Dielectric Properties of Styrene-Soclium Methacrylate Copolymers in the Glass Transition Region

Dielectric loss measurements have been conducted on high molecular weight copolymers containing 2.0, 3.9. 5.1. 6.5, 8.1, and 9.0 mol % of sodium methacrylate over a temperature range of Ca. 100-200 °C at frequencies from 10 1 to 10 4 Hz. After subtraction of the large conductivity loss, two overlapping loss tangent peaks are observed whose relative heights depend on composition and measurement frequency and whose positions are in agreement with torsion pendulum data. The dielectric data indicate that although clustering of multiplets occurs at all composi- tions, it is not clearly manifested until the number of ions in clustered multiplets exceeds the number of ions in isolat- ed multiplets in the surrounding matrix, which occurs at compositions containing more than ca. 5% salt, There is evi- dence for cluster dissociation at higher temperatures, and it is shown that this may account for the unusually high values of the WLF parameters C I and C2 and other theological anomalies.