Cationic Imidazolium Monomeric Surfactants: Their Synthesis and Surface Active Properties

A series of long-chain ester-based water-soluble cationics have been synthesized by using renewable raw materials like fatty acids and halogenated alcohols. The surface activity of the molecules has been determined by measurement of their conductance and surface tension in aqueous solution. The dynamics of surface activity of these surfactants have also been investigated in the presence of sodium halides (NaCl and NaBr) by surface tension measurement. A series of useful parameters like critical micelle concentration (CMC), surface tension at the CMC (γ CMC ), adsorption efficiency (pC 20 ), effectiveness of surface tension reduction (Π CMC ), Gibbs free energy of the micellization (Δ G 0mic ) and Gibbs free energy of adsorption (Δ G 0ads ) have been determined from the measurements obtained by surface tension and conductivity methods. Further with the application of the Gibbs adsorption isotherm, maximum surface excess concentration (Γ max ) and minimum surface area/molecule (A min ) at the air–water interface were also estimated. Thermal stability of these long chain cationics have been measured by thermal gravimetric analysis under a nitrogen atmosphere. Analysis of thermal stability measurement indicated that the thermal stability of these long chain imidazoliums increases with an increase in chain length.