Effect of tacticity on the segmental dynamics of polypropylene melts investigated by C-13 nuclear magnetic resonance

TitleEffect of tacticity on the segmental dynamics of polypropylene melts investigated by C-13 nuclear magnetic resonance
Publication TypeJournal Article
Year of Publication2001
AuthorsLippow, S. M., X. H. Qiu, and M. D. Ediger
JournalJournal of Chemical PhysicsJournal of Chemical Physics
Volume115
Pagination4961-4965
Date PublishedSep
Type of ArticleArticle
ISBN Number0021-9606
Accession NumberWOS:000170647600061
KeywordsGLOBAL DYNAMICS, LATTICE, local dynamics, MOLECULAR-DYNAMICS, NMR, SIMULATION
Abstract

C-13 nuclear magnetic resonance (NMR) T-1 and nuclear Overhauser effect measurements are reported for syndiotactic and isotactic polypropylene from their melting points to 525 K. These results indicate that the segmental dynamics of syndiotactic polypropylene are 1.7 times slower than for isotactic polypropylene at 500 K. Recent molecular dynamics computer simulations [Antoniadis, Samara, and Theodorou, Macromolecules 32, 8635 (1999)] predict this trend qualitatively but predict too large a dependence of dynamics upon tacticity. The contribution of normal mode relaxation to the decay of the C-H vector autocorrelation function is significantly larger for syndiotactic polypropylene than for either isotactic or atactic polypropylene. (C) 2001 American Institute of Physics.

Alternate JournalJ. Chem. Phys.