High-Resolution Solid-State NMR Characterization of Morphology in Annealed Polylactic Acid |
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| Authors: | D Ol?ák V Hronský P Vrábel I Chodák P Alexy |
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| Institution: | 1. Department of Physics, Technical University of Ko?ice, Ko?ice, Slovakia;2. Polymer Institute, Slovak Academy of Sciences, Bratislava, Slovakia;3. Institute of Polymer Materials, Slovak University of Technology, Bratislava, Slovakia |
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| Abstract: | Single-pulse 13C NMR spectra and spin-lattice relaxation times T1(1H), detected indirectly via 13C carbons, and T1(13C) were measured at 31°C for virgin pelletized and annealed polylactic acid (PLA) samples using the magic-angle spinning technique. The structural relaxation resulting in more regular crystals with narrower conformation distribution and increase in the lamellae thickness and crystallinity brought about by annealing at 100°C was deduced from the narrowing of the 13C NMR lines and proton spin-lattice relaxation times T1(1H). The spin-lattice relaxation times T1(13C) related to the respective carbons of the α-polymorph of PLA are also discussed in the study. |
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| Keywords: | Annealed PLA Molecular mobility Morphology Single-pulse MAS 13C NMR spectra T1(1H) and T1(13C) spin-lattice relaxation times |
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