Study of local and cooperative molecular movements in Polyethyleneoxide-Potassium thiocyanate complexes by mechanical measurements

The mechanical characteristics (internal friction and dynamic elastic modulus) of polyethylene oxide (PEO)-KSCN complexes are studied as a function of temperature (120-300 K) and frequency. The mechanical spectrum is characterized by the presence of the ?-relaxation at low temperatures and of the aa-relaxation at high temperatures, respectively arising from local and cooperative molecular motions. The salt addition modifies the ?-relaxation region, which consists of a single loss peak in pure PEO, and gives rise to two close low temperature relaxations. The behavior of the relaxation strengths with the salt content permits to assign them to local motions within the amorphous regions of the polymer. -- The aa-relaxation shifts to higher temperatures by increasing the KSCN content. Moreover, an enhancement of the amorphous phase of the polymer has been revealed in the low concentration region.