Liquid-to-liquid relaxation of polystyrene melts investigated by low-frequency anelastic spectroscopy.

ABSTRACT

Polystyrene melts with a narrow distribution of molecular weights far above the glass transition have been investigated by use of low-frequency anelastic spectroscopy. A liquid-to-liquid relaxation occurs when the molecular weight (Mn) is either above or below the critical molecular weight (Mc) for chain entanglement. As the molecular weight increases, the relaxation temperature (Tp) increases and the movement of the polymer chain is easier for short chains than for long chains. In the range we investigated (Mn∼1.0 × 104-2.1 × 105), the relaxation time (τp) corresponding to the dissipation peak is related to the molecular weight by [Formula see text]. This is consistent with theoretical prediction. We suggest that the dissociation of the chain clustering is responsible for the liquid-to-liquid relaxation.