Toward a Tunable Fibrous Scaffold: Structural Development during Uniaxial Drawing of Coextruded Poly(ε-caprolactone) Fibers

Abstract

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 asextruded 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.

Synthesis and thermal, optical and morphological characterization of oligomeric polyamides based on thiophene and alkyl/phenyl‐silane moieties. Study of the electrospun deposition process

“…thiophene). 1 H NMR (400 MHz, DMSO‐ d 6 , δ): 10.16 (s, 2H 9 ), 7.94 (d, J = 7.9 Hz, 4H 13 ), 7.59 (d, J = 7.3 Hz, 4H 12 ), 7.51 (m, 4H), 7.48‐7.37 (m, 12H ), 7.34 (d, J = 5.9 Hz, 2H 4 ), 7.25 ppm (d, J = 5.0 Hz, 2H 5 ). 13 C NMR (400 MHz, DMSO‐ d 6 , δ): 165.85 (C 10 ), 140.19 (C 1 ), 137.25 (C 11 ), 135.85 (C 12 ), 135.63 (C 8 ), 134.17 (C 14 ), 132.58 (C 16 ), 130.76 (C 3 ), 130.14 (C 17 ), 129.23 (C 6 ), 128.73 (C 2 ), 128.33 (C 4 ), 128.29 (C 18 ), 127.97 (C 13 ), 127.16 (C 19 ), 126.94 (C 5 ), 126.40 ppm (C 7 ).…”

“…The internal structure‐conformation and crystallinity are determined mainly by hydrogen bonding (amide groups‐polar) and Vander Waals forces (methylene chains‐apolar), interactions that affect their polymer length and, also, their dielectric properties. This type of material is widely applied, like other polymers such as polystyrene, polyacrylonitrile, and several polycarbonates, in electrospinning . Thus, electrospun is a technique employed for the formation and deposition of ordered nano‐ and micro‐structures, being able to control their diameter, spatial distribution, porosity, and orientation.…”

Structural insights into semicrystalline states of electrospun nanofibers: a multiscale analytical approach

“…Hence, very often measurements are performed on nanofiber membranes which make the data analysis more sophisticated based on a high number of nanofibers being simultaneously probed by a micrometer size X-ray beam. 22,28,29,39 In few reported studies on electrospun nanofibers, structural information from 2D SAXS profiles has been qualitatively discussed 28,40,41 and only very limited microscopic information such as nanofiber orientation has been extracted. 41 Recently, Kogikoski et al 42 reported on a quantitative analysis of the data based on simulations of the whole scattering profile to understand the structure and molecular arrangement in a polycaprolactone-polyaniline blend.…”

Design and Fabrication of Fibrous Nanomaterials Using Pull Spinning

“…Currently, fiber‐fabrication systems can be characterized as melt, dry, wet, or electrospinning—all of which produce nanofibers using high temperature and pressure (melt, dry, and wet spinning) or electric fields (5–20 kV, electrospinning) . Once formed, the fibers can be collected and processed using external pumps, alternating applied electric fields, spinnerets, coagulation, and wash chambers, or heated drum rolls to form aligned functional materials . Several electrospinning techniques have been developed to further control fiber deposition and structure, producing aligned fibrous nanostructures by minimizing the distance between a charged nozzle and grounded collector .…”