Synthesis, surface active and thermal properties of novel imidazolium cationic monomeric surfactants

Abstract

A series of long chain water soluble cationics have been synthesized by using renewable raw materials like fatty alcohols and epichlorohydrin. 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 (γcmc), adsorption efficiency (pC20), effectiveness of surface tension reduction (Πcmc), Gibbs free energy of the micellization (ΔG0mic) and Gibbs free energy of adsorption (ΔG0ads) have been determined from the measurements obtained by surface tension and conductivity method. Further with the application of the Gibbs adsorption isotherm, maximum surface excess concentration (θmax) and minimum surface area/molecule (Amin) at the air–water interface were also estimated. Thermal stability of these long chain cationics has been measured by thermal gravimetric analysis under nitrogen atmosphere. Analysis of thermal stability measurement indicated that the thermal stability of these long chain imidazoliums increase with an increase in chain length.