Hexadecylpyridinium chloride plus trimethyltetradecylammonium bromide mixed micelles in polyethylene glycol plus water mixtures

The conductances of hexadecylpyridinium chloride (HPyCl) + trimethyltetrade cylammonium bromide (TTAB) mixtures over the entire mole fraction range of HPyCl (alpha(HPyCl)) were measured in aqueous binary mixtures of polyethyle ne glycol (PEG) 200, 400, 600, and 4000 containing different amounts of eac h PEG in their respective binary mixtures at 30 degrees C. Each conductivit y curve showed a single break, except in the presence of PEG 4000 where two breaks were observed. From the conductivity (kappa) data, the critical mic ellar concentration (cmc), degree of counter ion association (chi), the equ ivalent conductivities (Lambda) from the slope of kappa versus C plots, and the standard Gibb's free energy of transfer of the surfactant hydrocarbon chain from the medium to the interior of the micelle (Delta G(HP)(o)) were computed. It was observed that micelle-PEG interactions in the case of HPyC l and TTAB were quite similar to mixed micelle-PEG interactions especially in the presence of PEG 200, 400, and 600. The results were explained on the basis of medium structure-breaking effects of PEG and adsorption of PEG on the micelle-solution interface. In the presence of PEG 4000, the micelle f ormation corresponding to the first break was found to be similar to that i n the presence of PEG 200, 400, and 600. The second break was designated to the polymer bound micellar aggregates, which became more stable as the amo unt of PEG 4000 was increased.