Comparison between Static (Sorption) and Dynamic (IGC) Methods in the Determination of Interaction Parameters in Polymer/Polymer Blends

IGC studies of binary cationic surfactant mixtures

Inverse gas chromatography (IGC) has been used to measure the interaction parameter between two twin-tailed cationic surfactants. Didodecyldimethylammonium (DDAB) and dioctadecyldimethylammonium (DODAB) bromides and their mixtures were used as stationary phases. IGC and DSC techniques have been used for the determination of the temperature zone of working. The activity coefficients at infinite dilution (on a mole fraction basis) were calculated for eleven probe solutes on each pure surfactant column. Values of interaction parameter between surfactants obtained at four weight fractions of the mixtures and at five temperatures are positive and suggested that the interactions is more unfavourable with the increment of DODAB concentration in the mixture. The results are interpreted on the basis of partial miscibility between DDAB and DODAB.

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, T(g). A single T(g) has been observed in PSMA-12/PPO blends containing less than 67wt% 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 degrees 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 T(g)s 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 T(g)s.