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Polymers 2018, 10(5), 506; https://doi.org/10.3390/polym10050506

Solid-State Nuclear Magnetic Resonance (NMR) and Nuclear Magnetic Relaxation Time Analyses of Molecular Mobility and Compatibility of Plasticized Polyhydroxyalkanoates (PHA) Copolymers

1
National Institute of Advanced Industrial Science and Technology (AIST), Shimoshidami 2266-98, Moriyama-ku, Nagoya 463-8560, Japan
2
Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Aichi 466-8555, Japan
*
Author to whom correspondence should be addressed.
Received: 19 April 2018 / Revised: 3 May 2018 / Accepted: 5 May 2018 / Published: 7 May 2018
(This article belongs to the Special Issue NMR in Polymer Science)
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Abstract

The molecular mobility and compatibility of plasticized polyhydroxyalkanoates (PHA) were investigated, focusing on changes due to copolymerization using either flexible poly (butylene succinate) (PBS) or rigid poly(lactic acid) (PLA) units. For the case of a poly(3-hydroxybutyrate) (PHB) unit in plasticized PHA, copolymerization of either PBS or PLA decreased 1H and 13C spin-lattice relaxation times in the laboratory frame (T1H and T1C) in the same manner, while PBS produced a lower 1H spin-lattice relaxation time in the rotating frame (T1ρH) than PLA. Both the signals of 1H MAS (magic-angle spinning) and 13C PST (pulse saturation transfer) MAS nuclear magnetic resonance (NMR) spectra were sharpened and increased by copolymerization with PBS. A variable temperature relaxation time analysis showed that the decrease of T1H values was dominated by the 1H spin diffusion via the interface between PHB and the added polyester because of the good compatibility. Meanwhile, the decrease of T1C values was dominated by increasingly rapid molecular motions of PHB because of the lowered crystallinity due to the plasticization. Slow molecular motions (kHz order) were enhanced more by the addition of PBS than PLA, although rapid molecular motions (MHz order) were enhanced by either polyester. Several NMR parameters were beneficial for analyzing the manufacturing process as the indexes of polymer compatibility and molecular motions. View Full-Text
Keywords: inedible biomass; polyester; copolymerization; plasticization; solid-state nuclear magnetic resonance (NMR); nuclear magnetic relaxation; variable temperature measurement inedible biomass; polyester; copolymerization; plasticization; solid-state nuclear magnetic resonance (NMR); nuclear magnetic relaxation; variable temperature measurement
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Nishida, M.; Tanaka, T.; Hayakawa, Y.; Nishida, M. Solid-State Nuclear Magnetic Resonance (NMR) and Nuclear Magnetic Relaxation Time Analyses of Molecular Mobility and Compatibility of Plasticized Polyhydroxyalkanoates (PHA) Copolymers. Polymers 2018, 10, 506.

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