The effects of n-propanol, n-butanol, n-pentanol and n-hexanol on the micellization of quaternary-ammonium dimeric surfactant C_(12)-2- C_(12)·2Br have been investigated using conductivity and steady fluorescence measurements. The results show that the surfactant and the alcohols form mixed micelles with addition of alcohols. In the mixed micelles, the alkyl chains of the alcohol molecules penetrate into the micelle interior and the hydroxyl groups lie in the palisade layer of the micelles, which weaken the electrostatic repulsion between the ionic head groups of the surfactants and result in a decrease of cmc and an increase of the ionization degree of the micelle. The effects become more striking with increasing the alkyl chain length of the alcohol molecules.

Key words: QUATERNARY AMMONIUM COMPOUNDS, SURFACTANTS, COLLOID, ALCOHOL