Method to produce transparent polymer aerogels using chain transfer agents

Patent metadata

Field	Value
Publication number	US-10626224-B2
Application number	US-201715728385-A
Country	US
Kind code	B2
Filing date	Oct 9, 2017
Priority date	Oct 9, 2017
Publication date	Apr 21, 2020
Grant date	Apr 21, 2020

Abstract

A method of producing a transparent polymer aerogel can include dissolving gel precursors consisting of radical polymerizable monomers and crosslinkers, radical initiators, and a chain transfer agent (CTA) in a reaction solvent, placing the gel precursors into a substrate, polymerizing the gel on the substrate, optionally removing the wet gel from the mold, optionally performing at least one solvent exchange on the gel, and drying the solvent-exchanged gel.

First claim

What is claimed is:

1. A method of producing a polymer aerogel, the method comprising:
dissolving gel precursors including radical polymerizable monomers and crosslinkers, radical initiators, and a chain transfer agent (CTA) in a reaction solvent, wherein the chain transfer agent is selected from a group consisting of: an organic thiol, dodecanethiol, carbon tetrachloride, and pentaphenylethane;
polymerizing the gel precursors to form a gel; and
drying the gel.

2. The method of claim 1 , wherein the reaction solvent is a polar, aprotic, organic solvent.

3. The method of claim 2 , wherein the polar, aprotic organic solvent is selected from a group consisting of: acetophenone, dimethylformamide, and n-methylpyrrolidone.

4. The method of claim 1 , wherein the radical initiators are selected from a group consisting of: organic peroxides and organic azo compounds.

5. The method of claim 1 , wherein the radical initiators are selected from a group consisting of: a UV radical initiator and a radical photoinitiator.

6. The method of claim 1 , wherein a concentration of the gel precursors in the reaction solvent in the precursor formulation is within a range from 5% to 70% by mass.

7. The method of claim 1 , wherein the radical polymerizable monomers are selected from a group consisting of: mono and difunctional acrylates, methacrylates and vinyl monomers.

8. The method of claim 1 , wherein the crosslinkers are selected from a group consisting of: tri, tetra, penta or hexa functional acrylates, methacrylates and vinyl monomers.

9. The method of claim 1 , wherein polymerization is carried out by activating the radical initiators by heating and/or by exposure to light of an appropriate wavelength.

10. The method of claim 1 , wherein polymerizing the gel precursors is performed on a substrate or a mold.

11. The method of claim 10 , wherein the gel is removed from the substrate or the mold prior to drying.

12. The method of claim 1 , wherein at least one solvent exchange is performed on the gel prior to drying.

13. The method of claim 12 , wherein performing at least one solvent exchange includes performing static or flow solvent exchange.

14. The method of claim 12 , wherein performing at least one solvent exchange includes exchanging the gel into a solvent suitable for extracting any oligomers.

15. The method of claim 14 , wherein the solvent suitable for extracting any oligomers is selected from a group consisting of: acetophenone, dimethylformamide, n-methylpyrrolidone, and tetrahydrofuran (THF).

16. The method of claim 12 , wherein performing at least one solvent exchange further includes exchanging the gel into a solvent having low solvent-polymer interaction strength, acetone, or heptanes.

17. The method of claim 1 , wherein the aerogel is dried by air, by a supercritical CO 2 process, or by freeze-drying.

18. The method of claim 1 , further comprising, after drying the gel to form an aerogel, applying the aerogel to a substrate.

19. The method of claim 17 , wherein the polymer aerogel is transparent and has a transmittance higher than 10% per mm of sample thickness.

20. The method of claim 1 , wherein the organic thiol contains organic molecules containing a halogen group and a thiol.

Assignees

• Palo Alto Res Ct Inc
• Xerox Corp

Inventors

• Chintapalli Mahati
• Keoshkerian Barkev
• Iftime Gabriel
• Overmeere Quentin Van

Classifications

• C08J2347/00

  Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, at least one having two or more carbon-to-carbon double bonds; Derivatives of such polymers (C08J2345/00 takes precedence; of conjugated diene rubbers C08J2309/00 - C08J2321/00) · CPC title

• C08J3/075

  Macromolecular gels · CPC title

• C08J11/22

  by treatment with organic oxygen-containing compounds · CPC title

• C08J2205/026

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

• C08F222/104

  of tetraalcohols, e.g. pentaerythritol tetra(meth)acrylate · CPC title