Phase behavior and a modified Kwei equation for ternary polymer blends containing stereoregular PMMA

Previously, poly(methyl methacrylate) (PMMA) was found to be almost immiscible with poly(vinyl acetate) (PVAc) regardless of tacticity of PMMA and casting solvent. Poly(vinyl phenol) (PVPh) was found successful previously in making immiscible atactic PMMA/PVAc miscible. In this investigation, tacticity effect of PMMA on a ternary composed of PMMA, PVAc and PVPh was studied. Isotactic PMMA ternary was shown to be miscible in all the studied compositions on the basis of single Tg observation. However, syndiotactic PMMA ternary demonstrated immiscibility at ca. 25% PVPh and miscibility was observed at higher PVPh concentrations. A modified Kwei equation based on the binary interaction parameters was proposed to describe the experimental Tg of the miscible ternary almost quantitatively.