Method for preparing polycarbosilane by using Grignard reagent

Abstract

The invention relates to a preparation method of polycarbosilane, the polycarbosilane is synthesized by copolycondensation of an aryl Grignard reagent and dichlorosilane, and the molecular weight after copolycondensation is 800-6000 g / mol; polycarbosilane is an important precursor for preparing novel materials such as silicon carbide fibers, ceramic micro powder and ceramic-based composite materials. The preparation method comprises the following steps: dissolving aryl halide, magnesium powder and iodine granules in tetrahydrofuran, and carrying out ultrasonic treatment under the protection of inert gas to obtain an aryl Grignard reagent; the preparation method comprises the following steps: dissolving dichlorosilane in tetrahydrofuran; transferring the double Grignard reagent into a dichlorosilane solution, and carrying out reflux stirring reaction; adding a glacial acetic acid solution and stirring for reaction; carrying out reduced pressure distillation, washing with ethanol and deionized water, and filtering; and drying the solid powder to obtain a product. The method is simple and convenient to operate, safe in reaction process and mild in reaction condition, and has a relatively great industrial prospect.

Description

Technical Field

[0001] The present invention relates to the field of synthesis technology, and in particular to a method for preparing polycarbosilane by using a Grignard reagent, and a preparation method and application thereof. Background Art

[0002] Polycarbosilane is a class of polymer compounds whose main chain is composed of alternating silicon and carbon atoms. The molecular chain of polycarbosilane is linear or branched, with good processability, and is an important precursor for the preparation of new materials such as silicon carbide fibers, ceramic porous materials, and ceramic-based composite materials. There are hydrogen or organic groups connected to the silicon and carbon atoms in the molecular chain, and the more active silicon-hydrogen bonds or double bonds can cross-link with each other. In recent years, a major factor that has attracted people's interest in the study of polycarbosilanes is their potential as silicon carbide precursors and special coatings, and many new polycarbosilanes have been synthesized directly or indirectly. However, polycarbosilane has gradually become the focus of research, because people have gradually realized that the use of polycarbosilane can not only be used as a precursor of silicon carbide, but also as a new type of polymer with potential uses in a wide range of applications. Therefore, studying the synthesis method of polycarbosilane has practical value and significance.

[0003] As a precursor for preparing new silicon carbide materials, polycarbosilane has the characteristics of high ceramic yield, excellent modifiable processability and good self-crosslinking, and is widely used in high-tech fields such as aerospace. In addition to its performance advantages, this advanced composite material is particularly suitable for preparing heat-resistant structural parts of any complex shape, and its production cost is relatively low, and its industrial application prospects are broad. In addition, polycarbosilane can also be used to prepare new materials such as silicon carbide fibers, corrosion-resistant coatings, adhesives, hollow ceramic microspheres, etc.

[0004] At present, there are mainly the following synthetic methods for preparing polycarbosilane: cracking synthesis method, one-pot method, catalytic polycondensation method, and Grignard method. Cracking synthesis method is the most commonly used method for preparing polycarbosilane. At present, liquid polysilane, the cracking product of polydimethylsilane, is often used as raw material in industry, and polycarbosilane is synthesized by normal pressure and high temperature cracking method; the one-pot method for synthesizing polycarbosilane mainly adds various materials into the same reactor in batches, controls the reaction conditions, and finally separates the product to synthesize liquid polycarbosilane. The advantage of this method is that it simplifies the intermediate steps, does not need to separate the intermediate products, and has a high synthesis yield; the catalytic polycondensation method is mainly divided into two steps. The first step is to synthesize polysilane composed of Si-Si bonds by polycondensing chlorosilane (usually using dichlorodimethylsilane) through metal sodium; the second step is the rearrangement of polysilane, generating Si-C bonds and Si-H bonds from Si-Si bonds. The disadvantage of this method is that the rearrangement requires a very high temperature (300-600°C) and the overall yield of PCS is low; the principle of the Grignard method is to use a di-Grignard reagent and a corresponding difunctional compound as raw materials for condensation, and synthesize linear polycarbosilanes through a coupling reaction.

[0005] Based on the needs of industry and practical applications, it is necessary to find a method for synthesizing polycarbosilane with a short process flow, simple operation, low equipment requirements, mild reaction conditions, no need for catalysts, no need for purification of intermediate products, easy acquisition of raw materials and low cost. This method can also mix multiple raw materials or add other substances containing unsaturated bonds to regulate the molecular structure, and can selectively design and synthesize polycarbosilanes with specific functions and properties. Summary of the invention

[0006] The object of the present invention is to provide a method for preparing polycarbosilane using a Grignard reagent, wherein tetrahydrofuran is used as an organic solvent, halogenated aromatic hydrocarbons are reacted with magnesium powder to synthesize aryl magnesium halide, the above solution is reacted with dichlorosilane, and then purified to generate a polycarbosilane product.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] A method for preparing polycarbosilane using a Grignard reagent comprises the following steps:

[0009] A. Obtain an aryl Grignard reagent;

[0010] B. dissolving dichlorosilane in a reaction solvent, then dropping the aryl Grignard reagent, heating the reaction, then cooling, adding a quenching agent to quench the reaction, and obtaining a crude product;

[0011] C. Purifying the crude product to obtain polycarbosilane;

[0012] The polycarbosilane includes one or more of linear polycarbosilane and hyperbranched polycarbosilane.

[0013] In the prior art, although Grignard reagents are also used to synthesize organosilicon, generally only small molecule organosilicon can be synthesized. This is mainly because, in the reaction using Grignard reagents, the Grignard reagents react more actively with water, oxygen, etc., and are prone to produce impurities such as by-products. If small molecule organosilicon is synthesized, these by-product impurities can be removed by conventional impurity removal means after the reaction. However, if a polymer material such as polycarbosilane is synthesized, even if only 1% of by-product impurities are produced, it is possible to cause the interruption of the polymerization reaction and the failure to successfully synthesize polycarbosilane. Other influencing factors include the content of the double Grignard reagent, the appropriate reaction conditions with the binary substituent, etc., which will also have a serious impact on the molecular weight of the polycarbosilane. After long-term research and continuous experiments, the present invention successfully prepared high molecular weight polycarbosilane by selecting and synthesizing a high content of double Grignard reagents, appropriate reaction conditions with the binary substituent, and post-treatment.

[0014] Preferably, in step A, the aromatic Grignard reagent includes one or more of an aromatic di-Grignard reagent and an aromatic tri-Grignard reagent; the operation of step A includes: mixing iodine particles, halogenated aromatic hydrocarbons, and magnesium powder in a reaction solvent, heating and performing ultrasonic reaction under the protection of an inert gas to obtain the aromatic Grignard reagent; the halogenated aromatic hydrocarbons include one or more of dihalogenated aromatic hydrocarbons and trihalogenated aromatic hydrocarbons.

[0015] Preferably, in step A, the aromatic Grignard reagent includes one or more of an aromatic di-Grignard reagent and an aromatic tri-Grignard reagent; the operation of step A includes: mixing iodine particles, halogenated aromatic hydrocarbons, and magnesium powder in a reaction solvent, heating and performing ultrasonic reaction under the protection of an inert gas to obtain the aromatic Grignard reagent; the halogenated aromatic hydrocarbons include one or more of dihalogenated aromatic hydrocarbons and trihalogenated aromatic hydrocarbons.

[0016] Preferably, when the polycarbosilane is a linear polycarbosilane, the halogenated aromatic hydrocarbon is a dihalogenated aromatic hydrocarbon, and the aromatic Grignard reagent is an aromatic bis-Grignard reagent; the dihalogenated aromatic hydrocarbon includes one or more of p-dibromobenzene, 4,4'-dibromobiphenyl, 2,7-dibromofluorene, and 9,9-dimethyl-2,7-dibromofluorene.

[0017] Preferably, when the polycarbosilane is a hyperbranched polycarbosilane, the halogenated aromatic hydrocarbon is a trihalogenated aromatic hydrocarbon, and the aromatic Grignard reagent is an aromatic tri-Grignard reagent; the trihalogenated aromatic hydrocarbon includes one or more of m-tribromobenzene, tribromobiphenyl, tribromonaphthalene, 2,4,6-tribromomethyltrimethylbenzene, and 2,4,6-tribromomethylbenzene.

[0018] Preferably, in step A, the inert gas includes one or more of nitrogen and argon; in step B, the reaction solvent includes tetrahydrofuran; the dichlorosilane includes one or more of dimethyldichlorosilane, methyl-phenyldichlorosilane, diphenyldichlorosilane, diethyldichlorosilane, methyl-vinyldichlorosilane, methyl-ethyldichlorosilane, methyl-propylenedichlorosilane, methyl-hexyldichlorosilane, methyl-octyldichlorosilane, methyl-dodecyldichlorosilane, methyl-7-octenyldichlorosilane, and divinyldichlorosilane; the quencher includes one or more of methanol, ethanol, butanol, formic acid, acetic acid, butyric acid, and water; in step C, the polycarbosilane includes one or more of saturated polycarbosilane and unsaturated polycarbosilane.

[0019] The content of tetrahydrofuran is above 99%, and most preferably 100%. The quenching agent is preferably glacial acetic acid, and preferably a 99% glacial acetic acid solution.

[0020] Preferably, when the polycarbosilane includes a saturated polycarbosilane, the dichlorosilane includes one or more of dimethyldichlorosilane, methyl-phenyldichlorosilane, diphenyldichlorosilane, diethyldichlorosilane, methyl-ethyldichlorosilane, methyl-hexyldichlorosilane, methyl-octyldichlorosilane, and methyl-dodecyldichlorosilane; when the polycarbosilane includes a saturated polycarbosilane, the dichlorosilane includes one or more of methyl-vinyldichlorosilane, methyl-propylenedichlorosilane, methyl-7-octenyldichlorosilane, and divinyldichlorosilane.

[0021] Preferably, in step A, the molar ratio of the halogenated aromatic hydrocarbon to the magnesium powder is 1:3; the ultrasonic power of the ultrasonic reaction is 300 to 2000 W, the reaction temperature of the ultrasonic reaction is 20° C. to 60° C., and the reaction time of the ultrasonic reaction is 1.5 to 2 h.

[0022] The time for the ultrasonic reaction during the first step is 1 to 2 hours, preferably 1.5 to 2 hours.

[0023] In step B, the molar ratio of the aromatic Grignard reagent to the dichlorosilane is 1:1-2; the reaction temperature of the temperature-raising reaction is 40-60°C, and the reaction time of the temperature-raising reaction is 18-24h; the cooling temperature is room temperature; and the reaction time of the quenching reaction is 1-2h.

[0024] The reaction time of the temperature-raising reaction in the second step is 18 to 24 hours, more preferably 20 to 24 hours, and most preferably 22 to 24 hours.

[0025] Preferably, in step B, the dropwise addition time of the double Grignard reagent is 0.1 to 0.5 hours.

[0026] The double Grignard reagent needs to be added slowly, with a total addition time of 0.1 to 0.5 hours to prevent the reaction from being too violent and difficult to control.

[0027] The dripping time of the Grignard reagent reaction solution is controlled to be 0.1 to 0.5 hours, preferably 0.2 to 0.5 hours.

[0028] Preferably, in step C, the method for removing the solvent in the crude product comprises vacuum distillation; the temperature of the vacuum distillation is lower than 80° C.; and the washing comprises washing with deionized water and ethanol alternately, which is repeated three times.

[0029] In step C, the purification treatment includes: removing the solvent in the crude product, washing, and drying to obtain the polycarbosilane.

[0030] Preferably, in step C, the purification treatment comprises: removing the solvent in the crude product by distillation under reduced pressure, washing with deionized water and ethanol alternately, and then drying to obtain the polycarbosilane.

[0031] Preferably, in step C, the temperature of the reduced pressure distillation is lower than 80° C.; and the washing comprises washing with deionized water and ethanol alternately, which is repeated three times.

[0032] The temperature during the evaporation of the solvent by reduced pressure distillation is controlled to be 80° C. or less, more preferably 70° C. or less. If the temperature during the evaporation of the solvent by reduced pressure distillation is too high, the efficiency of solvent collection will decrease.

[0033] Preferably, when an aromatic tri-Grignard reagent is selected to react with dichlorosilane, a hyperbranched polycarbosilane is obtained, and the trihaloaromatic hydrocarbons include one or more of m-tribromobenzene, tribromobiphenyl, tribromonaphthalene, 2,4,6-tribromomethyltrimethylbenzene, 2,4,6-tribromomethylbenzene and corresponding trihaloaromatic hydrocarbons.

[0034] Preferably, when the dichlorosilane includes one or more of methyl-vinyldichlorosilane, methyl-propylenedichlorosilane, methyl-7-octenyldichlorosilane, and divinyldichlorosilane, the obtained polycarbosilane is an unsaturated polycarbosilane and can be used as a UV curing coating.

[0035] A polycarbosilane product obtained by the method for preparing polycarbosilane using a Grignard reagent.

[0036] An application of the above polycarbosilane product is characterized in that it is used as one or more of a silicon carbide fiber precursor, a ceramic micropowder precursor, a ceramic-based composite material precursor, and a coating.

[0037] The prepared polycarbosilane can be used as an important precursor for new materials such as silicon carbide fiber, ceramic micropowder, ceramic-based composite materials, etc. When the prepared polycarbosilane is a hyperbranched polycarbosilane and an unsaturated polycarbosilane, it can be used as a coating. In particular, when the prepared polycarbosilane is an unsaturated polycarbosilane, it can be used as a UV curing coating.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] The present invention relates to a method for preparing polycarbosilane, which is synthesized by co-condensation of an aromatic di-Grignard reagent or an aromatic tri-Grignard reagent and dichlorosilane, and the molecular weight after co-condensation is 800-6000 g / mol; polycarbosilane is an important precursor for preparing new materials such as silicon carbide fiber, ceramic micropowder, ceramic-based composite materials, etc. The preparation method is as follows: halogenated aromatic hydrocarbons, magnesium powder and iodine particles are dissolved in tetrahydrofuran and ultrasonicated under N2 to obtain a di-Grignard reagent or a tri-Grignard reagent; dichlorosilane is dissolved in tetrahydrofuran; the Grignard reagent is transferred to the dichlorosilane solution, and the mixture is stirred under reflux for reaction; glacial acetic acid solution is added for stirring for reaction; vacuum distillation is performed, and the mixture is filtered after washing with ethanol and deionized water; and the solid powder is dried to obtain the product. The method is simple to operate, has a safe reaction process, mild reaction conditions, and has great industrial prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a flow chart for illustrating an example of the preparation process of the present invention.

[0041] Figure 2 This is the FT-TR spectrum of the polycarbosilane prepared in Example 1 of the present invention.

[0042] Figure 3 This is the FT-TR spectrum of the polycarbosilane prepared in Example 2 of the present invention.

[0043] Figure 4 The thermogravimetric diagrams of polycarbosilanes 1a, 1b, 1c and 1d prepared in the present invention are shown.

[0044] Figure 5 The thermogravimetric diagrams of polycarbosilanes 2a, 2b, 2c and 2d prepared in the present invention are shown. DETAILED DESCRIPTION

[0045] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings.

[0046] Example 1

[0047] like Figure 1As shown, in a 250mL Schlenk reaction bottle, 40mL of tetrahydrofuran, 1.08g of magnesium powder, 3.54g of p-dibromobenzene, and iodine particles are added to initiate the reaction. After the reaction is initiated, the reaction temperature is raised to the first reaction temperature of 55°C, and the reaction is carried out under nitrogen protection for 2h to obtain a Grignard reagent reaction solution. Under nitrogen protection, 40mL of tetrahydrofuran and 1.5mL of dimethyldichlorosilane are added to a 500mL three-necked flask, and an oil bath is used to raise the material temperature to the second reaction temperature of 50°C. The prepared Grignard reagent reaction solution is added dropwise using a constant pressure dropper, and the dropwise addition time is 0.2h. After the dropwise addition is completed, the reaction is kept warm for 24h and cooled to room temperature naturally. 15mL of 99% glacial acetic acid solution is added to the above to quench, and the organic solvent is evaporated by reduced pressure distillation at 65°C to obtain a crude product, which is repeatedly washed three times with anhydrous ethanol and deionized water to obtain the polycarbosilane 1a.

[0048] The molecular weight of the prepared polycarbosilane 1a is 4000 g / mol, the 5% thermal weight loss temperature is 245° C., and the 50% thermal weight loss temperature is 485° C.

[0049] Example 2

[0050] Tetrahydrofuran was used as an organic solvent, 4.68 g of 4,4'-dichlorobiphenyl and 1.08 g of magnesium powder were added, and iodine particles were added to initiate the reaction, and the reaction temperature for preparing the Grignard reagent was 60° C. Except that 1.5 mL of dimethyldichlorosilane was replaced by 2.0 mL of methyl-vinyl-dichlorosilane, the other steps were carried out in the same manner as in Example 1, and the crude product was purified to obtain the polycarbosilane.

[0051] Unsaturated polycarbosilane 1b with a molecular weight of 1600 g / mol was obtained. The UV curing coating prepared with 1b as the oligomer had a light curing time of 20 s, at which time the hardness reached 5H, the adhesion to tinplate reached level 1, and the flexibility was 0.5 mm.

[0052] Example 3

[0053] Tetrahydrofuran was used as an organic solvent, 4.86 g of 2,7-dibromofluorene and 1.08 g of magnesium powder were added, and iodine particles were added to initiate the reaction. The reaction temperature for preparing the Grignard reagent was 60° C. The other steps were carried out in the same manner as in Example 1, and the crude product was purified to obtain the polycarbosilane 1c.

[0054] The molecular weight of the prepared polycarbosilane 1c is 4200 g / mol, the 5% thermal weight loss temperature is 220° C., and the 50% thermal weight loss temperature is 290° C.

[0055] Example 4

[0056] Tetrahydrofuran was used as an organic solvent, 5.28 g of 9,9-dimethyl-2,7-dibromofluorene and 1.08 g of magnesium powder were added, and iodine particles were added to initiate the reaction. The reaction temperature for preparing the Grignard reagent was 50° C. The other steps were carried out in the same manner as in Example 1, and the crude product was purified to obtain the polycarbosilane 1d.

[0057] The molecular weight of the prepared polycarbosilane 1d is 5500 g / mol, the 5% thermal weight loss temperature is 195° C., and the 50% thermal weight loss temperature is 255° C.

[0058] Example 5

[0059] Tetrahydrofuran was used as an organic solvent, and the Grignard reagent was prepared in the same manner as in Example 1. In a 500-mL three-necked flask, 40 mL of tetrahydrofuran and 3.5 mL of diphenyldichlorosilane were added, and the Grignard reagent was transferred to the three-necked flask. The other steps were carried out in the same manner as in Example 1. The crude product was purified to obtain the polycarbosilane 2a.

[0060] The molecular weight of the prepared polycarbosilane 2a is 3200 g / mol, the 5% thermal weight loss temperature is 255° C., and the 50% thermal weight loss temperature is 600° C.

[0061] Example 6

[0062] Tetrahydrofuran was used as an organic solvent, 4.68 g of tribromobenzene and 1.08 g of magnesium powder were added, and iodine particles were added to initiate the reaction, and the reaction temperature for preparing the Grignard reagent was 60° C. Except that 3.5 mL of diphenyldichlorosilane was replaced by 1.5 mL of dimethyldichlorosilane, the other steps were carried out in the same manner as in Example 5, and the crude product was purified to obtain the polycarbosilane.

[0063] A hyperbranched polycarbosilane 2b with a molecular weight of 2800 g / mol was obtained.

[0064] Example 7

[0065] Tetrahydrofuran was used as an organic solvent, 4.86 g of 2,7-dibromofluorene and 1.08 g of magnesium powder were added, and iodine particles were added to initiate the reaction. The reaction temperature for preparing the Grignard reagent was 60° C. The other steps were carried out in the same manner as in Example 5, and the crude product was purified to obtain the polycarbosilane 2c.

[0066] The molecular weight of the prepared polycarbosilane 2c is 3200 g / mol, the 5% thermal weight loss temperature is 220° C., and the 50% thermal weight loss temperature is 290° C.

[0067] Example 8

[0068] Tetrahydrofuran was used as an organic solvent, 5.28 g of 9,9-dimethyl-2,7-dibromofluorene and 1.08 g of magnesium powder were added, and iodine particles were added to initiate the reaction. The reaction temperature for preparing the Grignard reagent was 50° C. The other steps were carried out in the same manner as in Example 5, and the crude product was purified to obtain the polycarbosilane 2d.

[0069] The molecular weight of the prepared polycarbosilane 2d is 3400 g / mol, the 5% thermal weight loss temperature is 180° C., and the 50% thermal weight loss temperature is 230° C.

[0070] Effect Example 1

[0071] Except for Example 2, the FT-TR spectra of Examples 1 to 8 are basically similar. Taking Example 1 as an example, the structural characterization of the prepared polycarbosilane 1a is as follows: Figure 2 As shown, it is proved that polycarbosilane was successfully obtained.

[0072] Figure 3 The FT-TR spectrum of polycarbosilane 1b prepared in Example 2 proves that it has the structure of polycarbosilane and has a peak at 1640 cm -1 The presence of double bond absorption peaks indicates that 1b is an unsaturated polycarbosilane.

[0073] Figure 4 The decomposition temperatures of the polycarbosilanes 1a, 1b, 1c, and 1d prepared in Examples 1 to 4 were compared. Figure 5 The decomposition temperatures of the polycarbosilanes 2a, 2b, 2c and 2d prepared in Examples 5 to 8 were compared. It was found that the heat resistance of polycarbosilanes with different structures was different, but all of them had good heat resistance.

[0074] The above disclosure is only the preferred embodiment of the present invention, which cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for preparing polycarbosilane using a Grignard reagent, characterized in that: The steps include: A. Obtain an aryl Grignard reagent; B. dissolving dichlorosilane in a reaction solvent, then dropping the aryl Grignard reagent, heating the reaction, then cooling, adding a quenching agent, quenching the reaction, and obtaining a crude product; C. Purifying the crude product to obtain polycarbosilane; The polycarbosilane includes one or more of linear polycarbosilane and hyperbranched polycarbosilane.

2. The method for preparing polycarbosilane using a Grignard reagent according to claim 1, characterized in that: In step A, the aromatic Grignard reagent includes one or more of an aromatic di-Grignard reagent and an aromatic tri-Grignard reagent; the operation of step A includes: mixing iodine particles, halogenated aromatic hydrocarbons, and magnesium powder in a reaction solvent, heating under the protection of an inert gas to perform an ultrasonic reaction, and obtaining the aromatic Grignard reagent; the halogenated aromatic hydrocarbons include one or more of dihalogenated aromatic hydrocarbons and trihalogenated aromatic hydrocarbons.

3. The method for preparing polycarbosilane using Grignard reagent according to claim 2, characterized in that: When the polycarbosilane is linear polycarbosilane, the halogenated aromatic hydrocarbon is a dihalogenated aromatic hydrocarbon, and the aromatic Grignard reagent is an aromatic bis-Grignard reagent; the dihalogenated aromatic hydrocarbon includes one or more of p-dibromobenzene, 4,4'-dibromobiphenyl, 2,7-dibromofluorene, and 9,9-dimethyl-2,7-dibromofluorene.

4. The method for preparing polycarbosilane using Grignard reagent according to claim 2, characterized in that: When the polycarbosilane is a hyperbranched polycarbosilane, the halogenated aromatic hydrocarbon is a trihalogenated aromatic hydrocarbon, and the aromatic Grignard reagent is an aromatic tri-Grignard reagent; the trihalogenated aromatic hydrocarbon includes one or more of m-tribromobenzene, tribromobiphenyl, tribromonaphthalene, 2,4,6-tribromomethyltrimethylbenzene, and 2,4,6-tribromomethylbenzene.

5. The method for preparing polycarbosilane using a Grignard reagent as claimed in claim 2, characterized in that: In step A, the inert gas includes one or more of nitrogen and argon; in step B, the reaction solvent includes tetrahydrofuran; the quencher includes one or more of methanol, ethanol, butanol, formic acid, acetic acid, butyric acid, and water; in step C, the polycarbosilane includes one or more of saturated polycarbosilane and unsaturated polycarbosilane.

6. The method for preparing polycarbosilane using a Grignard reagent as claimed in claim 5, characterized in that: When the polycarbosilane includes a saturated polycarbosilane, the dichlorosilane includes one or more of dimethyldichlorosilane, methyl-phenyldichlorosilane, diphenyldichlorosilane, diethyldichlorosilane, methyl-ethyldichlorosilane, methyl-hexyldichlorosilane, methyl-octyldichlorosilane, and methyl-dodecyldichlorosilane; when the polycarbosilane includes a saturated polycarbosilane, the dichlorosilane includes one or more of methyl-vinyldichlorosilane, methyl-propylenedichlorosilane, methyl-7-octenyldichlorosilane, and divinyldichlorosilane.

7. The method for preparing polycarbosilane using a Grignard reagent as claimed in claim 2, characterized in that: In step A, the molar ratio of the halogenated aromatic hydrocarbon to the magnesium powder includes 1:3; the ultrasonic power of the ultrasonic reaction includes 300 to 2000 W, the reaction temperature of the ultrasonic reaction includes 20° C. to 60° C., and the reaction time of the ultrasonic reaction includes 1.5 to 2 hours; in step B, the molar ratio of the aromatic Grignard reagent to the dichlorosilane includes 1:1 to 2; the reaction temperature of the temperature-raising reaction includes 40° C. to 60° C., and the reaction time of the temperature-raising reaction includes 18 to 24 hours; the dripping time of the Grignard reagent includes 0.1 to 0.5 hours; the cooling temperature includes room temperature; and the reaction time of the quenching reaction includes 1 to 2 hours; In step C, the purification treatment includes: removing the solvent in the crude product, washing, and drying to obtain the polycarbosilane.

8. The method for preparing polycarbosilane using a Grignard reagent as claimed in claim 7, characterized in that: In step C, the method for removing the solvent in the crude product comprises vacuum distillation; the temperature of the vacuum distillation is lower than 80° C.; and the washing comprises washing with deionized water and ethanol alternately, which is repeated three times.

9. A polycarbosilane product obtained by the method for preparing polycarbosilane using a Grignard reagent as claimed in claim 1.

10. An application of the polycarbosilane product as claimed in claim 9, characterized in that: Used as one or more of silicon carbide fiber precursor, ceramic micropowder precursor, ceramic matrix composite material precursor, and coating.

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