Analysis and characterization of unusual ternary polymer miscibility in poly(ether diphenyl ether ketone), poly(ether ether ketone), and poly(ether imide)

A rare case of ternary polymer miscibility has been demonstrated in the mixture (in the glassy amorphous domains) comprising three polymers: polyetherimide (PEI), a new semicrystalline meta-linked poly(ether diphenyl ether ketone) (PEDEKm), and semicrystalline poly(ether ether ketone) (PEEK). The Tg-composition relationship for the ternary miscible blend system was treated by extension of the conventional models. The narrow Tg breadth also suggests that the scale of mixing was fine. The ternary blend exhibit no cloud point transition within the wide temperature range (50–400°C) studied. The interactions between any pairs among the three polymers were estimated using the Flory-Huggins theory. The FT-IR result gave further evidence that no significant specific interactions existed in any of the three binary pairs. The results collectively supported that no significant binary Δχ existed in the ternary polymer blend, which is favorable for leading this rare ternary miscibility.