Conductivity and Thermally Srimulated Processes I Model Ionic Pplymers. I. Halato Telechelic Polybutadienes.

Abstract

The relaxation and conductivity properties of model ioncontaining macromolecules, i. e. halato-telechelic polybutadienes with various degrees of neutralization, were investigated from 100 to 350 K by means of thermally stimulated depolarization and polarization methods, stressing the comparison of materials based on alkaline (Na, K, Li) and alkalineearth (Ba, Ca, Mg) cations. It was shown that the behavior is largely determined by the thermal stability of ionic associations and their ability to trap impurity charge carriers. With alkaline-earth cations, the associations are thermally stable at least up to 350 K (i. e. more than 150 K above the glass transition temperature), which allows to observe a conductivity level smaller than that of the precursor polymer by several orders of magnitude. An opposite result is observed with alkaline cations as a consequence of the thermal breaking of unstable ionic associations. This dissociation first gives rise to a large relaxation process involving isolated carboxylate groups and then to a rapidly growing number of mobile ions which induce an important increase in conductivity. Generally speaking, and taking into account similar results previously obtained in various ionomers, it can be concluded that introducing a few percent ionic groups in polymers can modify their conductivity by several orders of magnitude (either decrease or increase depending on the type of cation involved).