An IGC Study of Interactions in SAN/SMA Blends

Inverse gas chromatography has generated surface energy and acid-base interaction data for copolymers of styrene/acrylonitrile (SAN) and styrene maleic anhydride, (SMA) at mole per-cent compositions of SAN-26, SMA-26, and SMA-18. Also measured were polymer pair interaction data for 1:1 weight ratio blends of the copolymers. Explicit values of the X interaction parameter over wide temperature ranges also were obtained from these experiments. SAN was shown to be amphoteric, while SMA polymer surfaces interact as bases. The surface and bulk compositions differ both in single copolymers and polymer blends, with an excess of styrene moieties at surfaces and interfaces resulting from thermodynamic drives to minimize the relevant energies. Miscibility-immiscibility relationships in polymer blends are strongly temperature-dependent. Blends were shown to be miscible below glass transition temperatures, and again at temperatures above about 190°C, with immiscible conditions between these temperature ranges.