Influence of proton ionophore and negative sites on the dielectric behavior of plasticized poly(vinyl chloride)s

Abstract

The dielectric behavior of a 50 50 blend of two poly(vinyl chloride) weight standards was measured, both before and after being plasticized with 200 parts per hundred of o-nitrophenyl octyl ether. To these dummy membranes were added the proton ionophore, tridodecylamine (TDDA), in the amounts of 0.01, 0.1, 1, and 10 wtwt −1% as well as a source of negative sites, potassium tetrakis-4-chlorophenyl borate (KTpClPB), in relative proportions (TDDA/KTpClPB) of 1:0, 1:1, 1.5:1, and 3:1. Because replicate membranes were cast from parent THF solutions, compositional changes were not a factor. Using a TA Instruments' DEA 2970 equipped with parallel plate sensors, nominally 0.15 mm thick films were scanned at 3°C min −1 in the dry and hydrated conditions from −100 to +100°C at seven frequencies (0.1, 1, 10, 100, 1000, 10 000 and 100 000 Hz). By 100°C, permittivity and loss factor increased with TDDA concentration more than 1000-fold over values measured at the glass transition temperature of ca. −75°C. Permittivity and loss factor also increased six orders of magnitude over a six orders of magnitude decrease in frequency. The absolute magnitudes of tan δ at the peaks decreased with increasing TDDA loading. In the wet conditions, tan δ converged to a single value of six at 10 wtwt −1% TDDA, regardless of the proportion of TDDA/KTpClPB and test frequency. The ionic conductivities at the temperature at which the peak of tan δ occurs were independent of TDDA concentration but increased with increasing frequency. Above a minimum of 1.5:1, the relative proportion of TDDA/KTpClPB was not as significant as the absolute amount of TDDA and/or KTpClPB present, and hydration had little overall effect on the dielectric properties.