Proton longitudinal NMR relaxation of poly(p-phenylene sulfide) in the laboratory and the rotating frames reference
Jurga J.1, Woźniak-Braszak A.2, Fojud Z.3, Jurga K.2
- 1Polymer Processing Division, Institute of Materials Technology, Poznan University of Technology, Piotrowo 3 St., 61-138 Poznań, Poland
- 2High Pressure Physics Division, Institute of Physics, Adam Mickiewicz University, Umultowska 85 St., 61-614 Poznań, Poland
- 3Department of Macromolecular Physics, Institute of Physics, Adam Mickiewicz University, Umultowska 85 St., 61-614 Poznań, Poland
Solid State Nuclear Magnetic Resonance, 25, pp.47-52, 2004
DOI:: 10.1016/j.ssnmr.2003.03.014
Abstract:
Spin-lattice NMR relaxation times T1 in the laboratory frame and T1ρ as well as T1ρ off in the rotating frame off-resonance were employed to the study of molecular dynamics of both pristine PPS and thermally treated poly(p-phenylene sulfide) (PPS). The temperature dependence of T1 was exponential in the whole temperature range studied, whereas T1ρ only in low temperatures. In the high temperature range the distribution of relaxation times T 1ρ and correlation times τc as well as activation energy Ea was observed. The distribution of activation energy determined from T1 minima at 15 and 30MHz and from low temperature slopes of T1ρ dependence as well as from spectral density functions (estimated from proton off-resonance technique) was attributed to the reorientation of phenylene groups around the sulfur-phenyl-sulfur axis in amorphous and crystalline phases of PPS. Furthermore, it is suggested that an additional relaxation mechanism related to interactions of protons with paramagnetic centers is operative in a low temperature range. After thermal treatment of PPS the low temperature minima disappeared and the relaxation times shortened in the low temperature regime. Both these facts were attributed to an increased contribution of spin diffusion in the relaxation process. © 2003 Elsevier Inc. All rights reserved.
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