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Title: Dynamics of T(2)G(2) helices in atactic and syndiotactic polystyrene: New evidence from dielectric spectroscopy and FTIR
Authors: Lupascu, Veronica ×
Picken, Stephen J
W├╝bbenhorst, Michael #
Issue Date: Jul-2006
Publisher: Amer chemical soc
Series Title: Macromolecules vol:39 issue:15 pages:5152-5158
Abstract: The local and cooperative dynamics in atactic (a-PS) and syndiotactic (s-PS) polystyrene were studied by broadband dielectric spectroscopy. Besides the known alpha-relaxation, two additional relaxation processes beta(1) and beta(2) were revealed in various samples of a-PS and s-PS films cast from solvent solutions. These new dynamic processes show Arrhenius behavior, a common activation energy around 80 kJ/mol, and cross the alpha-relaxation region without merging, indicating a molecular origin being phase-separated from the amorphous PS fraction. By Fourier transform infrared spectroscopy (FTIR) measurements, a clear link between the existence of T(2)G(2) helix conformation and the occurrence of the beta(1) and beta(2)-processes was established. Symmetry arguments and systematic differences in the relaxation parameters between a-PS and s-PS favor the assignment of the fast, beta(1), process to a helix defect mechanism (helix inversion), while the slow mode, beta(2), likely originates from cooperative helix inversion events that would point to spatially organized aggregates of helices, as suggested earlier for PS gels. The occurrence of such solvent-induced structures and their dynamics might have important implication for the interpretation of T-g reductions found in ultrathin PS films.
URI: 
ISSN: 0024-9297
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Soft Matter and Biophysics
× corresponding author
# (joint) last author

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