Crystallization of constrained polymers

Abstract

The invention provides micro- and nano-porous materials made from crosslinked polymers crystallized from supercritical fluids. The resulting products show an open cell porous network, and can be used for a variety of applications in medical fields, textiles, separation science and others. The invention also provides methods for obtaining such products.

What is claimed is:  
     
         1 . A method for producing porous structure in a polymer, the method comprising: 
 a) shaping a polymer;    b) constraining the structure of at least a portion of the polymer;    c) melting the polymer;    d) contacting the melted, constrained polymer with a solvent under conditions, and for a time sufficient to cause at least partial swelling of the polymer;    e) crystallizing the swollen polymer; and    f) removing the solvent, to yield a porous polymer.    
     
     
         2 . The method of  claim 1 , wherein the solvent is a supercritical fluid.  
     
     
         3 . The method of  claim 2 , wherein the supercritical fluid is propane.  
     
     
         4 . The method of  claim 1 , wherein steps a) and b) are performed simultaneously.  
     
     
         5 . The method of  claim 4 , wherein shaping is reactive extrusion.  
     
     
         6 . The method of  claim 1 , wherein the structure of at least a portion of the polymer is constrained by crosslinking.  
     
     
         7 . The method of  claim 6 , wherein the crosslinking is achieved by radiation.  
     
     
         8 . The method of  claim 6 , wherein the crosslinking is achieved by reacting functional groups on the polymer.  
     
     
         9 . The method of  claim 6 , wherein the crosslinking is achieved by chemical radical-initiation.  
     
     
         10 . The method of  claim 6 , wherein the crosslinking is achieved by photochemical reaction.  
     
     
         11 . The method of  claim 6 , further comprising extracting an uncrosslinked portion of the polymer from the crosslinked portion of the polymer with a solvent before crystallization to produce a solution comprising an uncrosslinked portion of polymer.  
     
     
         12 . The method of  claim 11 , further comprising extracting substantially the entire uncrosslinked portion of the polymer from the crosslinked polymer.  
     
     
         13 . The method of  claim 11 , further comprising impregnating the crosslinked portion of the polymer with a further material, wherein the further material penetrates the interior of the crosslinked portion of the polymer.  
     
     
         14 . The method of  claim 11 , further comprising impregnating the crosslinked portion of the polymer with a further material, wherein the further material remains substantially on the exterior of the crosslinked portion of the polymer.  
     
     
         15 . The method of  claim 13 , wherein the further material comprises a polymer.  
     
     
         16 . The method of  claim 14 , wherein the further material comprises a cell culture.  
     
     
         17 . The method of  claim 14 , wherein the further material comprises a pharmaceutically active material.  
     
     
         18 . The method of  claim 13 , wherein the further material comprises a lubricant.  
     
     
         19 . The method of  claim 13 , wherein the further material comprises a reactive crosslinking material.  
     
     
         20 . The method of  claim 11 , further comprising replacing the solution comprising uncrosslinked portion of polymer with solvent containing substantially no uncrosslinked portion of polymer.  
     
     
         21 . A method for making a shaped material, the method comprising: 
 allowing a solidifiable material to impregnate the interior of a porous structure;    solidifying the solidifiable material; and    removing the porous structure to produce a shaped material.    
     
     
         22 . The method of  claim 20 , wherein the porous structure has pore sizes between about 0.01 μm and 100 μm.  
     
     
         23 . The method of  claim 20 , wherein the solidifiable material is an inorganic sol.  
     
     
         24 . The method of  claim 22 , wherein the inorganic sol is a metal alkoxide or metalloid alkoxide.  
     
     
         25 . A porous crosslinked polymer having pore diameters from about 0.01 μm to about 100 μm, and having a open-cell, bicontinuous structure.  
     
     
         26 . A tissue scaffold comprising the porous crosslinked polymer of  claim 25 .  
     
     
         27 . A catalyst substrate comprising the porous crosslinked polymer of  claim 25 .  
     
     
         28 . A liquid or gas filter comprising the porous crosslinked polymer of  claim 25 .  
     
     
         29 . A method for growing cells comprising: 
 providing a porous crosslinked polymeric scaffold; at least a portion of the surface of which is coated with cells; and    allowing the cells to grow for a time, and under conditions, sufficient to produce new cell.    
     
     
         30 . The method of  claim 29 , wherein the cells produce a material excreted into an extracellular matrix.  
     
     
         31 . The method of  claim 29 , wherein the cells and new cells form tissue.  
     
     
         32 . A battery separator comprising a porous crosslinked polymer.  
     
     
         33 . A porous polymer having pore sizes between about 0.1 μm and 100 μm.  
     
     
         34 . The porous polymer of  claim 33 , having a volume porosity of from about 1% to about 90%.  
     
     
         35 . The porous polymer of  claim 33 , having an open-celled, bicontinuous pore structure.