Synthesis of some novel nonionic ethoxylated surfactants based on α-amino acids and investigation of their surface active properties

Abstract

Eight novel ethoxylated nonionic surfactants were prepared based on oil soluble α-amino acids. The L-phenylalanine and L-leucine were esterified and amidated with cetyl alcohol and palamitic acid, respectively; two amides and two esters of α-amino acids were obtained. The ethylene oxide was condensed with the prepared amides and esters to get three different polyethylene oxide units (40, 60, and 100) as phenylalanine derivatives. The amide and ester of α-L-leucine were ethoxylated at (60 ethylene oxides units). The analytical micro analysise, FTIR, 1H NMR, 13C NMR, mass spectra were carried out to confirm the chemical structures. The surface tension of the water soluble prepared compounds was measured at 25°C, further the surface active properties were determined and calculated. Such that critical micelle concentration (CMC), surface excess (Γmax); area per molecule (Amin), effectiveness (γ;CMC) free energy of micellization and adsorption (ΔGmic, ΔGad). From the data obtained it was found that the CMC of phenylalanine esters is greater than that obtained for the amide derivatives. The Γmax decreased as the ethylene oxide units (EO) increased. It was found also that the ΔGad was greater than the ΔGmic. The obtained data and discrepancy were discussed on the light of surfactant chemical structure.