Fast response nanofiber articles with tunable wettability and bulk properties

Abstract

A fibrous properties-switching article comprises a mat consisting of fibers having a fiber diameter of 2 microns or less. The fibers comprise a polymer, copolymer, polymer blend, or polymer network, wherein the fibers have a diameter of 2 gm or less. The surface and/or bulk property of the mat changes over a range of temperatures, wherein the polymer, copolymer, polymer blend, or polymer network undergoes a structural change over the range of temperatures. The fiber mat is formed by electrospinning. In an exemplary embodiment, a blend of polystyrene and poly((N-isopropyl acrylamide) (b1-PS/PNIPA) in dimethylformamide (DMF) is electrospun to form a mat consisting of fibers with a diameter less than 2 μm that shows a transition from a superhydrophilic surface to a nearly superhydrophobic surface over a temperature range from 30° C. to 45° C. A fiber mat formed by electrospinning a DMF solution comprising poly(N-isopropyl acrylamide-co-methacylicacid) (PNIPAMAA), comprises fibers having a diameter less than 2 μm and are cross linked after spinning. The crosslinked PNIPAMAA, (x1-PNIPAMAA) fiber mat displays a transition from a hydrophilic surface to a nearly hydrophobic surface over a temperature range from 30° C. to 45° C.

We claim: 
     
         1 . A fibrous properties-switching article, comprising a mat consisting of fibers, wherein the fibers comprise a polymer, copolymer, polymer blend, or polymer network, wherein the fibers have a diameter of 2 μm or less, wherein the polymer, copolymer, polymer blend, or polymer network undergoes a structural change over a range of temperatures, and wherein a surface and/or bulk property of the mat changes over the range of temperatures. 
     
     
         2 . The fibrous properties-switching article of  claim 1 , wherein the structural change is a conformational change and/or a change in solvation. 
     
     
         3 . The fibrous properties-switching article of  claim 1 , wherein the fiber mat comprises a polymer blend of polystyrene and poly((N-isopropyl acrylamide) (b1-PS/PNIPA). 
     
     
         4 . The fibrous properties-switching article of  claim 3 , wherein the polystyrene and the poly((N-isopropyl acrylamide) are in a weight ratio of 7 PS to 3 PNIPA. 
     
     
         5 . The fibrous properties-switching article of  claim 1 , wherein the fiber mat comprises a polymer network of crosslinked poly(N-isopropyl acrylamide-co-methacylicacid) (x1-PNIPAMAA). 
     
     
         6 . The fibrous properties-switching article of  claim 1 , wherein the surface property change comprises a change from hydrophobicity to hydrophilicity. 
     
     
         7 . The fibrous properties-switching article of  claim 6 , wherein a response rate for the change from hydrophobicity to hydrophilicity is less than one minute. 
     
     
         8 . The fibrous properties-switching article of  claim 6 , wherein a response rate for the change from hydrophobicity to hydrophilicity is less than 5 seconds. 
     
     
         9 . A method for preparing a fiber mat of a property switching material according to  claim 1  comprising:
 providing a solution comprising at least one polymer or copolymer; 
 optionally including a catalyst and/or a reagent for crosslinking; and 
 electrospinning the solution onto a target substrate to form a mat consisting of fibers, wherein the fibers are 2 μm or less in diameter. 
 
     
     
         10 . The method of  claim 9 , wherein the solution comprising at least one polymer is a blend of PS and PNIPA in dimethylformamide (DMF). 
     
     
         11 . The method of  claim 9 , wherein the solution comprising a copolymer is PNIPAMAA in DMF. 
     
     
         12 . The method of  claim 11 , wherein the catalyst is disodium hydrogen phosphate (DSHP). 
     
     
         13 . The method of  claim 11 , wherein the reagent is polyvinyl alcohol (PVA). 
     
     
         14 . The method of  claim 9 , further comprising heating the mat, wherein crosslinking of the fibers occurs.