A method for preparing polysilazane nanospheres by radical polymerization
Polysilazane nanospheres are prepared by free radical polymerization using azobisisobutyronitrile initiator and unsaturated organosilazane, which solves the complexity and low yield problems of traditional methods and prepares nanospheres with uniform morphology and good dispersion, which has broad application prospects.
Patent Information
- Application Number
- CN202310140639.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-02-21
- Publication Date
- 2025-10-10
- Estimated Expiration
- 2043-02-21
AI Technical Summary
It is difficult to efficiently prepare polysilazane nanoparticles with uniform morphology and good dispersion using existing technologies, and traditional methods are complex and have low yields.
Azobisisobutyronitrile is used as an initiator, and unsaturated organic silazane is reacted under low-temperature freezing vacuum by free radical polymerization. The reaction is then stirred in an oil bath and centrifuged, washed, and dried to obtain polysilazane nanospheres.
A simple and feasible preparation of polysilazane nanospheres has been achieved, solving the complexity and low yield problems of traditional methods. The nanospheres have rich surface active groups and are suitable for filling reinforcing materials and lithium-ion battery negative electrode materials.
Smart Images
Figure CN116082586B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of inorganic nanomaterial preparation, and in particular relates to a method for preparing polysilazane nanoparticles by utilizing free radical polymerization. Background Art
[0002] Ceramic nanoparticles possess numerous unique properties, finding widespread application in lubricants, reinforcements, and energy storage materials. Traditional ceramic preparation methods, such as mechanical milling, vacuum condensation, and vapor deposition, present challenges in producing ceramic nanomaterials. Traditional silicon carbide and silicon nitride offer superior thermal stability and mechanical properties, but their nanostructures are difficult to achieve.
[0003] Ceramic precursor materials offer excellent processability and design capabilities. They can be designed into a desired shape and then cured. Through the ceramicization process, complex ceramic materials can be obtained. Polymer ceramic precursors primarily include polysiloxane (Polysiloxane), polycarbosilane (Polycarbosilane, PCS), polyborosilazane (Polyborosilazane, PBSZ), polysilazane (Polysilazane, PSZ), and polyvinylsilazane (Polyvinylsilazane, PVSZ).
[0004] Polysilazane, an inorganic polymer with a Si-N repeating unit as a main chain structure, is an important precursor for Si-CN materials. Although the application of organosilazanes has been studied to some extent, their controllable preparation into nano-spherical particles remains difficult. Previous studies, such as those by Nghiem et al., used PS-b-PVSZ to obtain ordered mesoporous SiCN ceramics through self-assembly and pyrolysis. Similarly, Yu et al. dissolved PS-b-PVSZ as a block copolymer in DMF. Because PS is more soluble in DMF than PVSZ segments, a core-shell structure with PS as the shell and PVSZ as the core was formed. Nguyen et al. spin-coated PMMA-b-PVSZ onto a Si wafer and solvent-annealed it to self-assemble into an ordered structure. The PVSZ was cross-linked by UV irradiation for 5 minutes, and finally, the ordered SiCN nanophase ceramic material was obtained by UV etching of the organic matter for 10 hours. Yu Liu of Xiamen University employed a template method, using a polyethylene glycol / polypropylene glycol block copolymer as a template and a vinylsilazane precursor. Through the different selectivity of the hydroxyl and methyl groups in the template in the solvent, and the coupling between the silazane and hydroxyl moieties, self-assembly occurs in solution, encapsulating the polymer precursor. This is then crosslinked and cured at high temperatures using a thermal initiator. Subsequently, a high-temperature ceramicization treatment transforms the organic polymer in the precursor into an inorganic material. Separately, Zhang et al. reported the preparation of SiCNO ceramic nanoparticles (NPs) by crosslinking an oil-in-oil emulsion of a novel oligomeric silazane precursor followed by pyrolysis.
[0005] The process of preparing the ceramic precursor organopolysilazane micro- or nanomaterials based on the above method is complex and has low yield, so it is particularly important to develop a simple and feasible method for preparing organopolysilazane nanoparticles. Summary of the Invention
[0006] The present invention aims to provide a method for preparing polysilazane nanoparticles. The method uses azobisisobutyronitrile as an initiator and, through free radical polymerization, uses unsaturated organosilazane as a raw material to prepare polysilazane nanoparticles with uniform morphology and good dispersibility.
[0007] The purpose of the present invention is achieved through the following technical solutions.
[0008] In a first aspect, the present invention provides a method for preparing polysilazane nanospheres, characterized in that the method comprises the following steps:
[0009] (1) In a reaction tube, an unsaturated organosilazane is dissolved in a solvent, an initiator is added, and oxygen in the reaction system is removed by low-temperature freezing and vacuum;
[0010] (2) Stir the reaction tube at 30-65°C for 8-36 hours;
[0011] (3) The reaction solution is centrifuged to remove the solvent, and the precipitate is washed with anhydrous ethanol and dried to obtain polysilazane nanoparticles.
[0012] Preferably, the unsaturated organosilazane in step (1) is a compound represented by formula I:
[0013]
[0014] Wherein, R1 and R2 are the same or different, and at least one of R1 and R2 is selected from -CH=CH2. When R1 and R2 are different, the other group is selected from one of -H, C1-C4 alkyl, -C6H5 or -NH2. m and n represent the percentage of monomer composition, and m+n=1.
[0015] The C1-C4 alkyl group described in the present invention is selected from methyl, ethyl, propyl, n-butyl, isobutyl and tert-butyl.
[0016] In a specific embodiment of the present invention, the structure of the unsaturated organosilazane is as follows:
[0017]
[0018] Wherein, p+q+r=1, p, q, and r represent the percentage of monomer composition, with a value between 0 and 1, and p>0, and R2 is selected from vinyl or hydrogen.
[0019] Preferably, the initiator in step (1) is selected from one or a combination of two or more of azobisisobutyronitrile, azobisisoheptanenitrile and dimethyl azobisisobutyrate.
[0020] In a preferred embodiment of the present invention, the initiator is azobisisobutyronitrile.
[0021] In a specific embodiment of the present invention, the molar mass ratio of the unsaturated organosilazane to azobisisobutyronitrile is (12.5-200):1, specifically including 12.5:1, 25:1, 50:1, 100:1, and 200:1. In the most preferred embodiment of the present invention, the molar mass ratio of the unsaturated organosilazane to azobisisobutyronitrile is 100:1.
[0022] Preferably, the solvent in step (1) comprises one of acetonitrile, N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide and triethyl phosphate.
[0023] Preferably, the oxygen in the reaction system is removed by low-temperature freezing and vacuum in the present application, and the specific operation is as follows: the reaction tube is immersed in a dewar flask containing liquid nitrogen until the reactants are completely frozen, the vacuum valve is opened, the oxygen in the reaction system is removed until the vacuum gauge reaches 8.5-9.0 Pa, the vacuum valve is closed, and the above operation is repeated three times until no obvious bubbles are generated when the system is thawed, the air valve is opened, and the valve is closed after the argon is introduced.
[0024] Preferably, the reaction time in step (2) is 8 h.
[0025] Preferably, the drying condition in step (3) is vacuum drying at 80-90℃ for 12-16 h.
[0026] The method for preparing polysilazane nanospheres by radical polymerization provided by the present application has simple preparation method, and solves the problems of traditional template method such as complicated steps, low yield and difficult product collection. The polysilazane nanospheres prepared by the method have a large number of active groups on the surface, and have a wide application prospect in filling and reinforcing materials. In addition, the nanoparticles prepared by the method are not limited to single spherical particle structure, and different reaction monomers can be introduced, different nano-porous structures can be generated after the tube furnace is ceramicized, and the nanoparticles have certain application prospect in filtration and adsorption materials. In addition, the nanoparticles provided by the present application have certain activity to lithium ions after being ceramicized in the tube furnace, have lithium ion storage capacity, and have a wide application prospect in lithium ion battery negative materials. BRIEF DESCRIPTION OF DRAWINGS
[0027] Figure 1 Scanning electron microscope images of polysilazane nanospheres under different reaction times;
[0028] Figure 2 Scanning electron microscope images of polysilazane nanospheres under different initiator contents;
[0029] Figure 3 Scanning electron microscope images of polysilazane nanospheres under different reaction temperatures. DETAILED DESCRIPTION
[0030] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.
[0031] The unsaturated organosilazane PSZ1 used in the embodiments of the present application has the following structural formula:
[0032]
[0033] Preparation of Unsaturated Organosilazane PSZ1
[0034] To a 1000mL three-necked flask equipped with a mechanical stirrer, a high and low temperature cooling and heating cycle device (-20℃-100℃) and an ammonia inlet tube, n-hexane (550mL), methyldichlorosilane (55.25g, 0.48mol) and vinylmethyldichlorosilane (16.80g, 0.12mol) were added. After cooling to 0℃, ammonia was slowly introduced into the resulting mixture until the solution in the tail gas absorption bottle became alkaline. Ammonia was continued to be introduced for 2h before the reaction was stopped. The ammonium chloride salt obtained by the reaction was removed by vacuum filtration, and the resulting filtrate was freed of the solvent by a rotary evaporator and dried in vacuo to obtain 27.5g of polysilazane oligomer. 3-Aminopropyltriethoxysilane (13.5 g, 0.06 mol) was added to the above-mentioned polysilicon nitrogen oligomer at room temperature, stirred evenly, and allowed to stand for 12 h. The temperature was slowly raised to 78 ° C. in a nitrogen atmosphere. After stirring for 2 h, the temperature was gradually lowered to room temperature to finally obtain the unsaturated organosilazane PSZ1.
[0035] Example 1
[0036] 0.001 mol of unsaturated organosilazane (PSZ1) was dissolved in 10 mL of anhydrous acetonitrile, and 0.00164 g (0.00001 mol) of initiator azobisisobutyronitrile (AIBN) was placed in a 50 mL reaction tube. PVSZ solution was added and shaken for 5 minutes to disperse evenly. The oxygen in the reaction system was removed by low-temperature freezing and vacuum. The reaction tube was immersed in a Dewar flask filled with liquid nitrogen until the reactants were completely frozen. The vacuum valve was opened and the oxygen in the reaction system was removed until the vacuum gauge reached about 9.0 Pa. The vacuum valve was closed and thawed. This operation was repeated three times until no obvious bubbles were generated when the system thawed. The vent valve was opened, argon was introduced, and the valve was closed. The reaction was then stirred in an oil bath at 65 ° C for 4 hours. The reaction solution was removed and placed in a centrifuge tube and centrifuged at 8000 rpm / min for 10 minutes to remove excess solvent and unreacted parts. Anhydrous ethanol was added for ultrasonic dispersion for 10 minutes. This was repeated three times. The product was removed and dried in vacuum at 80 ° C for 12 hours to obtain the product.
[0037] Example 2
[0038] 0.001 mol of unsaturated organosilazane (PSZ1) was dissolved in 10 mL of anhydrous acetonitrile, and 0.00164 g (0.00001 mol) of initiator azobisisobutyronitrile (AIBN) was placed in a 50 mL reaction tube. PVSZ solution was added and shaken for 5 minutes to disperse evenly. The oxygen in the reaction system was removed by low-temperature freezing and vacuum. The reaction tube was immersed in a Dewar flask filled with liquid nitrogen until the reactants were completely frozen. The vacuum valve was opened and the oxygen in the reaction system was removed until the vacuum gauge reached about 9.0 Pa. The vacuum valve was closed and thawed. This operation was repeated three times until no obvious bubbles were generated when the system thawed. The vent valve was opened, argon was introduced, and the valve was closed. The reaction was then stirred in an oil bath at 65 ° C for 8 hours. The reaction solution was removed and placed in a centrifuge tube and centrifuged at 8000 rpm / min for 10 minutes to remove excess solvent and unreacted parts. Anhydrous ethanol was added for ultrasonic dispersion for 10 minutes. This was repeated three times. The product was removed and dried in vacuum at 80 ° C for 12 hours to obtain the product.
[0039] Example 3
[0040] Take 0.001mol of unsaturated organosilazane (PSZ1) and dissolve it in 10mL of anhydrous acetonitrile. Take 0.00164g (0.00001mol) of initiator azobisisobutyronitrile (AIBN) and place it in a 50mL reaction tube. Add PVSZ solution and shake for 5min to disperse evenly. Remove oxygen from the reaction system by low-temperature freezing and vacuum. Immerse the reaction tube in a Dewar flask filled with liquid nitrogen until the reactants are completely frozen. Open the vacuum valve and remove oxygen from the reaction system until the vacuum gauge reaches about 9.0Pa. Close the vacuum valve and thaw. Repeat this operation three times until no obvious bubbles are generated when the system thaws. Open the vent valve, pass argon and close the valve. Then stir the reaction in an oil bath at 65℃ for 12h. Remove the reaction solution and place it in a centrifuge tube. Centrifuge it at 8000rpm / min for 10min to remove excess solvent and unreacted parts. Add anhydrous ethanol and ultrasonically disperse it for 10min. Repeat this three times. Remove it and dry it in vacuum at 80℃ for 12h to obtain the product.
[0041] Example 4
[0042] Take 0.001mol of unsaturated organosilazane (PSZ1) and dissolve it in 10mL of anhydrous acetonitrile. Take 0.00164g (0.00001mol) of initiator azobisisobutyronitrile (AIBN) and place it in a 50mL reaction tube. Add PVSZ solution and shake for 5min to disperse evenly. Remove oxygen from the reaction system by low-temperature freezing and vacuum. Immerse the reaction tube in a Dewar flask filled with liquid nitrogen until the reactants are completely frozen. Open the vacuum valve and remove oxygen from the reaction system until the vacuum gauge reaches about 9.0Pa. Close the vacuum valve and thaw. Repeat this operation three times until no obvious bubbles are generated when the system thaws. Open the vent valve, introduce argon and close the valve. Then stir the reaction in an oil bath at 65℃ for 24h. Remove the reaction solution and place it in a centrifuge tube. Centrifuge it at 8000rpm / min for 10min to remove excess solvent and unreacted parts. Add anhydrous ethanol and ultrasonically disperse it for 10min. Repeat this three times. Remove the solution and dry it in vacuum at 80℃ for 12h to obtain the product.
[0043] Example 5
[0044] Take 0.001mol of unsaturated organosilazane and dissolve it in 10mL of anhydrous acetonitrile. Take 0.00164g (0.00001mol) of initiator azobisisobutyronitrile (AIBN) and place it in a 50mL reaction tube. Add PVSZ solution and shake for 5min to disperse evenly. Remove oxygen from the reaction system by low-temperature freezing and vacuum. Immerse the reaction tube in a Dewar flask filled with liquid nitrogen until the reactants are completely frozen. Open the vacuum valve and remove oxygen from the reaction system until the vacuum gauge reaches about 9.0Pa. Close the vacuum valve and thaw. Repeat this operation three times until no obvious bubbles are generated when the system thaws. Open the vent valve, introduce argon and close the valve. Then stir the reaction in an oil bath at 65℃ for 36h. Take out the reaction solution and place it in a centrifuge tube. Centrifuge it at 8000rpm / min for 10min to remove excess solvent and unreacted parts. Add anhydrous ethanol and ultrasonically disperse it for 10min. Repeat this three times. Take it out and dry it in vacuum at 80℃ for 12h to obtain the product.
[0045] Take an appropriate amount of the product obtained in Examples 1-5, adhere the product to a conductive tape, spray gold, and use SEM to observe the microscopic morphology of the particles. Figure 1 As shown in the figure, it can be clearly seen that the nanospheres prepared by the reaction for 8 hours in Example 2 have the most uniform size distribution. As the reaction time increases, the size distribution becomes gradually non-uniform. The technicians analyzed the reason and believed that it was due to the non-uniform reaction degree, resulting in the non-uniform particle size distribution range.
[0046] Example 6
[0047] The raw materials and preparation method were the same as those in Example 2, except that the amount of the initiator azobisisobutyronitrile (AIBN) used was 0.000815 g (0.000005 mol).
[0048] Example 7
[0049] The raw materials and preparation method were the same as those in Example 2, except that the amount of the initiator azobisisobutyronitrile (AIBN) used was 0.00326 g (0.00002 mol).
[0050] Example 8
[0051] The raw materials and preparation method were the same as those in Example 2, except that the amount of the initiator azobisisobutyronitrile (AIBN) used was 0.00656 g (0.00004 mol).
[0052] Example 9
[0053] The raw materials and preparation method were the same as those in Example 2, except that the amount of the initiator azobisisobutyronitrile (AIBN) used was 0.01312 g (0.00008 mol).
[0054] Take appropriate amounts of the products obtained in Example 6, Example 2, and Examples 7-9, adhere the products to a conductive tape, spray gold, and use SEM to observe the microscopic morphology of the particles. Figure 2 As shown in the figure, it can be clearly seen that when the amount of the initiator azobisisobutyronitrile (AIBN) used in Example 2 is 0.00001 mol, the prepared nanosphere product has the most uniform size distribution.
[0055] Example 10
[0056] The raw materials and preparation method were the same as those in Example 2, except that the reaction temperature of the oil bath system was 35°C.
[0057] Example 11
[0058] The raw materials and preparation method were the same as those in Example 2, except that the reaction temperature of the oil bath system was 45°C.
[0059] Example 12
[0060] The raw materials and preparation method were the same as those in Example 2, except that the reaction temperature of the oil bath system was 50°C.
[0061] Example 13
[0062] The raw materials and preparation method were the same as those in Example 2, except that the reaction temperature of the oil bath system was 55°C.
[0063] Take appropriate amount of the products obtained in Examples 10-13 and Example 2, adhere the products to the conductive tape, spray gold, and use SEM to observe the microscopic morphology of the particles. Figure 3 As shown in the figure, it can be clearly seen that when the oil bath reaction temperature is 65° C. in Example 2, the prepared nanosphere product has the most uniform size distribution.
[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing polysilazane nanospheres, characterized in that: The method comprises the following steps: (1) In a reaction tube, unsaturated organosilazane is dissolved in a solvent, an initiator is added, and oxygen in the reaction system is removed by low-temperature freezing and vacuum; (2) Stir the reaction tube at 65°C for 8 h; (3) The reaction solution is centrifuged to remove the solvent, and the precipitate is washed with anhydrous ethanol and dried to obtain polysilazane nanoparticles; The unsaturated organosilazane is prepared by the following method: To a 1000 mL three-necked flask equipped with a mechanical stirrer, a high and low temperature hot and cold cycle device, and an ammonia inlet tube, 550 mL of n-hexane, 0.48 mol of methyldichlorosilane, and 0.12 mol of vinylmethyldichlorosilane were added. After cooling to 0°C, ammonia was slowly introduced into the resulting mixture until the solution in the tail gas absorption bottle became alkaline. Ammonia was continued to be introduced for 2 h before stopping the reaction. The ammonium chloride salt obtained by the reaction was removed by filtration under reduced pressure. The solvent was removed from the filtrate by rotary evaporation and vacuum drying to obtain 27.5 g of polysilazane oligomer. 0.06 mol of 3-aminopropyltriethoxysilane was added to the above polysilazane oligomer at room temperature, stirred evenly, and allowed to stand for 12 h. The temperature was then slowly raised to 78°C in a nitrogen atmosphere, stirred for 2 h, and then gradually cooled to room temperature to obtain an unsaturated organosilazane. The initiator is azobisisobutyronitrile, and the molar mass ratio of the unsaturated organic silazane to azobisisobutyronitrile is 100:
1.
2. The preparation method according to claim 1, characterized in that The solvent described in step (1) includes one of acetonitrile, N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide and triethyl phosphate.
3. The preparation method according to claim 1, characterized in that The oxygen in the reaction system is removed by low-temperature freezing and vacuum, and the specific operation is as follows: immersing the reaction tube in a Dewar flask filled with liquid nitrogen until the reactants are completely frozen, opening the vacuum valve, removing the oxygen in the reaction system until the vacuum gauge reaches 8.5-9.0 Pa, closing the vacuum valve, thawing, repeating the above operation three times until no obvious bubbles are generated when the system is thawed, opening the vent valve, passing argon gas, and then closing the valve.
4. The preparation method according to claim 1, characterized in that The drying condition in step (3) is vacuum drying at 80-90°C for 12-16 h.