BLENDS OF POLY(ENAMINO NITRILE)

Poly(enamino nitrile) (PEAN) forms miscible blends with several commercial polymers including poly(ethylene oxide) (PEO), poly(4-vinylpyridine) (P4VP), and tertiary amide polymers such as poly(ethyloxazoline) (PEOX), poly(N-vinylpyrrolidine) (PNVP), and poly(N,N-dimethylacrylamide) (PDMA) as determined by the transparency of blend films and the observation of a single glass transition temperature which changes smoothly with composition. Binary blends containing more than 50 wt % of PEO showed PEO melting endotherms indicating the development of PEO crystallites in the homogeneous amorphous mixture. At higher temperatures PEO/PEAN blends undergo phase separation which signals the existence of a lower critical solution temperature. An endothermic transition associated with phase separation was clearly discernible by calorimetry, as was an exothermic transition associated with redissolution. These reversible phase separation and redissolution processes were observed by hot-stage optical microscopy. Strong hydrogen-bonding interaction between enamine hydrogen atoms and electronegative oxygen or nitrogen atoms on the other component polymers was evidenced by FT-IR and is suggested as a specific interaction which favors miscibilities in these blends.