Elastic and anelastic behavior in poly(ethylene)oxide complexed with Caesium salt

The variation with temperature of the internal friction and dynamic modulus of polyethylene oxide (PEO)-CsSCN polymeric electrolytes reveals the presence of molecular relaxations, which arise from localized (?) and cooperative (?a) conformational transitions. The ?a-relaxation, which takes its origin in the amorphous fraction of the complex, shifts to higher temperatures with the addition of salt. The enhancement of its strength up to a molar fraction x=0.08 testifies that salt dissolves in the amorphous fraction and decreases the crystallinity degree of the polymer. A two-phase structure, crystalline PEO and a PEO-salt amorphous complex, is proposed to form the system in the explored concentration range. Loss peaks followed from broad shoulders are observed in the low temperature region, where pure PEO shows a single ?-relaxation. The concentration behavior of their strength is strongly correlated to that of the ?a-relaxation. The analysis of these features, in terms of a parallel relaxation arising from a Gaussian distribution of activation energies, allows us to attribute them to localized segmental motions within the amorphous phase.