The physical properties of the ionic conductor, obtained by dissolution of lithium trifluoromethanesulphonylimide in polyethylene oxide, (PEO)nLi+((CF3SO2)2N)- have been investigated for several values of n. The phase diagram has been established from both DSC and NMR techniques. The diffusion coefficients of 7Li and 19F containing Species, determined by the pulsed magnetic field gradient (PMFG) technique, are interpreted as the measures of the cationic and anionic transport numbers, which are concentration dependent, and t+ reaches a value close to 0.3. This study is complemented by a systematic analysis of the behaviour of the 7Li relaxation time T1 versus temperature and concentration which is correlated to the glass temperature Tg.

For the first time, a very general theoretical method is proposed to interpret the full electron paramagnetic resonance (EPR) spectra at multiple temperatures and frequencies in the important case of S-state metal ions complexed in liquid solution. This method is illustrated by a careful analysis of the measured spectra of two Gd3+ (S = 7/2) complexes. It is shown that the electronic relaxation mechanisms at the origin of the EPR line shape arise from the combined effects of the modulation of the static crystal field by the random Brownian rotation of the complex and of the transient zero-field splitting. A detailed study of the static crystal field mechanism shows that, contrarily to the usual global models involving only second-order terms, the fourth and sixth order terms can play a non-negligible role. The obtained parameters are well interpreted in the framework of the physics of the various underlying relaxation processes. A better understanding of these mechanisms is highly valuable since they partly control the efficiency of paramagnetic metal ions in contrast agents for medical magnetic resonance imaging (MRI).