| Abstract: | Persistent electrical polarization (heterocharged electret formation) has been studied as a function of stereotacticity, crystallinity, and molecular weight in membranes of poly(vinyl alcohol) (PVA) prepared via different synthetic routes. Membranes of PVA–sodium polystyrenesulfonate (PSSNa) and PVA–poly(vinyl acetate) (PVAc) copolymers and PVA–PVAc–PSSNa were also investigated. The degree of persistent polarization a pure PVA membrane can support, was found to vary according to isotactic > syndiotactic > heterotactic triad concentrations. Increases in crystallinity tend to decrease persistent polarization, and such changes in crystallinity are probably responsible for the above observed order, since measurements of persistent polarization on noncrystalline PVA–PSSNa membranes were found to vary according to syndiotactic > heterotactic > isotactic with regard to the PVA. Within PVA–PSSNa membranes the presence of acetate groups reverses the behavior of PSSNa from anhancer to an inhibitor of electret formation. The results all support a model in which heterocharged electret formation involves an ion displacement in the direction of the applied field and stabilization of this ion displacement by local hydrogen bonding. |
