NMR experiments and molecular dynamics simulations of the segmental dynamics of polystyrene

TitleNMR experiments and molecular dynamics simulations of the segmental dynamics of polystyrene
Publication TypeJournal Article
Year of Publication2004
AuthorsHe, Y. Y., T. R. Lutz, M. D. Ediger, C. Ayyagari, D. Bedrov, and G. D. Smith
JournalMacromolecules
Volume37
Pagination5032-5039
Date PublishedJun
ISBN Number0024-9297
Accession NumberWOS:000222258600041
Keywords1,4-POLYBUTADIENE MELT, 2-DIMENSIONAL, ATACTIC POLYPROPYLENE MELTS, DIELECTRIC-RELAXATION, EXCHANGE NMR, NEUTRON-SCATTERING, NUCLEAR-MAGNETIC-RESONANCE, POLYMETHYLENE MELTS, SPIN-LATTICE RELAXATION, TEMPERATURE-DEPENDENCE, TETRABLOCK COPOLYMERS
Abstract

We have performed NMR spin-lattice relaxation experiments and molecular dynamics (MD) computer simulations on atactic polystyrene (a-PS). The segmental correlation times of three different molecular weight a-PS (M-n = 1600, 2100, 10 900 g/mol) were extracted from NMR by measuring the H-2 spin-lattice relaxation times (T-1) over a broad temperature range (390-510 K). MD simulations of an a-PS melt of molecular weight 2200 g/mol were carried out at 475, 500, and 535 K. Comparisons between experiments and simulations show that the MD simulations reproduce both the shape of the P-2(t) orientation autocorrelation function and its temperature dependence, while the simulated segmental correlation times are slower than experimental results by a factor of 1.8. If the simulations are resealed by this factor, they reproduce both the experimental T-1 values and the slight difference in dynamics between the backbone and side group of PS.

DOI10.1021/ma049843r