Polyimide prepolymer resins containing silicon and cardo structures and methods for making the same

Abstract

The application provides a kind of polyimide prepolymer resin containing silicon and Cardo structure and a preparation method thereof, and belongs to the field of material science.The preparation method is as follows: firstly, a mixture of a synthesized structure-symmetrical diamine monomer containing silicon and Cardo structure, a commercially available structure-symmetrical dianhydride monomer and an active end-capping agent is subjected to a polymerization reaction in a suitable organic solvent;secondly, a thermosetting polyimide resin glue liquid containing a dehydration cyclization is obtained;finally, a post-treatment is performed to obtain a target product, and the molecular structure is as follows:the application has a wide melt processing window, low melt viscosity and good melt stability;no crosslinking agent needs to be added during crosslinking and curing, no volatile substances are generated, and the synthesized resin has few defects;the performance can be adjusted and controlled, has good processing technology, is low in cost and easy to industrialize.

Description

Technical Field

[0001] This invention belongs to the field of materials science, and specifically relates to a novel method for preparing silicon-containing polyimide prepolymer resin. Background Technology

[0002] Polyimide (PI) is a class of high-performance polymers with imide rings in the main chain. Depending on the processing technology, PI can be classified into thermoplastic PI and thermosetting PI. PI materials possess excellent thermal stability (thermal decomposition temperature up to 500℃), good mechanical properties, excellent film-forming properties, and electrical properties, and are widely used in various high-tech fields.

[0003] Thermoplastic polyimides are typically linear high-molecular-weight polymers synthesized in a two-step process. While possessing high toughness, they also exhibit significant chain segment rigidity, a high glass transition temperature, and are relatively difficult to dissolve and melt, resulting in high melt viscosity, making processing challenging and molding processes difficult. Currently, common thermosetting polyimide resins primarily control the degree of polymerization and viscosity by adjusting the feed ratio of diamine and dianhydride. However, the resulting resin prepolymers often have a wide molecular weight distribution, with the actual degree of polymerization differing significantly from the theoretical design. This severely impacts the resin's melt viscosity and processing properties, leading to a decline in the temperature resistance, impact toughness, and molding quality of the prepared composite materials.

[0004] Therefore, how to prepare a simple, easy-to-process polyimide polymer with excellent thermal and mechanical properties and low cost is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a high-temperature resistant polyimide resin with excellent mechanical properties and its preparation method, aiming to overcome the problems of difficult processing and poor molding technology of thermoplastic polyimide resin; and to overcome the problem that although the thermal properties of thermosetting polyimide resin are improved after curing, the mechanical properties decrease and the resin becomes brittle.

[0006] To achieve the above objectives, the present invention provides the following solution: A polyimide prepolymer resin containing silicon and Cardo structure has the following main chain chemical structure: In its branched structure, R1 and R2 can be any of the following structures: , , , , , , , , , , , , , , The structures of R1 and R2 can be the same or different; the preferred structure is... , , The branched structures R3, R4, and R5 can be any one of the following structures: , , , , , , , , , , , The structures of R3, R4, and R5 can be the same or different, with the following preferred structure: , , , ; The end-capping agent ER can be any of the following structures: , , The preferred structure is as follows: .

[0007] Ar in the main chain repeating unit can be any of the following structures: , , , , , , , ; A method for preparing a polyimide prepolymer resin containing silicon and Cardo structure, comprising firstly, polymerizing a mixture of a synthesized diamine monomer with symmetrical silicon and Cardo structure, a commercially available symmetrical dianhydride monomer, and an active end-capping agent in a suitable organic solvent, followed by dehydration and cyclization to obtain a thermosetting polyimide resin solution, and then post-processing to obtain the target product, specifically including the following steps: Step 1: Under an inert gas environment, dinitro compounds containing silicon and Cardo structures are prepared via the Williamson reaction using dichlorosilane, bisphenol fluorene, and p-nitrochlorobenzene compounds as raw materials. The reaction is as follows: Among them, branches R1 and R2 can be any of the following structures: , , , , , , , , , , , , , , The structures of R1 and R2 can be the same or different, and the preferred structure is... , , R3, R4, and R5 can be any of the following structures: , , , , , , , , , , , The structures of R3, R4, and R5 can be the same or different, with the following preferred structure: , , , ; Specifically: Under an inert gas atmosphere, bisphenol fluorene was added to DMF. After the bisphenol fluorene dissolved, dichlorosilane was slowly added to the reaction solution at a molar ratio of 1:2 to 1:3. The reaction was maintained at 30 to 70°C for 4 to 12 hours. Then, potassium carbonate and p-nitrochlorobenzene were added to the reaction solution at a molar ratio of 1:1.2 to 1:1.5 for bisphenol fluorene and 1:1 to 1:1.5 for p-nitrochlorobenzene. The reaction was carried out at 110 to 160°C for 12 to 24 hours. After the reaction was completed, the mixture was cooled to room temperature, and an appropriate amount of deionized water was added to precipitate the product. The product was then washed multiple times with 50% ethanol aqueous solution to obtain the target product: a dinitro compound containing silicon and a Cardo structure. Step 2: The nitro groups in the silicon-containing and Cardo-structured dinitro compound prepared in Step 1 are reduced to prepare a structurally symmetrical diamine compound, as shown in the following reaction: Specifically: a dinitro compound containing silicon and Cardo structure is dissolved in an appropriate amount of anhydrous ethanol, Pd / C is added, the solution is heated to 50-90℃, and hydrazine hydrate is slowly added dropwise. After the addition is completed, the reaction is kept at this temperature for 6-12 hours. The mass ratio of Pd / C to the dinitro compound containing silicon and Cardo structure is 1:5-1:10, and the molar ratio of hydrazine hydrate to the dinitro compound containing silicon and Cardo structure is 5:1-15:1. After the reaction is completed, the mixture is filtered while hot. Then, ice-cold deionized water is added to the filtrate, the mixture is stirred, filtered, washed with water, and dried to obtain the target symmetrical diamine compound monomer containing silicon and Cardo structure. Step 3: Prepare a silicon-containing polyimide prepolymer by reacting the silicon-containing and Cardo-structured diamine compound prepared in Step 2 with a commercially available diacid anhydride containing a symmetrical structure, as follows: Wherein, the diacid anhydride Ar can be any one of the following structures: pyromellitic dianhydride, 4,4′-biphenyl ether dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 4,4′-(hexafluoroisopropene) diacid anhydride, and 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride, and their corresponding chemical structures are as follows: , , , , , , ; The end-capping agent ER is any one of the following structures: norbornene anhydride, m-ethynyl phthalic anhydride, or 4-phenylethynyl phthalic anhydride, and their corresponding chemical structures are as follows: , , The preferred structure .

[0008] Specifically: 3.1) At room temperature, under nitrogen protection, the diamine compound is dissolved in a polar solvent and stirred until dissolved. To avoid a violent reaction that could cause gelation of the reaction solution and prevent the target analyte from reaching the designed molecular weight, commercially available diacid anhydride is added to the reaction solution in three batches, with an interval of 20-25 minutes between each addition. After the diacid anhydride is added in batches, an appropriate amount of solvent is added to make the solid content 10-30 wt%. The reaction solution is reacted at room temperature for 8-24 hours. Then, a capping agent with active end groups is added to the reaction solution, and the reaction is continued for 8-24 hours to prepare a polyimide acid solution. The molar ratio of the diamine compound, diacid anhydride, and capping agent is m+1:m:2, where m is 1-20.

[0009] 3.2) Add the dehydrating agent and catalyst to the polyimide acid solution for chemical imidization to dehydrate and cyclize the imide ring. React at 30-80 °C for 12-24 h. After the reaction, the product is settled in the cleaning agent at room temperature, filtered, washed and dried to obtain polyimide prepolymer powder. Vacuum dry at 150-200 °C for 24-48 h to obtain the dried target compound.

[0010] Furthermore, the polar solvent in step 3.1) includes one of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, and m-cresol, wherein N-methylpyrrolidone and N,N-dimethylacetamide are preferred. Furthermore, the dehydrating agent in step 3.2) includes one or more of acetic anhydride, propionic anhydride, and valeric anhydride, and the amount used is 3 to 9 times the molar number of the diamine compound added in step 3.1), wherein acetic anhydride is preferred; Furthermore, the catalyst in step 3.2) includes one or more of triethylamine, pyridine, and isoquinoline, and the amount used is 3 to 9 times the molar number of the diamine compound added in step 3.1), wherein triethylamine is preferred; Furthermore, the cleaning agent in step 3.2) is one or more of methanol, ethanol, deionized water, and acetone, and the amount used is 10-100 times the volume of the polar solvent used in step 3.1), with methanol and ethanol being preferred.

[0011] Compared with existing technologies, the beneficial effects of this invention are as follows: (1) The polyimide prepolymer containing silyl ether prepared by this invention has a high glass transition temperature after curing. Addressing the current shortcomings of poor processing performance of high-performance polymers, the polyimide prepolymer prepared by this invention, due to the introduction of a large-volume non-planar Cardo structure in its main chain, effectively reduces the polymer molecular chain packing density, decreases the intermolecular forces, and improves the solubility of the prepolymer, resulting in a final product with good solubility and a wide processing window. The introduction of silyl ether bonds in the main chain effectively increases the mobility of the polymer molecular chains, reduces the molecular chain packing density, and increases the solubility, processability, and toughness of the prepolymer after curing, while also exhibiting good adhesive properties. The introduction of groups such as benzene rings on the side chains hinders the rotation of the polymer molecular chains, increasing polymer solubility. The introduction of rigid structures further enhances heat resistance. The introduction of active polar groups on the side chains gives the polymer a certain degree of activity during high-temperature processes, enabling further reactions and improving heat resistance. This provides the possibility for the future preparation of high-performance composite materials and has practical application value. Attached Figure Description

[0012] Figure 1 The wide-angle X-ray diffraction pattern of PSI-1 in Example 1; Figure 2 The infrared spectrum of the diamine compound APFPS in Example 2; Figure 3 For example 2, the diamine compound APFPS 1 H-NMR; Figure 4 The infrared spectrum of the PSI-2 prepolymer in Example 2; Figure 5 The TGA diagram of the PSI-2 prepolymer in Example 2 is shown. Figure 6 The DSC diagram of the PSI-2 prepolymer in Example 2 is shown below. Figure 7 The wide-angle X-ray diffraction pattern of PSI-3 in Example 3; Figure 8 The image shows the TGA diagram of the PSI-3 prepolymer from Example 3. Detailed Implementation

[0013] The following are preferred embodiments of the present invention. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention. Furthermore, unless otherwise specified, all raw materials required in this invention are commercially available products well-known to those skilled in the art.

[0014] Example 1 A method for preparing a silicon-containing and Cardo structured polyimide resin includes the following steps: (1) Preparation of dinitro compounds: Under nitrogen protection, 7 g (0.02 mol) of 9,9-di(4-hydroxyphenyl)fluorene was dissolved in 40 ml of DMF. After the 9,9-di(4-hydroxyphenyl)fluorene was completely dissolved, the reaction solution was heated to 30 °C. Then, 0.968 ml (0.01 mol) of dichlorodimethylsilane was slowly added to the reaction solution. After the addition was complete, the reaction solution was kept at 12 h and the reaction was monitored. After the reaction was completed, 3.31 g (0.024 mol) of potassium carbonate was added to the reaction solution and stirred evenly. Then, 3.14 g (0.02 mol) of p-nitrochlorobenzene was added to the reaction solution and the reaction was kept at 110 °C for 24 h. After the reaction was completed, the reaction solution was cooled to room temperature, and the mixture was poured into a mixture of ethanol and water. After filtration and drying, 7.78 g of dinitro compound dimethylbis(4-{9-[4-(4-nitrophenoxy)phenyl]-9H-fluorene-9-yl}phenoxy)silane (DPFPS) was obtained, with a yield of 77.95%.

[0015] (2) Preparation of diamine compounds: In a 250 ml round-bottom three-necked flask, 9.98 g (0.01 mol) of DPFPS and 1.1 g (10 wt%) of palladium on carbon were added to 40 ml of stirred anhydrous ethanol. After the reaction solution was heated to 90 °C, 5 ml (0.1 mol) of hydrazine hydrate was slowly added dropwise to the reaction solution through a constant pressure funnel, and then the reaction solution was kept at this temperature for 6 h. After the reaction was complete, Pd / C was removed by filtration. After the reaction solution was cooled to room temperature, an appropriate amount of deionized water was added to the reaction solution, and a large amount of white precipitate was precipitated. The precipitate was washed with water, filtered, and dried in a vacuum oven to obtain 8.81 g of the diamine compound 4-{4-[9-(4-{[(4-{9-[4-(4-aminophenoxy)phenyl]-9H-fluoren-9-yl}phenoxy]dimethylsilyl]oxy}phenyl)-9H-fluoren-9-yl]phenoxy}aniline (APPDA), with a yield of 94%.

[0016] (3) Preparation of silicon- and Cardo structure polyimide prepolymer: Under nitrogen protection, 9.38 g (0.01 mol) APPDA and 66.33 g N-methylpyrrolidone were added to a 100 ml flask equipped with mechanical stirrer and thermometer to make the compound uniformly dispersed. Then, 1.74 g 3,3',pyromellitic dianhydride (0.008 mol) was added to the flask in three portions, with an interval of 20 min between each addition. Before adding the anhydride, it was necessary to ensure that the previous addition was completely dissolved. The flask was placed in an ice-water bath and stirred at room temperature for 24 h. Then, 0.993 g (0.004 mol) 4-phenylethynyl phthalic anhydride was added to the reaction solution. An appropriate amount of solvent was added to make the solid content of the system 10 wt%. The mixture was stirred at room temperature for 24 h to obtain a light yellow viscous polyamic acid (PAA) solution. 2.81 ml (0.03 mol) of acetic anhydride and 4.2 ml (0.03 mol) of triethylamine were added dropwise to initiate chemical imidization. The reaction mixture was then stirred at 30°C for 24 hours to obtain a polyimide solution. This polyimide solution was then poured into 700 ml of anhydrous ethanol (a cleaning agent) under stirring, allowed to settle, filtered, and dried in a vacuum drying oven at 180°C for 24 hours to obtain the polyimide prepolymer. In this embodiment, the molar ratio of the diamine compound, diacid anhydride, and end-capping agent is m+1:m:2, where m is 4.

[0017] In this embodiment, the R1 structure is as follows: The R2 structure is The R3 structure is -H; the R4 structure is -H; the R5 structure is -H. The polyimide prepolymer prepared in this embodiment exhibits good solubility and thermal stability, providing possibilities for the future preparation of composite materials. Specifically, its solubility is as follows: at room temperature, it is soluble in common dichloromethane, chloroform, m-cresol, N,N-dimethylformimide, N,N-dimethylacetylimide, N-methylpyrrolidone, and polar high-boiling-point solvents with a solubility greater than 20 mg / ml. It also exhibits good thermal stability; during heating, the unsaturated bonds can be further crosslinked, further improving its thermal properties, with a Td5% at 504.58℃.

[0018] Example 2 (1) Preparation of dinitro compounds: Under nitrogen protection, 10.51 g (0.03 mol) of 9,9-di(4-hydroxyphenyl)fluorene was dissolved in 40 ml of DMF. After the 9,9-di(4-hydroxyphenyl)fluorene was completely dissolved, the reaction solution was heated to 70 °C. Then, 2 ml (0.01 mol) of dichlorodiphenylsilane was slowly added to the reaction solution. After the addition was complete, the reaction solution was kept warm for 4 h and the reaction was monitored. After the reaction was completed, 6.21 g (0.045 mol) of potassium carbonate was added to the reaction solution and mixed evenly. Then, 6.48 g (0.045 mol) of p-nitrochlorobenzene was added to the reaction solution, the temperature was raised to 160 °C, and the reaction was kept warm for 12 h. After the reaction was completed, the reaction solution was cooled to room temperature, and the mixture was poured into a mixture of ethanol and water. After filtration and drying, 6.28 g of the dinitro compound bis(4-{9-[4-(4-nitrophenoxy)phenyl]-9H-fluoren-9-yl}phenoxy)diphenylsilane (BNFPS) was obtained, with a yield of 74%.

[0019] (2) Preparation of diamine compounds: In a 250 ml round-bottom three-necked flask, 11.22 g (0.01 mol) of BNFPS and 2.2 g (20 wt%) of palladium on carbon were added to 40 ml of stirred anhydrous ethanol. After the reaction solution was heated to 50 °C, 15 ml (0.3 mol) of hydrazine hydrate was slowly added dropwise to the reaction solution through a constant pressure funnel. The reaction solution was then kept at this temperature for 12 h. After the reaction was complete, Pd / C was removed by filtration. After the reaction solution was cooled to room temperature, an appropriate amount of deionized water was added to the reaction solution, and a large amount of white precipitate was precipitated. The precipitate was washed with water, filtered, and dried in a vacuum oven to obtain 9.78 g of the diamine compound 4-{4-[9-(4-{[(4-{9-[4-(4-aminophenoxy)phenyl]-9H-fluoren-9-yl}phenoxy]diphenylsilyl]oxy}phenyl)-9H-fluoren-9-yl]phenoxy}aniline (APFPS), with a yield of 92%.

[0020] (3) Preparation of silicon-containing and Cardo structure polyimide prepolymer: Under nitrogen protection, 10.62 g (0.01 mol) APFPS and 31.29 g N,N-dimethylacetamide were added to a 100 ml flask equipped with a mechanical stirrer and thermometer to make the compound uniformly dispersed. Then, 2.795 g 3,3',4,4'-biphenyltetracarboxylic anhydride (0.0095 mol) was added to the flask in three portions, with an interval of 25 min between each addition. Before adding the anhydride, it was necessary to ensure that the previous addition was completely dissolved. The flask was placed in an ice-water bath and stirred at room temperature for 8 h. Then, 0.248 g (0.001 mol) 4-phenylethynyl phthalic anhydride was added to the reaction solution. An appropriate amount of solvent was added to make the solid content of the system 30 wt%. The mixture was stirred at room temperature for 8 h to obtain a pale yellow viscous polyamic acid (PAA) solution. 11.52 ml (0.09 mol) of propionic anhydride and 7.23 ml (0.09 mol) of pyridine were added dropwise to carry out chemical imidization. The reaction solution was then stirred at 80 °C for 12 h to obtain a polyimide solution. This polyimide solution was then poured into 1600 ml of deionized water (a cleaning agent) under stirring, allowed to settle, filtered, and dried in a vacuum drying oven at 200 °C for 36 h to obtain the polyimide prepolymer. In this embodiment, the molar ratio of the diamine compound, diacid anhydride, and end-capping agent is m+1:m:2, where m is 19.

[0021] In this embodiment, the R1 structure is as follows: The R2 structure is The R3 structure is -H; the R4 structure is -H; the R5 structure is -H. The polyimide prepolymer prepared in this embodiment exhibits good solubility and thermal stability, providing possibilities for future composite material preparation. Specifically, its solubility is as follows: at room temperature, it is soluble in common dichloromethane, chloroform, m-cresol, N,N-dimethylformimide, N,N-dimethylacetylimide, N-methylpyrrolidone, and polar high-boiling-point solvents with a solubility greater than 25 mg / ml. It also demonstrates good thermal stability; during heating, the unsaturated bonds can be further crosslinked, further improving the thermal properties (Td). 5% At 542.6℃.

[0022] Example 3 (1) Preparation of dinitro compounds: Under nitrogen protection, 7 g (0.02 mol) of 9,9-di(4-hydroxyphenyl)fluorene was dissolved in 40 ml of DMF. After the 9,9-di(4-hydroxyphenyl)fluorene was completely dissolved, the reaction solution was heated to 50 °C. Then, 1.6 ml (0.008 mol) of dichlorodiphenylsilane was slowly added to the reaction solution. After the addition was complete, the reaction solution was kept warm for 8 h and the reaction was monitored. After the reaction was completed, 3.16 g (0.025 mol) of potassium carbonate was added to the reaction solution and mixed evenly. Then, 4.34 g (0.025 mol) of o-nitro-p-chlorophenol was added to the reaction solution, the temperature was raised to 135 °C, and the reaction was kept warm for 18 h. After the reaction was completed, the reaction solution was cooled to room temperature, and the mixture was poured into a mixture of ethanol and water. After filtration and drying, 7.27 g of the dinitro compound 5-{4-[9-(4-{[(4-{9-[4-(3-hydroxy-4-nitrophenoxy)phenyl]-9H-fluoren-9-yl}phenoxy)diphenylsilyl]oxy}phenyl)-9H-fluoren-9-yl]phenoxy}-2-nitrophenol (BNFPS-OH) was obtained, with a yield of 63%.

[0023] (2) Preparation of diamine compounds: In a 250 ml round-bottom three-necked flask, 11.54 g (0.01 mol) of BNFPS-OH and 1.73 g (15 wt%) of palladium on carbon were added to 40 ml of stirred anhydrous ethanol. After the reaction solution was heated to 70 °C, 10 ml (0.2 mol) of hydrazine hydrate was slowly added dropwise to the reaction solution through a constant pressure funnel. The reaction solution was then kept at this temperature for 9 h. After the reaction was complete, Pd / C was removed by filtration. After the reaction solution was cooled to room temperature, an appropriate amount of deionized water was added to the reaction solution, and a large amount of white precipitate was precipitated. The precipitate was washed with water, filtered, and dried in a vacuum oven to obtain the diamine compound 2-amino-5-{4-[9-(4-{[(4-{9-[4-(4-amino-3-hydroxyphenoxy)phenyl]-9H-fluorene-9-yl}phenoxy]diphenylsilyl]oxy}phenyl)-9H-fluorene-9-yl]phenoxy}phenol, with a yield of 92%.

[0024] (3) Preparation of silicon-containing polyimide prepolymer: Under nitrogen protection, 10.94 g (0.01 mol) APFPS-OH and 49.64 g m-cresol were added to a 100 ml flask equipped with a mechanical stirrer and thermometer to make the compound uniformly dispersed. Then, 1.47 g 3,3',4,4'-biphenyltetracarboxylic dianhydride (0.005 mol) was added to the flask in three portions, with an interval of 20 min between each addition. Before adding the anhydride, it was necessary to ensure that the previous addition was completely dissolved. The flask was placed in an ice-water bath and stirred at room temperature for 16 h. Then, 2.48 g (0.01 mol) 4-phenylethynyl phthalic anhydride was added to the reaction solution. An appropriate amount of solvent was added to make the solid content of the system 20 wt%. The mixture was stirred at room temperature for 16 h to obtain a pale yellow viscous polyamic acid (PAA) solution. 11.84 ml (0.06 mol) of valeric anhydride and 7.045 ml (0.06 mol) of isoquinoline were added dropwise to carry out chemical imidization. The reaction solution was then stirred at 55 °C for 18 h to obtain a polyimide solution. The polyimide solution was then poured into 1000 ml of stirred acetone, allowed to settle, filtered, and vacuum dried at 150 °C for 48 h to obtain the polyimide prepolymer.

[0025] In this embodiment, the molar ratio of the diamine compound, diacid anhydride, and capping agent is m+1:m:2, where m is 1.

[0026] In this embodiment, the R1 structure is as follows: The R2 structure is The structure of R3 is -H; the structure of R4 is -H; the structure of R5 is -OH. The polyimide prepolymer prepared in this embodiment exhibits good solubility and thermal stability, providing possibilities for the future preparation of composite materials. Specifically, its solubility is as follows: at room temperature, it is soluble in common dichloromethane, chloroform, m-cresol, N,N-dimethylformimide, N,N-dimethylacetylimide, N-methylpyrrolidone, and polar high-boiling-point solvents with a solubility greater than 30 mg / ml. It also exhibits good thermal stability; during heating, unsaturated bonds and active hydroxyl groups can further crosslink and rearrange, further improving thermal properties (Td). 5% At 504.58℃.

[0027] Example 4 (1) Preparation of dinitro compounds: Under nitrogen protection, 8.75 g (0.025 mol) of 9,9-di(4-hydroxyphenyl)fluorene was dissolved in 45 ml of DMF. After the 9,9-di(4-hydroxyphenyl)fluorene was completely dissolved, the reaction solution was heated to 40 °C. Then, 2.03 g (0.01 mol) of vinylphenyl dichlorosilane was added to the reaction solution. The reaction solution was kept at this temperature for 4 h, and the reaction was monitored. After the reaction was completed, 4.49 g (0.0325 mol) of potassium carbonate was added to the reaction solution and mixed evenly. Then, 5.12 g (0.0325 mol) of p-nitrochlorobenzene was added to the reaction solution, the temperature was raised to 150 °C, and the reaction was kept at this temperature for 14 h. After the reaction was completed, the reaction solution was cooled to room temperature, and the mixture was poured into a mixture of ethanol and water. After filtration and drying, 7.35 g of the dinitro compound vinylbis(4-{9-[4-(4-nitrophenoxy)phenyl]-9H-fluoren-9-yl}phenoxy)phenylsilane (EPPPS) was obtained, with a yield of 71%.

[0028] (2) Preparation of diamine compounds: In a 250 ml round-bottom three-necked flask, 10.72 g (0.01 mol) of EPPPS and 1.28 g (12 wt%) of palladium on carbon were added to 50 ml of stirred anhydrous ethanol. After the reaction solution was heated to 60 °C, 8 ml (0.16 mol) of hydrazine hydrate was slowly added dropwise to the reaction solution through a constant pressure funnel. The reaction solution was then kept at this temperature for 10 h. After the reaction was complete, Pd / C was removed by filtration. After the reaction solution was cooled to room temperature, an appropriate amount of deionized water was added to the reaction solution, and a large amount of white precipitate was precipitated. The precipitate was washed with water, filtered, and dried in a vacuum oven to obtain 9.78 g of the diamine compound 4-{4-[9-(4-{[(4-{9-[4-(4-aminophenoxy)phenyl]-9H-fluoren-9-yl}phenoxy](vinyl)phenylsilyl]oxy}phenyl)-9H-fluoren-9-yl]phenoxy}aniline (APPPA), with a yield of 92%.

[0029] (3) Preparation of silicon-containing and Cardo structure polyimide prepolymer: Under nitrogen protection, 10.62 g (0.0105 mol) APPPA and 92.26 g N,N-dimethylformamide were added to a 250 ml flask equipped with mechanical stirrer and thermometer to make the compound uniformly dispersed. Then, 3.22 g 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride (0.01 mol) was added to the flask in three portions, with an interval of 22 min between each addition. Before adding the anhydride, it was necessary to ensure that the previous addition was completely dissolved. The flask was placed in an ice-water bath and stirred at room temperature for 20 h. Then, 0.248 g (0.001 mol) 4-phenylethynyl phthalic anhydride was added to the reaction solution. An appropriate amount of solvent was added to make the solid content of the system 15 wt%. The mixture was stirred at room temperature for 18 h to obtain a light yellow viscous polyamic acid (PAA) solution. 10.24 ml (0.08 mol) of propionic anhydride and 6.42 ml (0.08 mol) of pyridine were added dropwise to carry out chemical imidization. The reaction solution was then stirred at 70°C for 15 h to obtain a polyimide solution. This polyimide solution was then poured into 900 ml of methanol (a cleaning agent) under stirring, allowed to settle, filtered, and dried in a vacuum drying oven at 170°C for 40 h to obtain the polyimide prepolymer. In this embodiment, the molar ratio of the diamine compound, diacid anhydride, and end-capping agent is m+1:m:2, where m is 20.

[0030] In this embodiment, the R1 structure is as follows: The R2 structure is The R3 structure is -H; the R4 structure is -H; the R5 structure is -H. The polyimide prepolymer prepared in this embodiment exhibits good solubility and thermal stability, providing possibilities for future composite material preparation. Specifically, its solubility is as follows: at room temperature, it is soluble in common dichloromethane, chloroform, m-cresol, N,N-dimethylformimide, N,N-dimethylacetylimide, N-methylpyrrolidone, and polar high-boiling-point solvents with a solubility greater than 30 mg / ml. It also exhibits good thermal stability; during heating, the unsaturated bonds can be further crosslinked, further improving the thermal properties (Td). 5% At 512.4℃.

[0031] Example 5 (1) Preparation of dinitro compounds: Under nitrogen protection, 14.07 g (0.028 mol) of 9,9-bis(3-phenyl-4-hydroxy)phenylfluorene was dissolved in 55 ml of DMF. After the 9,9-bis(3-phenyl-4-hydroxy)phenylfluorene was completely dissolved, the reaction solution was heated to 60 °C. Then, 2.03 g (0.01 mol) of vinylphenyl dichlorosilane was added to the reaction solution. The reaction solution was kept at this temperature for 10 h, and the reaction was monitored. After the reaction was completed, 5.417 g (0.0392 mol) of potassium carbonate was added to the reaction solution and mixed evenly. Then, 6.803 g (0.0392 mol) of o-nitro-p-chlorophenol was added to the reaction solution, the temperature was raised to 140 °C, and the reaction was kept at this temperature for 16 h. After the reaction was completed, the reaction solution was cooled to room temperature, and the mixture was poured into a mixture of ethanol and water. After filtration and drying, 9.8 g of the dinitro compound 5-{4-[9-(4-{[vinyl(4-{9-[4-(3-hydroxy-4-nitrophenoxy)-3-phenylphenyl]-9H-fluoren-9-yl}phenoxy)phenylsilyl]oxy}phenyl)-9H-fluoren-9-yl]-2-phenylphenoxy}-2-nitrophenol (EPPPN) was obtained, with a yield of 71%.

[0032] (2) Preparation of diamine compounds: In a 250 ml round-bottom three-necked flask, 12.56 g (0.01 mol) of EPPPN and 2.26 g (18 wt%) of palladium on carbon were added to 70 ml of stirred anhydrous ethanol. After the reaction solution was heated to 80 °C, 7 ml (0.14 mol) of hydrazine hydrate was slowly added dropwise to the reaction solution through a constant pressure funnel, and then the reaction solution was kept at this temperature for 7 h. After the reaction was complete, Pd / C was removed by filtration. After the reaction solution was cooled to room temperature, an appropriate amount of deionized water was added to the reaction solution, and a large amount of white precipitate was precipitated. The precipitate was washed with water, filtered, and dried in a vacuum oven to obtain 11.84 g of the diamine compound 4-{4-[9-(4-{[(4-{9-[4-(4-aminophenoxy)phenyl]-9H-fluoren-9-yl}phenoxy](vinyl)phenylsilyl]oxy}phenyl)-9H-fluoren-9-yl]phenoxy}aniline (EPPPN), with a yield of 90%.

[0033] (3) Preparation of silicon- and Cardo structured polyimide prepolymer: Under nitrogen protection, 13.16 g (0.011 mol) of EPPPN and 49.14 g of m-cresol were added to a 250 ml flask equipped with a mechanical stirrer and thermometer to make the compound uniformly dispersed. Then, 3.22 g of 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride (0.01 mol) was added to the flask in three portions, with an interval of 20 min between each addition. Before adding the anhydride, it was necessary to ensure that the previous addition was completely dissolved. The flask was placed in an ice-water bath and stirred at room temperature for 10 h. Then, 0.496 g (0.002 mol) of 4-phenylethynyl phthalic anhydride was added to the reaction solution. An appropriate amount of solvent was added to make the solid content of the system 25 wt%. The mixture was stirred at room temperature for 12 h to obtain a pale yellow viscous polyamic acid (PAA) solution. 3.76 ml (0.04 mol) of acetic anhydride and 5.6 ml (0.04 mol) of triethylamine were added dropwise to initiate chemical imidization. The reaction solution was then stirred at 40 °C for 20 h to obtain a polyimide solution. This polyimide solution was then poured into 2000 ml of ethanol (a cleaning agent) and stirred. After sedimentation, the solution was filtered and dried in a vacuum drying oven at 160 °C for 44 h to obtain the polyimide prepolymer. In this embodiment, the molar ratio of the diamine compound, diacid anhydride, and end-capping agent is m+1:m:2, where m is 10.

[0034] In this embodiment, the R1 structure is as follows: The R2 structure is The R3 structure is The R4 structure is -H; the R5 structure is -OH. The polyimide prepolymer prepared in this embodiment exhibits good solubility and thermal stability, providing possibilities for future composite material preparation. Specifically, its solubility is as follows: at room temperature, it is soluble in common dichloromethane, chloroform, m-cresol, N,N-dimethylformimide, N,N-dimethylacetylimide, N-methylpyrrolidone, and polar high-boiling-point solvents with a solubility greater than 40 mg / ml. It also exhibits good thermal stability; during heating, the unsaturated bonds can be further crosslinked, further improving the thermal properties (Td). 5% At 532.4℃.

[0035] Example 6 (1) Preparation of dinitro compounds: Under nitrogen protection, 14.07 g (0.024 mol) of 9,9-bis(3-phenyl-4-hydroxy)phenylfluorene was dissolved in 60 ml of DMF. After the 9,9-bis(3-phenyl-4-hydroxy)phenylfluorene was completely dissolved, the reaction solution was heated to 55 °C. Then, 1.915 g (0.01 mol) of dichloro-3-chloropropylmethylsilane was added to the reaction solution. The reaction solution was kept at this temperature for 9 h, and the reaction was monitored. After the reaction was completed, 4.81 g (0.0348 mol) of potassium carbonate was added to the reaction solution and mixed evenly. Then, 7.84 g (0.0348 mol) of 2-nitro-4-chlorotrifluorotoluene was added to the reaction solution, and the temperature was raised to 145 °C. The reaction was kept at this temperature for 15 h. After the reaction was completed, the reaction solution was cooled to room temperature, and the mixture was poured into a mixture of ethanol and water. After filtration and drying, 10.13 g of the dinitro compound (3-chloropropyl)(methyl)bis[4-(9-{4-[4-nitro-3-(trifluoromethyl)phenoxy]-3-phenylphenyl}-9H-fluorene-9-yl)phenoxy]silane (CPPPS) was obtained, with a yield of 76%.

[0036] (2) Preparation of diamine compounds: In a 250 ml round-bottom three-necked flask, 13.34 g (0.01 mol) of EPPPN and 1.86 g (14 wt%) of palladium on carbon were added to 80 ml of stirred anhydrous ethanol. After the reaction solution was heated to 55 °C, 9 ml (0.18 mol) of hydrazine hydrate was slowly added dropwise to the reaction solution through a constant pressure funnel. The reaction solution was then kept at this temperature for 11 h. After the reaction was complete, Pd / C was removed by filtration. After the reaction solution was cooled to room temperature, an appropriate amount of deionized water was added to the reaction solution, and a large amount of white precipitate was precipitated. The precipitate was washed with water, filtered, and dried in a vacuum oven to obtain 11.87 g of the diamine compound 4-(4-{9-[4-({[4-(9-{4-[4-[4-amino-3-(trifluoromethyl)phenoxy]-3-phenylphenyl}-9H-fluoren-9-yl)phenoxy](3-chloropropyl)methylsilyl}oxy)phenyl]-9H-fluoren-9-yl}-2-phenylphenoxy)-2-(trifluoromethyl)aniline (APCPA), with a yield of 89%.

[0037] (3) Preparation of silicon-containing and Cardo structure polyimide prepolymer: Under nitrogen protection, 13.63 g (0.0107 mol) APCPA and 111 g N,N-dimethylacetamide were added to a 250 ml flask equipped with a mechanical stirrer and thermometer to make the compound uniformly dispersed. Then, 4.44 g (0.01 mol) 4,4'-(hexafluoroisopropene) phthalic anhydride was added to the flask in three portions, with an interval of 23 min between each addition. Before adding the anhydride, it was necessary to ensure that the previous addition was completely dissolved. The flask was placed in an ice-water bath and stirred at room temperature for 18 h. Then, 0.3475 g (0.0014 mol) 4-phenylethynyl phthalic anhydride was added to the reaction solution. An appropriate amount of solvent was added to make the solid content of the system 14 wt%. The mixture was stirred at room temperature for 10 h to obtain a pale yellow viscous polyamic acid (PAA) solution. 10.57 ml (0.0535 mol) of valeric anhydride and 6.29 ml (0.0535 mol) of isoquinoline were added dropwise to carry out chemical imidization. The reaction solution was then stirred at 60 °C for 19 h to obtain a polyimide solution. This polyimide solution was then poured into 1200 ml of deionized water (a cleaning agent) under stirring, allowed to settle, filtered, and dried in a vacuum drying oven at 185 °C for 22 h to obtain the polyimide prepolymer. In this embodiment, the molar ratio of the diamine compound, diacid anhydride, and end-capping agent is m+1:m:2, where m is 15.

[0038] In this embodiment, the R1 structure is as follows: The R2 structure is The R3 structure is The R4 structure is -H; the R5 structure is -CF3. The polyimide prepolymer prepared in this embodiment exhibits good solubility and thermal stability, providing possibilities for the future preparation of composite materials. Specifically, its solubility is as follows: at room temperature, it is soluble in common dichloromethane, chloroform, m-cresol, N,N-dimethylformimide, N,N-dimethylacetylimide, N-methylpyrrolidone, and polar high-boiling-point solvents with a solubility greater than 35 mg / ml. It also exhibits good thermal stability; during heating, the unsaturated bonds can be further crosslinked, further improving the thermal properties (Td5%) at 494.5℃.

[0039] The embodiments described above are merely illustrative of the implementation methods of the present invention, but should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.

Claims

1. A polyimide prepolymer resin containing silicon and Cardo structure, characterized in that, The main chain chemical structure of the polyimide prepolymer resin is shown below: In its branched structure, R1 and R2 can be any of the following structures: , , , , , , , , , , , , , , The structures R1 and R2 can be the same or different; the branched structures R3, R4, and R5 can be any of the following structures: , , , , , , , , , , , The structures of R3, R4, and R5 can be the same or different; Its end-capping agent ER can be any one of the following structures: , , ; Ar in the main chain repeating unit can be any of the following structures: ， ， ， ， ， ， ， 。 2. The polyimide prepolymer resin containing silicon and Cardo structure according to claim 1, characterized in that, In the main chain chemical structure of the polyimide prepolymer resin: R1 and R2 structures are preferred. , , ; Preferred structures for R3, R4, and R5: , , , ; Preferred structure of end-capping agent ER: .

3. A method for preparing a polyimide prepolymer resin containing silicon and Cardo structure as described in claim 1 or 2, characterized in that, First, a mixture of a symmetrically structured diamine monomer containing silicon and Cardo structure, a symmetrically structured dianhydride monomer, and an active end-capping agent is polymerized in an organic solvent. Second, a thermosetting polyimide resin solution is obtained through dehydration and cyclization. Finally, post-treatment is performed to obtain the target product.

4. The method for preparing the polyimide prepolymer resin containing silicon and Cardo structure according to claim 3, characterized in that, The steps are as follows: Step 1: Preparation of symmetrically structured diamine monomers containing silicon and Cardo structures In an inert gas environment, using dichlorosilane, bisphenol fluorene, and p-nitrochlorobenzene compounds as raw materials, a silicon-containing and Cardo-structured dinitro compounds with symmetrical structures were prepared via the Williamson reaction. These compounds served as diamine monomers, and the reaction is as follows: Step 2: The nitro groups in the silicon-containing and Cardo-structured dinitro compound prepared in Step 1 are reduced to prepare a structurally symmetrical diamine compound, as shown in the following reaction: Step 3: Prepare a silicon-containing polyimide prepolymer by reacting the silicon-containing and Cardo-structured diamine compound prepared in Step 2 with a diacid anhydride containing a symmetrical structure, as follows: Wherein, the dicarboxylic acid anhydride Ar is any one of the following structures: pyromellitic dianhydride, 4,4′-biphenyl ether dianhydride, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, 2,3,3',4'-biphenyltetracarboxylic acid dianhydride, 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride, 4,4′-(hexafluoroisopropene) phthalic anhydride, and 3,3',4,4'-diphenylsulfone tetracarboxylic acid dianhydride; the end-capping agent ER is any one of the following structures: norbornene phthalic anhydride, m-ethynyl phthalic anhydride, and 4-phenylethynyl phthalic anhydride.

5. The method for preparing the polyimide prepolymer resin containing silicon and Cardo structure according to claim 4, characterized in that, The specific steps are as follows: Step 1: Under an inert gas atmosphere, bisphenol fluorene is added to an organic solvent. After the bisphenol fluorene dissolves, dichlorosilane is slowly added to the reaction solution, wherein the molar ratio of dichlorosilane to bisphenol fluorene is 1:2 to 1:

3. The reaction is maintained at 30 to 70°C for 4 to 12 hours. Then, potassium carbonate and p-nitrochlorobenzene are added to the reaction solution, wherein the molar ratio of bisphenol fluorene to potassium carbonate is 1:1.2 to 1:1.5, and the molar ratio of bisphenol fluorene to p-nitrochlorobenzene is 1:1 to 1:1.

5. The reaction is carried out at 110 to 160°C for 12 to 24 hours. After the reaction is completed, the mixture is cooled to room temperature, and ethanol is added to deionize the water to precipitate the product. After washing, a dinitro compound is obtained. Step 2: Dissolve the dinitro compound containing silicon and Cardo structure in anhydrous ethanol, add Pd / C, heat the solution to 50~90℃, slowly add hydrazine hydrate dropwise, and after the addition is complete, keep the reaction at this temperature for 6~12h. The mass ratio of Pd / C to dinitro compound is 1:5~1:10, and the molar ratio of hydrazine hydrate to dinitro compound is 5:1~15:

1. After the reaction is complete, filter while hot, then add ice-cold deionized water to the filtrate, stir, filter, wash with water, and dry to obtain diamine compound. Step 3: Preparation of silicon-containing polyimide prepolymer Step 3.1) At room temperature and under nitrogen protection, dissolve the diamine compound obtained in step 2 in a polar solvent, and add diacid anhydride to the reaction solution in multiple portions. After all the diacid anhydride has been added, add solvent to make the solid content 10-30 wt%. After the reaction solution reacts at room temperature for 8-24 hours, add a capping agent with active end groups to the reaction solution and react for 8-24 hours to prepare a polyimide acid solution; the molar ratio of the diamine compound, diacid anhydride, and capping agent is m+1:m:2, where m is 1-20. Step 3.2) Add the dehydrating agent and catalyst to the polyimide acid solution for chemical imidization to dehydrate and cyclize the imide ring. React at 30-80 °C for 12-24 h. After the reaction is complete, the product is precipitated in the cleaning agent at room temperature, filtered, washed and dried to obtain polyimide prepolymer powder, and then vacuum dried to obtain the target compound.

6. The method for preparing the polyimide prepolymer resin containing silicon and Cardo structure according to claim 5, characterized in that, In step 3.1), the dibasic anhydride is added to the reaction solution in three portions, with an interval of 20-25 minutes between each addition.

7. The method for preparing the polyimide prepolymer resin containing silicon and Cardo structure according to claim 5, characterized in that, The polar solvent in step 3.1) includes one of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, and m-cresol.

8. A method for preparing the polyimide prepolymer resin containing silicon and Cardo structure as described in claim 5, characterized in that, The dehydrating agent in step 3.2) includes one or more of acetic anhydride, propionic anhydride, and valeric anhydride, and the amount used is 3 to 9 times the molar number of the diamine compound in step 3.1).

9. The method for preparing the polyimide prepolymer resin containing silicon and Cardo structure according to claim 5, characterized in that, The catalyst in step 3.2) includes one or more of triethylamine, pyridine, and isoquinoline, and the amount used is 3 to 9 times the molar number of the diamine compound in step 3.1).

10. The method for preparing the polyimide prepolymer resin containing silicon and Cardo structure according to claim 5, characterized in that, In step 3.2): The cleaning agent is one or more of methanol, ethanol, deionized water, and acetone, and the amount used is 10-100 times the volume of the polar solvent used in step 3.1). The vacuum drying temperature is 150~200℃, and the time is 24~48h.

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