阅读说明：本技术 一种柔性聚乙烯基倍半硅氧烷气凝胶的制备方法 (Preparation method of flexible polyvinyl silsesquioxane aerogel ) 是由 张思钊 熊仕显 胡杨彪 鄂殿玉 李政权 邹瑞萍 于 2020-05-11 设计创作，主要内容包括：本发明提供一种柔性聚乙烯基倍半硅氧烷气凝胶的制备方法,以乙烯基烷氧基硅烷为前驱体,经自由基聚合、水解缩聚形成三维网络交联结构,然后经老化、溶剂置换和干燥后得到一种柔性聚乙烯基倍半硅氧烷气凝胶,且在水解缩聚的过程中引入烷氧基硅烷,得到的气凝胶具有良好的柔韧性。(The invention provides a preparation method of a flexible polyvinyl silsesquioxane aerogel, which comprises the steps of taking vinyl alkoxy silane as a precursor, forming a three-dimensional network cross-linking structure through free radical polymerization and hydrolytic polycondensation, then aging, solvent replacement and drying to obtain the flexible polyvinyl silsesquioxane aerogel, and introducing alkoxy silane in the hydrolytic polycondensation process to obtain the flexible polyvinyl silsesquioxane aerogel with good flexibility.)

1. A preparation method of flexible polyvinyl silsesquioxane aerogel is characterized by comprising the following steps: the preparation method is characterized in that vinyl alkoxy silane is used as a precursor, and the preparation method comprises five process links of free radical polymerization, hydrolytic polycondensation, aging, solvent replacement and drying.

2. The method for preparing a flexible polyvinyl silsesquioxane aerogel according to claim 1, wherein the method comprises the following steps:

the preparation method comprises the following steps:

(1) free radical polymerization: fully mixing a certain amount of precursor and a free radical initiator, transferring the mixture into a hydrothermal kettle, replacing air in the reaction kettle with argon, sealing and heating the mixture for a period of time, taking out the mixture, cooling the mixture to room temperature to obtain viscous transparent liquid, adding alkoxy silane, and fully mixing the viscous transparent liquid;

(2) hydrolysis and polycondensation: fully mixing a solvent, water and a catalyst, adding the mixture into the transparent liquid mixed in the step (1), and fully mixing to obtain homogeneous sol;

(3) aging: sealing the obtained homogeneous sol in an aging tank, and heating for a period of time to obtain gel;

(4) solvent replacement: replacing the obtained gel with methanol solvent or ethanol solvent or propanol solvent or n-hexane solvent or isopropanol solvent or benzyl alcohol solvent, and finally replacing with tert-butanol solvent or deionized water solvent;

(5) and (3) drying: and drying the gel which is not subjected to solvent replacement or the gel which is subjected to solvent replacement to obtain the flexible polyvinyl silsesquioxane aerogel.

3. The method for preparing a flexible polyvinyl silsesquioxane aerogel according to claim 2, wherein the method comprises the following steps: the precursor in the step (1) is any one or a group consisting of vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane and vinyltributoxysilane;

the free radical initiator in the step (1) is any one or a group consisting of di-tert-butyl peroxide, azobisisobutyronitrile, dicumyl peroxide and diacyl peroxide;

the alkoxysilane in the step (1) is any one or any combination of methyldimethoxysilane, methyldiethoxysilane, dimethyldimethoxysilane, ethyldimethoxysilane and ethyldiethoxysilane.

4. The method for preparing a flexible polyvinyl silsesquioxane aerogel according to claim 2, wherein the method comprises the following steps: the molar ratio of the precursor to the free radical initiator in the step (1) is as follows: 1, (0.05-0.3); the molar ratio of the precursor to the oxysilane in the step (1) is 1 (2-10); the heating condition of the reaction kettle in the step (1) is as follows: heating for 12-72 h at 80-180 ℃.

5. The method for preparing a flexible polyvinyl silsesquioxane aerogel according to claim 2, wherein the method comprises the following steps: in the step (2), the solvent is any one or a group consisting of n-hexane, methanol, ethanol, benzyl alcohol, isopropanol and n-butanol; the catalyst in the step (2) is any one or a group consisting of tetramethylammonium hydroxide, tetraethylammonium hydroxide, ammonia water, sodium hydroxide, nitric acid, hydrochloric acid, tetrabutylammonium hydroxide and potassium hydroxide.

6. The method for preparing a flexible polyvinyl silsesquioxane aerogel according to claim 2, wherein the method comprises the following steps: the molar ratio of the precursor to the solvent, water and catalyst in the step (2) is 1 (3-15): (3-13): 0.01-0.06.

7. The method for preparing a flexible polyvinyl silsesquioxane aerogel according to claim 2, wherein the method comprises the following steps: and (4) after the homogeneous sol obtained in the step (3) is sealed in an aging tank, heating the homogeneous sol to 10-30 ℃ from 20-80 ℃ every 1-5 hours until the homogeneous sol reaches 80 ℃.

8. The method for preparing a flexible polyvinyl silsesquioxane aerogel according to claim 2, wherein the method comprises the following steps: and (4) replacing the gel with an ethanol solvent, an isopropanol solvent, a normal hexane solvent or a methanol solvent for 4-12 times at intervals of 4-12 hours, and finally replacing with a tert-butyl alcohol solvent or a deionized water solvent for 3-6 times at intervals of 3-6 hours.

9. The method for preparing a flexible polyvinyl silsesquioxane aerogel according to claim 2, wherein the method comprises the following steps: the drying in the step (5) refers to carbon dioxide supercritical fluid drying or vacuum freeze drying;

the carbon dioxide supercritical fluid drying is to place the gel in carbon dioxide supercritical fluid drying equipment, and carry out carbon dioxide supercritical fluid drying for a period of time under the conditions of certain pressure and temperature to obtain aerogel; and the vacuum freeze drying is to carry out vacuum freeze drying on the gel for a period of time under the conditions of certain vacuum degree and temperature to obtain the aerogel.

10. The method for preparing a flexible polyvinyl silsesquioxane aerogel according to claim 9, wherein the method comprises the following steps: the pressure for drying the carbon dioxide supercritical fluid is 13-20 MPa, the temperature is 35-50 ℃, and the drying time is 10-100 h; the vacuum degree of the vacuum freeze drying is 5-15 Pa, the temperature is-20-25 ℃, and the drying time is 6-96 hours.

Technical Field

The invention relates to the technical field of aerogel preparation, in particular to a preparation method of flexible polyvinyl silsesquioxane aerogel.

Background

The aerogel is an open-pore porous solid material which takes gas as a dispersion medium and is mainly concentrated in nanoscale (phi is more than or equal to 1nm and less than or equal to 100nm) in pore diameter and composed of a three-dimensional network framework, generally has the characteristics of low density, high specific surface area, high porosity, low thermal conductivity and the like, and has good application prospects in the fields of heat insulation, catalysis, adsorption and the like. However, the porous network structure of the aerogel causes the problems of low strength, poor toughness, poor flexibility and the like. These defects seriously hamper the practical application of aerogels. The flexible polyvinyl silsesquioxane aerogel prepared by free radical polymerization, hydrolytic polycondensation, aging, solvent replacement and drying has good flexibility, strength and other novel properties.

Disclosure of Invention

The invention aims to provide a preparation method of a flexible polyvinyl silsesquioxane aerogel, which overcomes the problems of low strength and poor flexibility of the aerogel obtained by the prior art.

The invention provides a preparation method of a flexible polyvinyl silsesquioxane aerogel, which comprises the steps of taking vinyl alkoxy silane as a precursor, forming a three-dimensional network cross-linking structure through free radical polymerization and hydrolytic polycondensation, then aging, solvent replacement and drying to obtain the flexible polyvinyl silsesquioxane aerogel, and introducing alkoxy silane in the hydrolytic polycondensation process to obtain the flexible polyvinyl silsesquioxane aerogel with good flexibility.

The invention provides a preparation method of a flexible polyvinyl silsesquioxane aerogel, which comprises the following steps:

(1) free radical polymerization: fully mixing a certain amount of precursor and a free radical initiator, transferring the mixture into a hydrothermal transfer kettle, replacing air in the reaction kettle with argon, sealing and heating the mixture for a period of time, taking out the mixture, cooling the mixture to room temperature to obtain viscous transparent liquid, adding alkoxy silane, and fully mixing the viscous transparent liquid;

(2) hydrolysis and polycondensation: fully mixing a solvent, water and a catalyst, adding the mixture into the mixed transparent liquid, and fully mixing to obtain homogeneous sol;

(3) aging: sealing the obtained homogeneous sol in an aging tank, and heating for a period of time to obtain gel;

(4) solvent replacement: replacing the obtained gel with methanol solvent or ethanol solvent or propanol solvent or n-hexane solvent or isopropanol solvent or benzyl alcohol solvent, and finally replacing with tert-butanol solvent or deionized water solvent;

(5) and (3) drying: and drying the gel which is not subjected to solvent replacement or the gel subjected to solvent replacement to obtain the flexible polyvinyl silsesquioxane aerogel.

Preferably, the precursor in step (1) is any one or a group consisting of vinyltrimethoxysilane, vinyltriethoxysilane and vinyltripropoxysilane.

Preferably, the radical initiator in step (1) is any one or any combination of di-tert-butyl peroxide, azobisisobutyronitrile, dicumyl peroxide and diacyl peroxide.

Preferably, the molar ratio of the precursor to the radical initiator in step (1) is: 1 (0.05-0.3), preferably 1 (0.1-0.3).

Preferably, the heating conditions of the reaction kettle in the step (1) are as follows: heating for 12-72 h at 80-180 ℃, preferably for 24-72 h at 100-140 ℃.

Preferably, the alkoxysilane in step (1) is any one or any group of methyldimethoxysilane, methyldiethoxysilane, dimethyldimethoxysilane, ethyldimethoxysilane, ethyldiethoxysilane.

Preferably, the molar ratio of the precursor to the oxysilane in step (1) is: 1 (2-10), preferably 1 (2-8).

Preferably, the solvent in the step (2) is any one or a group consisting of n-hexane, methanol, ethanol, benzyl alcohol, isopropanol and n-butanol.

Preferably, the catalyst in step (2) is any one or a group consisting of tetramethylammonium hydroxide, tetraethylammonium hydroxide, ammonia, sodium hydroxide, nitric acid, hydrochloric acid, tetrabutylammonium hydroxide and potassium hydroxide.

Preferably, the molar ratio of the precursor in the step (2) to the solvent, water and catalyst in the step (2) is: 1 (3-15) (3-13) (0.01-0.06), preferably 1 (4-15) (3-10) (0.01-0.05).

Preferably, after the homogeneous sol obtained in the step (3) is sealed in an aging tank, the temperature is raised by 10-30 ℃ every 1-5 hours from 20-80 ℃ until the temperature reaches 80 ℃, preferably 30-70 ℃, and the temperature is raised by 10-20 ℃ every 2-4 hours.

Preferably, the gel in the step (4) is replaced by an ethanol solvent, an isopropanol solvent, a normal hexane solvent or a methanol solvent for 4-12 times, and the interval is 4-12 hours each time; and finally, replacing 3-6 times by using a tert-butyl alcohol solvent or a deionized water solvent, wherein the interval is 3-6 h every time.

Preferably, the drying in step (5) refers to supercritical fluid drying with carbon dioxide or vacuum freeze drying.

The carbon dioxide supercritical fluid drying is to place the gel in carbon dioxide supercritical fluid drying equipment, and carry out carbon dioxide supercritical fluid drying for a period of time under the conditions of certain pressure and temperature to obtain aerogel; and the vacuum freeze drying is to carry out vacuum freeze drying on the gel for a period of time under the conditions of certain vacuum degree and temperature to obtain the aerogel.

Preferably, the vacuum degree of the vacuum freeze drying in the step (5) is 5-15 Pa, the temperature is-20-25 ℃, the drying time is 6-96 h, preferably, the vacuum degree is 5-10 Pa, the temperature is-20 ℃, and the drying time is 12-96 h.

Preferably, the pressure for drying the carbon dioxide supercritical fluid in the step (5) is 13-20 MPa, the temperature is 35-50 ℃, the drying time is 10-100 h, preferably the pressure is 15-20 MPa, the temperature is 35-40 ℃, and the drying time is 12-96 h.

The invention has the beneficial effects that:

1. the preparation method of the flexible polyvinyl silsesquioxane aerogel provided by the invention has the advantages that the preparation process is simple and easy to realize;

2. the preparation method of the flexible polyvinyl silsesquioxane aerogel provided by the invention improves the flexibility of the aerogel by introducing alkoxy and vinyl.

Specific reference is made to: the above statements and other aspects of the present invention will be apparent from the following description of various examples presented in accordance with the method of preparing a flexible polyvinylsilsesquioxane aerogel of the present invention.

Drawings

FIG. 1 is a schematic flow diagram of a method for preparing a flexible polyvinylsilsesquioxane aerogel according to the present invention.

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced and carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit of the invention.