The phase behaviour of poly(styrene-co-methacrylic acid)/poly(2,6-dimethyl-1,4-phenylene oxide) by inverse gas chromatography

The miscibility behaviour of blends of poly(styrene-co-methacrylic acide) (PSMA-12) containing 12% of methacrylic acid with poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) at five different compositions has been studied by inverse gas chromatography (IGC). The adequacy of two types of solvents (solvents and precipitants) has been tested in order to detect the glass transition temperature, Tg. A single Tg has been observed in PSMA-12/PPO blends containing less than 67 wt% of PPO. Two glass transition temperatures appeared, however, in blends containing higher PPO content. The polymer–polymer interaction parameters have been calculated in the molten state (260–280 °C), their values being in good agreement with the observed phase behaviour. Moreover, the methods proposed by Farooque–Deshpande and Huang for obtaining the true polymer–polymer interaction parameters have been compared. Finally, the ability of IGC in order to determine Tgs has been extended to a ternary system, PSMA-12/PPO/EMV4P-8 poly(ethylmethacrylate-co-4-vinylpyridine) which, depending on the composition, gives a single, two and even three Tgs.