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 (C(16)MeImCl) 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 C(16)MeImCl (aq) were also investigated. Two characteristic concentrations, namely the critical aggregation concentration and polymer saturation concentration, before free C(16)MeImCl micelles appear in C(16)MeImCl-NaCMC solutions have been identified. Effects of temperature, NaCMC concentration, and the charge density parameter of NaCMC on the self-aggregation of the C(16)MeImCl have been discussed to elucidate C(16)MeImCl-NaCMC interactions. The thermodynamic parameters for micellization of C(16)MeImCl were estimated both in absence and in the presence of NaCMC. The observed enthalpy-entropy compensation effect in C(16)MeImCl and C(16)MeImCl-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. (C) 2014 Elsevier Ltd. All rights reserved.