ABSTRACT
Abstract ................................................................................................. 402 11.1 Introduction ................................................................................ 402 11.2 Materials and Methods ............................................................... 404 11.3 Results and Discussion ............................................................... 405 11.4 Conclusions ................................................................................ 412 Acknowledgments ................................................................................. 413
Keywords .............................................................................................. 413 References ............................................................................................. 413
ABSTRACT
The chapter is focused on the study of segmental dynamics in electrospun PHB fibers and the same fibers subjected to cold rolling as well as in PHB films for the comparison of spin probe characteristics obtained by ESR technique. It was disclosed the presence of two TEMPO probe populations with different correlation times indicating the heterogeneous structure of intercrystalline areas in the films, fiber mats and the cold rolled fiber mats. The ESR data are in agree with the 2-mode model of amorphous state in semicrystalline polymers. The difference in peak intensities shows that effective correlation time in the electrospun fibers (3.5 ± 0.6×10-9 s) exceeds the same characteristic in the film (1.4 ± 0.3×10-9 s) that also indicates the slower molecular mobility in the low-dense amorphous fraction of PHB fibers as compared to the film. Taking into account the ESR technique data, the analysis of temperature, water and ozone impacts upon probe mobility enable us to suggest that fiber electrospinning and especially the cold-rolling procedure for the fiber mats lead to denser field formation in the intercrystalline area of PHB that furthers the fiber stabilization against the exterior aggressive factors.
