Broadband Dielectric Investigation on 2,6-Dihydroxynaphthalene/Poly(vinyl ethyl ether) Mixtures

Abstract

The relaxation dynamics of mixtures of 2,6-dihydroxynaphthalene and poly(vinyl ethyl ether) (DHN/PVEE), containing 1−20 wt % DHN, were investigated using dielectric relaxation spectroscopy (DRS). A single cooperative segmental relaxation was observed for all mixtures, which shifts to higher temperature and lower frequency upon addition of DHN. All mixtures are amorphous, as established by DSC. The fragility increases with DHN concentration, reflecting the combined contribution of the components. The modification of the DRS relaxation time of the PVEE α process by DHN was evaluated. Together with previously published data, a general feature of the influence of the guest component on the cooperative relaxation dynamics of the host in a miscible binary system becomes apparent: the influence of the guest approaches zero at approximately 60−100 °C above the Tg of the high Tg component, corresponding to the widely recognized critical temperature. The breadths of the α relaxations were found to be independent of temperature and composition. The small DHN molecules closely contact PVEE segments through intermolecular hydrogen bonding, and they are uniformly distributed in the PVEE matrix and have the same effect on all local environments of PVEE. The losses due to ionic conductivity exhibit the same shift factors for the α process in PVEE and all DHN/PVEE mixtures, suggesting that ion transport is highly coupled to the segmental relaxation of the polymer backbone.