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

The conductances of hexadecylpyridinium chloride (HPyCl) + trimethyltetradecylammonium bromide (TTAB) mixtures over the entire mole fraction range of HPyCl (alpha(HPyCl)) were measured in aqueous binary mixtures of polyethylene glycol (PEG) 200, 400, 600, and 4000 containing different amounts of each PEG in their respective binary mixtures at 30 degrees C. Each conductivity curve showed a single break, except in the presence of PEG 4000 where two breaks were observed. From the conductivity (kappa) data, the critical micellar concentration (cmc), degree of counter ion association (chi), the equivalent 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 HPyCl 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 formation corresponding to the first break was found to be similar to that in 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 amount of PEG 4000 was increased.