Crystalline morphology of electrospun poly(ε-caprolactone) (PCL) nanofibers

The crystalline morphologies of electrospun random and aligned poly(ε-caprolactone) (PCL) nanofibers, obtained by a plate collector and a two-parallel-conductive-plate collector, respectively, were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), two-dimensional wide-angle X-ray diffraction (2D WAXD), and polarized Fourier transform infrared (polarized FTIR) spectroscopy. The fiber orientations and diameters of the aligned nanofibers were found to depend on the gap size of the collector, which was much larger than those previously reported, thus easing and improving sample handling and characterization. The degree of crystallinity of the aligned nanofibers was higher than that of their randomly aligned counterparts. The crystallites in the nanofibers were highly oriented along the nanofiber axis, as were the molecular chains. The estimated crystallite size suggested that a single nanofiber was composed of dozens of nanofibrils and that each nanofibril was further composed of crystallites along the nanofiber axis with an amorphous region of extended PCL molecular chains between neighboring crystallites.