Miscibility of poly(hydroxyether of phenolphthalein) with aromatic polyesters and polycarbonate

Blends of poly(hydroxyether of phenolphthalein) (PHP) with poly(ethylene terephthalate) (PET), poly(butylene terephthalate) (PBT) and polycarbonate (PC) were studied by differential scanning calorimetry. It was found that PHP is miscible with PBT and PC. Both PHP/PBT and PHP/PC blends showed single, composition-dependent, glass transition temperature (Tg). PHP/PBT blends showed phase separation when heated to temperatures above the melting point of PBT. Phase separation of PHP/PC blends could not be induced by heating up to 300°C. The observed miscibility is proposed to be the result of specific interactions between the pendant hydroxyl of PHP (proton donor) and the ester group of PBT (proton acceptor) and/or the carbonate group (proton acceptor). However, PHP, like poly(hydroxyether of bisphenol A), does not exhibit miscibility with PET.