Effect of co-solutes on the physico-chemical properties of surfactant solutions

Abstract

Physico-chemical studies of some aqueous surfactant solutions were carried out by employing conductance, surface tension and spectrofluorometric techniques. From conductivity and surface tension measurements, critical micelle concentration (CMC), counter-ion association (<i style="">α</i>), equivalent conductance at infinite dilution (٨₀), surface excess concentration (<img src='/image/spc_char/italic_r.gif'>), minimum area per molecule (<i style="">A_min</i>), surface pressure at CMC <i style="">(</i>

<i style="">_CMC</i>), thermodynamic properties of micellization <i style="">(</i><i style=""><img src='/image/spc_char/delta.gif'>Gº_mic, </i><i style=""><img src='/image/spc_char/delta.gif'>Hº_mic, </i><i style=""><img src='/image/spc_char/delta.gif'>Sº_mic</i>) and adsorption <i style="">(</i><i style=""><img src='/image/spc_char/delta.gif'>Gº_ads, </i><i style=""><img src='/image/spc_char/delta.gif'>Hº_ads </i>and <i style=""><img src='/image/spc_char/delta.gif'>Sº_ads</i>) have been obtained for an anionic [<i style="">bis </i>(2-ethylhexyl) sulphosuccinate sodium salt (AOT)], a cationic [cetyl trimethyl ammonium bromide (CTAB)] and a nonionic [polyethylene (23) lauryl ether (Brij-35)] surfactant solutions. Effect of mixing co-solutes (dioxane and glycerol) on the physico-chemical properties of surfactant systems at 298.15, 308.15 and 318.15 K has been investigated. Surfactants micellar characteristics and their interaction with co-solutes were also investigated by fluorescence measurements of solutions using pyrene as a fluorescence probe.