MISCIBILITY OF POLY(STYRENE-CO-ACRYLIC ACID) WITH POLYMETHACRYLATES OR POLY(METHACRYLATE-CO-4-VINYLPYRIDINE)

The miscibility of poly(styrene-co-acrylic acid) with polymethacrylates or poly(methacrylate-co-4-vinylpyridine) was studied by differential scanning calorimetry and inverse gas chromatography using decane, octane and benzene as molecular probes. The results showed that poly(isobutyl methacrylate) is immiscible with styrene-acrylic acid copolymers of different acrylic acid content as evidenced from the appearance of two glass transition temperatures determined with both techniques. Positive values of the apparent polymer-polymer interaction parameter chi(23) (app.) obtained with all probes in the temperature range 160-180 degrees C over the entire blend composition confirm the immiscibility of these blends. Blends of the former styrene-acrylic acid copolymers are, however, miscible in all proportions with poly(ethyl methacrylate), poly(ethyl methacrylate-co-4-vinylpyridine) and poly(isobutyl methacrylate-co-4-vinylpyridine). A single composition dependent-glass transition temperature and negative values of chi(23) (app.) were obtained with these blends