Molecular dynamics in PANI/CSA as seen by quasielastic neutron scattering

Molecular dynamics has been measured in fully hydrogenated (PANI-h 5 /CSA) and partially deuterated (PANI-d 4 /CSA) samples. Quasielastic neutron scattering (QENS) measurements have been performed on time of flight (IN6 at ILL - Grenoble - France), backscattering (IN16 at ILL) and on time-of-flight inverted geometry (IRIS at RAL-Chilton-Great Britain) spectrometers. The obtained results suggest that the polymer chains are very stiff objects giving none quasielastic contribution and that all the counter-ions are not dynamically equivalent. The so-called rotation rate distribution model can satisfactorily describe the motion of methyl groups of CSA ions. This rotation can be considered as a quasi free one at high temperatures (270 < T < 330 K) while for T < 270 K the inter molecular effects turn more effective to broaden the correlation times distribution. Finally, an overall motion of the CSA ion itself has been detected on IN 16 and on IRIS at high temperature. This dynamics also experiences a transition around 280 K. It is noticeable that all these changes of dynamics exactly occur in the temperature range in which a metal-insulator electrical transition is also observed.