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High-field electron paramagnetic resonance in polymers and glasses: criteria for the optimal choice of the spin probe

V. BERCU1,* , M. MARTINELLI1, C. A. MASSA1, L. A PARDI1, D. LEPORINI2,3

Affiliation

  1. Istituto per i processi Chimico-Fisici, (IPCF-CNR) via G.Moruzzi 1, I-56124 Pisa, Italy
  2. Dipartimento di Fisica "Enrico Fermi", Università di Pisa, Largo B. Pontecorvo 3, I-56127 Pisa, Italy
  3. SOFT-INFM-CNR, Largo B. Pontecorvo 3, I-56127 Pisa, Italy

Abstract

The reorientation of guest paramagnetic molecules free radicals spin probes in the host polymers and glass formers is studied by High-Field High-Frequency Paramagnetic Resonance (HF2EPR) spectroscopy at three different Larmour frequencies, 95, 190 and 285 GHz. The structural change of the host that occurs close to glass transition temperature changes the reorientation regime of the molecular spin probe. For the slow tumbling regime of the rotational motion, the line shape exhibits larger sensitivity of the free radicals spin probe to both the static and the dynamics of the environment. Change of the reorientation rate lead to considerable line shifts, whereas broadening effects are not dominant. Discussion is focused on the suitable choice of the spin probe used in the HF2EPR spectroscopy in the study of the polymeric and glass formers systems..

Keywords

Polymers, Glass formers, Spin probe, High-field High-frequency electron paramagnetic resonance.

Submitted at: Nov. 14, 2006
Accepted at: June 15, 2007

Citation

V. BERCU, M. MARTINELLI, C. A. MASSA, L. A PARDI, D. LEPORINI, High-field electron paramagnetic resonance in polymers and glasses: criteria for the optimal choice of the spin probe, Journal of Optoelectronics and Advanced Materials Vol. 9, Iss. 6, pp. 1785-1788 (2007)