A natural polymer conductive aerogel and its preparation method

Abstract

The present invention discloses a natural polymer conductive aerogel and a preparation method thereof, relating to the technical field of conductive aerogels. When preparing the natural polymer conductive aerogel of the present invention, modified nanocellulose is first made into a wet gel, and then freeze-dried together with ammonium bicarbonate to make an aerogel. Finally, a carbonization process is carried out in a mixed gas atmosphere of nitrogen and hydrogen to make the natural polymer conductive aerogel; the modified nanocellulose wet gel is that microcrystalline cellulose is wrapped by long chains of α,ω-dihydroxydimethylsiloxane oligomers and has a three-dimensional network structure; the natural polymer conductive aerogel prepared by the present invention not only has good toughness, but also has strong adsorption capacity.

Description

Technical Field

[0001] The present invention relates to the technical field of conductive aerogels, and particularly to a natural polymer conductive aerogel and a preparation method thereof. Background Technique

[0002] Carbon aerogel is a new type of porous carbon material, a nanoscale porous amorphous material discovered by Pekala et al. in 1989, which is obtained by high-temperature carbonization of aerogel. After high-temperature carbonization of low-density, low-thermal-conductivity and network-structured organic aerogel, the obtained aerogel not only retains the porous network structure of the organic aerogel, but also endows it with excellent electrical conductivity.

[0003] CN201610605988 discloses a modified chitosan / nanocellulose composite aerogel and its preparation method and application. First, chitosan is sulfur-modified to obtain modified chitosan, and then it is compounded with nanocellulose to prepare a sulfur-containing modified chitosan / nanocellulose composite porous aerogel. Although the adsorption effect is good, the obtained product does not have electrical conductivity and has poor toughness.

[0004] For the conductive aerogel prepared by carbonizing natural polymer aerogel, although the porosity is high, the pores are often large. Even with electrostatic adsorption, the adsorption effect of natural polymer aerogel cannot be fully developed. In order to improve the adsorption efficiency, the present application studies and prepares a natural polymer conductive aerogel with high toughness and strong adsorption capacity. Summary of the Invention

[0005] The purpose of the present invention is to provide a natural polymer conductive aerogel and a preparation method thereof to solve the problems raised in the above background technique.

[0006] A preparation method of a natural polymer conductive aerogel, the preparation method of the natural polymer conductive aerogel successively includes: preparation of modified nanocellulose wet gel, preparation of aerogel, and preparation of natural polymer conductive aerogel; characterized in that the preparation of modified nanocellulose wet gel includes placing pretreated microcrystalline cellulose in an ionic liquid containing 2,2,6,6-tetramethylpiperidine oxide, and then adding an α,ω-dihydroxy dimethylsiloxane oligomer to react to obtain a modified nanocellulose wet gel.

[0007] Preferably, the process of preparing the aerogel includes adding an ammonium bicarbonate solution to the modified nanocellulose wet gel treated with acetone, sealing, heating to 40-50 °C, reacting, and performing freeze-drying and low-temperature vacuum drying treatments to obtain the aerogel.

[0008] Preferably, the preparation of the natural polymer conductive aerogel includes: placing the aerogel in a tube furnace, replacing the air in the furnace with a mixed gas of hydrogen and nitrogen, and performing high-temperature sintering to obtain the natural polymer conductive aerogel.

[0009] Preferably, a method for preparing a natural polymer conductive aerogel includes the following specific steps:

[0010] (1) Place the pretreated microcrystalline cellulose in an ionic liquid 20 - 30 times the mass of the microcrystalline cellulose. After stirring evenly until dissolved, add an α,ω-dihydroxy dimethylsiloxane oligomer 0.3 - 0.5 times the mass of the microcrystalline cellulose, and stir at room temperature at 150 - 300 rpm for 24 - 28 h to obtain a modified nanocellulose wet gel.

[0011] (2) Add a 10 - 25% ammonium bicarbonate solution 0.15 - 0.3 times the mass of the modified nanocellulose wet gel to the modified nanocellulose wet gel treated with acetone. Seal and heat to 40 - 50 °C, react for 30 - 50 min, then transfer to a freeze dryer and immediately perform freeze drying and low-temperature vacuum drying to obtain an aerogel.

[0012] (3) Place the aerogel in a tube furnace, replace the air in the furnace with a mixed gas of hydrogen and nitrogen, with the mass ratio of nitrogen to hydrogen being 0.5:1 - 1:1. Heat to 800 - 1000 °C at a rate of 4 - 5 °C / min, hold for 2 - 3 h, and cool to room temperature to obtain the natural polymer conductive aerogel.

[0013] Preferably, in the above step (1): The process of pretreating microcrystalline cellulose is as follows: Disperse the microcrystalline cellulose in a 3 - 5% formic acid solution 50 - 60 times the mass of the microcrystalline cellulose, perform ultrasonic treatment at 20 °C and 50 - 60 kHz for 3 - 5 h, add distilled water 100 - 200 times the mass of the microcrystalline cellulose, and quickly filter with filter paper under vacuum conditions to obtain the pretreated microcrystalline cellulose.

[0014] Preferably, in the above step (1): In the ionic liquid, the mass ratio of the imidazole-based ionic liquid to 2,2,6,6-tetramethylpiperidine oxide is 10:0.05 - 10:0.15.

[0015] Preferably, in the above step (1), the preparation method of the α, ω-dihydroxydimethylsiloxane oligomer is as follows: Octamethylcyclotetrasiloxane, acetic anhydride and alumina are mixed in a mass ratio of 5:1:0.08 to 5:1.5:0.1 and placed in a three-necked flask, heated to 120 °C and refluxed for 8 to 10 h, cooled to 50 °C and then filtered by suction. The filtrate is washed 3 to 5 times with a mixed solution of sodium chloride and ammonium bicarbonate with a mass fraction of 10%. After washing, it is placed in a three-necked flask, and deionized water 2 to 3 times the mass of octamethylcyclotetrasiloxane is added, reacted at 70 °C for 3 to 4 h, cooled to room temperature, washed 3 to 5 times with deionized water, separated and subjected to vacuum distillation to obtain the α, ω-dihydroxydimethylsiloxane oligomer.

[0016] Preferably, in the above step (2), the process of treating the modified nanocellulose wet gel with acetone is as follows: The modified nanocellulose wet gel is immersed in acetone, and the acetone is replaced every 24 h, and replaced three times to obtain the modified nanocellulose wet gel treated with acetone.

[0017] Preferably, in the above step (2), during freeze-drying, the freezing temperature is -48 to -52 °C, the freezing time is 12 to 15 h, and during low-temperature vacuum drying, the pressure is 1 Pa and the drying time is 48 h.

[0018] Preferably, the natural polymer conductive aerogel prepared by the preparation method of the natural polymer conductive aerogel comprises the following raw materials in weight fractions: 20 to 30 parts of modified nanocellulose wet gel, 3 to 9 parts of ammonium bicarbonate solution; the modified nanocellulose wet gel dissolves microcrystalline cellulose in an ionic liquid containing 2,2,6,6-tetramethylpiperidine oxide, and after dissolution, α, ω-dihydroxydimethylsiloxane oligomer is added; the ionic liquid is an imidazole-based ionic liquid containing 2,2,6,6-tetramethylpiperidine oxide; the mass fraction of the ammonium bicarbonate solution is 10 to 25%.

[0019] Preferably, the modified nanocellulose wet gel dissolves microcrystalline cellulose in an ionic liquid containing 2,2,6,6-tetramethylpiperidine oxide, and after dissolution, α, ω-dihydroxydimethylsiloxane oligomer is added; the ionic liquid is an imidazole-based ionic liquid containing 2,2,6,6-tetramethylpiperidine oxide; the mass fraction of the ammonium bicarbonate solution is 10 to 25%.

[0020] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0021] When the present invention prepares the natural polymer conductive aerogel, the modified nanocellulose is first made into a wet gel, then dried to form an aerogel, and finally carbonized to form the natural polymer conductive aerogel;

[0022] Dissolve microcrystalline cellulose in an ionic liquid containing 2,2,6,6 - tetramethylpiperidine - 1 - oxide. After dissolution, add α,ω - dihydroxydimethylsiloxane oligomer to modify the nanocellulose hydrogel. 2,2,6,6 - tetramethylpiperidine - 1 - oxide oxidizes the hydroxyl groups on the surface of nanocellulose to carboxyl groups, improving the dissolution of the crystalline region of microcrystalline cellulose. At the same time, under the catalysis of 2,2,6,6 - tetramethylpiperidine - 1 - oxide, the remaining hydroxyl groups of microcrystalline cellulose and the generated carboxyl groups cross - link with α,ω - dihydroxydimethylsiloxane oligomer to form a modified nanocellulose hydrogel with long - chain wrapping and a three - dimensional network structure, increasing the strength of the modified nanocellulose hydrogel, and thus enhancing the toughness of the conductive aerogel;

[0023] During drying, add ammonium bicarbonate to the modified nanocellulose hydrogel, first seal and heat, and then perform freeze - drying. When heated, ammonium bicarbonate decomposes to produce ammonia, water, and carbon dioxide. Sealing makes the gas remain inside the modified nanocellulose hydrogel. At the same time, ammonia reacts with hydroxyl and carboxyl groups to amino - functionalize the modified nanocellulose hydrogel, forming bridges inside the hydrogel. After freeze - drying, due to thermal expansion and contraction, the pores inside the aerogel are first dispersed by the bridges and then shrink, the pores become smaller, the porosity increases, and the adsorption capacity is enhanced. Finally, during the carbonization process, use nitrogen and hydrogen as protective gases. On the one hand, ammonia is supplied to the aerogel for continuous reaction, and on the other hand, the generated carbon dioxide is adsorbed and removed from the aerogel to prevent the carbon dioxide generated during drying from affecting the adsorption properties of the conductive aerogel. Detailed implementation mode

[0024] The following will combine the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

[0025] To more clearly illustrate the method provided by the present invention, it is described in detail through the following embodiments. The test methods for each index of the natural polymer conductive aerogels prepared in the embodiments and comparative examples are as follows:

[0026] Toughness: The elastic modulus of the natural polymer conductive aerogels prepared in the embodiments and comparative examples is detected by the static method.

[0027] Adsorption property: The specific surface area and pore size of the natural polymer conductive aerogels prepared in the embodiments and comparative examples are tested by an adsorption instrument.

[0028] Example 1

[0029] A natural polymer conductive aerogel, by weight, mainly includes:

[0030] 20 parts of modified nanocellulose hydrogel and 3 parts of ammonium bicarbonate solution.

[0031] A preparation method of a natural polymer conductive aerogel, and the preparation method of the natural polymer conductive aerogel is as follows:

[0032] (1) Disperse microcrystalline cellulose in a 5% formic acid solution with a mass 50 times that of the microcrystalline cellulose, perform ultrasonic treatment at 20 °C and 50 kHz for 3 h, add distilled water with a mass 100 times that of the microcrystalline cellulose, and quickly filter with filter paper under vacuum conditions to obtain pretreated microcrystalline cellulose; prepare an ionic liquid by mixing 1,2,4-triazole ionic liquid and 2,2,6,6-tetramethylpiperidine oxide in a mass ratio of 10:0.05; mix octamethylcyclotetrasiloxane, acetic anhydride and alumina in a mass ratio of 5:1:0.08 and place them in a three-necked flask, heat to 120 °C and reflux for 8 h, cool to 50 °C and then perform suction filtration, wash the filtrate 3 times with a mixed solution of 10% sodium chloride and sodium bicarbonate by mass, place the washed product in a three-necked flask, add deionized water with a mass 2 times that of octamethylcyclotetrasiloxane, react at 70 °C for 3 h, cool to room temperature, wash 3 times with deionized water, separate the liquid and perform vacuum distillation to obtain α,ω-dihydroxydimethylsiloxane oligomer; place the pretreated microcrystalline cellulose in an ionic liquid with a mass 20 times that of the microcrystalline cellulose, stir evenly until dissolved, add α,ω-dihydroxydimethylsiloxane oligomer with a mass 0.3 times that of the microcrystalline cellulose, stir at room temperature and 150 rpm for 28 h to obtain modified nanocellulose hydrogel;

[0033] (2) Immerse the modified nanocellulose hydrogel in acetone, change the acetone every 24 h for three times to obtain the modified nanocellulose hydrogel treated with acetone; add 0.15 times the mass of the modified nanocellulose hydrogel of a 10% ammonium bicarbonate solution to the modified nanocellulose hydrogel treated with acetone, seal it, heat to 40 °C, react for 30 min, then transfer it to a freeze dryer and immediately perform freeze drying and low-temperature vacuum drying treatment. When freeze drying, the freezing temperature is -48 °C and the freezing time is 12 h. When performing low-temperature vacuum drying treatment, the pressure is 1 Pa and the drying time is 48 h to obtain an aerogel;

[0034] (3) Mix nitrogen and hydrogen in a mass ratio of 0.5:1 to obtain a mixed gas; place the aerogel in a tube furnace, displace the air in the furnace with the mixed gas, heat to 800 - 1000 °C at a rate of 4 °C / min, hold for 2 h, and cool to room temperature to obtain a natural polymer conductive aerogel.

[0035] Example 2

[0036] A natural polymer conductive aerogel, by weight, mainly includes:

[0037] 25 parts of modified nanocellulose hydrogel and 5 parts of ammonium bicarbonate solution.

[0038] A preparation method of a natural polymer conductive aerogel, and the preparation method of the natural polymer conductive aerogel is as follows:

[0039] (1) Disperse microcrystalline cellulose in a 4% formic acid solution with a mass 55 times that of microcrystalline cellulose, perform ultrasonic treatment at 20 °C and 55 kHz for 4 h, add distilled water with a mass 150 times that of microcrystalline cellulose, and quickly filter with filter paper under vacuum conditions to obtain pretreated microcrystalline cellulose; prepare an ionic liquid by mixing 1,2,4-triazole ionic liquid and 2,2,6,6-tetramethylpiperidine oxide in a mass ratio of 10:0.1; mix octamethylcyclotetrasiloxane, acetic anhydride and alumina in a mass ratio of 5:1:0.09 and place them in a three-necked flask, heat to 120 °C and reflux for 9 h, cool to 50 °C and then perform suction filtration, wash the filtrate 4 times with a mixed solution of 10% sodium chloride and sodium bicarbonate by mass, place it in a three-necked flask after washing, add deionized water with a mass 3 times that of octamethylcyclotetrasiloxane, react at 70 °C for 4 h, cool to room temperature, wash 4 times with deionized water, separate the liquid and perform vacuum distillation to obtain α,ω-dihydroxydimethylsiloxane oligomer; place the pretreated microcrystalline cellulose in an ionic liquid with a mass 25 times that of microcrystalline cellulose, stir evenly until dissolved, add α,ω-dihydroxydimethylsiloxane oligomer with a mass 0.4 times that of microcrystalline cellulose, stir at room temperature and 200 rpm for 26 h to obtain modified nanocellulose hydrogel;

[0040] (2) Immerse the modified nanocellulose hydrogel in acetone, change the acetone every 24 h, change it three times to obtain the modified nanocellulose hydrogel treated with acetone; add a 15% ammonium bicarbonate solution with a mass 0.2 times that of the modified nanocellulose hydrogel treated with acetone, seal it, heat to 45 °C, react for 40 min, then transfer it to a freeze dryer and immediately perform freeze drying and low-temperature vacuum drying treatment. When freeze drying, the freezing temperature is -50 °C and the freezing time is 14 h. When performing low-temperature vacuum drying treatment, the pressure is 1 Pa and the drying time is 48 h to obtain an aerogel;

[0041] (3) Mix nitrogen and hydrogen in a mass ratio of 0.8:1 to obtain a mixed gas; place the aerogel in a tube furnace, displace the air in the furnace with the mixed gas, heat to 9000 °C at a rate of 4.5 °C / min, keep it warm for 2.5 h, and cool to room temperature to obtain a natural polymer conductive aerogel.

[0042] Example 3

[0043] A natural polymer conductive aerogel, by weight, mainly includes:

[0044] 30 parts of modified nanocellulose wet gel and 6 parts of ammonium bicarbonate solution.

[0045] A preparation method of a natural polymer conductive aerogel, and the preparation method of the natural polymer conductive aerogel is as follows:

[0046] (1) Disperse microcrystalline cellulose in a 5% formic acid solution with a mass 60 times that of the microcrystalline cellulose, perform ultrasonic treatment at 20 °C and 60 kHz for 5 h, add distilled water with a mass 200 times that of the microcrystalline cellulose, and quickly filter with filter paper under vacuum conditions to obtain pretreated microcrystalline cellulose; prepare an ionic liquid by mixing 1,3-dimethyl-3-imidazolium hexafluorophosphate ionic liquid and 2,2,6,6-tetramethylpiperidine 1-oxyl in a mass ratio of 10:0.15; mix octamethylcyclotetrasiloxane, acetic anhydride and alumina in a mass ratio of 5:1.5:0.1, place them in a three-necked flask, heat to 120 °C and reflux for 10 h, cool to 50 °C and then perform suction filtration, wash the filtrate 5 times with a mixed solution of 10% sodium chloride and sodium bicarbonate by mass fraction, place the washed product in a three-necked flask after washing, add deionized water with a mass 3 times that of octamethylcyclotetrasiloxane, react at 70 °C for 4 h, cool to room temperature, wash 5 times with deionized water, separate the liquid and perform vacuum distillation to obtain α,ω-dihydroxydimethylsiloxane oligomer; place the pretreated microcrystalline cellulose in an ionic liquid with a mass 30 times that of the microcrystalline cellulose, stir evenly until dissolved, add α,ω-dihydroxydimethylsiloxane oligomer with a mass 0.5 times that of the microcrystalline cellulose, stir at room temperature and 300 rpm for 24 h to obtain a modified nanocellulose wet gel;

[0047] (2) Immerse the modified nanocellulose wet gel in acetone, replace the acetone every 24 h for three times to obtain a modified nanocellulose wet gel treated with acetone; add a 25% ammonium bicarbonate solution with a mass 0.3 times that of the modified nanocellulose wet gel to the modified nanocellulose wet gel treated with acetone, seal it, heat to 50 °C, react for 50 min, then transfer it to a freeze dryer and immediately perform freeze drying and low-temperature vacuum drying treatment. When freeze drying, the freezing temperature is -52 °C and the freezing time is 15 h. When performing low-temperature vacuum drying treatment, the pressure is 1 Pa and the drying time is 48 h to obtain an aerogel;

[0048] (3) Mix nitrogen and hydrogen in a mass ratio of 1:1 to obtain a mixed gas; place the aerogel in a tube furnace, displace the air in the furnace with the mixed gas, heat to 1000 °C at a rate of 5 °C / min, hold for 3 h, and cool to room temperature to obtain a natural polymer conductive aerogel.

[0049] Comparative Example 1

[0050] The prescription composition of Comparative Example 1 is the same as that of Example 2. The difference between this natural polymer conductive aerogel and its preparation method and those of Example 2 lies only in step (1). Step (1) is modified as follows: Microcrystalline cellulose is dispersed in a 4% formic acid solution with a mass 55 times that of microcrystalline cellulose, sonicated at 20 °C and 55 kHz for 4 h, distilled water with a mass 150 times that of microcrystalline cellulose is added, and it is quickly filtered with filter paper under vacuum conditions to obtain pretreated microcrystalline cellulose; an ionic liquid is prepared by mixing an imidazole-based ionic liquid and 2,2,6,6-tetramethylpiperidine 1-oxyl in a mass ratio of 10:0.1; the pretreated microcrystalline cellulose is placed in an ionic liquid with a mass 25 times that of microcrystalline cellulose, stirred evenly until dissolved, and stirred at 200 rpm at room temperature for 26 h to obtain a modified nanocellulose wet gel. The remaining steps are the same as those of Example 2.

[0051] Comparative Example 2

[0052] The prescription composition of Comparative Example 2 is the same as that of Example 2. The difference between this natural polymer conductive aerogel and its preparation method and those of Example 2 lies only in step (1). Step (1) is modified as follows: Microcrystalline cellulose is dispersed in a 4% formic acid solution with a mass 55 times that of microcrystalline cellulose, sonicated at 20 °C and 55 kHz for 4 h, distilled water with a mass 150 times that of microcrystalline cellulose is added, and it is quickly filtered with filter paper under vacuum conditions to obtain pretreated microcrystalline cellulose; octamethylcyclotetrasiloxane, acetic anhydride, and alumina are mixed in a mass ratio of 5:1:0.09 and placed in a three-necked flask, heated to 120 °C and refluxed for 9 h, cooled to 50 °C and then filtered by suction, the filtrate is washed 4 times with a mixed solution of 10% sodium chloride and sodium bicarbonate by mass, after washing, it is placed in a three-necked flask, deionized water with a mass 3 times that of octamethylcyclotetrasiloxane is added, reacted at 70 °C for 4 h, cooled to room temperature, washed 4 times with deionized water, separated and subjected to vacuum distillation to obtain α,ω-dihydroxydimethylsiloxane oligomers; the pretreated microcrystalline cellulose is placed in an ionic liquid with a mass 25 times that of microcrystalline cellulose, stirred evenly until dissolved, and then α,ω-dihydroxydimethylsiloxane oligomers with a mass 0.4 times that of microcrystalline cellulose are added, and stirred at 200 rpm at room temperature for 26 h to obtain a modified nanocellulose wet gel. The remaining steps are the same as those of Example 2.

[0053] Comparative Example 3

[0054] The prescription composition of Comparative Example 3 is the same as that of Example 2. The difference between this natural polymer conductive aerogel and its preparation method and those of Example 2 lies only in step (2). Modify step (2) as follows: Immerse the modified nanocellulose wet gel in acetone, and replace the acetone every 24 h for three times to obtain the modified nanocellulose wet gel treated with acetone; Seal the modified nanocellulose wet gel treated with acetone, heat it to 45 °C, react for 40 min, then transfer it to a freeze dryer and immediately perform freeze drying and low-temperature vacuum drying treatments. When performing freeze drying, the freezing temperature is -50 °C and the freezing time is 14 h. When performing low-temperature vacuum drying treatment, the pressure is 1 Pa and the drying time is 48 h to obtain the aerogel. The remaining steps are the same as those of Example 2.

[0055] Comparative Example 4

[0056] The prescription composition of Comparative Example 4 is the same as that of Example 2. The difference between this natural polymer conductive aerogel and its preparation method and those of Example 2 lies only in step (3). Modify step (3) as follows: Place the aerogel in a tubular furnace, displace the air in the furnace with nitrogen, heat it to 800 - 1000 °C at a rate of 4 - 5 °C / min, hold for 2 - 3 h, and then cool to room temperature to obtain the natural polymer conductive aerogel. The remaining steps are the same as those of Example 2.

[0057] Comparative Example 5

[0058] Comparative Example 5 is the sulfur-modified chitosan aerogel prepared in Example 1 of CN201610605988.

[0059] Effect Example

[0060] Table 1 below gives the analysis results of the properties of the rubber materials prepared from the natural polymer conductive aerogels of Examples 1 and 2 and Comparative Examples 1, 2, 3, and 4 of the present invention.

[0061] Table 1

[0062] <![CDATA[Impact toughness (kJ / m 2 )]]> <![CDATA[Specific surface area (m 2 / g)]]> Average pore diameter (nm) Example 1 6.0 372 5.08 Example 2 6.1 365 5.13 Example 3 5.9 369 5.02 Comparative Example 1 4.2 310 6.52 Comparative Example 2 4.9 327 6.34 Comparative Example 3 5.8 361 7.10 Comparative Example 4 5.7 319 6.49 Comparative Example 5 4.3 360 5.16

[0063] By comparing the experimental data of the examples and comparative examples in Table 1, it can be clearly found that the natural polymer conductive aerogels prepared in Examples 1 and 2 have good impact toughness, a large specific surface area, and a small average pore size, indicating excellent toughness and adsorption properties;

[0064] From the comparison of the experimental data of Example 1, Example 2, Example 3 and Comparative Examples 1 and 2, it can be found that when preparing the natural polymer conductive aerogel, adding α,ω-dihydroxy dimethyl siloxane oligomer and under the catalysis of 2,2,6,6-tetramethylpiperidine oxide, the remaining hydroxyl groups and generated carboxyl groups of microcrystalline cellulose crosslink with the α,ω-dihydroxy dimethyl siloxane oligomer to form a modified nano-cellulose hydrogel with long-chain wrapping and a three-dimensional network structure, increasing the strength of the modified nano-cellulose hydrogel, thereby enhancing the toughness of the conductive aerogel. However, only using α,ω-dihydroxy dimethyl siloxane oligomer cannot enhance the toughness of the conductive aerogel;

[0065] From the comparison of the experimental data of Example 1, Example 2, Example 3 and Comparative Example 3, it can be found that during freeze-drying, adding ammonium bicarbonate to the modified nano-cellulose hydrogel to amino-functionalize the modified nano-cellulose hydrogel, forming bridges inside the hydrogel, dividing the aerogel with larger pores, reducing the air voids, increasing the specific surface area of the conductive aerogel, and enhancing the adsorption capacity. When ammonium bicarbonate is not added, the average pore size of the prepared conductive aerogel is larger and the adsorption capacity is weaker.

[0066] From the comparison of the experimental data of Example 1, Example 2, Example 3 and Comparative Example 4, it can be found that during the sintering process, omitting hydrogen and using only nitrogen as the protective gas results in a larger average pore size and a smaller specific surface area of the aerogel, indicating that the protective gas can not only supplement ammonia for continuous reaction, but also reduce the influence of carbon dioxide generated during drying on the adsorption property of the aerogel.

[0067] From the comparison of the experimental data of Example 1, Example 2, Example 3 and Comparative Example 5, it can be found that after sulfur-containing modification of chitosan to obtain modified chitosan, and then compounding with nano-cellulose to prepare a sulfur-containing modified chitosan / nano-cellulose composite porous aerogel, the average pore size is smaller and the specific surface area is larger, but without using α,ω-dihydroxy dimethyl siloxane oligomer and 2,2,6,6-tetramethylpiperidine oxide, the toughness is poor, indicating that under the catalysis of 2,2,6,6-tetramethylpiperidine oxide, α,ω-dihydroxy dimethyl siloxane oligomer can react with microcrystalline cellulose to form a three-dimensional network structure with stronger toughness.

[0068] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, in any aspect, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be construed as limiting the claimed rights.

Claims

1. A preparation method of a natural polymer conductive aerogel, characterized in that, The preparation method of the natural polymer conductive aerogel includes: preparation of modified nano-cellulose hydrogel, preparation of aerogel, and preparation of natural polymer conductive aerogel; The preparation method of the natural polymer conductive aerogel includes the following specific steps: (1) Octamethylcyclotetrasiloxane, acetic anhydride and alumina are mixed in a mass ratio of 5:1:0.08 to 5:1.5:0.1 and placed in a three-necked flask, heated to 120 °C and refluxed for 8 to 10 h, cooled to 50 °C, then filtered by suction. The filtrate is washed 3 to 5 times with a mixed solution of sodium chloride and ammonium bicarbonate with a mass fraction of 10%. After washing, it is placed in a three-necked flask, and deionized water 2 to 3 times the mass of octamethylcyclotetrasiloxane is added, and the reaction is carried out at 70 °C for 3 to 4 h. After cooling to room temperature, it is washed 3 to 5 times with deionized water, separated by liquid separation and subjected to vacuum distillation to obtain α,ω-dihydroxydimethylsiloxane oligomer; the pretreated microcrystalline cellulose is placed in an ionic liquid 20 to 30 times the mass of the microcrystalline cellulose. After stirring evenly until dissolved, α,ω-dihydroxydimethylsiloxane oligomer 0.3 to 0.5 times the mass of the microcrystalline cellulose is added, and stirred at room temperature at 150 to 300 rpm for 24 to 28 h to obtain a modified nano-cellulose hydrogel; (2) A solution of ammonium bicarbonate with a mass fraction of 10% to 25% and 0.15 to 0.3 times the mass of the modified nano-cellulose hydrogel is added to the modified nano-cellulose hydrogel treated with acetone, sealed, heated to 40 to 50 °C, and reacted for 30 to 50 min. Then it is transferred to a freeze dryer, and immediately subjected to freeze drying and low-temperature vacuum drying to obtain an aerogel; (3) The aerogel is placed in a tubular furnace, and the air in the furnace is replaced with a mixed gas, which is a mixture of nitrogen and hydrogen with a mass ratio of 0.5:1 to 1:

1. It is heated to 800 to 1000 °C at a rate of 4 to 5 °C / min, held for 2 to 3 h, and cooled to room temperature to obtain a natural polymer conductive aerogel.

2. The preparation method of a natural polymer conductive aerogel according to claim 1, characterized in that In the above step (1): The process of pretreating microcrystalline cellulose is as follows: The microcrystalline cellulose is dispersed in a formic acid solution with a mass fraction of 3% to 5% and 50 to 60 times the mass of the microcrystalline cellulose, ultrasonicated at 20 °C and 50 to 60 kHz for 3 to 5 h, and distilled water 100 to 200 times the mass of the microcrystalline cellulose is added, and it is quickly filtered with filter paper under vacuum conditions to obtain pretreated microcrystalline cellulose.

3. The preparation method of a natural polymer conductive aerogel according to claim 1, characterized in that In the above step (1): In the ionic liquid, the mass ratio of the imidazole-based ionic liquid to 2,2,6,6-tetramethylpiperidine oxide is 10:0.05 to 10:0.

15.

4. The preparation method of a natural polymer conductive aerogel according to claim 1, characterized in that, In the above step (2): The process of treating the modified nano-cellulose hydrogel with acetone is as follows: The modified nano-cellulose hydrogel is immersed in acetone, and the acetone is replaced every 24 h for three times to obtain the modified nano-cellulose hydrogel treated with acetone.

5. The preparation method of a natural polymer conductive aerogel according to claim 1, characterized in that, In the above step (2): During freeze drying, the freezing temperature is -48 to -52 °C, and the freezing time is 12 to 15 h. During low-temperature vacuum drying, the pressure is 1 Pa and the drying time is 48 h.

6. The preparation method of a natural polymer conductive aerogel according to claim 1, characterized in that The natural polymer conductive aerogel prepared by the preparation method of the natural polymer conductive aerogel comprises raw materials in the following weight fractions: 20-30 parts of modified nano-cellulose wet gel and 3-9 parts of ammonium bicarbonate solution.

7. The preparation method of a natural polymer conductive aerogel according to claim 1, characterized in that The modified nano-cellulose wet gel is prepared by dissolving microcrystalline cellulose in an ionic liquid containing 2,2,6,6-tetramethylpiperidine oxide, and adding α,ω-dihydroxy dimethylsiloxane oligomer after dissolution; the ionic liquid is an imidazole-based ionic liquid containing 2,2,6,6-tetramethylpiperidine oxide; the mass fraction of the ammonium bicarbonate solution is 10-25%.