Miscibility Enhancement via Ion-Dipole Interactions. 2. LCST Behavior of Polystyrene Ionomer/Poly(Alkylene Oxide) Systems

摘要

A study of LCST behavior is used to show that ion-dipole interactions can lead to truly thermodynamic miscibility in polymers which are immiscible in their absence. Blends of polystyrene (PS) ionomers with poly(propylene oxide) (PPrO) at low PPrO contents are miscible at low temperatures: they undergo phase separation and become opaque upon heating but recover their transparency upon cooling. The degree of miscibility enhancement (related to the strength of the interaction) can be compared in different systems by comparing the positions of the cloud point curves. Thus, an increase in the ion content of the PS ionomer shifts the cloud point curve to higher temperatures. A decrease in the counterion site in the PS ionomer also increases the strength of the interaction and leads to an upward shift of the cloud point curves. The effect of molecular weight is similar to that seen in nonionic blends. Reprints. (jes)