Influence of thermal history on molecular relaxation of salt-blended polyethylene oxide

The dependence of the molecular relaxations on thermal history for polyethylene oxide (PEO) blended with thiocyanates of sodium and barium was studied. By analyzing the internal friction characteristics as a function of temperature and frequency, local (?) and cooperative (?a) molecular relaxations have been revealed. Pure PEO and PEO-NaSCN samples, prepared by a slow evaporation of the solvent, have a semi-crystalline structure: a 'quenching' procedure imposed on them maintains the same structure, but shifts the glass transition to lower temperatures, probably as an effect of decreasing constraints of the crystalline phases on the amorphous regions. For the blend with the divalent cation, the structure is essentially amorphous with a small content of PEO crystals and the 'quenching' procedure gives rise to a single amorphous phase with a higher glass transition temperature. Finally, different thermal histories also produce small changes in the low-temperature ?-relaxation, which are discussed accordingly with the revealed phase behavior.