Influence of sodium carboxymethylcellulose on the aggregation behavior of aqueous 1-hexadecyl-3-methylimidazolium chloride solutions.

The influence of sodium carboxymethylcellulose (NaCMC) on the aggregation phenomena of a surface active ionic liquid 1-hexadecyl-3-methylimidazolium chloride (C16MeImCl) was studied in aqueous solutions using electrical conductivity and surface tension measurements. The counterion condensation behavior of NaCMC (aq) and the premicellar ion-association behavior of C16MeImCl (aq) were also investigated. Two characteristic concentrations, namely the critical aggregation concentration and polymer saturation concentration, before free C16MeImCl micelles appear in C16MeImCl-NaCMC solutions have been identified. Effects of temperature, NaCMC concentration, and the charge density parameter of NaCMC on the self-aggregation of the C16MeImCl have been discussed to elucidate C16MeImCl-NaCMC interactions. The thermodynamic parameters for micellization of C16MeImCl were estimated both in absence and in the presence of NaCMC. The observed enthalpy-entropy compensation effect in C16MeImCl and C16MeImCl-NaCMC systems provided important insight as to how micellization processes are governed by the bulk structural property of the solution with respect to that of the water.