Helical jump motions of poly(L-lactic acid) chains in the α phase as revealed by solid-state NMR

The Journal of Physical Chemistry. B
Wei ChenToshikazu Miyoshi

Abstract

The molecular dynamics of Poly(L-lactic Acid) (PLLA) chains in the α phase was investigated by Solid-State NMR spectroscopy. (13)C high-resolution NMR clearly indicates that the crystalline signals split into 2, 3, and 4 signals for the CH3, CH and CO groups, respectively at 25 °C, while the amorphous signals give a broad component at the bottom of the crystalline signals. (13)C NMR spectra show that the crystalline line shape changes with increasing temperatures well above the glass transition temperature (Tg) and imply the presence of the molecular dynamics in the crystalline region. Comparisons of the evolution-time dependence of CODEX data and simulation results based on reorientation of chemical shift anisotropy (CSA) indicate that the chains in the α phase perform helical jump motions in the slow dynamic range at temperatures above 115 °C. The mixing-time dependence of the CODEX data yields an activation energy of Ea of (95 ± 8) kJ/mol for the helical jump motions. Moreover, two-dimensional exchange NMR with highly resolved signals for the CO group provides cross peaks among four well resolved signals due to the helical jumps. Comparison of 2D buildup curves of the cross peaks and calculated data determines that helical j...Continue Reading

References

Jan 1, 1968·Biopolymers·P De Santis, A J Kovacs
Feb 1, 2008·Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics·Y-F YaoS Rastogi
Nov 7, 2009·The Journal of Physical Chemistry. B·Toshikazu MiyoshiWei Hu
May 27, 2010·Biomacromolecules·Calistor NyamboManjusri Misra
Jul 1, 2009·Macromolecular Rapid Communications·Yefeng YaoSanjay Rastogi
Jan 24, 2013·Physical Chemistry Chemical Physics : PCCP·Tomasz PawlakMarek J Potrzebowski

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Citations

May 14, 2016·Advanced Drug Delivery Reviews·Julia PretulaStanislaw Penczek
Aug 30, 2020·Materials·Monika Dobrzyńska-MizeraMaria Laura Di Lorenzo

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