Synthesis, characterization and surface properties of N-(2-hydroxyalkyl)-N′-(2-hydroxyethyl)imidazolium surfactants

1,2-Epoxyalkane on reaction with imidazole in the presence of catalytic amount of zinc perchlorate under solvent-free conditions have been converted into N-(2-hydroxyalkyl) imidazoles which on reaction with 2-bromoethanol or 2-chloroethanol gives imidazolium surfactants. These new surfactants have been investigated for their aggregation behavior by surface tension, conductivity and fluorescence techniques. Many important physiochemical parameters, such as the critical micelle concentration (cmc), surface tension at cmc (γcmc), Gibbs free energy of micellization (ΔG°mic), Gibbs free energy of adsorption (ΔG°ads), degree of counterion binding (β) and aggregation number (Nagg) has been determined utilizing surface tension, conductivity and fluorescence data. Further with the application of the Gibbs adsorption isotherm, maximum excess concentration (Γmax) and minimum surface area/molecule (Amin) of surfactant molecules at the air–water interface is also estimated. The size of aggregates in aqueous solutions has been investigated using dynamic light scattering (DLS) technique where micelle size have been found to increase with increase in alkyl chain length of surfactants. Thermal stability of these new cationics has been found to be decreasing with elongation of chain length as assessed by thermalgravimetric analysis.