Fiber having non-uniform composition and method for making same

Abstract

A fiber having a non-uniform composition is disclosed. The fiber includes a first domain having a first composition and a second domain having a second composition different from the first composition. The fiber includes an interphase region intermediate the first and second domains that includes a blend of the first and second compositions to provide a gradual transition from the first domain composition to the second domain composition. A method for making such fibers is also disclosed.

1 . A fiber having a radially non-uniform composition comprising:
 a first domain of a first composition;   a second domain of a second composition different from the first composition; and   an interphase region intermediate the first domain and the second domain, the interphase region comprising a blend of the first composition and the second composition.   
     
     
         2 . The fiber of  claim 1 , wherein the first domain forms a fiber core and the second domain forms an annular sheath surrounding the core, the interphase region annularly disposed intermediate the core and the sheath. 
     
     
         3 . The fiber of  claim 1 , wherein the interphase region has a thickness of about 0.25 microns to about 200 microns. 
     
     
         4 . The fiber of  claim 1 , wherein the interphase region comprises a plurality of annular interphase domains in which each annular interphase domain has a weight ratio of the first composition to the second composition that is different from each domain directly adjacent thereto. 
     
     
         5 . The fiber of  claim 4 , wherein each annular interphase domain has a thickness of about 0.25 microns to about 50 microns. 
     
     
         6 . The fiber of  claim 1 , wherein the first composition and the second composition comprise different polymers. 
     
     
         7 . The fiber of  claim 1 , wherein the first composition and the second composition comprise a same polymer. 
     
     
         8 . The fiber of  claim 1 , further comprising a third composition different from each of the first and second compositions. 
     
     
         9 . The fiber of  claim 1  comprising a core forming an innermost domain, an annular sheath forming an outermost domain, a middle domain intermediate the core and the sheath, a first interphase region intermediate the core and the middle domain, and a second interphase region intermediate the middle domain and the sheath. 
     
     
         10 . The fiber of  claim 1 , wherein the first or second composition comprises a material selected from the group consisting of polycaprolactone, poly-l-lactic acid, poly-d-lactic acid, polydioxanone, trimethylene carbonate, polyhydroxybutyrate, polyhydroxyvalerate, poly(FAD-SA), poly(CPP-SA), poly(FA-SA), poly(EAD-SA), poly glycolide, copolymers thereof, and combinations thereof. 
     
     
         11 . The fiber of  claim 1 , wherein the first composition comprises a p-doped polymeric material and wherein the second composition comprises a n-doped polymeric material. 
     
     
         12 . The fiber of  claim 1  having a diameter in the range of between about 5 microns and about 300 microns. 
     
     
         13 . The fiber of  claim 1  having a diameter in the range of between about 5 microns and about 20 microns. 
     
     
         14 . A fiber containing a radially gradient composition. 
     
     
         15 . The fiber of  claim 14 , wherein the radially gradient composition is defined by a plurality of discrete domains in which the weight ratio of a first component to a second component in each domain increases as the radial distance increases. 
     
     
         16 . The fiber of  claim 14 , wherein the radially gradient composition encompasses an interphase region of the fiber positioned intermediate a central core and a sheath of the fiber. 
     
     
         17 . The fiber of  claim 14 , wherein the radially gradient composition comprises a biodegradable material selected from the group consisting of polycaprolactone, poly-l-lactic acid, poly-d-lactic acid, polydioxanone, trimethylene carbonate, polyhydroxybutyrate, polyhydroxyvalerate, poly(FAD-SA), poly(CPP-SA), poly(FA-SA), poly(EAD-SA), poly glycolide, copolymers thereof, and combinations thereof, wherein the amount of the biodegrable material in the fiber decreases along the radial distance from an outer surface to the center of the fiber. 
     
     
         18 . A method comprising:
 providing a first fiber component having a first composition and a second fiber component having a second composition different from the first composition;   extruding a plurality of fibrils from the fiber components;   commingling the fibrils in a predetermined architecture; and   coalescing the fibrils to form a fiber having a radially non-uniform composition having a first domain comprising the first component, a second domain comprising the second component, and an interphase region positioned intermediate the first and second domains and comprising a blend of the first and second components.   
     
     
         19 . The method of  claim 18 , wherein the interphase region is formed having a thickness in the range of about 0.25 microns to about 50 microns. 
     
     
         20 . The method of  claim 18 , wherein the interphase region comprises a plurality of annular domains. 
     
     
         21 . The method of  claim 18 , further comprising after the step of commingling but before the step of coalescing, statically mixing the composition of at least two fibrils.