Associative and segregative phase behaviour of a mixed aqueous cationic surfactant and anionic hydrophilic polymer system

The phase behaviour of a mixture of a highly charged hydrophilic polymer, dextran sulphate sodium salt, and a cationic surfactant, tetradecyltrimethylammonium bromide, was investigated in aqueous solution of different ionic strengths. The system has the interesting and novel property that at certain ionic strengths it displays both segregative and associative phase behaviour separated by a single-phase region within the same phase diagram. By increasing the ionic strength further the segregative area increases and the associative area disappears. ition, the effect of cosolutes n-octane and 1-octanol on the above-mentioned phase behaviour has been studied. The effect of the former was to increase the miscibility and the latter to decrease the miscibility.