CN-122011492-A - Preparation method of super-elastic cellulose aerogel

Abstract

The invention discloses a preparation method of super-elastic cellulose aerogel. According to the method, firstly, cellulose crystal form transformation is induced through molecular chain rearrangement, accessibility and reactivity of hydroxyl on the surface of the fiber are obviously improved, and then, gas phase or in-situ mediated covalent crosslinking reaction is introduced into a three-dimensional porous aerogel framework, so that a uniform and continuous polymer topology network is constructed on the surface of the fiber. The formed covalent crosslinking structure effectively shields the hydrogen bonding action among fibers while maintaining the fiber rigidity, so that the aerogel still has excellent elastic recovery and fatigue resistance under the condition of large deformation. The obtained cellulose aerogel has super elasticity, high strength and structural stability, and is suitable for flexible sensing, buffer protection and extreme environment application.

Inventors

• NIE SHUANGXI
• Luo Qiguan
• GAO FENG
• LIU ZHEYING
• WU ZHENGMEI
• YU KANG
• Bai Yayu
• LUO BIN
• CAI CHENCHEN

Assignees

• 广西大学

Dates

Publication Date

20260512

Application Date

20260211

Claims (9)

1. 1. A method for preparing a super-elastic cellulose aerogel, which is characterized by comprising the following steps: S1, taking cellulose nano fibers as a raw material, directionally freezing a dispersion liquid of the cellulose nano fibers to enable ice crystals to directionally grow to obtain frozen gel with an oriented pore channel structure, and obtaining cellulose aerogel with a three-dimensional porous structure after freeze drying; S2, soaking the cellulose aerogel obtained in the step S1 in anhydrous ethylenediamine, and inducing rearrangement of cellulose molecular chains and crystal form transformation so as to improve the reactivity of hydroxyl groups on the surface of the fiber, thereby obtaining activated cellulose aerogel; S3, placing the cellulose aerogel obtained in the step S2 after the activation treatment in a closed reactor containing water vapor and methyltrimethoxysilane vapor, and generating a polysiloxane crosslinked network in situ at the pore wall of the aerogel and fiber connection nodes through gas phase hydrolysis-condensation reaction; s4, drying to obtain the super-elastic cellulose aerogel.
2. 2. The method according to claim 1, wherein the cellulose nanofibers in step (1) are cellulose nanofibers produced by TEMPO oxidation, and the mass fraction of the dispersion is 1%.
3. 3. The method of claim 1, wherein step (1) is performed by directional freezing with-196 ℃ liquid nitrogen, and the temperature of freeze drying is-28 ℃.
4. 4. The method according to claim 1, wherein the soaking treatment in step (2) is performed at room temperature for 8 hours.
5. 5. The method of claim 1, wherein the molar ratio of water vapor to methyltrimethoxysilane in step (3) is 1:1.
6. 6. The process according to claim 1, wherein the temperature of the gas phase hydrolysis-condensation reaction in step (3) is 85 ℃ for 6 hours.
7. 7. The method according to claim 1, wherein the drying treatment in step (4) is performed at a temperature of 105 ℃ for a time of 1 hour.
8. 8. The method of claim 1, wherein the resulting superelastic cellulose aerogel retains greater than 90% recovery from deformation after 20000 compression cycles.
9. 9. The method of claim 1, wherein the use of the super-elastic cellulose aerogel is in flexible sensing, buffering energy absorption, or extreme environmental applications, wherein the extreme environment comprises a high humidity environment, an organic solvent environment, or a high and low temperature alternating environment.

Description

Preparation method of super-elastic cellulose aerogel Technical Field The invention belongs to the technical field of preparation of cellulose-based porous materials and aerogel, and particularly relates to a method for preparing cellulose aerogel with super elasticity by improving the reactivity of the fiber surface and constructing a high-efficiency covalent cross-linked network. Background Because of low density, large specific surface area and strong structural designability, the cellulose aerogel has wide application prospect in the fields of flexible sensing, buffering energy absorption, heat insulation protection and the like. However, the existing cellulose aerogel has the problem of insufficient mechanical properties, and especially under the condition of large deformation or repeated cyclic compression, the structure collapse, irreversible deformation or performance decay easily occurs, so that the practical application of the cellulose aerogel is severely limited. The main reason for the above problem is the presence of a large number of strong hydrogen bonding interactions between cellulose molecules. In the aerogel compression process, the pore wall fibers are easy to irreversibly adhere, so that the structure is difficult to recover. In order to improve the elastic performance, the prior art attempts to weaken the interaction among fibers by introducing elastic polymers, physical coating or non-covalent modification and the like, but the problems of uneven crosslinking, insufficient interfacial binding force or falling off in the circulating process exist, and the long-term stable super-elasticity is difficult to realize while the strength of the material is maintained. Therefore, there is a need for a preparation method that can construct a stable, uniform and efficient covalent cross-linked structure inside cellulose aerogel, thereby simultaneously compromising strength, elasticity and structural stability. Disclosure of Invention The invention aims to provide a method for preparing super-elastic cellulose aerogel based on efficient covalent crosslinking, which realizes high elastic recovery capacity and mechanical stability of the cellulose aerogel under the conditions of large deformation and multiple cycles by improving the surface reactivity of fibers and constructing a continuous covalent crosslinking network in an aerogel framework. In order to achieve the above purpose, the invention adopts the following technical scheme: the invention provides a preparation method of super-elastic cellulose aerogel, which comprises the following steps: S1, taking cellulose nano fibers as a raw material, directionally freezing a dispersion liquid of the cellulose nano fibers to enable ice crystals to directionally grow to obtain frozen gel with an oriented pore channel structure, and obtaining cellulose aerogel with a three-dimensional porous structure after freeze drying; S2, soaking the cellulose aerogel obtained in the step S1 in anhydrous Ethylenediamine (EDA), and inducing rearrangement of cellulose molecular chains and crystal form transformation to improve the reactivity of hydroxyl groups on the surface of the fiber, so as to obtain activated cellulose aerogel; S3, placing the cellulose aerogel obtained in the step S2 after the activation treatment in a closed reactor containing water vapor and methyltrimethoxysilane vapor, and generating a polysiloxane crosslinked network in situ at the pore wall of the aerogel and fiber connection nodes through a gas phase hydrolysis-condensation reaction to construct a continuous and uniform polymer topological structure; s4, drying to obtain the super-elastic cellulose aerogel. Further, the cellulose nanofiber in the step (1) is cellulose nanofiber prepared by a TEMPO oxidation method, and the mass fraction of the dispersion liquid is 1%. Further, step (1) was subjected to directional freezing using liquid nitrogen at-196 ℃, and the temperature of freeze-drying was-28 ℃. Further, the temperature of the soaking treatment in the step (2) is room temperature, and the time is 8 hours. Further, the molar ratio of the water vapor to the methyltrimethoxysilane in the step (3) is 1:1. Further, the temperature of the vapor phase hydrolysis-condensation reaction in step (3) was 85 ℃ for 6 hours. Further, the temperature of the drying treatment in the step (4) is 105 ℃ and the time is 1 hour. The super-elastic cellulose aerogel prepared by the method still maintains the deformation recovery rate of more than 90% after 20000 compression cycles. The super-elastic cellulose aerogel prepared by the method can be used for flexible sensing, buffering and energy absorption or extreme environment application. The extreme environment includes a high humidity environment, an organic solvent environment, or a high-low temperature alternating environment. Compared with the prior art, the invention has at least the following beneficial effects: (1) By constructing a high-efficien