Volume 72, Number 4, November 2005
|Page(s)||590 - 596|
|Section||Condensed matter: structural, mechanical and thermal properties|
|Published online||19 October 2005|
The onset of the fast dynamics in glassy polystyrene observed by the detrapping of guest molecules: A high-field Electron Paramagnetic Resonance study
Dipartimento di Fisica “Enrico Fermi”, Universitá di Pisa Largo B. Pontecorvo 3, I-56127 Pisa, Italy
2 IPCF-CNR - via G. Moruzzi 1, I-56124 Pisa, Italy
3 SOFT-INFM-CNR - P.zza A. Moro 2, I-00185, Roma, Italy
Accepted: 27 September 2005
The reorientation of the paramagnetic molecule TEMPO dissolved in glassy polystyrene (PS) is studied by high-field Electron Paramagnetic Resonance spectroscopy. Two different regimes separated by a crossover region are evidenced. Below the rotational times are nearly temperature independent with no apparent distribution. TEMPO is trapped. In the temperature range 180– a large increase of the rotational mobility is observed with widening of the distribution of correlation times which exhibits two components: i) a delta-like, temperature-independent component representing the fraction of TEMPO w still trapped; ii) a strongly temperature-dependent component representing the fraction of untrapped TEMPO undergoing activated motion over an exponential distribution of barrier heights. Above a steep decrease of w is evidenced. The detrapping of TEMPO and the onset of its large increase of the rotational mobility at are interpreted as signatures of the onset of the fast motion detected by neutron scattering at .
PACS: 64.70.Pf – Glass transitions / 76.30.-v – Electron paramagnetic resonance and relaxation / 61.25.Hq – Macromolecular and polymer solutions; polymer melts; swelling
© EDP Sciences, 2005
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.