Phase behavior and its viscoelastic responses of poly(methyl methacrylate) and poly(styrene-co-maleic anhydride) blend systems

The phase behavior and viscoelastic properties of the poly(methyl methacrylate) (PMMA) and poly(styrene-co-maleic anhydride) (SMA) blend systems have been investigated. In homogeneous region, the blends of different compositions behave as a classical polymer melt. On the other hand, in phase-separated region, the blends of symmetric and off-symmetric compositions show different characteristic thermorheological responses corresponding to the different morphologies, which has been confirmed by TEM analysis and qualitatively corroborated by utilizing Palierne's emulsion model. Except for the well-known characteristic deviations of the storage modulus at low frequencies, the curves that describe the relationships between other rheological functions such as master curves obtained through time-temperature superposition (tTS) principle, van Gurp-Palmen Plots, Han Plots, and Cole-Cole Plots, also show significantly different shapes corresponding to symmetric and off-symmetric composition. Based on these findings we propose that such characteristic fingerprints can be used not only for marking phase separation but also for inferring the resulting morphology. It is also shown that van Gurp-Palmen Plots and Cole-Cole Plots are more sensitive than other rheological functions. In addition, on comparing the validity of tTS principle in different blend systems, we argue that the morphology is responsible for whether tTS principle holds or not for polymer blend.