Method for preparing nanoscale colloid molecules by selectively depositing SiO2 on bottle brush polymer

Abstract

The invention discloses a method for preparing nanoscale colloid molecules by selectively depositing SiO2 on a bottle brush polymer, which comprises the following steps of: S1, dissolving the bottle brush polymer with a tert-butyl ester group in a good solvent A, and performing hydrolysis reaction under an acidic condition to hydrolyze the tert-butyl ester group to form a carboxyl group to obtain a bottle brush polymer template; and S2, dissolving the bottle brush polymer template in the good solution B, adding an alkaline reagent, mixing and dispersing with the silicon source precursor, and selectively depositing the silicon source precursor on the carboxyl group to obtain the nano-scale SiO2 colloid molecule. Furthermore, a silicon source containing amino, sulfydryl or fluorine and other groups can be used as a surface modifier to be added into the solution obtained in the step S2, and surface modified SiO2 colloidal molecules are prepared. According to the method disclosed by the invention, the nano-scale colloid molecules with different spatial configurations can be obtained by controlling the structural parameters, the chemical composition and the precursor feeding amount of the bottle brush polymer, and the method has the characteristics of designability, controllability, large-scale preparation and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of colloidal molecule synthesis, and in particular to a method for selectively depositing SiO2 on a bottlebrush polymer to prepare nano-scale colloidal molecules. Background Art

[0002] With the understanding of materials at different scales, the self-assembly of nanoparticles from bottom to top to obtain macroscopically ordered materials has gradually become a powerful approach to obtaining materials with specific functions in recent years. Such materials can be applied in many fields such as catalysis, photonic crystals, and biomedical cancer treatment. By controlling the chemical composition, size, and shape of individual nanoparticle building blocks, the assembly behavior can be regulated, and thus the physical properties of the macroscopic material can be regulated. Due to the more precise interparticle interactions inside and the controllability of the chemical composition in specific surface regions, colloidal molecules have become an important part of the building blocks of macroscopic materials. Existing studies have shown that colloidal molecules composed of spherical substrates or multiple spherical units have isotropic and orientation-lacking interaction forces, which fundamentally limits the wide application of their methods and the further increase in structural complexity. Secondly, colloidal molecules smaller than 100 nm or even smaller sizes are crucial in fields such as drug delivery, optical components, and biophotonic materials. At the same time, the precise regulation of colloidal molecules at this size can reduce the defects of the assembly. However, it still poses a huge challenge to achieve the precise synthesis of nano-colloidal molecules in the 10 - 100 nm scale range, that is, to simultaneously meet shape diversity, stability, and controllability, as well as mass preparation.

[0003] Due to its good stability, easy functionalization, good biocompatibility, large specific surface area, etc., silica nanoparticles are widely used in fields such as construction, optical imaging, catalysis, adsorption, and batteries. The traditional synthesis methods of silica particles mainly include the Stober method and the reverse microemulsion method. However, it is difficult to prepare nano-scale silica colloidal molecules in large quantities based on the above methods. Bottlebrush polymers are a type of polymer with high molecular weight and high-density side-chain grafting, having rich chemical composition controllability and molecular structure designability. Their nano-scale size (10 - 100 nm) highly matches that of colloidal molecules. Using this as a template is expected to in-situ synthesize colloidal molecules, and through the precise regulation of the regional chemical composition and structure of the bottlebrush polymer, the precise positioning and reduction of the silicon precursor can be achieved, breaking through the limitations of traditional linear templates. However, there is currently no report on synthesizing silica colloidal molecules using a bottlebrush polymer as a template. Summary of the Invention

[0004] Aiming at the problem that the existing preparation methods of silica nanoparticles are difficult to prepare nano-scale silica colloidal molecules in large quantities, the present invention provides a method for selectively depositing SiO2 on a bottlebrush polymer to prepare nano-scale colloidal molecules.

[0005] The method of the present invention prepares SiO2 colloidal molecules using bottlebrush polymers as templates. Through the preparation method of bottlebrush polymers, the chemical compositions of the spacer region and the deposition region, and the regulation of N sc and N bb it can simultaneously meet the requirements of controlling the structural morphology, size, stability and functionality of colloidal molecules. Mild reaction conditions and high template stability enable the large-scale preparation of colloidal molecules.

[0006] The method for selectively depositing SiO2 on bottlebrush polymers to prepare nano-scale colloidal molecules provided by the present invention comprises the following steps:

[0007] S1. Dissolve the bottlebrush polymer with tert-butyl ester groups in a good solvent A, and then carry out a hydrolysis reaction under acidic conditions to hydrolyze the tert-butyl ester groups to form carboxyl groups (-COOH) to obtain a bottlebrush polymer template.

[0008] The bottlebrush polymer is a single-arm or multi-arm block bottlebrush polymer with tert-butyl ester groups in the main chain or side chain. The bottlebrush polymer can be designed to obtain various configurations, such as diblock homopolymer bottlebrush polymers, triblock homopolymer bottlebrush polymers, triblock core-shell bottlebrush polymers, three-arm core-shell bottlebrush polymers, etc.

[0009] S2. Dissolve the bottlebrush polymer template in a good solution B, add an alkaline reagent and a silicon source precursor and mix them evenly. Due to electrostatic interaction, the silicon source precursor is selectively deposited on the carboxyl groups, and stand at room temperature for 20-30 h to form silicon dioxide nanoparticles, obtaining nano-scale SiO2 colloidal molecules. The silicon source precursor is selected from any one of tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane or methyltriethoxysilane; the dosage of the silicon source precursor is 1-100 equivalents of the molar amount of carboxyl groups on the bottlebrush polymer template.

[0010] Preferably, the component on the bottlebrush polymer template that has an induction effect on the deposition of SiO2 is poly(5-norbornene-2-carboxylic acid) or polyacrylic acid exposed on the outside, which can be one of the linear and bottlebrush configurations; the component that does not have an SiO2 deposition effect is a polymer of one or more of acrylic monomers or styrene monomers, which can be a single homopolymer, a random copolymer of the two or a block copolymer.

[0011] The bottlebrush polymer is synthesized by combining methods such as atom transfer radical polymerization, reversible addition-fragmentation chain transfer polymerization, ring-opening metathesis polymerization, etc.

[0012] Preferably, in step S1, the good solvent A is selected from dichloromethane or tetrahydrofuran. The concentration of the bottlebrush polymer in the solution is 0.01-0.1 g / mL.

[0013] Preferably, in step S1, an acidic condition is formed by adding an acidic reagent, and the acidic reagent is selected from sorbic acid or trifluoroacetic acid. The addition amount of the acidic reagent is 0.25 - 1 times the volume of the good solvent A.

[0014] Preferably, in step S2, the good solvent B is selected from any one of tetrahydrofuran, acetone, chloroform, methyl ethyl ketone, and ethyl acetate.

[0015] Preferably, in step S2, the basic reagent is selected from any one of ammonia water, sodium hydroxide solution, calcium hydroxide solution, potassium hydroxide solution, triethylamine, and n-butylamine. The dosage of the basic reagent is 1% - 4.2% of the volume of the good solvent B.

[0016] The method for selectively depositing SiO2 on the bottlebrush polymer to prepare nano-scale colloidal molecules of the present invention may further include step S3: adding a silicon source containing groups such as amino (-NH2), mercapto (-SH), or fluorine (-F) as a surface modifier to the solution obtained in step S2, and standing at room temperature to obtain surface-modified and modified SiO2 colloidal molecules. That is, modified SiO2 colloidal molecules with surface components such as -NH2, -SH, or -F are obtained.

[0017] Preferably, the surface modifier is selected from any one of 3-aminopropyltriethoxysilane, anilinomethyltriethoxysilane, tridecafluorooctyltrimethoxysilane, (3,3,3-trifluoropropyl)trimethoxysilane, and (3-mercaptopropyl)trimethoxysilane. The dosage of the added surface modifier is 5 - 20 equivalents of the molar amount of carboxyl groups on the block bottlebrush polymer.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] (1) By controlling the structural parameters, chemical composition, and precursor feeding amount of the bottlebrush polymer, the preparation method of the present invention can obtain nano-scale colloidal molecules with different spatial configurations, and further regulate the final configuration, size, and functionality of the colloidal molecules, having the characteristics of designability, controllability, and large-scale preparation. The bottlebrush polymer can be designed to obtain various configurations, such as diblock homopolymer bottlebrush polymers, triblock homopolymer bottlebrush polymers, triblock core-shell bottlebrush polymers, and three-arm core-shell bottlebrush polymers, etc., to realize the controllable synthesis of colloidal molecules with complex configurations such as dumbbell-shaped, heterojunction, and triangular, fundamentally solving the problem of colloidal molecule configuration regulation. Secondly, according to the precursor feeding amount and the polymerization degree of the polyacrylic acid block, its size is regulated, and the size of the colloidal molecules can be precisely controlled within the range of 10 - 100 nm, expanding the size range of the colloidal molecules. Further, surface composition modification endows the colloidal molecules with the ability of directional assembly, broadening the application fields and the diversity of subsequent assemblies.

[0020] (2) Compared with the linear polymer template, the synthesis of SiO2 colloidal molecules using the bottlebrush polymer as a template improves the success rate and yield. The yield can reach over 85%, enabling macroscale preparation and becoming a general method for synthesizing SiO2 colloidal molecules.

[0021] (3) The preparation method of the present invention provides rich and unique assembly units, offers a strong driving force for subsequent assembly, can be used for further assembly to construct more complex colloidal materials, provides the possibility for diverse and complex assembly structures, is conducive to the development of the field of macroscale materials self-assembled from nanoparticles from bottom to top, and realizes the leap from microscale to macroscale.

[0022] Other advantages, objectives, and features of the present invention will be partially reflected by the following description and partially understood by those skilled in the art through the research and practice of the present invention. Brief Description of the Drawings

[0023] Figure 1 It is a schematic diagram of the synthesis route of dumbbell-shaped SiO2 colloidal molecules in Example 1.

[0024] Figure 2 It is SEM images of dumbbell-shaped SiO2 colloidal molecules with different magnifications obtained using the triblock bottlebrush polymer PCNB 159 -b-P(NB-g-nBMA 48 ) 254 -b-PCNB 248 as a template, with a template concentration of 0.25 mg / mL and under the condition of n(-COOH):n(-TMOS) = 1:20.

[0025] Figure 3 It is TEM images of dumbbell-shaped SiO2 colloidal molecules with different magnifications obtained using the triblock bottlebrush polymer PCNB 159 -b-P(NB-g-nBMA 48 ) 254 -b-PCNB 248 as a template, with a template concentration of 0.25 mg / mL and under the condition of n(-COOH):n(-TMOS) = 1:20.

[0026] Figure 4 It is a schematic diagram of the synthesis route of SiO2-PSt colloidal molecules in Example 4.

[0027] Figure 5 It is using the diblock bottlebrush polymer PCNB 100 -b-P(NB-g-PSt 80 ) 20SEM images of SiO2-PSt colloidal molecules obtained using as a template, with a template concentration of 1.0 mg / mL, under the conditions of n(-COOH):n(-TMOS) = 1:5 and 1:10.

[0028] Figure 6 is a dumbbell-shaped SiO2 colloidal molecule synthesized using a bottle-brush polymer template with a poly(n-butyl methacrylate) homopolymer side chain in the middle block 100 -b-P(NB-g-PSt 80 ) 20 SEM images of SiO2-PSt colloidal molecules obtained using as a template, with a template concentration of 1.0 mg / mL, under the conditions of n(-COOH):n(-TMOS) = 1:5 and 1:10.

[0029] Figure 7 is a schematic diagram of the synthesis route of the three-arm SiO2 colloidal molecule in Example 5.

[0030] Figure 8 is a SEM image of SiO2 colloidal molecules prepared under different conditions using a three-arm diblock bottle-brush polymer 3f-(P((MA-g-PnBMA 48 ) 0.5 -r-MMA 0.5 ) 88 -b-P(AA 0.5 -r-MMA 0.5 ) 254 ) as a template.

[0031] Figure 9 is Figure 8 an enlarged view of a single colloidal molecule cropped based on . Detailed implementation mode

[0032] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0033] Example 1

[0034] A method for synthesizing dumbbell-shaped SiO2 colloidal molecules using a bottle-brush polymer template with a poly(n-butyl methacrylate) homopolymer side chain in the middle block of the bottle-brush includes the following steps:

[0035] (1) Synthesis of initiator NB-C2-Br: Take norbornene dicarboxylic anhydride (20 g, 0.12 mol), 2-aminoethanol (14.02 g, 0.12 mol), 4-(dimethylamino)pyridine (DMAP) (15.0 g, 0.12 mol) in a 500 mL round-bottom flask. After adding 200 mL of toluene to dissolve, reflux at 150 °C for 15 h under nitrogen protection to obtain NB-C2-OH. Then evaporate the toluene to dryness and dissolve it with DCM. Extract it three times successively with HCl, Na2CO3, and water, then dry it with anhydrous MgSO4, filter by suction and rotary evaporate. Subsequently, place all the obtained products in a 500 mL Schlenk flask, add 100 mL of ultra-dry N,N′-dimethylpyrrolidone (NMP), and dropwise add 50% (in NMP) of 2-bromo-2-methylpropionyl bromide (29.7 mL, 0.24 mol) under ice bath conditions. Stir at room temperature for 24 h, then place it in an oil bath at 40 °C and evacuate with a cold trap to make it react for 12 h. After the reaction, precipitate it in saturated NaHCO3 solution. Then dissolve it with DCM, extract it three times successively with HCl, Na2CO3, and water, then dry it with anhydrous MgSO4, filter by suction and rotary evaporate to obtain NB-C2-Br. The synthesis reaction principle is as follows:

[0036]

[0037] (2) Synthesis of bottlebrush polymer with tert-butyl group: Synthesized by the grafting-from method. First, obtain the macromolecular initiator, i.e., the bottlebrush polymer backbone, by ring-opening metathesis polymerization. Weigh a certain amount of Grubbs third-generation catalyst (G3) in a 4 mL glass bottle, add dichloromethane to dissolve it, and successively add a certain amount of tert-butyl 5-norbornene-2-carboxylate (M1), NB-C2-Br (M2), tert-butyl 5-norbornene-2-carboxylate (M3), which are all pre-dissolved in dichloromethane, with the ratio of n(G3):n(M1):n(M2):n(M3) = 1:50:200:50, 1:100:200:100, 1:200:200:200. React at room temperature for 20 - 40 min to obtain the polymer backbone P(tBNB) a -b-P(NB-Br) b -b-P(tBNB) c . Among them, the feeding amount of tert-butyl 5-norbornene-2-carboxylate determines the final size of the SiO2 colloidal molecules. Then, use the backbone as an initiator to obtain the bottlebrush polymer by atom transfer radical polymerization. First, take a certain amount of the backbone P(tBNB) a -b-P(NB-Br) b -b-P(tBNB) c, CuBr and n-butyl methacrylate (nBMA) were bubbled in a Schlenk flask for about 40 min. Meanwhile, 4,4-dinonyl-2,2'-bipyridine in an equimolar amount to CuBr was dissolved in a small amount of nBMA and bubbled for about 40 min, and then the 4,4-dinonyl-2,2'-bipyridine solution was added with a syringe and bubbled for about 40 min. Finally, the reaction system was placed in an oil bath at 70 °C and reacted for 6 h. Subsequently, the copper salt was removed by passing through a silica gel column and precipitated three times in methanol and then dried to finally obtain the triblock bottlebrush polymer poly(tert-butyl 5-norbornene-2-carboxylate)-block-poly(norbornene-graft-poly(n-butyl methacrylate))-block-poly(tert-butyl 5-norbornene-2-carboxylate), abbreviated as PtBNB-b-P(NB-g-PnBMA)-b-PtBNB.

[0038] (3) Hydrolysis of the bottlebrush polymer: First, poly(tert-butyl 5-norbornene-2-carboxylate)-block-poly(norbornene-graft-poly(n-butyl methacrylate))-block-poly(tert-butyl 5-norbornene-2-carboxylate) was dissolved in a certain amount of dichloromethane to make it completely dissolved and in a low concentration state (in the concentration range of 0.01 - 0.1 g / mL); then trifluoroacetic acid was added, and the amount of trifluoroacetic acid was 0.5 times the volume of dichloromethane. It was stirred at room temperature for 24 h, then concentrated, then dissolved in tetrahydrofuran, precipitated with petroleum ether and centrifuged three times, and the precipitate was dried in a vacuum oven at 40 °C to finally obtain the bottlebrush polymer template poly(5-norbornene-2-carboxylic acid)-block-poly(norbornene-graft-poly(n-butyl methacrylate))-block-poly(5-norbornene-2-carboxylic acid) with carboxyl groups (-COOH), abbreviated as PCNB-b-P(NB-g-PnBMA)-b-PCNB.

[0039] (4) Selective deposition of SiO₂ to synthesize colloidal molecules: The bottlebrush polymer template PCNB-b-P(NB-g-PnBMA)-b-PCNB was dissolved in tetrahydrofuran to make its concentration 0.25 mg / mL. Subsequently, ammonia water was added, and the amount of ammonia water was 4.2% of the volume of tetrahydrofuran. After mixing evenly by ultrasonic for dozens of seconds, tetramethoxysilane (TMOS) was added. TMOS was selectively deposited at both ends of the bottlebrush polymer. By controlling different molar ratios of -COOH and TMOS, n(-COOH):n(TMOS) = 1:5, 1:10, 1:20, 1:50, etc., and left standing at room temperature for 24 h, dumbbell-shaped SiO₂ colloidal molecules with different sizes were obtained.

[0040] Subsequently, step (5) can be selectively carried out according to actual needs: surface modification of SiO2 colloidal molecules: 3-aminopropyltriethoxysilane is further added as a surface modifier to the above dumbbell-shaped SiO2 colloidal molecule solution system, and it is left standing at room temperature for 24 h to obtain dumbbell-shaped SiO2 colloidal molecules with a surface chemical composition of -NH2. If (3,3,3-trifluoropropyl)trimethoxysilane is added as a surface modifier and according to the same modification method, dumbbell-shaped SiO2 colloidal molecules with a surface chemical composition of -F are obtained.

[0041] Figure 1 is a schematic diagram of the synthesis route of dumbbell-shaped SiO2 colloidal molecules in Example 1. Based on the influence of the size of the bottlebrush polymer on the distance between the two silica spheres in the colloidal molecules, the polymer P(tBNB) 159 -b-P(NB-Br) 254 -b-P(tBNB) 248 is used as the skeleton to synthesize the bottlebrush polymer, and P(tBNB) is obtained by atom transfer radical polymerization 159 -b-P(NB-g-PnBMA 48 ) 254 -b-P(tBNB) 248 bottlebrush polymer, and finally P(CNB) is obtained after hydrolysis 159 -b-P(NB-g-PnBMA 48 ) 254 -b-P(CNB) 248 triblock bottlebrush polymer template. Specifically, M W = 1998.0 Kg / mol and M n = 1883.0 Kg / mol can be calculated by GPC. From the dispersity coefficient is calculated to be 1.06, which indicates that the obtained bottlebrush polymer has a uniform mass distribution. Further, the silicon source precursor tetramethoxysilane (TMOS) is added to the solution of the bottlebrush polymer template, and TMOS is selectively deposited at both ends of the bottlebrush polymer PAA. After standing at room temperature for 24 h, dumbbell-shaped SiO2 colloidal molecules are obtained.

[0042] Figure 2 are SEM images of dumbbell-shaped SiO2 colloidal molecules prepared under the condition of n(-COOH):n(TMOS) = 1:20 at different magnifications. Uniform dumbbell-shaped molecules are shown in the figure. Since the lengths of the two PAA at both ends in the template are not uniform, the sizes of the two SiO2 nanospheres of the obtained colloidal molecules are different, which indicates that the size of the final colloidal molecules can be regulated according to the degree of polymerization of the PAA block in the template.

[0043] Figure 3TEM images of dumbbell-shaped SiO2 colloidal molecules prepared under the condition of n(-COOH):n(TMOS)=1:20 at different magnifications. It can be seen that, consistent with the results of the SEM images, the polymer template between the two SiO2 nanospheres can be clearly observed in the TEM images. Due to the hindrance of the middle bottlebrush polymer template, the two SiO2 nanospheres do not infinitely diffuse into one SiO2 nanosphere. At the same time, due to the affinity between PnBMA and SiO2, the distance between the nanoparticles is not large, providing a basis for the dumbbell-shaped colloidal molecules, indicating that the bottlebrush polymer as a template is crucial. There are a small number of SiO2 trinano-spheres in the figure, which is due to the stacking effect of two dumbbells. The stacked part in the TEM image is dark while the single nanoparticles are light, which can be proved hereby.

[0044] Example 2

[0045] A method for synthesizing dumbbell-shaped SiO2 colloidal molecules with a bottlebrush polymer template having a polystyrene homopolymer as the side chain of the middle-block bottlebrush, comprising the following steps:

[0046] (1) Synthesis of the bottlebrush polymer: The backbone P(tBNB) a -b-P(NB-Br) b -b-P(tBNB) c of the bottlebrush polymer is obtained by ring-opening metathesis polymerization of tert-butyl 5-norbornene-2-carboxylate, NB-C2-Br, and tert-butyl 5-norbornene-2-carboxylate in sequence; The bottlebrush polymer is obtained by atom transfer radical polymerization using the backbone as an initiator. First, a certain amount of the backbone P(tBNB) a -b-P(NB-Br) b -b-P(tBNB) c , CuBr, and styrene (St) are bubbled in a Schlenk flask for about 30 min, and then N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA) equimolar to CuBr is added by syringe and bubbled for about 30 min. Finally, the reaction system is placed in an oil bath at 65 °C and reacted for 10 h. Subsequently, the copper salt is removed by passing through a silica gel column and precipitated three times in a mixed solution of methanol and water and then dried to finally obtain the triblock bottlebrush polymer (tert-butyl 5-norbornene-2-carboxylate)-block-poly(norbornene-graft-polystyrene)-block-poly(tert-butyl 5-norbornene-2-carboxylate), abbreviated as (PtBNB-b-P(NB-g-PSt)-b-PtBNB).

[0047] The subsequent steps are the same as those in Example 1.

[0048] Example 3

[0049] A method for synthesizing dumbbell-shaped SiO2 colloidal molecules using a bottlebrush polymer template with a core-shell structure where the middle block bottlebrush is the core, comprising the following steps:

[0050] (1) Synthesis of a bottlebrush polymer with poly(tert-butyl methacrylate) and polystyrene block polymers as the side chains of the middle block bottlebrush: Ring-opening metathesis polymerization is used to polymerize tert-butyl 5-norbornene-2-carboxylate, NB-C2-Br, and tert-butyl 5-norbornene-2-carboxylate in sequence to obtain the backbone P(tBNB) a -b-P(NB-Br) b -b-P(tBNB) c of the bottlebrush polymer. Using the backbone as an initiator, atom transfer radical polymerization is carried out to obtain the bottlebrush polymer. First, a certain amount of the backbone P(tBNB) a -b-P(NB-Br) b -b-P(tBNB) c , CuBr, and tert-butyl acrylate (tBA) are bubbled in a Schlenk flask for about 30 min, and then an equimolar amount of N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA) with respect to CuBr is added using a syringe and bubbling is continued for about 30 min. Finally, the reaction system is placed in an oil bath at 65 °C and reacted for 2 h. Subsequently, the copper salt is removed by passing through a silica gel column and the product is precipitated three times in a mixed solution of methanol and water and then dried to obtain poly(tert-butyl 5-norbornene-2-carboxylate)-block-poly(norbornene-graft-poly(tert-butyl acrylate))-block-poly(tert-butyl 5-norbornene-2-carboxylate), abbreviated as PtBNB-b-P(NB-g-PtBA)-b-PtBNB. Then, using the polymer obtained above as an initiator, a certain amount of the backbone P(tBNB) a -b-P(NB-g-PtBA) b -b-P(tBNB) c , CuBr, and styrene (St) are bubbled in a Schlenk flask for about 30 min, and then an equimolar amount of N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA) with respect to CuBr is added using a syringe and bubbling is continued for about 30 min. Finally, the reaction system is placed in an oil bath at 65 °C and reacted for 6 h. Subsequently, the copper salt is removed by passing through a silica gel column and the product is precipitated three times in a mixed solution of methanol and water and then dried to finally obtain the triblock bottlebrush polymer poly(tert-butyl 5-norbornene-2-carboxylate)-block-poly(norbornene-graft-(poly(tert-butyl methacrylate)-b-polystyrene))-block-poly(tert-butyl 5-norbornene-2-carboxylate), abbreviated as (PtBNB-b-P(NB-g-(PtBA-b-PSt))-b-PtBNB).

[0051] The subsequent steps are the same as those in Example 1.

[0052] Example 4

[0053] A method for synthesizing a heterojunction structure of SiO2 colloidal molecules (SiO2-PSt) of a bottle-brush polymer template with a polystyrene homopolymer as the side chain of the block bottle-brush includes the following steps:

[0054] (1) Synthesis of bottle-brush polymer with tert-butyl groups: Synthesized by the grafting-through method. First, the macromonomer norbornene-graft-polystyrene (NB-g-PSt) was synthesized by atom transfer radical polymerization. A certain amount of initiator NB-C2-Br, CuBr, and styrene (St) were bubbled in a Schlenk flask for about 30 min, and then an equimolar amount of N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA) with CuBr was added by syringe and bubbled for another about 30 min. Finally, the reaction system was placed in an oil bath at 65 °C and reacted for 20 h. Subsequently, the copper salt was removed by passing through a silica gel column, and the product was precipitated three times in a mixed solution of methanol and water and then dried to obtain NB-g-PSt. Then, tert-butyl 5-norbornene-2-carboxylate (M1) and norbornene-graft-polystyrene (M2) were successively polymerized by ring-opening metathesis polymerization to obtain the diblock bottle-brush polymer poly(tert-butyl 5-norbornene-2-carboxylate)-block-poly(norbornene-graft-polystyrene). Among them, the ratio is n(G3):n(M1):n(M2) = 1:100:20, 1:100:50.

[0055] (2) Hydrolysis of the bottle-brush polymer: Poly(tert-butyl 5-norbornene-2-carboxylate)-block-poly(norbornene-graft-polystyrene) was dissolved in a certain amount of dichloromethane to make it completely dissolved and at a low concentration; then 0.5 equivalent of trifluoroacetic acid based on the volume of dichloromethane was added, and the mixture was stirred at room temperature for 24 h, then concentrated, then dissolved in tetrahydrofuran, precipitated with petroleum ether and centrifuged three times, and dried in a vacuum oven at 40 °C to finally obtain the bottle-brush polymer template poly(5-norbornene-2-carboxylic acid)-block-poly(norbornene-graft-polystyrene) with carboxyl groups (-COOH), abbreviated as PCNB-b-P(NB-g-PSt).

[0056] (3) Synthesis of colloidal molecules by selective deposition of SiO₂: Dissolve the bottlebrush polymer template PCNB-b-P(NB-g-PSt) in tetrahydrofuran to a concentration of 1.0 mg / mL. Subsequently, add ammonia water, and the amount of ammonia water is 1.0% of the volume of tetrahydrofuran. After mixing evenly by ultrasonic for dozens of seconds, add tetramethoxysilane (TMOS). TMOS selectively deposits on the bottlebrush polymer. By controlling different molar ratios of -COOH and TMOS, n(-COOH):n(TMOS) = 1:1, 1:2, 1:5, 1:10, 1:20, and let it stand at room temperature for 24 h to obtain SiO₂-PSt colloidal molecules of different sizes.

[0057] Figure 4 It is a schematic diagram of the synthesis route of SiO₂-PSt colloidal molecules in Example 4. Using the diblock bottlebrush polymer PCNB 100 -b-P(NB-g-PSt 80 ) 20 as the template. Different from Example 1, the side chain component of the bottlebrush polymer selected in this example is PSt because there are large chemical property differences between PSt and SiO₂, which is convenient for synthesizing SiO₂-Polymer heterogeneous colloidal molecules.

[0058] Figure 5 Using the diblock bottlebrush polymer PCNB 100 -b-P(NB-g-PSt 80 ) 20 as the template, with a template concentration of 1.0 mg / mL, SEM images of SiO₂-PSt heterogeneous colloidal molecules obtained under the conditions of n(-COOH):n(-TMOS) = 1:5 and 1:10. The left figure is obtained under the condition of n(-COOH):n(-TMOS) = 1:5, and the right figure is obtained under the condition of n(-COOH):n(-TMOS) = 1:10. It can be clearly observed from the figure that the monodisperse SiO₂-PSt heterogeneous colloidal molecules, the three-dimensional spheres are SiO₂ nanoparticles, and the black shaded part is the PSt cluster. Since PSt is not conductive, it appears as a shadow in the SEM. In addition, a small amount of aggregates can also be observed, which is because assembly occurred during the sample preparation and drying process. At the interface between tetrahydrofuran and air, due to the hydrophilicity of SiO₂, it is located on the outside of the aggregates, and PSt shows hydrophobicity and is located on the inside of the aggregates, forming the morphology of a dark inner shadow and outer SiO₂ nanoparticles. It can also be observed from the figure that the sizes of the SiO₂-PSt heterogeneous colloidal molecules obtained in the left and right figures are different. This shows that in addition to being able to control the size of the final colloidal molecules according to the degree of polymerization of the PAA block in the template in Example 1, the size of the colloidal molecules can also be regulated by the feeding amount of the precursor tetramethoxysilane.

[0059] Figure 6using the diblock bottlebrush polymer PCNB 100 -b-P(NB-g-PSt 80 ) 20 as a template, with a template concentration of 1.0 mg / mL, TEM images of SiO2-PSt heterogeneous colloidal molecules obtained under the conditions of n(-COOH):n(-TMOS) = 1:5 and 1:10. The left figure was obtained under the condition of n(-COOH):n(-TMOS) = 1:5, and the right figure was obtained under the condition of n(-COOH):n(-TMOS) = 1:10. This figure also verifies the conclusion that the size of colloidal molecules can be regulated according to the feeding amount of the precursor tetramethoxysilane.

[0060] Example 5

[0061] A method for synthesizing three-arm SiO2 colloidal molecules using a bottlebrush polymer template of a random polymer with poly(n-butyl methacrylate) and poly(methyl methacrylate) as the block bottlebrush side chains, comprising the following steps:

[0062] (1) Synthesis of 3f-Br: Add TME (12.0150 g, 0.1 mol), triethylamine TEA (19.45 mL, 0.14 mol) and 100 mL of ultra-dry dichloromethane (DCM) to a 100 mL Schlenk flask, mix well, displace nitrogen and seal. Mix 2-bromoisobutyryl bromide (14.83 mL, 0.14 mol) with 20 mL of DCM, and under ice bath and nitrogen protection, add this mixed solution dropwise to the Schlenk flask. After the addition is complete, react at room temperature for 24 h. After the reaction is completed, filter to remove the white solid, and wash the organic phase three times with 1 M HCl, saturated NaHCO3 solution and deionized water, and then dry the organic phase with anhydrous MgSO4. After rotary evaporation and concentration, the product is passed through a silica gel column, and the product is eluted with PE / EA (v / v = 10 / 1), filtered and concentrated to obtain a white solid product 3f-Br (41.9661 g, 74%). The synthesis reaction principle is as follows:

[0063]

[0064] Synthesis of bottlebrush polymers with tert-butyl groups. Synthesized by the grafting-from method. First, 3f-(poly((2-hydroxyethyl methacrylate-trimethylsilyl)-random-methyl methacrylate)-block-poly(tert-butyl methacrylate-random-methyl methacrylate)) was obtained by atom transfer radical polymerization. First, a certain amount of initiator 3f-Br, CuBr, methyl methacrylate (MMA), and 2-(trimethylsilyl)ethyl methacrylate (HEMA-TMS) were placed in a Schlenk flask and bubbled for about 40 min. At the same time, an equimolar amount of 4,4-dinonyl-2,2-bipyridine with CuBr was dissolved in a small amount of MMA and bubbled for about 40 min. Then, the 4,4-dinonyl-2,2-bipyridine solution was added with a syringe and bubbled for about 40 min. Finally, the reaction system was placed in an oil bath at 70 °C and reacted for 12 h. Subsequently, the copper salt was removed by passing through a silica gel column and precipitated three times in methanol and then dried to obtain 3f-P((HEMA-TMS)-r-MMA). Then, a certain amount of the above polymer was taken as the initiator, CuBr, methyl methacrylate (MMA), and tert-butyl acrylate (tBA) were placed in a Schlenk flask and bubbled for about 40 min. At the same time, an equimolar amount of 4,4-dinonyl-2,2-bipyridine with CuBr was dissolved in a small amount of tBA and bubbled for about 40 min. Then, the 4,4-dinonyl-2,2-bipyridine solution was added with a syringe and bubbled for about 40 min. Finally, the reaction system was placed in an oil bath at 70 °C and reacted for 12 h. Subsequently, the copper salt was removed by passing through a silica gel column and precipitated three times in methanol and then dried to obtain the polymer 3f-(P((HEMA-TMS)-r-MMA)-block-P(tBA-r-MMA)). Then, the obtained polymer, potassium fluoride, 2,6-di-tert-butylphenol, and tetrabutylammonium fluoride were placed in a Schlenk flask and dissolved in tetrahydrofuran under a nitrogen atmosphere. 1.5 equivalents of 2-bromoisobutyryl bromide were slowly added dropwise under an ice bath condition, and then stirred at room temperature for 24 h to obtain a macroinitiator 3f-(poly((2-bromo-2-methylhydroxyethyl acrylate)-random-methyl methacrylate)-block-poly(tert-butyl methacrylate-random-methyl methacrylate)), abbreviated as 3f-(P((HEMA-Br)-r-MMA)-b-P(tBA-r-MMA)). Finally, through atom transfer radical polymerization: a certain amount of the macroinitiator, CuBr, and n-butyl methacrylate (nBMA) were placed in a Schlenk flask and bubbled for about 40 min. At the same time, an equimolar amount of 4,4-dinonyl-2,2-bipyridine with CuBr was dissolved in a small amount of nBMA and bubbled for about 40 min. Then, the 4,4-dinonyl-2,2-bipyridine solution was added with a syringe and bubbled for about 40 min. Finally, the reaction system was placed in an oil bath at 70 °C and reacted for 6 h.The product 3f-(poly((2-hydroxyethyl methacrylate-graft-poly(n-butyl methacrylate)-random-methyl methacrylate)-block-poly(tert-butyl methacrylate-random-methyl methacrylate))), abbreviated as 3f-(P((HEMA-g-PnBMA)-r-MMA)-b-P(tBA-r-MMA)), was obtained by subsequent removal of copper salts through silica gel column chromatography and precipitation three times in methanol followed by drying.

[0065] (2) Hydrolysis of the bottlebrush polymer: The above bottlebrush polymer was dissolved in a certain amount of dichloromethane to form a completely dissolved and low-concentration state. Then, 0.5 equivalent of trifluoroacetic acid based on the volume of dichloromethane was added, and the mixture was stirred at room temperature for 24 h. Subsequently, it was concentrated, then dissolved in tetrahydrofuran, precipitated with petroleum ether and centrifuged three times, and dried in a vacuum oven at 40 °C to finally obtain a three-armed two-block bottlebrush polymer template 3f-(poly((2-hydroxyethyl methacrylate-graft-poly(n-butyl methacrylate)-random-methyl methacrylate)-block-poly(methacrylic acid-random-methyl methacrylate))) with carboxyl groups (-COOH).

[0066] (3) Selective deposition of SiO2 to synthesize colloidal molecules: The bottlebrush polymer template was dissolved in tetrahydrofuran to a concentration of 0.2 mg / mL. Then, ammonia water was added, and the amount of ammonia water used was 4.2% of the volume of tetrahydrofuran. After ultrasonic mixing for dozens of seconds, tetramethoxysilane (TMOS) was added. TMOS was selectively deposited on the bottlebrush polymer. By controlling different molar ratios of -COOH and TMOS, n(-COOH):n(TMOS) = 1:10, 1:30, 1:5, and standing at room temperature for 24 h, three-armed SiO2 colloidal molecules were obtained.

[0067] Figure 7 It is a schematic diagram of the synthetic route of three-armed SiO2 colloidal molecules in Example 5. Using the three-armed two-block bottlebrush polymer 3f-(P((MA-g-PnBMA 48 ) 0.5 -r-MMA 0.5 ) 88 -b-P(AA 0.5 -r-MMA 0.5 ) 254 ) as a template, with a template concentration of 0.2 mg / mL, the SEM image of the three-armed SiO2 colloidal molecules obtained under the condition of n(-COOH):n(-TMOS) = 1:10 is shown in the left figure of Figure 8 ; the SEM image of the three-armed SiO2-PSt colloidal molecules obtained with a template concentration of 0.5 mg / mL and n(-COOH):n(-TMOS) = 1:30 is shown in the right figure of Figure 8 as shown in the figure. FromFigure 8 The partial single colloidal molecule diagrams in the left and right figures in the middle are further magnified to obtain Figure 9 the two diagrams shown. The left figure corresponds to Figure 8 the left figure of Figure 8 and the right figure corresponds to Figure 8 and Figure 9 the right figure of

[0068] As described above, it is only a preferred embodiment of the present invention and does not impose any formal restrictions on the present invention. Although the present invention has been disclosed above with the preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments by using the disclosed technical content without departing from the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing nanoscale colloidal molecules by selectively depositing SiO2 on a bottle brush polymer, characterized in that: The following steps are involved: S1, dissolving a bottle brush polymer having a tert-butyl ester group in a good solvent A, and then performing a hydrolysis reaction under acidic conditions to hydrolyze the tert-butyl ester group to form a carboxyl group, thereby obtaining a bottle brush polymer template; S2. Dissolve the bottle brush polymer template in good solution B, add alkaline reagent and mix and disperse with silicon source precursor. Due to electrostatic interaction, silicon source precursor selectively deposits on carboxyl groups. Let stand at room temperature for 20-30 hours to form silica nanoparticles and obtain nanoscale SiO2 colloidal molecules.

2. The method for preparing nanoscale colloidal molecules by selectively depositing SiO2 on a bottle brush polymer according to claim 1, characterized in that: In step S1, the bottle brush polymer is a single-arm or multi-arm block bottle brush polymer containing tert-butyl ester groups in the main chain or the side chain.

3. The method for preparing nanoscale colloidal molecules by selectively depositing SiO2 on a bottle brush polymer as claimed in claim 2, characterized in that: The component on the bottle brush polymer template that has the effect of inducing SiO2 deposition is the exposed poly(5-norbornene-2-carboxylic acid) or polyacrylic acid, and the component that does not have the effect of SiO2 deposition is a polymer of one or more of acrylic monomers or styrene monomers.

4. The method for preparing nanoscale colloidal molecules by selectively depositing SiO2 on a bottle brush polymer as claimed in claim 1, characterized in that: In step S1, the good solvent A is selected from dichloromethane or tetrahydrofuran, and an acidic condition is formed by adding an acidic reagent, and the acidic reagent is selected from sorbic acid or trifluoroacetic acid.

5. The method for preparing nano-scale colloidal molecules by selectively depositing SiO2 on bottle brush polymers according to claim 1, characterized in that: In step S2, the good solvent B is selected from any one of tetrahydrofuran, acetone, chloroform, butanone, and ethyl acetate.

6. The method for preparing nano-scale colloidal molecules by selectively depositing SiO2 on bottle brush polymers 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, triethylamine and n-butylamine.

7. The method for preparing nano-scale colloidal molecules by selectively depositing SiO2 on bottle brush polymers according to claim 1, characterized in that: The silicon source precursor is selected from any one of tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane or methyltriethoxysilane; the amount of the silicon source precursor is 1-100 equivalents of the molar amount of carboxyl groups on the bottle brush polymer template.

8. The method for preparing nano-scale colloidal molecules by selectively depositing SiO2 on bottle brush polymers according to claim 1, characterized in that: The method further comprises step S3: adding a silicon source containing at least one of amino, thiol or fluorine groups as a surface modifier to the solution obtained in step S2, and standing at room temperature to obtain surface-modified SiO2 colloidal molecules.

9. The method for preparing nano-scale colloidal molecules by selectively depositing SiO2 on a bottle brush polymer as claimed in claim 8, characterized in that: The surface modifier is selected from any one of 3-aminopropyltriethoxysilane, anilinemethyltriethoxysilane, tridecafluorooctyltrimethoxysilane, (3,3,3-trifluoropropyl)trimethoxysilane and (3-mercaptopropyl)trimethoxysilane.

10. A nanometer-scale SiO2 colloidal molecule, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 9.

Images