Tuning phase diagram of ternary polymer blends by tacticity

Previously, a ternary blend consisting of poly(vinyl phenol) (PVPh), poly(vinyl cinnamate) (PVCN) and poly(methyl methacrylate) (PMMA) was reported to exhibit a closed-loop behavior of immiscibility. In that study, PMMA was atactic PMMA and three binary pairs of PVPh, PVCN and PMMA were all miscible. In this article, isotactic and syndiotactic PMMAs (designated as iPMMA and sPMMA) were used to replace atactic PMMA to blend with PVPh and PVCN. For iPMMA ternary blends, the ternary phase diagram was found to demonstrate a closed-loop immiscibility behavior similar to the previous study. However, a completely miscible region was observed in sPMMA ternaries even though sPMMA and PVCN were found to be not miscible.