Modulation of Aggregation Behaviour of Anionic Surfactant in the Presence of Aqueous Quaternary Ammonium Salts

The self-aggregation of sodium dodecylsulphate (SDS), an anionic surfactant, in aqueous solutions of tetraalkylammonium bromide salts (R4NBr, where R = propyl, butyl and pentyl) was determined at various temperatures in the range 288.15-318.15 K. The critical micelle concentration (CMC) determined from conductivity data was used to study the thermodynamics of the surfactant. The presence of bromide salts was found to affect the micellization of SDS in accordance with the hydrophobicity of the tetraalkylammonium cations, thus the CMC values follow the order no additive > Pr4NBr > Bu4NBr > Pen(4)NBr. The results from conventional conductivity methods were combined with those of spectroscopic techniques like fluorescence and UV-Vis studies.