Synthesis, surface adsorption and micelle formation of a class of morpholinium gemini surfactants

A series of novel gemini surfactants with morpholinium headgroup, 4, 4′-(alkane-4, n-4′)bis(4-decyl, dodecyl or tetradecyl morpholinium)bromide (Mm-n-Mm, m = 10, 12, 14, n = 3, 4), were synthesized and characterized using 1H NMR. The surfactants were investigated for their adsorption and micellization in aqueous solutions through surface tension and conductivity methods It was found that the physicochemical properties, such as surface activity and thermodynamic property of the aqueous surfactant system, were dependent on the lengths of both hydrophobic tail chain and spacer. With the increase of the hydrophobic chain length or the decrease of spacer length, the cmc value of the surfactant decreases and the ability to reduce the surface tension is stronger. The calculation result of thermodynamic parameters indicated that the surfactants we synthesized are more inclined to aggregate in solution as compared with traditional m-s-m type gemini surfactants, and the micellization of Mm-n-Mm was an entropy-driven process.