Phase Behavior of Ternary Blends of Tactic Poly(methyl methacrylate)s and Poly(vinylidene chloride-co-acrylonitrile)

Abstract

Previously, isotactic and atactic poly(methyl methacrylate)s (PMMAs) were found to be miscible with poly(vinylidene chloride-co-acrylonitrile) (Saran F) because all the prepared films were transparent and showed composition dependent glass transition temperatures (Tgs). However, the syndiotactic PMMA/Saran F blends were immiscible because most of the cast films were translucent and had two glass transition temperatures. Atactic PMMA is known to be miscible with syndiotactic PMMA according to literature. So atactic PMMA is miscible with both Saran F and syndiotactic PMMA but Saran F and syndiotactic PMMA are immiscible. It will be interesting to study the miscibility of ternary blends of atactic and syndiotactic PMMAs and Saran F. Therefore an investigation based on this is reported in this article. Calorimetry was used as the principal tool to study miscibility. A blend composed of atactic and syndiotactic PMMAs was prepared previously and confirmed to be miscible. An approximate phase diagram of the ternary blends was established based on differential scanning calorimetry data. The results indicated that for all the studied compositions, the thernary blends were determined to be miscible. Most of the blend Tg values were fitted well by the Fox equation. For the syndiotactic PMMA/Saran F (wt ratio=1) blend, adding of at least 12.5 wt% of atactic PMMA was sufficient to cause the immiscible blends to be miscible.