(383e) Effects of Sugar Surfactant Architecture On Mixed Micelle Formation with Cationic Surfactants

Sugar surfactants find many applications in industry as nonionic detergents due to their highly hydrophilic polar headgroups and biodegradability. However, pure sugar surfactants sometimes display specific interactions between headgroups that make them difficult to assemble into micelles or lyotropic liquid crystals. Mixed surfactant systems can be used to overcome these difficulties, and are often found to exhibit better surface properties than pure surfactants. Effects of variation in chain length of sugar surfactants mixed with other other non-ionic, cationic and anionic surfactants have been studied in the past. Prior studies relied on critical micellar concentration (CMC) as the means to gain insight into the thermodynamics of such mixed surfactant systems. More direct routes of measuring heats of mixing, solvation and assembly, in particular isothermal titration calorimetry (ITC), provide a desirable alternative because they do not require variable temperature experiments and they can be accomplished with a small amount of surfactant.

This study focuses on the behavior of sugar surfactants with varying structural characteristics (head group size and stereochemistry, tail chain length, and fluorination of the tail) in presence of a common cationic surfactant, cetyltrimethylammonium bromide. ITC is used to directly measure enthalpies of micellization and surfactant mixing and to observe the effects of changing each surfactant characteristic independently. Such a study of mixed surfactant system using ITC will establish how mixed micelles form and how surgar-based surfactants partition into cationic micelles with only small amounts of the sugar-based surfactant. The results of these experiments will help to establish the characteristics of sugar-based surfactants required for effective mixing with CTAB and for the development of synergy in the properties of the mixed surfactant system.