Abstract
Blends of Poly (methyl methacrylate) (PMMA) and poly (α-methylstyrene-co-acrylonitrile) (αMSAN) exhibit an LCST behavior and are miscible at lower temperatures than the cloud points. The temperature dispersion of dynamic viscoelasticity of the blend system was measured in the single-phase and phase-separated states. It was found that some thermal histories during sample preparation bring the structural equilibrium to PMMA and αMSAN. Such a thermal condition was used for all the measurements to attain the experimental reproducibility. Temperature dispersion curves of dynamic viscoelastic functions, E', E" and tan δ, for the blends in single-phase and phase-separated cases located between those of PMMA and αMSAN in order of the component ratio. The shapes of the curves of phase-separated blends, however, become quite different from those of single-phase ones at temperatures above 80°C. The curves of E' and tanδ of blend samples in phase-separation show the broad relaxation and locate close to those of the rich component. Correspondingly, the peaks of the E" curves of phase-separated samples become broader than those for single-phase. Only the PMMA/αMSAN(40/60) blend in a phase-separated state shows two peaks on the E" curve when it was annealed at 200°C. These two peaks become more apparent with the annealing time suggesting the phase separation proceeds.
