Toward a tunable fibrous scaffold: Structural development during uniaxial drawing of coextruded poly(ε-caprolactone) fibers

A continuous fibrous composite tape of poly(ethylene oxide) (PEO) and poly(ε-caprolactone) (PCL) was produced using novel multilayer coextrusion fiber manufacturing. A three-step washing process was utilized to remove the PEO matrix, resulting in a PCL fiber mat (>99 wt %). Synchrotron X-ray radiation was utilized to determine the optimized postprocessing uniaxial drawing conditions to achieve efficient crystalline orientation. An examination of small-/wide-angle X-ray scattering (SAXS/WAXS) revealed two regimes in the uniaxial drawing process; at DR < 5, crystalline orientation kinetics were dominant, while at DR > 5, amorphous chain alignment kinetics were dominant. Uniaxial drawing was shown to be an effective tool for tuning individual fiber size from 2.6 ± 0.6 μm by 1.6 ± 0.4 μm in the as-extruded state to 0.31 ± 0.05 μm by 0.13 ± 0.02 μm in the oriented state, while increasing specific surface area 3.5-fold. The elastic modulus and tensile strength of the PCL fiber mat were also increased by a factor of 30 and ∼10, respectively, through uniaxial drawing. Compared to electrospun PCL fiber systems produced with individual fiber dimensions similar to those of the as-extruded and oriented PCL fiber mats, the melt-processed PCL fibers exhibit a 6-fold increase in specific surface area over the corresponding circular, electrospun PCL fibers while maintaining similar thermomechanical properties. The elastic modulus of the oriented, coextruded PCL fiber mat was increased by a factor of 50 compared to the corresponding electrospun PCL fiber mat, while exhibiting a 2.5-fold increase in specific surface area. The ability to melt-process and utilize uniaxial drawing to produce PCL fibers in high volume with a consistent, tunable range of properties that are similar or enhanced when compared to traditional electrospun fibers provides a unique advantage in the field of tissue engineering, surface modification, and drug delivery.