Interactions Between Sodium p-Perfluorononenyloxy Benzene Sulfonate and Alkyl Quaternary Ammonium Salts

p-Perfluorononenyloxy benzene sulfonate(C9F17OC6H4SO3Na, OBS) a low-cost fluorinated surfactant. However, its surface activity is poor. In this work, OBS was mixed with different cationic hydrogenated surfactants, namely CnNR[CnH2n+1N(CH3)(3)Br(CnNM, n = 8, 10) and CnH2n+1N(CH2CH3)(3)Br (CnNE, n=8, 10, 12)]. The effects of the molar ratio Of OBS to CnNR, the hydrophobic chain length and the head-group size of CnNR(R=M or E) on the critical micelle concentration(cmc), the minimum surface tension (gamma(cmc)), the maximum surface amount adsorbed(Gamma(tm)) and the limited surface area per molecule (A(min)) for the mixtures of the cationic-anionic hydrogenated-fluorinated surfactants were investigated. The results showed that, after mixed with CnNR, both the cmc and gamma(cmc) of the system were greatly lowered, i. e. the efficiency was totally enhanced. The OBS-C8NE surfactant mixtures with molar ratio of 1 1 showed the best surface activity, i. e. the lowest erne and gamma(cmc), compared with the OBS-C-8 NE mixtures with other molar ratios. Mean- while, when the molar ratio was apart from equimolarity, the cmc of OBS-excess systems were smaller than that of C-8 NE-excess systems, but the gamma(cmc) was not found to be significantly changed. Compared with single surfactant systems, the Gamma(tm) for the mixtures of OBS-C-8 NE was significantly increased and the A(min) was significantly decreased. When OBS was mixed with CnNE with different alkyl chain length, the sequence of cmc for the Mixtures was C8NE>C10NE>C12NE. It suggested that the increase of hydrophobic chain length of CnNE would induce the decrease of cmc of the mixtures. When the head-group size of CnNR(n=8, 10) in the mixture was changed from -triethylammonium to -trimethylammonium, no significant change of the surface activity was found for the mixtures.