The miscibility behavior of a regularly alternating copoly(amide-enaminonitrile) with several commercial polymers (poly(ethylene oxide) (PEO), poly(4-vinylpyridine) (P4VP), and poly(N-vinylpyrrolidone) (PNVP)) was studied by using FTIR spectroscopy and thermal analyses (DSC, TGA, and TMA). Blends of the copolymer with PNVP or P4VP (20-80 wt %) gave transparent films and single glass transition temperatures that changed smoothly with composition, and an enhancement in the thermal stability of the poly(amide-enaminonitrile) component of the blends was observed. With the semicrystalline PEO, miscible blends were obtained at less than or equal to 60 wt % PEO. In addition to melting endotherms of PEO crystallites that were observable for greater than or equal to 40 wt % of PEO samples, the presence of higher temperature endotherms between 140 and 180 degrees C is consistent with phase separation of the miscible blends (lower critical solution temperatures, LCST). On the time scale of DSC : studies, the phase separation of the PEO/copolymer blends is apparently irreversible. When compared to the miscibility behavior of PEO/poly(enaminonitriles) homopolymer blends (based on LOST data, PEO crystallinity, and FTIR carbonyl spectral changes), the interaction of the copolymer with PEO is weaker because of the presence of the amide group. The amide groups apparently prefer to self-associate in the copolymer in preference to interaction with PEG. Similar behavior is also observed for PNVP or P4VP blends with the copolymer.