The rheological properties of polystyrene/poly(vinylmethylether) blend near the critical region and in the homogenous region

Abstract

The rheological properties of polystyrene/poly(vinylmethylether) (PS/PVME) blend near the critical region and in the homogeneous region were investigated. The blend had a lower critical solution temperature (LCST) of 112 degrees C obtained by a turbidity experiment using a light scattering (LS) apparatus at a heating rate of 1 degrees C/h. Four different blend compositions (critical (30/70 PS/PVME by weight) and three off-critical (10/90, 50/50, and 70/30) as well as neat PS and PVME were prepared. For the critical composition, logarithmic plots of shear modulus (G') versus loss modulus (G ") showed temperature dependence even in the homogenous region determined by LS, while those plots become temperature independent in the homogeneous region for off-critical compositions. Logarithmic plots of blend viscosity versus composition exhibited a negative deviation at constant temperature; however, these showed a maximum at a certain composition when the reference temperature is taken as fixed T - T-g (under approximately iso-free volume condition). (C) 1999 Elsevier Science Ltd. All rights reserved.