl / H2O solution in step (1) and the 0.01 mM NH2-PDMS-NH2 / C7H8 solution in step (2) into glass bottles with volumes of 0.3 mL and 3 mL respectively, stir and mix them for 10 s using a vortex shaker, and emulsify for 5 min at a power of 40 KHz using a water bath ultrasonic instrument to obtain an emulsion containing POMosomes. After natural drying, observe the morphology of POMosomes using a scanning electron microscope and a transmission electron microscope.

[0053] As Figure 2 、 3 shown. When NH2-PDMS-NH2 is used as the polymer ligand, its diffusion rate enables it to combine with {Mo 72 V 30} to produce a dense assembly layer, and it can crosslink {Mo 72 V 30} at the interface. The shear modulus is about 20 mN m -1 , and the interface has both strength and elasticity, which can produce a hollow POMosomes shell structure.

[0054] Example 3

[0055] In this example, a hollow shell structure of Pomosomes is prepared. The specific preparation method is as follows:

[0056] (1) Prepare a 0.2 mg / mL {Mo 72 V 30} / H2O / 8 mM RbCl / H2O solution according to Example 2 above, and prepare an RCP PDMS-5NH2 / C7H8 with a molar concentration of 0.01 mM according to Example 1 above.

[0057] (2) Load the 0.2 mg / mL {Mo 72 V 30} / H2O / 8 mM RbCl / H2O solution and 0.01 mM RCPPDMS-5NH2 / C7H8 solution in steps (1) into glass bottles with volumes of 1 mL and 15 mL respectively, stir and mix them for 10 s using a vortex shaker, and emulsify for 1 h at a power of 40 KHz using a water bath ultrasonic instrument to obtain an emulsion containing POMosomes. After natural drying, observe the morphology of POMosomes using a scanning electron microscope and a transmission electron microscope.

[0058] As Figure 4 、 5 shown. When using RCP PDMS-5NH2 as the polymer ligand, its diffusion rate is relatively fast, and it has multiple functional groups that can crosslink {Mo 72 V 30}, and the functional group spacing is relatively high (1600 g / mol), which can produce a hollow POMosomes shell structure.

[0059] Example 4

[0060] In this example, a hollow nanoshell structure of Pomosomes is prepared. The specific preparation method is as follows:

[0061] (1) Prepare a 0.2 mg / mL {Mo 72 V 30} / H2O / 8 mM RbCl / H2O solution according to Example 2 above, and prepare an RCP PDMS-53NH2 / C7H8 with a molar concentration of 0.01 mM according to Example 1 above.

[0062] (2) Load the 0.2 mg / mL {Mo 72 V 30The / H2O / 8 mM RbCl / H2O solution and the 0.01 mM RCPPDMS-53NH2 / C7H8 solution were respectively filled into glass bottles with volumes of 1 mL and 15 mL, stirred and mixed for 10 s using a vortex shaker, and emulsified for 30 min at a power of 40 KHz using a water bath ultrasonic instrument to obtain an emulsion containing POMosomes. After natural drying, the morphology of POMosomes was observed using a scanning electron microscope and a transmission electron microscope.

[0063] As Figure 6 , 7 shown. When using RCP PDMS-53NH2 with a molecular weight of 20000 g / mol as the polymer ligand, a hollow POMosomes shell structure can be prepared.

[0064] Example 5

[0065] In this example, a Pomosomes hollow shell structure was prepared, and the specific preparation method was as follows:

[0066] (1) Prepare a 0.2 mg / mL {Mo 72 V 30} / H2O / 8 mM RbCl / H2O solution according to Example 2 above, prepare a 0.1 mM PDMS-NH2 / C7H8 solution with a molar concentration according to Example 1 above, and a 0.1 mg / mL PS-b-P2VP / C7H8 solution.

[0067] (2) Fill the 0.2 mg / mL {Mo 72 V 30} / H2O / 8 mM RbCl / H2O solution and the 0.1 mM PDMS-NH2 / C7H8 solution in steps (1) into glass bottles with volumes of 1 mL and 12 mL respectively, stir and mix for 10 s using a vortex shaker, emulsify for 1 h at a power of 40 KHz using a water bath ultrasonic instrument, add 6 mL of 0.1 mg / mL PS-b-P2VP / C7H8 solution, and stir magnetically for 35 min to obtain an emulsion containing POMosomes. After natural drying, the morphology of POMosomes was observed using a scanning electron microscope.

[0068] As Figure 8 shown. When using PDMS-NH2 and PS-b-P2VP together as the polymer ligand, a POMosomes shell structure can be prepared.

[0069] Comparative Example 1

[0070] The difference between this comparative example and Example 2 is that the number of functional groups of the positively charged polymer is different: 0.2 mg / mL {Mo 72 V30} / H2O / 8 mM RbCl / H2O solution and 0.01 mM of PDMS-NH2 (the molecular weight of this polymer is 2000 g / mol) / C7H8 were mixed in volumes of 1 mL and 15 mL respectively. After ultrasonic emulsification for 30 min, a scanning electron microscope photograph was taken after drying. As Figure 9 shown, when PDMS-NH2 was used as the polymer ligand, the interfacial rigidity was insufficient to prepare a shell structure.

[0071] This is because PDMS-NH2 has only one amino group that can bind to the polyoxometalate and cannot produce a cross-linking effect. There is a lack of interaction between the assemblies, resulting in insufficient interfacial mechanical strength. During the solvent evaporation process, the emulsion droplets rupture and POMosomes cannot be produced.

[0072] Comparative Example 2

[0073] The difference between this comparative example and Example 2 is that the molecular weight and the number of functional groups of the positively charged polymer are different, and the volume ratio of the positively charged polymer to the polyoxometalate is different:

[0074] 0.2 mg / mL {Mo 72 V 30} / H2O / 8 mM RbCl / H2O solution and 0.01 mM of RCPPDMS-42NH2 (the molecular weight of this polymer is 50000 g / mol) / C7H8 were mixed in volumes of 1 mL and 15 mL respectively. After ultrasonic emulsification for 30 min, a scanning electron microscope photograph was taken after drying. As Figure 10 shown, when RCP PDMS-42NH2 was used as the polymer ligand, there were too many interfacial assembly defects to prepare a shell structure, denoted as POMosomes.

[0075] This is because the molecular weight of RCP PDMS-42NH2 is too large and the diffusion rate is too slow, resulting in difficulty in self-regulation after its assembly with the polyoxometalate. There are too many defects in the interfacial assembly layer, and the emulsion droplets are difficult to resist the compression force during the solvent evaporation process and collapse, and POMosomes cannot be synthesized.

[0076] Comparative Example 3

[0077] The difference between this comparative example and Example 5 is that the positively charged polymer is different, and the molar ratio of the positively charged polymer to the polyoxometalate is different:

[0078] 0.2 mg / mL {Mo 72 V 30} / H2O / 8 mM RbCl / H2O solution and 0.1 mg / mL of PS-b-P2VP (the molecular weight of this polymer is 16,500 g / mol) / C7H8 were mixed at volumes of 1 mL and 15 mL respectively. After ultrasonic emulsification for 1 h, scanning electron microscope photos were taken after drying. As Figure 11 shown, when using PS-b-P2VP as the polymer ligand, the interfacial elasticity is insufficient to prepare the POMosomes shell structure.

[0079] This is because the number of functional groups of PS-b-P2VP is high and the average molecular weight between functional groups is low. When it is used as a ligand, the interfacial mechanical strength is too high and the elasticity is insufficient, resulting in the compression force caused by solvent evaporation during the drying process to damage the assembly shell layer, and the broken emulsion droplet shell layers are connected to each other to produce a porous network structure.

[0080] Comparative Example 4

[0081] The difference between this comparative example and Example 5 is that the positively charged polymers are different, and the molar ratio of the positively charged polymer to the polyoxometalate is different, and the order of adding the polymer solution to the system is different:

[0082] Prepare 0.2 mg / mL {Mo 72 V 30} / H2O / 8 mM RbCl / H2O solution, 0.1 mM PDMS-NH2 / C7H8 and a mixed solution of 0.1 mg / mL of PS-b-P2VP (the molecular weight of this polymer is 16,500 g / mol) / C7H8 according to Example 2 above. They were mixed at volumes of 1 mL and 15 mL respectively. After ultrasonic emulsification for 1 h, scanning electron microscope photos were taken after drying. As Figure 12 shown, when using PDMS-NH2 and PS-b-P2VP as the polymer ligands together and adding them to the system simultaneously, the ligand participating in the assembly is PS-b-P2VP, and the interfacial elasticity is insufficient to prepare the POMosomes shell structure.

[0083] This is because after PDMS-NH2 and PS-b-P2VP are premixed and added to the system simultaneously, when mixed with the polyoxometalate, mainly PS-b-P2VP participates in the assembly. Therefore, when using PDMS-NH2 and PS-b-P2VP as the two ligands to synthesize POMosomes, it is necessary to first add the PDMS-NH2 with a small molecular weight, and after assembling with the polyoxometalate, then add the PS-b-P2VP with a large molecular weight to participate in the assembly.

[0084] In summary, in the present invention, the electrostatic interaction between the functionalized polymer in the oil phase and the polyoxometalate in the aqueous phase at the liquid-liquid interface blocks the oil-water interface, thereby providing a certain rigidity and elasticity to the interface, preparing a robust POMosomes shell structure without the need for other auxiliary means to increase the interface strength. By selecting the functionalized polymer, some properties of the polymer, such as the cross-linked structure, can be imparted to the interface, providing a new idea for the preparation of multifunctional shell structures.

[0085] Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a hollow shell structure of Pomosomes, characterized in that, The method includes the following steps: (1) Dissolve the positively charged polymer in the oil phase, and disperse the polyoxometalate and the inorganic salt in the aqueous phase. The polyoxometalate can form an assembly with the positively charged polymer through electrostatic interaction; the inorganic salt is used to reduce the electrostatic repulsion between polyoxometalates; The positively charged polymer is one of bis(3-aminopropyl) terminated polydimethylsiloxane and aminopropylmethylsiloxane-dimethylsiloxane random copolymer. Alternatively, the positively charged polymer contains both monoamino-terminated polydimethylsiloxane and styrene-(2-vinylpyridine) block copolymer; the number of amino groups contained in the aminopropylmethylsiloxane-dimethylsiloxane random copolymer is 5 - 53; And when the positively charged polymer contains both monoamino-terminated polydimethylsiloxane and styrene-(2-vinylpyridine) block copolymer, first add the monoamino-terminated polydimethylsiloxane with a smaller molecular weight, assemble it with the polyoxometalate, and then add the styrene-(2-vinylpyridine) block copolymer with a larger molecular weight to participate in the assembly; The molecular weight of the positively charged polymer is 2000 - 20000 g / mol, and the average molecular weight between amino groups in the positively charged polymer is 377 - 3000 g / mol; The polyoxometalate is {Mo 72 V 30}; The inorganic salt is rubidium chloride, sodium chloride or potassium chloride; The molar ratio of the positively charged polymer to the polyoxometalate is (0.38 - 17.52):1; (2) Mix the oil phase and the aqueous phase and then emulsify them. After standing, an emulsion containing the Pomosomes hollow shell structure is obtained.

2. The preparation method according to claim 1, wherein The molar concentration of the positively charged polymer in the oil phase is 0.01 - 0.046 mM, and the mass concentration of the polyoxometalate in the aqueous phase is 0.05 - 0.5 mg / mL; the addition amount of the inorganic salt is 8 mM.

3. The preparation method according to claim 1, characterized in that, The emulsification is achieved by a water bath ultrasonic device and a magnetic stirrer; the dissolution of the positively charged polymer and the polyoxometalate is achieved by a vortex mixer and a water bath ultrasonic device.

4. A Pomosomes hollow shell structure prepared by the preparation method according to any one of claims 1-3, characterized in that, The Pomosomes hollow shell structure is spherical, and the particle size is 0.2 - 3 µm.

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