MISCIBILITY AND PHASE-BEHAVIOR IN BLENDS CONTAINING RANDOM COPOLYMERSOF POLY(ETHER ETHER KETONE) AND PHENOLPHTHALEIN POLY(ETHER ETHER KETONE)

The miscibility and phase behavior of polysulfone (PSF) and poly(hydro xyether of bisphenol A) (phenoxy) with a series of copoly(ether ether ketone) (COPEEK), a random copolymer of poly(ether ether ketone) (PEEK ), and phenolphthalein poly(ether ether ketone) (PEK-C) was studied us ing differential scanning calorimetry. A COPEEK copolymer containing 6 mol % ether ether ketone (EEK) repeat units is miscible with PSF, whe reas copolymers containing 12 mol % EEK and more are not. COPEEK copol ymers containing 6 and 12 mol % EEK are completely miscible with pheno xy, but those containing 24 mol % EEK and more are immiscible with phe noxy. Moreover, a copolymer containing 17 mol % EEK is partially misci ble with phenoxy; the blends show two transitions in the midcompositio n region and single transitions at either extreme. Two T(g)s were obse rved for the 50/50 blend of phenoxy with the copolymer containing 17 m ol % EEK, whereas a single composition-dependent T-g appeared for all the other compositions. An FTIR study revealed that there exist hydrog en-bonding interactions between phenoxy and the copolymers. The streng ths of the hydrogen-bonding interactions in the blends of the COPEEK c opolymers containing 6 and 12 mol % EEK are the same as that in the ph enoxy/PEK-C blend. However, for the blends of copolymers containing 17 , 24, and 28 mol % EEK, the hydrogen-bonding interactions become incre asingly unfavorable and the self-association of the hydroxyl groups of phenoxy is preferable as the content of EEK units in the copolymer in creases. The observed miscibility was interpreted qualitatively in ter ms of the mean-field approach. (C) 1996 John Wiley & Sons, Inc.