Networked polymeric nanofibers, process for producing same, gas adsorbent, and gas separation material

Abstract

The invention provides networked polymeric nanofibers having a structure in which amorphous polymeric fibers are branched at multiple sites and having a diameter of from 1 nanometer to 100 nanometers. A solution of a polymer such as polystyrene in a good solvent thereof is rapidly frozen to form a nanoscale phase-separation structure of the polymer and the frozen solvent. The networked polymeric nanofibers can then be obtained upon removing the frozen solvent.

1 . A networked polymeric nanofiber having a diameter of from 1 nanometer to 100 nanometers, and having a structure in which amorphous polymeric fibers are branched at multiple sites. 
     
     
         2 . The networked polymeric nanofiber according to  claim 1 , wherein the networked polymeric nanofiber has a specific surface area of from 10 m 2 /g to 1,000 m 2 /g. 
     
     
         3 . The networked polymeric nanofiber according to  claim 1 , wherein the amorphous polymer is one or more compounds selected from the group consisting of polystyrene, polycarbonate, poly(2,6-dimethyl-p-phenyleneoxide), polysulfone, poly(p-phenylene ether-sulfone), polyacrylonitrile, polyetherimide, and polyvinyl chloride. 
     
     
         4 . A process for producing a networked polymeric nanofiber, the process comprising the steps of:
 (a) dissolving an amorphous polymer in a good solvent thereof to obtain a polymer solution;   (b) rapidly freezing the amorphous polymer solution to form a nanoscale phase-separation structure of the polymer and solidified solvent molecules; and   (c) removing the good solvent from the frozen amorphous polymer solution.   
     
     
         5 . The process according to  claim 4 , wherein the step of removing the good solvent includes a step of displacing the good solvent with a poor solvent of the amorphous polymer. 
     
     
         6 . The process according to  claim 5 , wherein the poor solvent is methanol. 
     
     
         7 . The process according to  claim 5 , wherein the solvent displacing step includes a step of increasing temperature in a stepwise manner. 
     
     
         8 . The process according to  claim 5 , wherein the step of removing the good solvent further includes a step of performing solvent exchange. 
     
     
         9 . The process according to  claim 8 , wherein the solvent exchange is performed by using the poor solvent or butanol. 
     
     
         10 . The process according to  claim 4 , wherein the step of removing the good solvent includes a step of performing freeze drying, or vacuum drying at a temperature no greater than the glass transition point of the amorphous polymer. 
     
     
         11 . The process according to  claim 4 , wherein the amorphous polymer is one or more compounds selected from the group consisting of polystyrene, polycarbonate, poly(2,6-dimethyl-p-phenyleneoxide), polysulfone, poly(p-phenylene ether-sulfone), polyacrylonitrile, polyetherimide, and polyvinyl chloride. 
     
     
         12 . The process according to  claim 4 , wherein the good solvent is one or more compounds selected from the group consisting of benzene, carbon tetrachloride, chlorobenzene, chloroform, cyclohexanone, o-dichlorobenzene, dimethylformamide, 1-methyl-2-pyrrolidone, nitrobenzene, 1,1,2,2-tetrachloroethane, and p-xylene. 
     
     
         13 . A gas adsorbent that uses the networked polymeric nanofiber of  claim 1 . 
     
     
         14 . A gas separation material that uses the networked polymeric nanofiber of  claim 1 . 
     
     
         15 . An organic molecule removing agent that uses the networked polymeric nanofiber of  claim 1 .