In our study we used natural biodegradable polymer poly-3-hydroxybutyrate of the 16F series from Biomer (FRG), produced by bacterial fermentation. The viscosity-average molecular weight of PHB was 2.06×10
5. The fibers were obtained by the ES method using a single-capillary electrospinning laboratory unit at a capillary diameter of 0.1 mm, electric current voltage of 12 kV, electrode gap of 18 cm, and solution conductivity of 10 μS/cm. For producing fibrous matrices with antiseptic properties served ZnTPP and Fe(III)ClTPP complexes [11 –13 (
link)]. Electrospinning solutions were prepared in chloroform at 50°C using an automatic magnetic stirrer. The PHB concentration in the solution was 7 wt %, and the content of the complexes in the electrospinning solution, 1, 3, or 5 wt % of the PHB mass.
The electrospinning conditions exert a great influence on the nature and structure of fiber distribution in the material. Importantly, the structure of the material as a whole is irregular, with randomly oriented fibers. In this study, fiber distribution was examined by a set of methods of optical and scanning electron microscopy.
Mechanical properties were evaluated by the uniaxial stretching method on a DEVOTRANS (Turkey) tensile testing machine in accordance with GOST (State Standard) R 53226-2008 “Nonwoven fabrics: Methods for strength determination.”
Ozonation of the materials was carried out with the use of ozonizer in the laboratory of the Emanuel Institute of Biochemical Physics, Russian Academy of Sciences. Ozone was generated from oxygen by electric discharge process, where an increase in voltage led to that in the gas concentration. The experiment was carried out at the working ozone concentration of 5.5×10
–5 M. The absorbed ozone volume was estimated using an SF-46 Lomo spectrophotometer via measuring the optical density of the medium at a wavelength of 254 nm. The gas flow rate was 101.8 mL/min, and the time of ozonation of the material samples ranged from 3 to 5 min.
The X-ray diffraction analysis of the PHB fibers was carried out on a diffractometer with a linear position-sensitive (coordinate) detector [8 (
link), 9 (
link)] (Cu
Kα radiation, sample-detector distance 110 mm, measurements in the region of small and large scattering angles using transmission geometry) and on an HZG4 diffractometer (Freiberger Präzisionsmechanik, FRG) with a diffracted beam graphite monochromator in the Bragg-Brentano reflection geometry (Cu
Kα radiation, measurements in the region of large scattering angles using reflection geometry). X-band ESR spectra were recorded on an EPR-V automated spectrometer (Russia). TEMPO stable nitroxyl radical was used as a probe. The radical was introduced into the fibers from the gas phase at a temperature of 50°C; its concentration in the polymer did not exceed 10
–3 M. The geometry of the fibrous materials was examined with a Micromed Polar 3 ToupCam 5.1 MP (China) optical microscope in reflected light at magnification 200x and with a Hitachi TM-3000 scanning electron microscope (Japan) (at an accelerating voltage of 20 kV; a 100–200 Ǻ thick gold layer was sprayed on the surface of a nonwoven fibrous material sample). The DSC study of the samples was conducted on a Netzsch DSC 204 F1 instrument in an argon atmosphere at a heating rate of 10°C/min.
Ol’khov A.A., Tyubaeva P.M., Zernova Y.N., Kurnosov A.S., Karpova S.G, & Iordanskii A.L. (2021). Structure and Properties of Biopolymeric Fibrous Materials Based on Polyhydroxybutyrate–Metalloporphyrin Complexes. Russian Journal of General Chemistry, 91(3), 546-553.
