Mixed micelles of cationic surfactants in aqueous polyethylene glycol 1000

The conductances of tetradecyltrimethylammonium bromide (TTAB) + dodecyltri methylammonium bromide (DTAB) mixtures over the entire mole fraction range of TTAB (alpha(TTAB)) were measured in aqueous polyethylene glycol 1000 (PE G) containing 1, 2, 5 and 10 wt% of PEG at 30 degrees C. From the conductiv ity data, various micellar parameters were computed. The results have been explained on the basis of the medium effects as well as the adsorption of a dditive molecules at micelle-solution interface. The non-ideality in TTAB+D TAB mixtures was evaluated by using the regular solution theory and Motomur a's formulation based on the excess thermodynamic quantities. It has been f ound that the regular solution interaction parameter (beta) and micellar mo le fraction (<(x(2)(m))over bar>) remain almost unaffected even in the pres ence of up to 10 wt% of PEG. These results suggest that the additive remain s only in the aqueous phase and perhaps only changing the environment surro unding the micelles by adsorbing at the micelle-solution interface.