Changes in the structural parameters and molecular dynamics of polyhydroxybutyrate-chitosan mixed compositions under external influences

Differential scanning calorimetry (DSC), EPR probe analysis, large-angle X-ray diffraction (XRD), and UV spectroscopy are used to study the molecular dynamics and structure of hydroxybutyrate (PHB) copolymer, chitosan, and mixed compositions thereof upon thermal treatment in an aquatic medium. It is shown that, in mixed compositions, starting from 30% PHB, the correlation time increases by an order of magnitude, indicative of a sharp slowdown of the molecular mobility of the probe, and, concurrently, the degree of crystallinity decreases abruptly, as evidenced by DSC and XRD analyses. The diffusion coefficient of rifampicin in mixed compositions also decreases with increasing PHB content. A short-term (1 h) thermal treatment (at 70A degrees C) in water results in an increase in the molecular mobility of the probe in the system. Crystallinity changes in complex ways.