Method of Aerogel Synthesis

Abstract

The present disclosure provides a method of producing a aerogel comprising of reacting first monomer with a second monomer in a reaction solvent to form a composition comprising a precursor polymer; forming a gel; conducting a solvent exchange process on the gel such that the resulting gel comprises an exchange solvent that has a freezing point; cooling the gel to a temperature below the freezing point of the exchange solvent; and subjecting the cooled gel to vacuum conditions to obtain the aerogel.

We claim: 
     
         1 . A method of producing a aerogel, the method comprising:
 (a) reacting first monomer with a second monomer in a reaction solvent to form a composition comprising a precursor polymer;   (b) forming a gel;   (c) conducting a solvent exchange process on the gel such that the resulting gel comprises an exchange solvent that has a freezing point;   (d) cooling the gel from step (c) to a temperature below the freezing point of the exchange solvent; and   (e) subjecting the cooled gel to vacuum conditions to obtain the aerogel.   
     
     
         2 . The method of  claim 1 , wherein the solvent exchange process of step (c) comprises at least two rounds of solvent exchange. 
     
     
         3 . The method of  claim 1 , wherein the solvent exchange process is performed in a pressure vessel. 
     
     
         4 . The method of  claim 3 , further comprising compressing a gas or using pressurized gas in the pressure vessel. 
     
     
         5 . The method of  claim 1 , further comprising adding a dye to step (a) or step (b). 
     
     
         6 . The method of  claim 1 , wherein step (b) further comprises contacting the precursor polymer with a chemical imidizing agent to form the gel by imidization. 
     
     
         7 . The method of  claim 1 , wherein step (b) further comprises casting the composition from step (a) onto a substrate by spin casting, gravure coating, three roll coating, knife over roll coating, slot die extrusion, or dip coating. 
     
     
         8 . The method of  claim 1 , wherein step (b) further comprises heating the gel. 
     
     
         9 . The process of  claim 1  wherein the first monomer is an acid monomer. 
     
     
         10 . The process of  claim 9  wherein the second monomer is a diamino monomer. 
     
     
         11 . The method of  claim 10 , further comprising adding polyetheramine to the first monomer and second monomer before the formation of the polymer. 
     
     
         12 . The method of  claim 9 , wherein the at least one acid monomer is a tetracarboxylic acid, a tetraester, a diester acid, a trimethylsilyl ester, or a dianhydride. 
     
     
         13 . The method of  claim 10 , wherein the at least one diamino monomer is 4,4′’-oxydianiline, 3,4′-oxydianiline, p-phenylenediamine, m-phenylenediamine, 4,4′-diamino-2,2′-dimethylbiphenyl, or diaminobenzanilide. 
     
     
         14 . The method of  claim 1 , wherein the exchange solvent is selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutanol, tert-butanol, 3-methyl-2-butanol, 3,3-dimethyl-2-butanol, 2-pentanol, 3-pentanol, 2,2-dimethylpropan-1-ol, cyclohexanol, diethylene glycol, cyclohexanone, acetone, acetyl acetone, 1,4-dioxane, diethyl ether, dichloromethane, trichloroethylene, chloroform, carbon tetrachloride, water, and mixtures thereof. 
     
     
         15 . An aerogel prepared by the process of:
 (a) reacting a first monomer with a second monomer in a reaction solvent to form a composition comprising a precursor polymer;   (b) forming a gel;   (c) conducting a solvent exchange process on the gel such that the resulting gel comprises an exchange solvent that includes a freezing point;   (d) cooling the gel from step (c) to a temperature below the freezing point of the exchange solvent; and   (e) subjecting the cooled gel to vacuum conditions to obtain the aerogel.   
     
     
         16 . The aerogel of  claim 15 , wherein the first monomer is 3,3′,4,4′-biphenyl tetracarboxylic dianhydride, pyromellitic dianhydride, 3,3′,4,4′-benzophenone tetracarboxylic dianhydride, or 4,4′-oxydiphthalic anhydride. 
     
     
         17 . The aerogel of  claim 16 , wherein the second monomer is 4,4′-oxydianiline, 3,4′-oxydianiline, p-phenylenediamine, m-phenylenediamine, 4,4′-diamino-2,2′-dimethylbiphenyl, or diaminobenzanilide. 
     
     
         18 . The aerogel of  claim 15 , wherein the reaction solvent is selected from the group consisting of dimethylsulfoxide, diethylsulfoxide, N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N-methyl-2-pyrrolidone, 1-methyl-2-pyrrolidinone, N-cyclohexyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, diethyleneglycoldimethoxyether, o-dichlorobenzene, phenols, cresols, xylenol, catechol, butyrolactones, hexamethylphosphoramide, and mixtures thereof. 
     
     
         19 . The aerogel of  claim 18 , wherein the exchange solvent is selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutanol, tert-butanol, 3-methyl-2-butanol, 3,3-dimethyl-2-butanol, 2-pentanol, 3-pentanol, 2,2-dimethylpropan-1-ol, cyclohexanol, diethylene glycol, cyclohexanone, acetone, acetyl acetone, 1,4-dioxane, diethyl ether, dichloromethane, trichloroethylene, chloroform, carbon tetrachloride, water, and mixtures thereof. 
     
     
         20 . The aerogel of  claim 1 , wherein step (b) further comprises casting the composition from step (a) onto a substrate by spin casting, gravure coating, three roll coating, knife over roll coating, slot die extrusion, or dip coating.