Preparation method of small-sized silica nanoparticles synthesized based on copolymer template

Abstract

The present invention relates to a preparation method for synthesizing small-sized silica nanoparticles based on a copolymer template, comprising the following steps: dissolving a binary random copolymer or a block-random copolymer in a good solvent to obtain a copolymer solution; adding a poor solvent to the copolymer solution to obtain a polymer micelle seed solution; adding an alkaline reagent to the polymer micelle seed solution for mixing, and adding a silicon precursor for mixing and dispersion, generating a sol-gel reaction to obtain symmetrical or asymmetrical small-sized silica nanoparticles; adding a silane coupling agent containing a long carbon chain or a long fluorocarbon chain to the asymmetrical small-sized silica nanoparticles for modification to obtain small-sized silica nanoparticles with amphiphilicity. Compared with the prior art, the present invention can realize the synthesis of small-sized silica nanoparticles in high-concentration polymers or silicon precursors.

Description

Technical Field

[0001] The present invention relates to the technical field of nanoparticle synthesis, in particular to a preparation method for synthesizing small-sized silicon dioxide nanoparticles based on a copolymer template. Background Art

[0002] Silica micro-nanomaterials are widely used in architecture, polymer composite membranes, optical imaging, catalysis, adsorption, batteries and other fields due to their advantages such as good stability, easy functionalization, good biocompatibility and large specific surface area. Traditional silica synthesis methods mainly include the Stober method and the reverse microemulsion method, which usually produce spherical silica particles. In addition, the preparation technology can also be improved to synthesize a series of non-spherical silica particles or their hybrid materials, such as rod-shaped, tubular, core-shell, hollow, mesoporous and snowman-shaped structures. However, the silica particles prepared by these methods usually have a large size (>100 nanometers) and a wide monodispersity.

[0003] Ultrafine materials, due to their small size, possess unique capabilities, such as serving as next-generation drug delivery vehicles or radiosensitizers for magnetic resonance imaging. However, these inorganic ultrafine particles primarily consist of metal nanoparticles, quantum dots, and organic luminescent groups. The ability to produce large quantities of ultrafine silica colloidal particles with excellent biosafety would represent a breakthrough in this field. In recent years, several studies have focused on the preparation of ultrafine silica particles. For example, monodisperse silica particles were prepared using polylysine as a template in an inverse microemulsion system, but the resulting particles were relatively large, approximately 50 to 70 nanometers. Another approach used PEO-bP (MMA-r-TMSPMA) as a template to induce the self-collapse and in situ hydrolysis of the polymer chains, producing silica particles 15 to 20 nanometers in size through polymer-solvent repulsion. Still another approach used a random copolymer, P(St-r-AA), as a template to induce polymer chain collapse through electrostatic repulsion, producing single-chain templated silica particles. However, in these methods, the concentration of the polymer or silicon precursor should not be too high, as this can cause the polymer to aggregate and settle, or form beaded particles. Therefore, there is an urgent need for methods that can increase the concentration of the polymer or silicon precursor to prepare small-sized silica colloidal particles on a large scale. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing small-sized silica colloidal particles based on a copolymer template in order to overcome the problem that the concentration of polymer or silicon precursor is not too high when preparing small-sized silica colloidal particles in the prior art.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] The technical solution of the present invention is to provide a preparation method for synthesizing small-sized silica nanoparticles based on a copolymer template, comprising the following steps:

[0007] dissolving the binary random copolymer or the block-random copolymer in a good solvent to obtain a copolymer solution;

[0008] adding a poor solvent to the copolymer solution to obtain a polymer micelle seed solution;

[0009] An alkaline reagent is added to the polymer micelle seed solution and mixed, and a silicon precursor is added and mixed and dispersed to cause a sol-gel reaction to obtain symmetrical or asymmetrical small-sized silicon dioxide nanoparticles with an average diameter of 17-58 nm.

[0010] In some specific embodiments, a silane coupling agent containing a long carbon chain or a long fluorocarbon chain is added to the asymmetric small-sized silica nanoparticles for modification, and the reaction obtains amphiphilic small-sized silica nanoparticles with an average diameter of 17-60 nm.

[0011] In some specific embodiments, the binary random copolymer is poly(acrylic acid monomer-r-styrene monomer), the acrylic acid monomer is selected from any one of acrylic acid, 2-methylacrylic acid, 2-ethylacrylic acid or tert-butyl acrylate, and the styrene monomer is selected from any one of styrene, p-methylstyrene, p-trifluoromethylstyrene, p-chlorostyrene or p-fluorostyrene. When the binary random copolymer is used as a template, symmetrical small-sized silica nanoparticles are prepared.

[0012] In some specific embodiments, the block-random copolymer is block-b-poly(acrylic monomer-r-styrene monomer), the block is selected from any one of polystyrene, polyethylene oxide, poly(p-fluorostyrene) or polypropylene oxide, the acrylic monomer is selected from any one of acrylic acid, 2-methacrylic acid, 2-ethylacrylic acid or tert-butyl acrylate, and the styrene monomer is selected from any one of styrene, p-methylstyrene, p-trifluoromethylstyrene, p-chlorostyrene or p-fluorostyrene. When the block-random copolymer is used as a template, asymmetric small-sized silica nanoparticles are prepared.

[0013] In some specific embodiments, the good solvent is selected from any one of N,N-dimethylformamide, dichloromethane, chloroform, tetrahydrofuran, toluene, anisole, ethyl acetate, xylene or methyl isobutyl ketone.

[0014] In some embodiments, the poor solvent is selected from any one of ethanol, methanol, propanol, ethylene glycol, phenylethyl alcohol, n-butanol, isobutanol or glycerol;

[0015] The concentration of the copolymer in the poor solvent is 0.01-20 mg / mL.

[0016] More preferably, the concentration of the copolymer in the poor solvent is 0.05-10 mg / mL.

[0017] In some specific embodiments, the alkaline agent is selected from any one of aqueous ammonia, sodium hydroxide solution, calcium hydroxide solution, potassium hydroxide solution, n-butylamine, n-octylamine, ethanolamine, diethylamine, ethylenediamine or triethylamine;

[0018] The volume ratio of the alkaline reagent to the poor solvent is 0.1%-30%.

[0019] In some specific embodiments, the silicon precursor is selected from any one of tetraethyl orthosilicate (TEOS), tetramethyl orthosilicate (TMOS), methyltrimethoxysilane or methyltriethoxysilane;

[0020] The concentration of the silicon precursor in the poor solvent is 0.01 to 1000 mg / mL.

[0021] More preferably, the concentration of the silicon precursor in the poor solvent is 0.5 to 600 mg / mL.

[0022] In some specific embodiments, in step S3, the dispersion is ultrasonic dispersion, and the ultrasonic time is 30s-1h; the sol-gel reaction time is 1-48h.

[0023] More preferably, the ultrasonication time is 30 s-0.5 h, and the sol-gel reaction time is 1-24 h.

[0024] In some specific embodiments, the silane coupling agent containing a long carbon chain or a long fluorocarbon chain is selected from any one of γ-aminopropyltriethoxysilane, trifluoromethyltriethoxysilane, hexafluoropropanetrimethoxysilane, dodecyltriethoxysilane, γ-glycidyloxypropyltrimethoxysilane or γ-(methacryloyloxy)propyltrimethoxysilane;

[0025] The final concentration of the added silane coupling agent containing a long carbon chain or a long fluorocarbon chain is 0.01-500 mg / mL, and the reaction time is 1-48 hours.

[0026] More preferably, the final concentration of the added silane coupling agent containing a long carbon chain or a long fluorocarbon chain is 0.01-200 mg / mL, and the reaction time is 1-24 h.

[0027] The copolymer is dissolved in a very small amount of a good solvent to obtain a fully dissolved copolymer solution. A large amount of a poor solvent is then added to cause the solvophobic segments of the copolymer to collapse inward under solvophobic interactions, resulting in a collapsed polymer micelle seed solution. An alkaline agent is then added to deprotonate the solvophilic segments of the copolymer, causing them to become negatively charged. Like charges repel each other, generating electrostatic interactions. This reduces aggregation between molecular chains and, because the reaction system is negatively charged, allows the polymer micelles and subsequently formed silica particles to be stably dispersed within the system. Finally, a silicon precursor is added to induce a sol-gel reaction, resulting in symmetrical or asymmetrical small-sized silica nanoparticles. A silane coupling agent containing long carbon or fluorocarbon chains is added to the asymmetrical small-sized silica nanoparticles to modify the nanoparticles, producing amphiphilic small-sized silica nanoparticles. On the one hand, the present invention regulates the ratio of solvophobic repeating units on the polymer molecular chain. The larger the ratio of solvophobic repeating units, the larger the size of the polymer collapse template, which leads to larger silica particle size. On the other hand, by regulating the amount of silicon precursor added, the system is dominated by hydrolysis reaction, thereby obtaining small-sized silica nanoparticles with an average diameter of 17-60nm.

[0028] Compared with the existing technology, the present invention can achieve product synthesis under high concentration polymer or silicon precursor conditions. The polymer concentration can reach 20 mg / mL, and the silicon precursor concentration can reach 1000 mg / mL. By controlling the structure and composition of the copolymer, symmetrical, asymmetrical or amphoteric small-sized silica nanoparticles can be obtained. The reaction system of the present invention has low chemical corrosivity, simple experimental operation steps, is suitable for large-scale production, and facilitates the widespread application of nanoparticles. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the synthetic route for preparing small-sized silica nanoparticles of the present invention.

[0030] Figure 2 The transmission electron microscope image and the actual image of the silicon dioxide nanoparticles in Example 1 are shown.

[0031] Figure 3 This is a transmission electron microscope image of the silicon dioxide nanoparticles of Example 5.

[0032] Figure 4 These are the transmission electron microscope images and actual images of the silicon dioxide nanoparticles of Example 6.

[0033] Figure 5 This is a transmission electron microscope image of the silicon dioxide nanoparticles of Example 7. DETAILED DESCRIPTION

[0034] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0035] In the following examples, unless otherwise specified, raw materials or processing techniques are conventional commercially available raw materials or conventional processing techniques in the art.

[0036] like Figure 1 The figure shows a schematic diagram of the synthesis route for preparing small-sized silica nanoparticles in the examples. The copolymers used in the examples are copolymers synthesized in the laboratory or purchased commercially. The method for synthesizing the copolymers in the laboratory is RAFT polymerization or ATRP polymerization. The copolymer is dissolved in a very small amount of a good organic solvent to obtain a fully dissolved copolymer solution. A large amount of a poor solvent is then added to cause the solvophobic segments of the copolymer to collapse inward under solvophobic interactions, thereby obtaining a collapsed polymer micelle seed solution. An alkaline reagent is then added to deprotonate the solvophilic segments of the copolymer and cause them to become negatively charged, generating electrostatic interactions. Finally, a silicon precursor is added to cause a sol-gel reaction to occur, thereby obtaining symmetrical or asymmetrical small-sized silica nanoparticles. A silane coupling agent containing a long carbon chain or a long fluorocarbon chain is added to the asymmetrical small-sized silica nanoparticles to modify the nanoparticles, thereby preparing small-sized silica nanoparticles with amphiphilic properties.

[0037] Example 1:

[0038] Laboratory synthesized random copolymer: poly (acrylic acid-r-styrene) or P (AA 0.3 -r-St 0.7 ) 134 , P(AA 0.3 -r-St 0.7 ) 134 The molar percentage of acrylic acid (AA) is 30%, the molar percentage of styrene (St) is 70%, and the molar percentage of P(AA 0.3 -r-St 0.7 ) 134 The number of repeating units is 134.

[0039] 100 mg of the polymer was dissolved in 0.2 mL of N,N-dimethylformamide and fully dissolved. Then, 19.8 mL of methanol was added to the above solution. The concentration of the polymer solution was 5 mg / mL. Then, 2 mL of ammonia water was added to the above solution and mixed evenly. Finally, 1000 mg of tetramethyl orthosilicate (the concentration in methanol was about 50 mg / mL) was added to the above solution. Ultrasonic treatment was performed for 10 minutes. The solution was allowed to stand at room temperature for 48 hours to undergo a sol-gel reaction, thereby obtaining symmetrical silica particles with an average diameter of 35 nm.

[0040] like Figure 2 Shown are transmission electron microscope images and actual images of the symmetrical silica particles prepared in this example.

[0041] Example 2:

[0042] Laboratory synthesized random copolymer: poly (methacrylic acid-r-styrene) or P (MAA 0.9 -r-St 0.1 ) 109 , P(MAA 0.9 -r-St 0.1 ) 109 The molar percentage of methacrylic acid (MAA) is 90%, the molar percentage of styrene (St) is 10%, and the molar percentage of P(MAA 0.9 -r-St 0.1 ) 109 The number of repeating units is 109.

[0043] 100 mg of the polymer was dissolved in 0.5 mL of N,N-dimethylformamide and fully dissolved. Then, 99.5 mL of methanol was added to the above solution. The concentration of the polymer solution was 1 mg / mL. Then, 10 mL of ammonia water was added to the above solution and mixed evenly. Finally, 1000 mg of TMOS (the concentration in methanol was approximately 10 mg / mL) was added to the above solution. The solution was ultrasonicated for 10 minutes and allowed to stand at room temperature for 48 hours to undergo a sol-gel reaction, thereby obtaining symmetrical silica particles with an average diameter of 25 nm.

[0044] Example 3:

[0045] Laboratory synthesized random copolymer: poly (acrylic acid-r-styrene) or P (AA 0.5 -r-St 0.5 ) 178 , P(AA 0.5 -r-St 0.5 ) 178 The molar percentage of acrylic acid (AA) is 50%, the molar percentage of styrene (St) is 50%, and the molar percentage of P(AA 0.5 -r-St0.5 ) 178 The number of repeating units is 178.

[0046] 100 mg of the polymer was dissolved in 0.3 mL of tetrahydrofuran and fully dissolved. Then, 19.7 mL of ethanol was added to the above solution. The concentration of the polymer solution was 5 mg / mL. 2 mL of ammonia water was added to the above solution and mixed evenly. Finally, 1000 mg of TEOS (the concentration in ethanol was about 50 mg / mL) was added to the above solution. The mixture was ultrasonicated for 10 minutes and allowed to stand at room temperature for 48 hours to undergo a sol-gel reaction, thereby obtaining symmetrical silica particles with an average diameter of 26 nm.

[0047] Example 4:

[0048] Laboratory synthesized random copolymer: poly (methacrylic acid-r-styrene) or P (MAA 0.3 -r-St 0.7 ) 156 , P(MAA 0.3 -r-St 0.7 ) 156 The molar percentage of methacrylic acid (MAA) is 30%, the molar percentage of styrene (St) is 70%, and the molar percentage of P(MAA 0.3 -r-St 0.7 ) 156 The number of repeating units is 156.

[0049] 1 mg of the polymer was dissolved in 0.3 mL of tetrahydrofuran and fully dissolved. Then, 99.7 mL of ethanol was added to the above solution. The concentration of the polymer solution was 0.01 mg / mL. Then, 4.2 mL of ammonia water was added to the above solution and mixed evenly. Finally, 2000 mg of TEOS (the concentration in ethanol was about 20 mg / mL) was added to the above solution. The solution was ultrasonicated for 10 minutes and allowed to stand at room temperature for 24 hours to undergo a sol-gel reaction, thereby obtaining symmetrical silica particles with an average diameter of 19 nm.

[0050] Example 5:

[0051] Laboratory synthesis of block-random copolymers: polyethylene oxide-b-poly(acrylic acid-r-styrene) or PEO 45 -bP(AA 0.3 -r-St 0.7 ) 127 , PEO 45 -bP(AA 0.3 -r-St 0.7 ) 127 The number of polyethylene oxide repeating units in the middle block is 45.

[0052] 10 mg of the polymer was dissolved in 0.3 mL of N,N-dimethylformamide and fully dissolved. Then, 49.7 mL of ethanol was added to the above solution. The concentration of the polymer solution was 0.2 mg / mL. Then, 2.1 mL of ammonia reagent was added to the above solution and mixed evenly. Finally, 2000 mg of TEOS (the concentration in ethanol was about 40 mg / mL) was added to the above solution. Ultrasonic treatment was performed for 120 seconds, and the solution was allowed to stand at room temperature for 24 hours to undergo a sol-gel reaction, thereby obtaining asymmetric silica particles with an average diameter of 43 nm.

[0053] like Figure 3 , which is a transmission electron microscope image of the asymmetric silica particles prepared in this example.

[0054] Example 6:

[0055] Laboratory synthesis of block-random copolymers: polyethylene oxide-b-poly(acrylic acid-r-styrene) or PEO 220 -bP(AA 0.3 -r-St 0.7 ) 127 , PEO 220 -bP(AA 0.3 -r-St 0.7 ) 127 The number of polyethylene oxide repeating units in the middle block is 220.

[0056] 10 mg of the polymer was dissolved in 0.3 mL of N,N-dimethylformamide and fully dissolved. 99.7 mL of ethanol was then added to the solution to a concentration of 0.1 mg / mL. 4.2 mL of ammonia was then added to the solution and mixed thoroughly. Finally, 2000 mg of TEOS (at a concentration of approximately 20 mg / mL in ethanol) was added to the solution. The mixture was ultrasonicated for 120 seconds and allowed to stand at room temperature for 15 hours to undergo a sol-gel reaction, yielding asymmetric silica particles. 100 mg of hexafluoropropanetrimethoxysilane was then added to the reaction system, and the reaction continued for 10 hours to yield amphiphilic silica particles with an average diameter of 35 nm.

[0057] like Figure 4 Shown are transmission electron microscope images and actual images of the amphiphilic silica particles prepared in this example.

[0058] Example 7:

[0059] Laboratory synthesized random copolymer: poly (acrylic acid-r-styrene) or P (AA 0.3 -r-St 0.7 ) 134 , P(AA 0.3 -r-St0.7 ) 134 The molar percentage of acrylic acid (AA) is 30%, the molar percentage of styrene (St) is 70%, and the molar percentage of P(AA 0.3 -r-St 0.7 ) 134 The number of repeating units is 134.

[0060] 100 mg of the polymer was dissolved in 0.2 mL of tetrahydrofuran and fully dissolved. Then, 19.8 mL of ethanol was added to the above solution. The concentration of the polymer solution was 5 mg / mL. Then, 0.86 mL of ammonia water was added to the above solution and mixed evenly. Finally, 20,000 mg of tetramethyl orthosilicate (the concentration in ethanol was about 1000 mg / mL) was added to the above solution. The mixture was ultrasonicated for 10 minutes and allowed to stand at room temperature for 48 hours to undergo a sol-gel reaction, thereby obtaining symmetrical silica particles with an average diameter of 23 nm.

[0061] like Figure 5 , which is a transmission electron microscope image of the silicon dioxide particles prepared in this example.

[0062] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A method for preparing small-sized silica nanoparticles based on a copolymer template, characterized in that: The steps include: dissolving the binary random copolymer or the block-random copolymer in a good solvent to obtain a copolymer solution; adding a poor solvent to the copolymer solution to obtain a polymer micelle seed solution; An alkaline reagent is added to the polymer micelle seed solution, and a silicon precursor is added and mixed and dispersed to produce a sol-gel reaction to obtain symmetrical or asymmetrical small-sized silica nanoparticles with an average diameter of 17-60 nm; Wherein, the binary random copolymer is poly(acrylic acid monomer- r -styrene monomer), the acrylic monomer is selected from any one of acrylic acid, 2-methacrylic acid, 2-ethylacrylic acid or tert-butyl acrylate, and the styrene monomer is selected from any one of styrene, p-methylstyrene, p-trifluoromethylstyrene, p-chlorostyrene or p-fluorostyrene; The block-random copolymer is a block- b- Poly(acrylic acid monomer- r -styrene monomer), the block is selected from any one of polystyrene, polyethylene oxide, poly(p-fluorostyrene) or polypropylene oxide, the acrylic monomer is selected from any one of acrylic acid, 2-methacrylic acid, 2-ethylacrylic acid or tert-butyl acrylate, and the styrene monomer is selected from any one of styrene, p-methylstyrene, p-trifluoromethylstyrene, p-chlorostyrene or p-fluorostyrene; The good solvent is selected from any one of N,N-dimethylformamide, dichloromethane, chloroform, tetrahydrofuran, toluene, anisole, ethyl acetate, xylene or methyl isobutyl ketone; The poor solvent is selected from any one of ethanol, methanol, propanol, ethylene glycol, phenylethyl alcohol, n-butanol, isobutanol or glycerol; The concentration of the copolymer in the poor solvent is 0.01-20 mg / mL; The silicon precursor is selected from any one of tetraethyl orthosilicate, tetramethyl orthosilicate, methyltrimethoxysilane or methyltriethoxysilane; The concentration of the silicon precursor in the poor solvent is 0.01~1000 mg / mL.

2. The method for preparing small-sized silica nanoparticles based on copolymer template synthesis according to claim 1, characterized in that: A silane coupling agent containing a long carbon chain or a long fluorocarbon chain is added to the asymmetric small-sized silica nanoparticles for modification, and the reaction obtains amphiphilic small-sized silica nanoparticles with an average diameter of 17-60 nm.

3. The method for preparing small-sized silica nanoparticles based on copolymer template synthesis according to claim 1, characterized in that: The alkaline agent is selected from any one of ammonia water, sodium hydroxide solution, calcium hydroxide solution, potassium hydroxide solution, n-butylamine, n-octylamine, ethanolamine, diethylamine, ethylenediamine or triethylamine; The volume ratio of the alkaline reagent to the poor solvent is 0.1%-30%.

4. The method for preparing small-sized silica nanoparticles based on copolymer template synthesis according to claim 1, characterized in that: The dispersion is ultrasonic dispersion, and the ultrasonic time is 30 s-1 h; the sol-gel reaction time is 1-48 h.

5. The method for preparing small-sized silica nanoparticles based on copolymer template synthesis according to claim 2, characterized in that: The silane coupling agent containing a long carbon chain or a long fluorocarbon chain is selected from any one of g-aminopropyltriethoxysilane, trifluoromethyltriethoxysilane, hexafluoropropanetrimethoxysilane, dodecyltriethoxysilane, g-glycidyloxypropyltrimethoxysilane or g-(methacryloyloxy)propyltrimethoxysilane; The final concentration of the added silane coupling agent containing a long carbon chain or a long fluorocarbon chain is 0.01-500 mg / mL, and the reaction time is 1-48 h.

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