Comparative Structural Dynamic Analysis of Ultrathin Fibers of Poly-(3-Hydroxybutyrate) Modified by Tetraphenyl–Porphyrin Complexes with the Metals Fe, Mn, and Zn

Abstract

Complex studies combining X-ray diffraction analysis, thermophysical and dynamic measurements by the probe method, and scanning electron microscopy have been performed. The specific features of the crystalline and amorphous structures of ultrathin fibers based on poly(3-hydroxybutyrate) (PHB) containing tetraphenylporphyrin (TPP) complexes with manganese (in the form of MnCl₂), zinc, and iron (in the form of FeCl₃) in minor concentrations (0–5%) have been considered. It is shown that the addition of these complexes to PHB fibers changes the fiber morphology, and an increase in crystallinity and a symbatic decrease in the molecular mobility in dense and loose amorphous PHB regions are observed in the following sequence: PHB/TPP, PHB/Zn–TPP, PHB/MnCl₂–TPP, and PHB/FeCl₃–TPP. The effect of temperature on fibers (their annealing at 140°C) sharply increases the crystallinity and molecular mobility in amorphous regions of the fibers. Their exposure in an aqueous medium at 70°C leads to an increase in the melting enthalpy and retardation of the molecular dynamics only in the initial PHB; in modified fibers, however, this exposure reduces the enthalpy significantly. In this case, the molecular mobility of chains in amorphous regions increases. The fibrous materials obtained have bactericidal properties and should find application in designing new therapeutic systems of antibacterial and antitumor action.