Method for one-step synthesis, cross-linking and drying of aerogels

Patent metadata

Field	Value
Publication number	US-2017218160-A1
Application number	US-201515500376-A
Country	US
Kind code	A1
Filing date	Jul 31, 2015
Priority date	Jul 31, 2014
Publication date	Aug 3, 2017
Grant date	—

Abstract

A method of synthesizing aerogels and cross-linked aerogels in a single step and in a single pot without requiring any solvent exchange is described. Porous matrices are synthesized through a modification of hydrolysis condensation of alkoxides in which addition of water is minimized. The reaction occurs in an ethanol-water azeotrope mixture; the water in the azeotrope slowly hydrolyzes the alkoxide. Additionally, after gelation, the porous matrix is dried in supercritical ethanol rather than liquid CO 2 , which allows for elimination of solvent exchange steps. These modifications allow for the preparation of aerogel monoliths in any size in one step and in one pot and much faster than conventional procedures. In addition, the method provides for custom aerogel parts with large dimensions, as well as high volume fabrication of aerogels. The custom aerogel parts may be used in a variety of thermal insulation applications.

First claim

1 . A method for producing an aerogel, comprising:
providing a first solution comprising an alkoxide; providing a second solution comprising a catalyst; mixing the first and second solutions to provide a gelation mixture; optionally pouring the solutions into a mold; wherein the mixing of the first and second solutions results in formation of a wet gel as a result of hydrolysis of the alkoxide and polymerization of the hydrolyzed alkoxide; and after gelation, drying the wet gel in an organic solvent and water azeotrope mixture heated at supercritical temperature and pressure to form an aerogel, wherein the drying is performed with the wet gel outside of any mold.

2 . The method of claim 1 , wherein the drying step is performed in the presence of, and the first solution and second solution comprise, an ethanol-water azeotrope mixture.

3 - 4 . (canceled)

5 . The method of claim 1 , wherein the method includes no solvent exchange step.

6 . The method of claim 1 , wherein the wet gel is not dried in liquid or supercritical CO 2 .

7 . The method of claim 1 , wherein the alkoxide is tetraethyl orthosilicate (TEOS) or tetramethyl orthosilicate (TMOS).

8 - 11 . (canceled)

12 . The method of claim 1 , wherein the catalyst is an acid, a metal salt or a base.

13 - 18 . (canceled)

19 . The method of claim 1 , wherein the first solution further comprises a first acrylic monomer and the second solution further comprises a second acrylic monomer, wherein the first acrylic monomer is hexanedioldiacryate or acrylated dipentaerthritol and wherein the second acrylic monomer is hexanedioldiacrylate or acrylated dipentaerthritol.

20 - 21 . (canceled)

22 . The method of claim 19 wherein the first solution or second solution further comprises a photoinitiator.

23 . (canceled)

24 . The method of claim 22 , wherein photopolymerization is induced by exposure of the gel to a source of visible light at an intensity sufficient to cause photopolymerization.

25 - 26 . (canceled)

27 . A method for producing an aerogel, comprising:
mixing a first solution comprising an alkoxide, a photoinitiator, and a first acrylic monomer and a second solution comprising a catalyst and a second acrylic monomer and optionally pouring the solutions into a mold, wherein such mixing step results in the formation of a wet gel as a result of hydrolysis of the alkoxide and polymerization of the hydrolyzed alkoxide; exposing the wet gel to a source of visible light with sufficient intensity to catalyze cross-linking of the wet gel; drying the wet gel in an organic solvent and water azeotrope mixture heated at supercritical temperature and pressure to form a cross-linked aerogel.

28 . The method of claim 27 , wherein the drying step is performed in the presence of, and the first solution and second solution comprise, an ethanol-water azeotrope mixture, or wherein only water in the ethanol-water azeotrope mixture catalyzes the hydrolysis of the alkoxide, or wherein the first solution and second solution contain no water beyond that contained in the ethanol-water azeotrope mixture.

29 - 30 . (canceled)

31 . The method of claim 27 , wherein the method includes no solvent exchange step.

32 . The method of claim 27 , wherein the wet gel is not dried in liquid or supercritical CO 2 .

33 . The method of claim 27 , wherein the alkoxide is tetraethyl orthosilicate (TEOS) or tetramethyl orthosilicate (TMOS).

34 - 37 . (canceled)

38 . The method of claim 27 , wherein the first acrylic monomer is hexanedioldiacryate or acrylated dipentaerthritol and wherein the second acrylic monomer is hexanedioldiacryate or acrylated dipentaerthritol.

39 . (canceled)

40 . The method of claim 27 , wherein the catalyst is an acid, a metal salt, or a base.

41 - 46 . (canceled)

47 . A thermal insulation product comprising an aerogel prepared according the method of claim 1 .

48 - 54 . (canceled)

55 . The method of claim 1 , wherein the alkoxide is present in an amount ranging from about 0.1% v/v to 50% v/v based on total volume of the gelation mixture.

56 . The method of claim 1 , wherein the gelation mixture comprises an amine present in an amount ranging from about 0.1% v/v to 20% v/v based on total volume of the gelation mixture.

57 . The method of claim 1 , wherein the gelation mixture comprises a supercritical organic solvent present in an amount ranging from about 20% v/v to 90% v/v based on total volume of the gelation mixture, and wherein the organic solvent is chosen from one or more of ethanol, methanol, butanol, propanol, acetone, or dimethylsulfoxide.

58 - 59 . (canceled)

Assignees

• Bertino Massimo
• Univ Virginia Commonwealth

Inventors

• Bertino Massimo

Classifications

• C08J2205/026

  Aerogel, i.e. a supercritically dried gel · CPC title

• C01B33/1585

  Dehydration into aerogels · CPC title

• C08J2201/022

  premixing or pre-blending a part of the components of a foamable composition, e.g. premixing the polyol with the blowing agent, surfactant and catalyst and only adding the isocyanate at the time of foaming · CPC title

• C08J2205/042

  Nanopores, i.e. the average diameter being smaller than 0,1 micrometer · CPC title

• C08J2333/08

  Homopolymers or copolymers of acrylic acid esters · CPC title