Hollow mesoporous silica microspheres, methods for their preparation and uses thereof

Abstract

This invention relates to the field of hollow mesoporous materials technology, specifically to a hollow mesoporous silica microsphere and its applications. This invention overcomes the limitations of previous synthesis techniques in precisely controlling the structure of mesoporous spherical silica materials. It utilizes a novel template agent, polybenzimidazole terminally grafted with PEG, and obtains spherical silica with high porosity, large specific surface area, and good mesoporous stability through a hydrolysis-condensation reaction of tetraalkoxysilane. This significantly increases loading efficiency and stability, and can be widely applied in biomaterials, medical excipients, food, daily chemical cosmetics, electronics, and other technical fields, especially in sunscreen products.

Description

Technical Field

[0001] This invention relates to the field of hollow mesoporous materials technology, specifically to a hollow mesoporous silica microsphere and its applications. Background Technology

[0002] Hollow mesoporous silica microspheres have an extremely wide range of applications due to their excellent properties, such as being colorless and odorless, chemically stable, having strong ultraviolet reflection capabilities, large specific surface area, and easy surface functionalization. These applications include biomaterials, medical excipients, food, daily chemical cosmetics, and electronics.

[0003] Currently, research on hollow mesoporous silica microspheres has gradually shifted from industrial catalysis to applications such as drug sustained release and cosmetic sunscreens, as exemplified by patent WO2013 / 068236. Taking the application of hollow mesoporous silica in sunscreen products (such as sunscreen cosmetics) as an example, the wavelength range of ultraviolet (UV) radiation is generally 100–400 nm. Based on wavelength, UV radiation is generally divided into three regions: Region C (short-wave UV, 200–280 nm); Region B (medium-wave UV, 280–320 nm); and Region A (long-wave UV, 320–400 nm). To obtain excellent shielding performance against the full spectrum of UV (UVA+UVB) in sunscreen products, it is usually necessary to load and combine hollow mesoporous silica with other inorganic / organic sunscreen agents, such as composite nano-TiO2 or UV absorbers containing double bonds / conjugated heterocycles. Furthermore, the requirements for waterproof, sweatproof, and long-lasting effects in sunscreen products necessitate that the mesoporous silica used possess characteristics such as large specific surface area, good adsorption performance, and easy dispersion.

[0004] Methods for synthesizing hollow mesoporous silica include hard template methods, soft template methods, and silica self-templating methods. Hard template methods yield mesoporous materials with uniform particle size and good dispersibility, but the yield is low and the outer shell is easily damaged. Soft template methods mainly include micelle methods, bubble methods, emulsion drop methods, and polymer aggregation methods. The micelle method is a common one. In its preparation process, a surfactant is usually used as a soft template, and an appropriate amount of porogen is added to the system to form micelles. Silica then coats the template surface through a sol-gel process, followed by the removal of the template agent and porogen agent using extraction or calcination to obtain the product. Soft template methods yield hollow mesoporous silica with high yield, simple and controllable reaction process, and strong loading capacity, and are also a major research focus reported in the literature. However, in the existing technology, although the template method can construct porous silica, the resulting pores are mostly micropores or mesopores with poor internal connectivity, insufficient surface openness (external specific surface area ratio <30%), or prone to varying degrees of aggregation, or even severe aggregation, making it difficult to achieve efficient physical / chemical interaction with guest substances, thus limiting its application in loading and compounding organic / inorganic sunscreens.

[0005] Therefore, it is necessary to develop a new type of hollow mesoporous silica microsphere through structural improvement in order to obtain advantages such as good internal connectivity, high porosity, mesoporous stability, and good dispersibility, so as to improve the loading efficiency and long-lasting stability of sunscreen agents. Summary of the Invention

[0006] This invention is made in view of the above-mentioned problems. Its purpose is to synthesize a novel polymer-based template agent through structural design, and to use the novel template agent to precisely control the hydrolysis and condensation of tetraalkoxysilane, thereby obtaining spherical silica with high porosity, large specific surface area, good mesoporous stability and good dispersibility, which greatly increases the loading efficiency of sunscreen agents and the stability of the system.

[0007] Specifically, in order to solve the above problems, a first aspect of the present invention provides a method for preparing hollow mesoporous silica microspheres, comprising the following sequential steps:

[0008] (1) After thoroughly mixing the organosilicon source solution and the template agent solution, add an alkaline reagent to carry out condensation polymerization to obtain the organosilicon product after condensation polymerization.

[0009] (2) The organosilicon product obtained by condensation polymerization is subjected to heat treatment to decompose the template agent and thereby obtain the hollow mesoporous silica microspheres.

[0010] The template agent is a polybenzimidazole with PEG grafted to its end.

[0011] In one embodiment, the PEG-terminated polybenzimidazole is prepared by a method comprising the following sequential steps:

[0012] (i) Reaction of 3,3',4,4'-biphenyltetramine with excess 1,3,5-m-phenyltricarboxylic acid to obtain carboxyl-terminated hyperbranched polybenzimidazole;

[0013] (ii) React the carboxyl-terminated hyperbranched polybenzimidazole with sufficient sulfoxide to obtain acyl chloride-terminated hyperbranched polybenzimidazole;

[0014] (iii) React the acyl chloride-terminated hyperbranched polybenzimidazole with terminal hydroxymethoxy polyethylene glycol to obtain the PEG-terminated polybenzimidazole.

[0015] In one implementation, the method includes:

[0016] The organosilicon source in step (1) is selected from tetraalkoxysilane; and / or

[0017] The organosilicon source solution in step (1) is obtained by dissolving the organosilicon source in a solvent, and the concentration is 30%-50% by weight; and / or

[0018] The template agent solution in step (1) is obtained by dissolving the template agent in a solvent, and the concentration is 0.01 g / ml - 0.1 g / ml; and / or

[0019] The alkaline reagent in step (1) is selected from: tetramethylammonium hydroxide aqueous solution and ammonia water, wherein the concentration of the tetramethylammonium hydroxide aqueous solution is 1%-10% by weight, and the concentration of the ammonia water is 1%-10% by weight; and / or

[0020] Step (1) is carried out under stirring at a stirring rate of 2000-5000 rpm; and / or

[0021] The condensation polymerization in step (1) is carried out at 30-50°C; and / or

[0022] In step (1), the weight ratio of the organosilicon source solution, template agent solution, and alkaline reagent is (5-25):(5-50):1; and / or

[0023] The heat treatment in step (2) is to calcine at 700-900℃ for 4-10 hours.

[0024] In one implementation, the method includes:

[0025] The tetraalkoxysilane is selected from: tetraethoxysilane and tetraisopropoxysilane; and / or

[0026] The solvent used in the organosilicon source solution in step (1) is toluene; and / or

[0027] The solvent used in the template agent solution in step (1) is a mixed solution of ethanol and DMF, wherein the volume ratio of ethanol to DMF is (2-5):1.

[0028] In one implementation, the method includes:

[0029] In step (i), a 5%-20% by weight methanesulfonic acid solution of phosphorus pentoxide is used as the reaction solvent; and / or

[0030] The solid content of the reaction solution in step (i) is 3%-30% by weight; and / or;

[0031] In step (i), the molar ratio of 3,3',4,4'-biphenyltetramine to 1,3,5-m-phenyltricarboxylic acid is 3:10; and / or

[0032] Step (i) is performed at 110°C-130°C.

[0033] In one embodiment, step (ii) of the method is performed under ice bath conditions at 0-10°C.

[0034] In one implementation, the method includes:

[0035] In step (iii), the molar ratio of acyl chloride-terminated hyperbranched polybenzimidazole to hydroxyl-terminated methoxy polyethylene glycol is 1:6; and / or

[0036] In step (iii), N,N-dimethylacetamide containing excess triethylamine is used as the reaction solvent; and / or

[0037] In step (iii), the weight-average molecular weight of the terminal hydroxymethoxy polyethylene glycol is 3,000-40,000.

[0038] A second aspect of the present invention provides hollow mesoporous silica microspheres, which are prepared by the method described in the first aspect above.

[0039] A third aspect of the present invention provides the use of hollow mesoporous silica microspheres prepared by the method according to the first aspect above, or hollow mesoporous silica microspheres according to the second aspect above, in the preparation of sunscreen products.

[0040] A fourth aspect of the present invention provides a sunscreen article comprising:

[0041] Hollow mesoporous silica microspheres prepared by the method according to the first aspect above or hollow mesoporous silica microspheres according to the second aspect above were used; and

[0042] Sunscreen agent loaded within the hollow mesoporous silica microspheres.

[0043] The special mechanism and beneficial technical effects of this invention are as follows:

[0044] This invention first synthesizes a hydrophobic rigid core, namely polybenzimidazole (PBI) with a hyperbranched structure; then, a hydrophilic polymer PEG is grafted around the core, with the weight-average molecular weight of PEG controlled in the range of 3000-40000. This structure, with its specially designed and synthesized template agent, is less affected by solvent, reaction temperature, and stirring rate during the preparation of silica mesoporous microspheres. The resulting mesoporous spherical silica has uniform size and is not prone to aggregation. The rigid structure of PBI and its good heat resistance within a certain temperature range provide good support during subsequent high-temperature calcination for pore formation, preventing pore collapse. The flexible side chains of PEG are uniformly distributed around the rigid core and possess certain crystallinity, easily forming a regular structure, ensuring good pore interconnectivity, high porosity, and large specific surface area after high-temperature pore formation.

[0045] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0046] Figure 1 This is the infrared spectrum of the template agent of Embodiment 1 of the present invention.

[0047] Figure 2 The image shown is a SEM image of the hollow mesoporous silica microspheres from Example 1, which shows that a structural system with regular structure and good dispersion has been formed.

[0048] Figure 3 This is a TEM image of the hollow mesoporous silica microspheres from Example 1, showing that they form a microstructure with high porosity and good interconnectivity. Detailed Implementation

[0049] As mentioned above, there is an urgent need in the existing technology to synthesize a novel hollow mesoporous silica microsphere that has the advantages of excellent internal connectivity, porosity, mesoporous stability and dispersibility.

[0050] To at least partially address one or more of the above-mentioned problems and other potential problems, a first exemplary embodiment of the present invention provides a method for preparing hollow mesoporous silica microspheres, comprising the following sequential steps:

[0051] (1) After thoroughly mixing the organosilicon source solution and the template agent solution, add an alkaline reagent to carry out condensation polymerization to obtain the organosilicon product after condensation polymerization.

[0052] (2) The organosilicon product obtained by condensation polymerization is subjected to heat treatment to decompose the template agent and thereby obtain the hollow mesoporous silica microspheres.

[0053] The template agent is a polybenzimidazole with PEG grafted to its end.

[0054] There are no particular limitations on the polybenzimidazole with PEG grafted at the ends, and different structures can be used, but it is preferably prepared by a method including the following sequential steps:

[0055] (i) Reaction of 3,3',4,4'-biphenyltetramine with excess 1,3,5-m-phenyltricarboxylic acid to obtain carboxyl-terminated hyperbranched polybenzimidazole;

[0056] (ii) React the carboxyl-terminated hyperbranched polybenzimidazole with sufficient sulfoxide to obtain acyl chloride-terminated hyperbranched polybenzimidazole;

[0057] (iii) React the acyl chloride-terminated hyperbranched polybenzimidazole with terminal hydroxymethoxy polyethylene glycol to obtain the PEG-terminated polybenzimidazole.

[0058] There are no particular restrictions on the organosilicon source in step (1), but it is preferably selected from tetraalkoxysilane, and more preferably from tetraethoxysilane and tetraisopropoxysilane.

[0059] Typically, the organosilicon source solution in step (1) can be obtained by dissolving the organosilicon source in a solvent at a concentration of 30%-50% by weight.

[0060] Typically, the template agent solution in step (1) can be obtained by dissolving the template agent in a solvent, with a concentration of 0.01 g / ml to 0.1 g / ml.

[0061] Typically, the alkaline reagent in step (1) can be selected from: an aqueous solution of tetramethylammonium hydroxide and ammonia, wherein the concentration of the aqueous solution of tetramethylammonium hydroxide is 1%-10% by weight and the concentration of the ammonia is 1%-10% by weight.

[0062] Typically, step (1) is carried out under stirring at a stirring rate of 2000-5000 rpm.

[0063] Typically, the condensation polymerization in step (1) is carried out at 30-50°C.

[0064] Typically, in step (1), the weight ratio of the organosilicon source solution, template agent solution, and alkaline reagent is (5-25):(5-50):1.

[0065] Typically, the heat treatment in step (2) is a continuous calcination at 700-900°C for 4-10 hours.

[0066] Typically, the solvent used in the organosilicon source solution in step (1) is toluene.

[0067] Typically, the solvent used in the template agent solution of step (1) is a mixture of ethanol and DMF, wherein the volume ratio of ethanol to DMF is (2-5):1.

[0068] Typically, in step (i), a 5%-20% by weight methanesulfonic acid solution of phosphorus pentoxide is used as the reaction solvent.

[0069] Typically, the solid content of the reaction solution in step (i) is 3% to 30% by weight.

[0070] Typically, in step (i), the molar ratio of 3,3',4,4'-biphenyltetramine to 1,3,5-m-phenyltricarboxylic acid is 3:10.

[0071] Typically, step (i) is performed at 110°C–130°C.

[0072] Typically, step (ii) is performed under ice bath conditions at 0-10°C.

[0073] Preferably, in step (iii), the molar ratio of acyl chloride-terminated hyperbranched polybenzimidazole to hydroxyl-terminated methoxy polyethylene glycol is 1:6.

[0074] Preferably, in step (iii), N,N-dimethylacetamide containing excess triethylamine is used as the reaction solvent.

[0075] Preferably, in step (iii), the weight-average molecular weight of the terminal hydroxymethoxy polyethylene glycol is 3000-40000.

[0076] Hollow mesoporous silica microspheres

[0077] In order to at least partially solve one or more of the above-mentioned problems and other potential problems, a second exemplary embodiment of the present invention provides hollow mesoporous silica microspheres, which are prepared by the method described in the first exemplary embodiment above.

[0078] use

[0079] In order to at least partially solve one or more of the above-mentioned problems and other potential problems, a third exemplary embodiment of the present invention provides the use of hollow mesoporous silica microspheres prepared by the method according to the first exemplary embodiment described above or hollow mesoporous silica microspheres according to the second exemplary embodiment described above in the preparation of sunscreen products.

[0080] Sunscreen products

[0081] To at least partially address one or more of the above-mentioned problems and other potential problems, a fourth exemplary embodiment of the present invention provides a sunscreen article comprising:

[0082] Hollow mesoporous silica microspheres prepared by the method described in the first example embodiment above, or hollow mesoporous silica microspheres described in the second example embodiment above; and

[0083] Sunscreen agent loaded within the hollow mesoporous silica microspheres.

[0084] The following describes embodiments of the present invention. These embodiments are exemplary and are only used to explain the present invention, and should not be construed as limiting the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0085] The m-PEG-OH molecules with different weight-average molecular weights used in the embodiments of this invention are methoxylated polyethylene glycol hydroxyl groups, with a methoxy group at one end of the molecule. The end is capped, and the other end retains the active hydroxyl (-OH) group, with the following structural formula: All were purchased from Chongqing Yusi Pharmaceutical Technology Co., Ltd.

[0086] Example 1

[0087] The steps for preparing hollow mesoporous silica microspheres are as follows:

[0088] (1) Synthetic template agent - polybenzimidazole with PEG grafted at the end

[0089] 150g of methanesulfonic acid solution (obtained by dissolving 20g of phosphorus pentoxide in 130g of methanesulfonic acid) was added to a dry and clean three-necked flask under nitrogen protection. Then, 6.42g of 3,3',4,4'-biphenyltetramine was added. After it was fully dissolved, 2.14g of 1,3,5-m-phenyltricarboxylic acid was slowly added in three batches. After each addition, the temperature was raised to 120℃ and the reaction was carried out for 6 hours to obtain the prepared reaction solution.

[0090] In another dry and clean nitrogen-protected three-necked flask, 18.9 g of 1,3,5-m-phenyltricarboxylic acid was dissolved in 200 g of methanesulfonic acid solution (40 g of phosphorus pentoxide was dissolved in 160 g of methanesulfonic acid). Then, all the prepared reaction solutions were slowly transferred to the three-necked flask in three batches. After each batch, the temperature was raised to 120 °C and the reaction was carried out for 4 hours.

[0091] After the reaction was completed, the mixture was cooled to room temperature, and the reaction solution was precipitated in deionized water and washed to obtain the reaction product. The product was diluted with ammonia water to 3% by weight to remove methanesulfonic acid and phosphoric acid. Then, it was repeatedly washed with deionized water until neutral and dried under vacuum at 120°C for 10 hours to obtain carboxyl-terminated hyperbranched polybenzimidazole b-PBI-COOH.

[0092] 10g of the synthesized b-PBI-COOH was placed in a dry, clean, nitrogen-protected three-necked flask and placed in an ice bath at 10°C. Then, 50ml of thionyl chloride was slowly added, and the mixture was stirred for 10 hours. As the carboxyl acyl chloride reaction proceeded, the solid gradually dissolved, and the reaction solution gradually became clear. After the reaction was completed, the thionyl chloride was removed by vacuum distillation at 60°C to obtain acyl chloride-terminated hyperbranched polybenzimidazole b-PBI-COCl.

[0093] 13.74 g of b-PBI-COCl was dissolved in a mixed solution of 112 ml N,N-dimethylacetamide and 8 ml triethylamine. After complete dissolution, 60 mmol of terminal hydroxymethoxy polyethylene glycol m-PEG-OH-20000 (weight average molecular weight of 20000) was added. The mixture was stirred at room temperature for 5 hours. As the reaction proceeded, a large amount of triethylamine hydrochloride precipitated out. After the reaction was completed, the mixture was filtered, rinsed three times with ice-cold pure water, and then washed three times with warm water. The mixture was collected and dried to obtain polybenzimidazole b-PBI-PEG with PEG grafted to the template end.

[0094] (2) Synthesis of hollow mesoporous silica microspheres

[0095] Accurately weigh 15g of template agent b-PBI-PEG into a 2000mL beaker, then add 600ml of ethanol and 300ml of a mixed solution of N,N'-dimethylformamide (DMF). After complete dissolution, slowly add a toluene-diluted solution of tetraethoxysilane (180g of tetraethoxysilane dissolved in 250g of toluene) to the flask. After stirring evenly, increase the stirring speed to 4000rpm and raise the temperature to 40℃. Subsequently, slowly add 60g of 3% (w / w) ammonia solution to carry out condensation polymerization. After maintaining the temperature and stirring for 8 hours, sonicate for 2 hours. After the experiment, collect the product by centrifugation and wash with deionized water until neutral, wash three times with ethanol, and dry to obtain the condensed polymerized organosilicon product.

[0096] The dried, condensed, polymerized organosilicon product was placed in a crucible and calcined at 850°C for 8 hours in a muffle furnace under static air atmosphere until the template agent b-PBI-PEG was completely decomposed, thus obtaining hollow mesoporous silica microspheres.

[0097] Example 2

[0098] It is basically the same as Example 1, except that m-PEG-OH-3000 (weight average molecular weight is 3000) is used.

[0099] Example 3

[0100] It is basically the same as Example 1, except that m-PEG-OH-5000 (weight average molecular weight of 5000) is used.

[0101] Example 4

[0102] It is basically the same as Example 1, except that m-PEG-OH-10000 (weight average molecular weight is 10000) is used.

[0103] Example 5

[0104] It is basically the same as Example 1, except that m-PEG-OH-2000 (weight average molecular weight is 2000) is used.

[0105] Example 6

[0106] It is basically the same as Example 1, except that m-PEG-OH-40000 (weight average molecular weight is 40000) is used.

[0107] Comparative Example 1

[0108] It is basically the same as Example 1, except that m-PEG-OH-400 (weight-average molecular weight of 400) is used.

[0109] Comparative Example 2

[0110] This is essentially the same as Example 1, except that m-PEG-OH-50000 (weight-average molecular weight of 50000) is used.

[0111] Comparative Example 3 (Conventional Methods in the Prior Art)

[0112] Accurately weigh 5 g of hexadecyltrimethylammonium bromide (CTAB) into a 500 mL three-necked flask, add 150 mL of anhydrous ethanol and 100 mL of deionized water, sonicate for 20 min, then heat to 40 °C, stir at 2000 rpm for 30 min. Next, add 25 mL of a mixture of toluene and 50 mL of tetraethyl orthosilicate (TEOS) to the reaction solution, maintaining stirring and temperature, and slowly add 10 mL of a 5% (w / w) ammonia solution, stirring at 2000 rpm and 40 °C for 10 h. After the experiment, centrifuge the product and wash it three times each with deionized water and anhydrous ethanol. Then, dry the product in a 60 °C oven for 24 h, and then calcine it in a crucible at 650 °C for 4 h to obtain hollow mesoporous silica microspheres.

[0113] Test characterization

[0114] 1. Fourier Transmission Infrared Spectroscopy (FT-IR)

[0115] The structure of the sample was analyzed by infrared analysis using a Nicolet 6700 Fourier transform infrared spectrometer from Thermofisher, USA. A small amount of sample was mixed with potassium bromide powder and ground evenly before being compressed into a tablet for measurement.

[0116] 2. Scanning electron microscopy (SEM) analysis

[0117] The microstructure of the sample, including its morphology, was observed using a Hitachi S-3400N(II) scanning electron microscope.

[0118] 3. Transmission electron microscopy (TEM) analysis

[0119] The internal structure and particle size of the sample were observed using a JEM-2100 transmission electron microscope from Nippon Electronics Corporation. An appropriate amount of sample was placed in anhydrous ethanol and ultrasonically dispersed to prepare an extremely dilute dispersion, which was then dropped onto a regular copper grid or a microgrid copper grid for testing.

[0120] 4. Specific surface area analysis

[0121] This paper uses the ASAP20220 surface area and microporous physical adsorption analyzer from Micron Instruments, USA, to analyze the pore structure of the samples. Static volumetric method and N2 were used as the adsorption / desorption medium.

[0122] 5. Evaluation of hydrophilicity and lipophilicity

[0123] The particulate matter was analyzed by precipitation method. The particulate matter was added to the polar solvent water and the non-polar solvent toluene, respectively. After ultrasonic vibration for 15 min, it was allowed to stand for 48 h and the precipitation was observed.

[0124] The above-described Examples 1-6 and Comparative Examples 1-3 were tested, and the results are shown in Table 1 below.

[0125] Table 1

[0126]

[0127] As can be seen from Table 1 above, compared with the prior art (Comparative Example 3), the hollow mesoporous silica microspheres prepared by the method of the present invention (Examples 1-6) have significantly larger specific surface area and mesopore volume, better system dispersibility, and better hydrophilicity and oleophilicity. Furthermore, the weight-average molecular weight of the polyethylene glycol grafted in the template agent also has a significant impact on the technical effect. An excessively high molecular weight (weight-average molecular weight of 50,000) leads to severe agglomeration (Comparative Example 2), while an excessively low molecular weight (weight-average molecular weight of 400) results in a decrease in hydrophilicity and oleophilicity; therefore, strict control of the molecular weight range is necessary.

[0128] 6. Sunscreen loading test

[0129] Apply sunscreen as follows:

[0130] (1) 1.0 g of hollow mesoporous silica microspheres from Examples 1-6 and Comparative Examples 1 and 3 were added to 100 mL of ethanol solution, sonicated for 10 min, and then transferred to a brown three-necked flask. 0.7 g of commercially available organic sunscreen (PEG-25 para-aminobenzoic acid) was added and stirred at room temperature for 3 h.

[0131] (2) After the reaction is completed, the microspheres are centrifuged, washed three times each with deionized water and anhydrous ethanol, and dried at 60°C for 10 h to obtain hollow mesoporous silica microspheres loaded with sunscreen.

[0132] The loading results are shown in Table 2 below.

[0133] Table 2

[0134]

[0135] As can be seen from Table 2 above, compared with the conventional method of the prior art (Comparative Example 3) and the case where the weight-average molecular weight of the polyethylene glycol grafted in the template agent is too low (Comparative Example 1), the hollow mesoporous silica microspheres obtained by the method of the present invention (Examples 1-6) have a much larger difference in specific surface area before and after loading sunscreen, which means that the amount of sunscreen loaded is significantly greater.

[0136] Overall, the above results demonstrate that, compared with the prior art, the hollow mesoporous silica microspheres of the present invention achieve good internal connectivity, high porosity, stable mesopores, good dispersibility, and high loading efficiency for sunscreen agents, thus achieving significant and beneficial technical effects.

Claims

1. A method for preparing hollow mesoporous silica microspheres, comprising the following sequential steps: (1) After thoroughly mixing the organosilicon source solution and the template agent solution, add an alkaline reagent to carry out condensation polymerization to obtain the organosilicon product after condensation polymerization. (2) The organosilicon product obtained by condensation polymerization is subjected to heat treatment to decompose the template agent and thereby obtain the hollow mesoporous silica microspheres. The template agent is a PEG-terminated polybenzimidazole, which is prepared by a method comprising the following sequential steps: (i) Reaction of 3,3',4,4'-biphenyltetramine with excess 1,3,5-m-phenyltricarboxylic acid to obtain carboxyl-terminated hyperbranched polybenzimidazole; (ii) React the carboxyl-terminated hyperbranched polybenzimidazole with sufficient sulfoxide to obtain acyl chloride-terminated hyperbranched polybenzimidazole; (iii) React the acyl chloride-terminated hyperbranched polybenzimidazole with terminal hydroxy methoxy polyethylene glycol to obtain the PEG-terminated polybenzimidazole. In step (iii), the weight-average molecular weight of the terminal hydroxymethoxy polyethylene glycol is 3,000-40,000.

2. The method according to claim 1, wherein: The organosilicon source in step (1) is selected from tetraalkoxysilane; and / or The organosilicon source solution in step (1) is obtained by dissolving the organosilicon source in a solvent, and the concentration is 30%-50% by weight; and / or The template agent solution in step (1) is obtained by dissolving the template agent in a solvent, and the concentration is 0.01 g / ml - 0.1 g / ml; and / or The alkaline reagent in step (1) is selected from: tetramethylammonium hydroxide aqueous solution and ammonia water, wherein the concentration of the tetramethylammonium hydroxide aqueous solution is 1%-10% by weight, and the concentration of the ammonia water is 1%-10% by weight; and / or Step (1) is carried out under stirring at a stirring rate of 2000-5000 rpm; and / or The condensation polymerization in step (1) is carried out at 30-50°C; and / or In step (1), the weight ratio of the organosilicon source solution, template agent solution, and alkaline reagent is (5-25):(5-50):1; and / or The heat treatment in step (2) is to calcine at 700-900℃ for 4-10 hours.

3. The method according to claim 2, wherein: The tetraalkoxysilane is selected from: tetraethoxysilane and tetraisopropoxysilane; and / or The solvent used in the organosilicon source solution in step (1) is toluene; and / or The solvent used in the template agent solution in step (1) is a mixed solution of ethanol and DMF, wherein the volume ratio of ethanol to DMF is (2-5):

1.

4. The method according to claim 1, wherein: In step (i), a 5%-20% by weight methanesulfonic acid solution of phosphorus pentoxide is used as the reaction solvent; and / or The solid content of the reaction solution in step (i) is 3%-30% by weight; and / or; In step (i), the molar ratio of 3,3',4,4'-biphenyltetramine to 1,3,5-m-phenyltricarboxylic acid is 3:10; and / or Step (i) is performed at 110°C-130°C.

5. The method according to claim 1, wherein: Step (ii) is performed under ice bath conditions at 0-10°C.

6. The method according to claim 1, wherein: In step (iii), the molar ratio of acyl chloride-terminated hyperbranched polybenzimidazole to hydroxyl-terminated methoxy polyethylene glycol is 1:6; and / or In step (iii), N,N-dimethylacetamide containing excess triethylamine is used as the reaction solvent.

7. Hollow mesoporous silica microspheres, which are prepared by the method according to any one of claims 1-6.

8. Use of hollow mesoporous silica microspheres prepared by any one of claims 1-6 or hollow mesoporous silica microspheres according to claim 7 in the preparation of sunscreen products.

9. Sunscreen products, which include: Hollow mesoporous silica microspheres prepared by the method according to any one of claims 1-6 or hollow mesoporous silica microspheres according to claim 7; and Sunscreen agent loaded within the hollow mesoporous silica microspheres.

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