Mixtures of Poly (metyl methacrylate) (PMMA) and poly (α-methylstyrene-co-acrilonitrile) (αMSAN) exhibit a LCST type of phase behavior. Dynamic rheological properties of PMMA/αMSAN blends of various compositions were measured at temperatures below, near, and above the phase-separation temperature. The time-temperature superposition was tried to obtain the master curves of G' and G" at 160°C. The time-temperature superposition principle failed above a certain temperature due to a phase separation. The “breakdown” temperature is close to the cloud temperature Tc of the blend samples. Comparison of logG' vs. logG" relation between the two components and the blends was made. The results show that the slopes of logG' vs. logG" plots in the terminal region are dependent on the composition of the blends. The rheological measurements have been found to be useful for characterizing the phase-separation of PMMA/αMSAN blends.
