Solid State 13C Nuclear Magnetic Resonance Study of Morphology and Molecular Mobility in Quenched Poly(3-hydroxybutyrate)
A. Baran, P. Vrábel and D. Olčák
Department of Physics, Faculty of Electrical Engineering and Informatics, Technical University of Košice, Park Komenského 4, 042 00 Košice, Slovakia
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Single pulse magic angle spinning 13C NMR spectra and the carbon spin-lattice relaxation times T1(13C) were used for the study of morphology and molecular mobility in poly(3-hydroxybutyrate) quenched in cold water after melting in a twin-screw extruder. The crystallinity of the quenched sample was found to be comparable with that of virgin material, and the decrease in dimensions of the crystallites grown after quenching was deduced from the single pulse magic angle spinning 13C NMR spectra. The spin-lattice relaxation curves for the carbons of the CO, CH, CH2 and CH3 groups were found to be bi-exponential, which enables the molecular mobility within crystalline and amorphous domains to be studied. The spin-lattice relaxation times T1(13C) estimated for the carbons of the CO, CH, CH2 groups show the chain mobility enhancement within crystalline domains of the quenched sample, but the influence of the quenching on the CH3 group rotation and on the main chain motion within amorphous regions was not observed.

DOI: 10.12693/APhysPolA.131.1144
PACS numbers: 61.41.+e, 81.05.Lg, 76.60.-k, 74.25.nj