Assessment of time-temperature superposition of linear viscoelastic behaviour of strongly interacting polymer blends: N-methylated nylon-2,lO and lightly sulfonated polystyrene ionomers

The applicability of time-temperature superposition of dynamic mechanical data for miscible polymer blends that exhibit strong intermolecular interactions was investigated. Blends of the lithium salt of lightly sulfonated polystyrene ionomers (Li-SPS), 9-12mol% sulfonation, and N-methylated nylon-2,lO (mPA) were miscible over the composition range studied, 30-70 wt% ionomer. Time-temperature superposition (TTS) of the storage and loss shear moduli measured at frequencies of 0.01-500 rad s-’ was applicable over the temperature range from 95 to 185°C. The molecular-weight distribution of the ionomer had no effect on the applicability of TTS. The success of TTS was attributed to the complexation of the metal sulfonate and amide groups, which couple the relaxation times of the two polymers in the blend. Na-SPS (9.5 mol%) and mPA were immiscible and TTS failed for these blends. TTS was obeyed for blends of Zn-SPS and mPA, though these blends appeared to be immiscible or partially miscible.