Synthesis, characterization and surface properties of long chain β-hydroxy-γ-alkyloxy-N-methylimidazolium surfactants

A series of long chain water soluble cationics have been synthesized by reacting β-hydroxy-γ-alkyloxy bromo or chloro ethers with N-methylimidazole. 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 (τmax) 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 imidazoliniums increase with an increase in chain length.

Graphical abstractLong chain water soluble ionic liquids, exhibiting better surface properties, have been synthesized from renewable feed stock, fatty alcohols.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Six long chain cationics have been synthesized. ► Long chain cationics showed superior surface properties as compared to conventional cationic surfactants. ► Long chain cationics exhibited better thermal stability. ► Lower concentration of additive (sodium halide) markedly reduced the critical micelle concentration of these new cationics.