Hydropohobic aerogels

Abstract

Methods of making hydrophobic aerogels are described. Disclosed methods include forming a surface-modified metal oxide aerogel precursor from a sol comprising a solvent, a metal oxide precursor, and a hydrophobic surface modifying agent. The resulting modified precursor can be dried to from hydrophobic aerogels. Methods of forming the surface-modified metal oxide aerogel precursor include hydrolyzing the metal oxide precursor and co-condensing the hydrolyzed metal oxide precursor and the hydrophobic surface modifying agent. Hydrophobic aerogels and hydrophobic aerogel articles are also disclosed.

1 . A method of preparing a hydrophobic aerogel comprising forming a surface-modified metal oxide aerogel precursor from a sol comprising a solvent, a metal oxide precursor, and a hydrophobic surface modifying agent; and drying the surface-modified metal oxide aerogel precursor to form the hydrophobic aerogel. 
     
     
         2 . The method of  claim 1 , wherein forming the surface-modified metal oxide aerogel precursor comprises hydrolyzing the metal oxide precursor and co-condensing the hydrolyzed metal oxide precursor and the hydrophobic surface modifying agent. 
     
     
         3 . The method of  claim 1 , further comprising solvent-exchanging the surface-modified metal oxide aerogel precursor with an alkyl alcohol to form an alcogel. 
     
     
         4 . The method of  claim 1 , further comprising supercritically drying the aerogel precursor or the alcogel to form the hydrophobic aerogel. 
     
     
         5 . The method of  claim 1 , wherein the solvent comprises water. 
     
     
         6 . The method of  claim 1 , wherein the solvent comprises an alkyl alcohol. 
     
     
         7 . The method of  claim 1 , wherein the metal oxide precursor comprises an organosilane. 
     
     
         8 . The method of  claim 7 , wherein the organosilane comprises a tetraalkoxysilane selected from the group consisting of tetraethoxysilane, tetramethoxysilane, and combinations thereof. 
     
     
         9 . The method according to  claim 7 , wherein the organosilane comprises methyltrimethoxysilane. 
     
     
         10 . The method according to  claim 6 , wherein the organosilane comprises a polysilicate. 
     
     
         11 . The method of  claim 1 , wherein the hydrophobic surface modifying agent comprises 1,1,1,3,3,3-hexamethyldisilazane. 
     
     
         12 . The method of  claim 1 , wherein the molar ratio of the hydrophobic surface modifying agent to the metal oxide precursor is no greater than 1. 
     
     
         13 . The method of  claim 1 , wherein the molar ratio of the hydrophobic surface modifying agent to the metal oxide precursor is at least 0.2. 
     
     
         14 . The method of  claim 1 , wherein the sol further comprises at least one of hydrochloric acid and oxalic acid. 
     
     
         15 . The method of  claim 1 , further comprising applying the sol to a substrate prior to forming surface-modified metal oxide gel. 
     
     
         16 . The method of  claim 15 , wherein the sol is applied to the substrate prior to forming the surface-modified metal oxide aerogel precursor. 
     
     
         17 . The method of  claim 15 , wherein the substrate is non-woven substrate. 
     
     
         18 . The method of  claim 15 , wherein the substrate is a bonded web. 
     
     
         19 . An aerogel article made according to the method of  claim 15 . 
     
     
         20 . A hydrophobic aerogel made by the method of  claim 1 , wherein a sample of the hybrid aerogel placed in a jar containing deionized water at 22° C. remains floating after 30 minutes.