Effect of stereoregularity on local molecular dynamics of hydrogenated polynorbornenes as studied by solid-state NMR

Bibliographic Details
Main Author:	Makita, Yuta
Language:	English
Published:	University of Akron / OhioLINK 2017
Subjects:	Polymers
Online Access:	http://rave.ohiolink.edu/etdc/view?acc_num=akron1512744939777343

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spelling	ndltd-OhioLink-oai-etd.ohiolink.edu-akron15127449397773432021-08-03T07:04:56Z Effect of stereoregularity on local molecular dynamics of hydrogenated polynorbornenes as studied by solid-state NMR Makita, Yuta Polymers Recently, a study on stereospecific ring-opening metathesis polymerization has been conducted on norbornenes making the synthesis and the study of hydrogenated polynorbornene (hPNB) stereoisomers possible. The stereoregular hPNBs are unique as the tacticity is defined differently compared to polypropylene or polystyrene and the stereoregular hPNB are semicrystalline with an all-trans configuration at room temperature. In addition, the thermal and structural behavior was unique as atactic-hPNB observed a reversible crystal-crystal phase transition between monoclinic and pseudohexagonal while isotactic-hPNB observed an irreversible crystal-crystal phase transition where the conformation changed to gauche-trans-gauche and syndiotactic-hPNB showed no crystal-crystal transition.The molecular dynamics of atactic- syndiotactic- and isotactic-hPNBs under various temperatures below melting temperature were studied using center-band only detection of exchange (CODEX) and chemical shift anisotropy lineshape analysis. As a result, it was shown that syndiotactic-hPNB observed no molecular dynamics while both atactic- and isotactic-hPNB observed slow local motion in the pentane ring that corresponded to changes in the puckered conformation below the crystal-crystal transition temperature (Tcc). The amplitude of motion for atactic-hPNB was shown to be around 10° – 20° while the amplitude of motion for isotactic-hPNB was shown to be 12° – 28°. The larger amplitude for the local motion of isotactic-hPNB suggested that the slow dynamics influenced the change in conformation in the crystal structure of isotactic-hPNB around Tcc. On the contrary the small amplitude motion of atactic-hPNB, along with the loose crystal packing structure caused by the atactic nature of the polymer, induced a larger amplitude rotational motion around a central axis above Tcc. The results suggested that the amplitude of the slow local motion influenced the behavior of Tcc experienced by stereoregular hPNBs. Furthermore, the unique dynamic geometry (the coexistence of a rotational motion and local fluctuation motion) of atactic-hPNB above Tcc correlated well with the increase in long period from the ultrasmall X-ray scattering data. The study of the molecular dynamics of stereoregular hPNBs provided unique insight to the relationship between local dynamics, structure, and phase transition, elucidating good macroscopic properties for the hPNBs. 2017 English text University of Akron / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=akron1512744939777343 http://rave.ohiolink.edu/etdc/view?acc_num=akron1512744939777343 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.
collection	NDLTD
language	English
sources	NDLTD
topic	Polymers
spellingShingle	Polymers Makita, Yuta Effect of stereoregularity on local molecular dynamics of hydrogenated polynorbornenes as studied by solid-state NMR
author	Makita, Yuta
author_facet	Makita, Yuta
author_sort	Makita, Yuta
title	Effect of stereoregularity on local molecular dynamics of hydrogenated polynorbornenes as studied by solid-state NMR
title_short	Effect of stereoregularity on local molecular dynamics of hydrogenated polynorbornenes as studied by solid-state NMR
title_full	Effect of stereoregularity on local molecular dynamics of hydrogenated polynorbornenes as studied by solid-state NMR
title_fullStr	Effect of stereoregularity on local molecular dynamics of hydrogenated polynorbornenes as studied by solid-state NMR
title_full_unstemmed	Effect of stereoregularity on local molecular dynamics of hydrogenated polynorbornenes as studied by solid-state NMR
title_sort	effect of stereoregularity on local molecular dynamics of hydrogenated polynorbornenes as studied by solid-state nmr
publisher	University of Akron / OhioLINK
publishDate	2017
url	http://rave.ohiolink.edu/etdc/view?acc_num=akron1512744939777343
work_keys_str_mv	AT makitayuta effectofstereoregularityonlocalmoleculardynamicsofhydrogenatedpolynorbornenesasstudiedbysolidstatenmr
_version_	1719452997566595072

Effect of stereoregularity on local molecular dynamics of hydrogenated polynorbornenes as studied by solid-state NMR

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