Copolymer modification preparation method of aerogel

Abstract

The invention belongs to the technical field of aerogel materials, and particularly relates to an aerogel copolymer modification preparation method which comprises the following steps: S1, pre-hydrolysis, S2, pH adjustment, S3, in-situ copolymerization and grafting, and S4, post-treatment. According to the preparation method, tetraethoxysilane is taken as a silicon source, KH-590 is taken as a silane coupling agent, butyl acrylate and the like are taken as monomers, ammonium persulfate-sodium hydrogen sulfite is taken as an initiator, the specific ratio and process parameters of the raw materials are controlled, and an organic-inorganic molecular interpenetrating network is constructed. In-situ chemical bonding of an organic phase and an inorganic phase is achieved through molecular design, a three-dimensional interpenetrating network structure is formed, the flexibility of the material is remarkably improved while low density, high specific surface area and low heat conductivity coefficient of the aerogel are kept, and the problems that the material is large in brittleness and fragile are solved.

Description

Technical Field

[0001] This invention relates to the field of aerogel materials technology, and more specifically to a method for preparing copolymer-modified aerogels. Background Technology

[0002] Aerogels, as materials with high porosity, low density, and excellent thermal insulation properties, are widely used in aerospace, construction, and environmental protection. However, traditional aerogels still have certain limitations in performance, especially in mechanical strength, toughness, and interfacial stability, making it difficult to meet the requirements of some high-performance applications. To overcome these shortcomings, in recent years, researchers have modified aerogels by combining them with organic materials to enhance their mechanical properties and thermal stability, thereby expanding their application areas and service life. Currently, aerogel modification methods mainly include organic-inorganic composites and surface functionalization, which can effectively improve the comprehensive performance of aerogels, such as enhancing their structural stability, improving thermal insulation efficiency, and improving flexibility and resilience. However, existing aerogel modification preparation methods still face problems such as complex reaction processes, weak material interfacial bonding, and poor performance stability, which restricts the production efficiency and product quality of modified aerogels.

[0003] Patent application CN202111024795.6 discloses a method for preparing in-situ fluorinated modified superhydrophobic flexible silica aerogel. This aerogel uses fluorosilanes and organosilanes as silicon sources, and alcohols and deionized water as solvents. It employs a two-step acid-base catalytic method, mixing the components in a specific ratio. The mixture undergoes in-situ fluorination modification, sol-gel process, solvent replacement, and aging. Finally, the sample is dried using supercritical carbon dioxide drying to obtain an in-situ fluorinated modified superhydrophobic flexible silica aerogel material. However, fluorosilanes (such as perfluorodecyltriethoxysilane) have long fluorocarbon chains, resulting in high steric hindrance and low reactivity, making it difficult for them to fully participate in network cross-linking. Therefore, when the material is under stress, there is no effective stress transfer path at the interface, making it prone to microcrack propagation. Patent application CN202110599140.5 discloses a silica nanofiber / polyimide composite aerogel, its preparation method, and its application. This invention solves the technical problems of existing silica aerogels being brittle and lacking flexibility. The silica nanofiber / polyimide composite aerogel provided by this invention features an interwoven three-dimensional network structure of silica nanofibers, with effective adhesion formed by polyimide cross-linking between the fibers. The silica nanofiber membrane used in this scheme is prepared by electrospinning to obtain a silicon source precursor / polymer hybrid fiber membrane, which is then calcined. However, after high-temperature calcination, the number of silanol groups on the surface of the silica nanofibers is significantly reduced. The polyimide only bonds the fibers through physical coating and cross-linking, with no strong covalent bond between them. The interfacial interaction is mainly based on weak hydrogen bonds and van der Waals forces, resulting in low bonding strength and an inability to form a stable interpenetrating structure. When the material is under stress, the stress cannot be effectively transferred through the interface, making it prone to breakage at interfacial defects.

[0004] Therefore, developing a copolymer modification preparation method that is simple, highly reproducible, can achieve a tight bond between the organic and inorganic interfaces, and can simultaneously take into account the thermal insulation and mechanical properties of aerogels has become an urgent technical problem to be solved in the field of aerogel preparation. Summary of the Invention

[0005] To address the aforementioned issues, this invention provides a copolymer modification preparation method for aerogels. Step S1 involves pre-embedding polymerizable active sites in silica sol; step S2 involves precisely controlling the acid-base environment of the reaction system; step S3 involves achieving in-situ free radical copolymerization and chemical grafting of organic monomers; and step S4 involves strengthening and gently drying the hybrid network. Ultimately, an organic-inorganic hybrid aerogel with low density, high porosity, excellent thermal insulation properties, high resilience, and resistance to repeated folding is obtained.

[0006] The technical solution of the present invention to solve the above problems is as follows: A method for preparing copolymer-modified aerogel includes the following steps: S1. Pre-hydrolysis: The silicon source is mixed with a mixed solvent, then the mixture is adjusted to acidity, a silane coupling agent is added, and a pre-hydrolysis reaction is carried out at 30±2℃ for 50-70 min to obtain a pre-modified silica sol. S2. pH adjustment: Adjust the pH value of the silica sol obtained in step S1 to 5.7-6.0; S3. In-situ copolymerization and grafting: Initiator solution and an anhydrous ethanol solution containing monomer 1, monomer 2 and monomer 3 are added sequentially to the silica sol after adjustment in step S2. The polymerization reaction is carried out at 60-70℃ for 6-8 hours under an inert atmosphere to form a hybrid wet gel. S4. Post-processing: The hybrid wet gel obtained in step S3 is subjected to aging, solvent replacement and drying in sequence to obtain aerogel.

[0007] Further, the mass ratio of the silicon source, mixed solvent, and silane coupling agent in step S1 is 100:190-210:1.7-2.3.

[0008] Further, the mixed solvent in step S1 is composed of anhydrous ethanol and deionized water in a mass ratio of 8:11.5-12.5.

[0009] Furthermore, the silicon source mentioned in step S1 is tetraethyl orthosilicate.

[0010] Furthermore, the silane coupling agent mentioned in step S1 is KH-590.

[0011] Further, in step S3, the mass ratio of monomer 1, monomer 2, monomer 3, initiator solid, and silicon source in step S1 is 11.7-12.3:4.8-5.2:0.8-1.2:0.045-0.055:100, and the mass ratio of monomer 1 and anhydrous ethanol is 12:10-15.

[0012] Further, in step S3, monomer 1, monomer 2, and monomer 3 are butyl acrylate, polyethylene glycol monomethyl ether acrylate, and ethylene glycol dimethacrylate, respectively.

[0013] Further, the initiator solution in step S3 is composed of ammonium persulfate solution and sodium bisulfite solution, wherein the mass ratio of ammonium persulfate to sodium bisulfite is 0.025-0.035:0.02.

[0014] Furthermore, the aging process described in step S4 is 18-24 hours at 65±2℃.

[0015] Furthermore, the solvent replacement in step S4 uses anhydrous ethanol.

[0016] The present invention has the following beneficial effects: This invention constructs an organic-inorganic covalently bonded interpenetrating network aerogel system through a four-step synergistic design: pre-hydrolysis, pH adjustment, in-situ copolymerization, and post-treatment. This significantly improves the toughness and durability of the material while maintaining the aerogel's low density, high specific surface area, and low thermal conductivity. Step S1 involves pre-embedding thiol chain transfer sites on the silicon-oxygen framework through acidic pre-hydrolysis, controlling hydrolysis kinetics to ensure framework support and pore structure uniformity, and laying the molecular-level reaction foundation for subsequent chemical anchoring. Step S2 precisely adjusts the pH to the 5.7-6.0 range, activating the redox initiator and achieving a precise match between the free radical generation rate and the silanol polycondensation rate. This allows for the simultaneous construction of the inorganic-organic dual network, avoiding phase separation and providing a suitable reaction environment for in-situ copolymerization and grafting. Step S3 relies on the active sites pre-embedded in step S1 and... The S2-controlled optimized system utilizes the thiol chain transfer effect to in-situ polymerize and graft a three-monomer system of butyl acrylate, polyethylene glycol monomethyl ether acrylate, and ethylene glycol dimethacrylate. The cross-linked polymer chains are chemically anchored to the silicon framework via CS covalent bonds. The three monomers synergistically enhance each other. Ethyl glycol dimethacrylate acts as a cross-linking agent to construct a three-dimensional polymer network framework, providing rigid support and structural stability. Butyl acrylate, through its long-chain alkyl side chains, imparts intrinsic flexibility to the material, allowing the chain segments to conformate and dissipate stress under pressure, significantly improving resilience. In a sol-gel system, polyethylene glycol segments of polyethylene glycol monomethyl ether acrylate are pre-adsorbed and dispersed with silanol groups. During the aging stage, the terminal hydroxyl groups further form hydrogen bonds and dynamic Si-OC bonds with the silanol groups, thereby constructing an interpenetrating network structure at the nanoscale. This significantly enhances interfacial toughness, dissipates stress concentration, and endows the material with excellent resilience and resistance to crack propagation during folding. Ethylene dimethacrylate prevents plastic flow, butyl acrylate provides energy dissipation, and polyethylene glycol monomethyl ether acrylate strengthens interfacial compatibility, ultimately constructing an interpenetrating network structure that enables the aerogel to... While maintaining high porosity and low density, it also possesses excellent flexibility, high resilience, and folding fatigue resistance, completely solving the problems of brittle cracking and performance degradation caused by weak interfacial bonding in traditional aerogels. Step S4, the post-treatment, through the synergistic operation of aging, solvent replacement, and supercritical drying, eliminates interfacial tension, solidifies the interpenetrating network structure, improves the inorganic framework, and retains porous characteristics, compensating for minor defects in the previous reactions. Ultimately, it achieves the comprehensive excellent properties of aerogels, including low density, high porosity, high specific surface area, low thermal conductivity, high resilience, and high folding resistance. The four steps are interconnected and indispensable, elevating the physical blending modification of traditional aerogels to synergistic enhancement through chemical bonding. While maintaining lightweight and porous characteristics, it fundamentally solves the technical bottlenecks of high brittleness, easy cracking, and poor interfacial compatibility. The aerogels prepared by controlling the monomer ratio possess high flexibility, high resilience, and compressibility, ultimately endowing the aerogels with low density, high porosity, high specific surface area, excellent thermal insulation, and outstanding flexibility and elastic recovery ability. Attached Figure Description

[0017] Figure 1 The graph shows the porosity and resilience test results of the aerogels prepared in Examples 1-3 and Comparative Examples 1-5. Figure 2 The graph shows the specific surface area test results of the aerogels prepared in Examples 1-3 and Comparative Examples 1-5. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] All raw materials used in the following examples are commercially available products. Polyethylene glycol monomethyl ether acrylate (PEG) has an active ingredient content of 99% and a molecular weight of 480; it is manufactured by Wuhan Lanabai Pharmaceutical Chemical Co., Ltd. Example 1

[0020] A method for preparing copolymer-modified aerogel includes the following steps: S1. Pre-hydrolysis: Tetraethyl orthosilicate was mixed with a mixed solvent, and the pH was adjusted to 4.0±0.1 with 0.1M hydrochloric acid solution. Silane coupling agent KH-590 was added, and the pre-hydrolysis reaction was carried out at 28℃ for 50 min to obtain a pre-modified silica sol. The mass ratio of tetraethyl orthosilicate, mixed solvent, and silane coupling agent KH-590 was 100:190:1.7. The mixed solvent consisted of anhydrous ethanol and deionized water in a mass ratio of 8:11.5. S2. pH adjustment: Adjust the pH of the silica sol obtained in step S1 to 5.7-6.0 using 0.1M ammonia solution; S3. In-situ copolymerization and grafting: Ammonium persulfate solution and sodium bisulfite solution are added sequentially to the silica sol adjusted in step S2. Then, anhydrous ethanol solution containing monomers 1, 2, and 3 is added dropwise at a rate of 0.5 mL / min. The polymerization reaction is carried out at 60 °C for 6 h under a nitrogen atmosphere to form a hybrid wet gel. The mass ratio of monomers 1, 2, 3, solid initiator, and silicon source in step S1 is 11.7:4.8:0.8:0.045:100. The mass ratio of monomer 1 to anhydrous ethanol is 12:10. Monomers 1, 2, and 3 are butyl acrylate, polyethylene glycol monomethyl ether acrylate, and ethylene glycol dimethacrylate, respectively. The initiator solution is composed of ammonium persulfate solution and sodium bisulfite solution, with a mass ratio of ammonium persulfate to sodium bisulfite of 0.025:0.02. S4. Post-treatment: The hybrid wet gel obtained in step S3 was aged at 63℃ for 18h; the aged wet gel was taken out and completely immersed in anhydrous ethanol for solvent replacement. The anhydrous ethanol was replaced every 12h until the replaced anhydrous ethanol did not turn blue when tested with anhydrous copper sulfate; the gel after solvent replacement was placed in a supercritical carbon dioxide drying kettle, and the anhydrous ethanol was replaced three times by circulating liquid carbon dioxide at 5MPa and 15℃. Then the temperature was raised to 35℃ and the pressure was raised to 10MPa. This condition was maintained for 5h. Finally, the pressure was slowly and uniformly released to atmospheric pressure and the temperature was lowered to room temperature to obtain the aerogel. Example 2

[0021] A method for preparing copolymer-modified aerogel includes the following steps: S1. Pre-hydrolysis: Tetraethyl orthosilicate is mixed with a mixed solvent, and then the pH value is adjusted to 4.0±0.1 with 0.1M hydrochloric acid solution. Silane coupling agent KH-590 is added, and the pre-hydrolysis reaction is carried out at 30℃ for 60 min to obtain pre-modified silica sol. The mass ratio of tetraethyl orthosilicate, mixed solvent, and silane coupling agent KH-590 is 100:200:2. The mixed solvent is composed of anhydrous ethanol and deionized water in a mass ratio of 8:12. S2. pH adjustment: Adjust the pH of the silica sol obtained in step S1 to 5.7-6.0 using 0.1M ammonia solution; S3. In-situ copolymerization and grafting: Ammonium persulfate solution and sodium bisulfite solution are added sequentially to the silica sol adjusted in step S2. Then, an anhydrous ethanol solution containing monomer 1, monomer 2 and monomer 3 is added dropwise at a rate of 0.5 mL / min. The polymerization reaction is carried out at 65 °C for 7 h under a nitrogen atmosphere to form a hybrid wet gel. The mass ratio of monomer 1, monomer 2, monomer 3, initiator solid and silicon source in step S1 is 12:5:1:0.05:100. The mass ratio of monomer 1 and anhydrous ethanol is 12:12. Monomer 1, monomer 2 and monomer 3 are butyl acrylate, polyethylene glycol monomethyl ether acrylate and polyethylene glycol dimethacrylate, respectively. The initiator solution is composed of ammonium persulfate solution and sodium bisulfite solution. The mass ratio of ammonium persulfate to sodium bisulfite is 0.03:0.02. S4. Post-treatment: The hybrid wet gel obtained in step S3 is aged at 65°C for 20 hours; the aged wet gel is taken out and completely immersed in anhydrous ethanol for solvent replacement. The anhydrous ethanol is replaced every 12 hours until the replaced anhydrous ethanol does not turn blue when tested with anhydrous copper sulfate; the gel after solvent replacement is placed in a supercritical carbon dioxide drying kettle, and the anhydrous ethanol is replaced three times by circulating liquid carbon dioxide at 5 MPa and 15°C. Then the temperature is raised to 35°C and the pressure is increased to 10 MPa. This condition is maintained for 5 hours. Finally, the pressure is slowly and uniformly released to atmospheric pressure and the temperature is lowered to room temperature to obtain the aerogel. Example 3

[0022] A method for preparing copolymer-modified aerogel includes the following steps: S1. Pre-hydrolysis: Tetraethyl orthosilicate was mixed with a mixed solvent, and the pH was adjusted to 4.0±0.1 with 0.1M hydrochloric acid solution. Silane coupling agent KH-590 was added, and the pre-hydrolysis reaction was carried out at 32℃ for 70 min to obtain a pre-modified silica sol. The mass ratio of tetraethyl orthosilicate, mixed solvent, and silane coupling agent KH-590 was 100:210:2.3. The mixed solvent consisted of anhydrous ethanol and deionized water in a mass ratio of 8:12.5. S2. pH adjustment: Adjust the pH of the silica sol obtained in step S1 to 5.7-6.0 using 0.1M ammonia solution; S3. In-situ copolymerization and grafting: Ammonium persulfate solution and sodium bisulfite solution are added sequentially to the silica sol adjusted in step S2. Then, an anhydrous ethanol solution containing monomers 1, 2, and 3 is added dropwise at a rate of 0.5 mL / min. The polymerization reaction is carried out at 70 °C for 8 h under a nitrogen atmosphere to form a hybrid wet gel. The mass ratio of monomers 1, 2, 3, solid initiator, and silicon source in step S1 is 12.3:5.2:1.2:0.055:100. The mass ratio of monomer 1 to anhydrous ethanol is 12:15. Monomers 1, 2, and 3 are butyl acrylate, polyethylene glycol monomethyl ether acrylate, and ethylene glycol dimethacrylate, respectively. The initiator solution is composed of ammonium persulfate solution and sodium bisulfite solution, with a mass ratio of ammonium persulfate to sodium bisulfite of 0.035:0.02. S4. Post-treatment: The hybrid wet gel obtained in step S3 was aged at 67°C for 24 hours; the aged wet gel was taken out and completely immersed in anhydrous ethanol for solvent replacement. The anhydrous ethanol was replaced every 12 hours until the replaced anhydrous ethanol did not turn blue when tested with anhydrous copper sulfate; the gel after solvent replacement was placed in a supercritical carbon dioxide drying vessel, and the anhydrous ethanol was replaced three times with liquid carbon dioxide at 5 MPa and 15°C. Then the temperature was raised to 35°C and the pressure was raised to 10 MPa. This condition was maintained for 5 hours. Finally, the pressure was slowly and uniformly released to atmospheric pressure and the temperature was lowered to room temperature to obtain the aerogel.

[0023] Comparative Example 1 A method for preparing copolymer-modified aerogel includes the following steps: S1. Pre-hydrolysis: Tetraethyl orthosilicate is mixed with a mixed solvent, and then the pH value is adjusted to 4.0±0.1 with 0.1M hydrochloric acid solution. Silane coupling agent KH-590 is added, and the pre-hydrolysis reaction is carried out at room temperature for 70 min to obtain pre-modified silica sol. The mass ratio of tetraethyl orthosilicate, mixed solvent, and silane coupling agent KH-590 is 100:210:1. The mixed solvent is composed of anhydrous ethanol and deionized water in a mass ratio of 1:1. S2. pH adjustment: Adjust the pH of the silica sol obtained in step S1 to 5.7-6.0 using 0.1M ammonia solution; S3. In-situ copolymerization and grafting: Ammonium persulfate solution and sodium bisulfite solution are added sequentially to the silica sol adjusted in step S2. Then, an anhydrous ethanol solution containing monomers 1, 2, and 3 is added dropwise at a rate of 0.5 mL / min. The polymerization reaction is carried out at 30 °C for 8 h under a nitrogen atmosphere to form a hybrid wet gel. The mass ratio of monomers 1, 2, 3, solid initiator, and silicon source in step S1 is 12.3:5.2:1.2:0.01:100. The mass ratio of monomer 1 to anhydrous ethanol is 12:15. Monomers 1, 2, and 3 are butyl acrylate, polyethylene glycol monomethyl ether acrylate, and ethylene glycol dimethacrylate, respectively. The initiator solution is composed of ammonium persulfate solution and sodium bisulfite solution, with a mass ratio of ammonium persulfate to sodium bisulfite of 0.01:0.02. S4. Post-treatment: The hybrid wet gel obtained in step S3 is aged at 30°C for 24 hours; the aged wet gel is taken out and completely immersed in anhydrous ethanol for solvent replacement. The anhydrous ethanol is replaced every 12 hours until the replaced anhydrous ethanol does not turn blue when tested with anhydrous copper sulfate; the gel after solvent replacement is placed in a supercritical carbon dioxide drying kettle, and the anhydrous ethanol is replaced three times by circulating liquid carbon dioxide at 5 MPa and 15°C. Then the temperature is raised to 35°C and the pressure is increased to 10 MPa. This condition is maintained for 5 hours. Finally, the pressure is slowly and uniformly released to atmospheric pressure and the temperature is lowered to room temperature to obtain an aerogel.

[0024] Comparative Example 2 A method for preparing copolymerized aerogel, wherein step S1 does not involve the addition of silane coupling agent KH-590, and all other steps are the same as in Example 1.

[0025] Comparative Example 3 A method for preparing copolymer-modified aerogel, omitting step S2, is identical to that in Example 1.

[0026] Comparative Example 4 A method for preparing copolymer-modified aerogel, wherein step S3 does not include monomer 2, namely polyethylene glycol monomethyl ether acrylate, and the rest is the same as in Example 1.

[0027] Comparative Example 5 A method for preparing copolymerized aerogel, wherein silane coupling agent KH-590 is not added in step S1, step S2 is omitted, and monomers 1 (butyl acrylate), 2 (polyethylene glycol monomethyl ether acrylate), and 3 (ethylene glycol dimethacrylate) are not added in step S3, and the rest are the same as in Example 1.

[0028] Performance testing Specific surface area: Tested according to the requirements of GB / T 19587-2017 "Determination of specific surface area of ​​solid substances by gas adsorption BET method".

[0029] Thermal conductivity: Tested according to the requirements of GB / T 10294-2008 "Determination of steady-state thermal resistance and related properties of thermal insulation materials - protective hot plate method".

[0030] Compressibility: When preparing the test sample, the gelation process should take place in a cylindrical container with a diameter of 20 mm and a height of 30 mm. The experiment adopts the compression method. A universal testing machine is used with a compression rate of 2 mm / min to compress the test sample to 40%. After that, the load is removed and the test sample is allowed to recover before the rebound rate is measured.

[0031] Flexibility: Using a universal testing machine, a sample with a length of 60mm, a width of 15mm, and a thickness of 10mm is clamped with a fixture with a rubber pad. The initial spacing of the fixture is adjusted to 30mm. The fixture is controlled to move back and forth periodically with an amplitude of ±5mm at a rate of 10mm / min. One stretching and compression process is considered as one fold. The test is repeated until the sample is damaged, and the number of folds is recorded.

[0032] The performance test results are shown in Table 1. Figure 1-2 As shown.

[0033] Table 1 Performance Test Results

[0034] From Table 1 and Figure 1 , 2 As can be seen, compared with the embodiments, the various properties of the aerogel in Comparative Example 1 have decreased. This is because Comparative Example 1 deviates from the core process parameters of this technical solution. The deviation of the key process parameters makes it impossible for the synergistic effect of each step such as pre-hydrolysis, copolymerization, and aging to be exerted, and it is impossible to construct a stable organic-inorganic three-dimensional interpenetrating network, thereby causing the degradation of various properties.

[0035] From Table 1 and Figure 1 , 2As can be seen, compared with the examples, the properties of the aerogel in Comparative Example 2 all decreased. This is because Comparative Example 2 did not add the silane coupling agent KH-590, which prevented the organic polymer chains from forming CS covalent bonds with the inorganic framework through the thiol chain transfer reaction. The interface relied solely on physical adsorption, resulting in extremely poor interfacial compatibility. The organic chains were prone to agglomeration, which destroyed the uniformity of the porous network. At the same time, the interfacial bonding force was greatly weakened, making it impossible to achieve effective stress transfer. This led to the failure of the stability and mechanical enhancement effect of the hybrid structure. The weak bonding force also caused a large amount of organic phase to be lost during drying and solvent replacement, resulting in the disintegration of the hybrid structure. Ultimately, this led to a decline in various properties, namely, the density increased due to phase separation, the porosity decreased due to pore collapse, the specific surface area decreased due to the excessively large microphase size, the thermal conductivity increased due to the increased heat transfer path in the solid phase, and the resilience and folding number deteriorated sharply due to the unstable interface and the inability to effectively transfer stress.

[0036] From Table 1 and Figure 1 , 2 As can be seen, compared with the examples, the properties of the aerogel in Comparative Example 3 all decreased. This is because the pH adjustment step was omitted in Comparative Example 3. On the one hand, when the polymerization was initiated under acidic conditions, the initiation efficiency of ammonium persulfate-sodium bisulfite decreased significantly, and the low monomer conversion rate prevented the effective formation of the organic network, thus losing its support and toughening effect on the porous structure. On the other hand, the strongly acidic environment caused excessive hydrolysis and rapid condensation of the silicon source, forming dense inorganic agglomerates and destroying the integrity of the porous structure. The low monomer polymerization efficiency and excessive condensation of the silicon source resulted in uneven pore structure, increased density, decreased porosity, reduced specific surface area due to the accumulation between inorganic particles, increased thermal conductivity due to uneven pore size distribution, and significantly reduced resilience and folding times due to discontinuous organic phase and insufficient skeletal support.

[0037] From Table 1 and Figure 1 , 2 It can be seen that, compared with the examples, the properties of the aerogel in Comparative Example 4 are all reduced. This is because Comparative Example 4 did not add monomer 2, namely polyethylene glycol monomethyl ether acrylate, resulting in a lack of flexible thermoplastic segments in the organic phase. Only rigid butyl acrylate and ethylene glycol dimethacrylate are retained, which cannot dissipate energy through conformational transformation and molecular chain slip. The toughness of the hybrid aerogel material is significantly reduced. The lack of energy dissipation mechanism causes stress concentration at the crack tip. The resilience and folding number are reduced due to insufficient flexibility. The density is slightly increased due to the increase in the rigidity of the organic phase. The porosity and specific surface area do not change much due to the reduced phase separation. The thermal conductivity increases due to the density difference of the organic phase.

[0038] From Table 1 and Figure 1 , 2As can be seen, compared with the examples, the aerogel of Comparative Example 5 exhibited the worst performance. This is because Comparative Example 5 lacked the silane coupling agent KH-590, omitted step S2, and had no organic monomers involved. Specifically, the absence of organic monomers prevented the construction of the three-dimensional organic network, thus failing to achieve the toughening modification effect of the aerogel. Furthermore, pure silicon-based aerogels inherently possess brittleness, and their rigid siloxane skeleton lacks stress buffering capacity, making them prone to brittle fracture failure. The absence of the silane coupling agent resulted in the loss of the covalent grafting "molecular bridge" effect between the organic and inorganic phases, completely eliminating the interfacial bonding effect and resulting in extremely low interfacial compatibility. The omission of the pH adjustment step triggered redox-induced system deactivation, excessive hydrolysis of the silicon source, and rapid condensation, ultimately forming a dense inorganic bulk structure, which in turn destroyed the core characteristic of the porous structure of the aerogel. The synergistic effect of these multiple mechanistic defects led to the complete failure of the organic-inorganic hybrid system, resulting in a severe decline in the various properties of the prepared aerogel.

[0039] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing copolymer-modified aerogel, characterized in that, Includes the following steps: S1. Pre-hydrolysis: The silicon source is mixed with a mixed solvent, then the mixture is adjusted to acidity, a silane coupling agent is added, and a pre-hydrolysis reaction is carried out at 30±2℃ for 50-70 min to obtain a pre-modified silica sol. S2. pH adjustment: Adjust the pH value of the silica sol obtained in step S1 to 5.7-6.0; S3. In-situ copolymerization and grafting: Initiator solution and an anhydrous ethanol solution containing monomer 1, monomer 2 and monomer 3 are added sequentially to the silica sol after adjustment in step S2. The polymerization reaction is carried out at 60-70℃ for 6-8 hours under an inert atmosphere to form a hybrid wet gel. S4. Post-processing: The hybrid wet gel obtained in step S3 is subjected to aging, solvent replacement and drying in sequence to obtain aerogel.

2. The method for preparing copolymer-modified aerogel according to claim 1, characterized in that, The mass ratio of silicon source, mixed solvent and silane coupling agent in step S1 is 100:190-210:1.7-2.

3.

3. The method for preparing copolymer-modified aerogel according to claim 1, characterized in that, The mixed solvent in step S1 is composed of anhydrous ethanol and deionized water in a mass ratio of 8:11.5-12.

5.

4. The method for preparing copolymer-modified aerogel according to claim 1, characterized in that, The silicon source mentioned in step S1 is tetraethyl orthosilicate.

5. The method for preparing copolymer-modified aerogel according to claim 1, characterized in that, The silane coupling agent mentioned in step S1 is KH-590.

6. The method for preparing copolymer-modified aerogel according to claim 1, characterized in that, In step S3, the mass ratio of monomer 1, monomer 2, monomer 3, initiator solid, and silicon source in step S1 is 11.7-12.3:4.8-5.2:0.8-1.2:0.045-0.055:100, and the mass ratio of monomer 1 and anhydrous ethanol is 12:10-15.

7. The method for preparing copolymer-modified aerogel according to claim 1, characterized in that, In step S3, monomer 1, monomer 2, and monomer 3 are butyl acrylate, polyethylene glycol monomethyl ether acrylate, and ethylene glycol dimethacrylate, respectively.

8. The method for preparing copolymer-modified aerogel according to claim 1, characterized in that, The initiator solution in step S3 is composed of ammonium persulfate solution and sodium bisulfite solution, wherein the mass ratio of ammonium persulfate to sodium bisulfite is 0.025-0.035:0.

02.

9. The method for preparing copolymer-modified aerogel according to claim 1, characterized in that, The aging process described in step S4 is 18-24 hours at 65±2℃.

10. The method for preparing copolymer-modified aerogel according to claim 1, characterized in that, The solvent replacement in step S4 uses anhydrous ethanol.

Images