Composite Ultrathin Fibers of Poly-3-Hydroxybutyrate and a Zinc Porphyrin: Structure and Properties

Abstract

Ultrathin fibers of poly-3-hydroxybutyrate (P3HB), a biodegradable polymer, modified by addition of a zinc porphyrin (content up to 5% with respect to P3HB), are prepared by electrospinning. The f ibers are investigated by differential scanning calorimetry, spin-probe electron paramagnetic resonance, scanning electron microscopy, and IR spectroscopy. We show that P3HB fibers modified with the porphyrin complex exhibit superior crystallinity and retardation of molecular motion in the amorphous regions of polymer. Subjecting the fibers to heat treatment at 140°C results in drastic increases in crystallinity and molecular motion in the amorphous regions of pure P3HB and P3HB, which contain 1% of the porphyrin complex. At a porphyrin content of 3%, a sharp drop in crystallinity of P3HB fibers is observed. The effects that aqueous thermal treatment at 70°C has on the structure and dynamics of our ultrathin fibers suggest that the processed samples become more crystalline. The molecular motion in the prepared fibers slows down as a result of relatively short (up to 100 min) ozone treatment, whereas the molecular motion intensifies at more advanced degrees of oxidation of the fibers.