Synthesis and physicochemical studies of methyl‐12‐[1′‐β‐d‐lactosyl]‐octadec‐9‐ene‐1‐oate: A novel biosurfactant analog

Abstract

AbstractSynthesis of a new glycolipid and biosurfactant analog, methyl‐12‐[1′‐β‐d‐lactosyl]‐octadec‐9‐ene‐1‐oate (LOD), has been done from easily accessible renewable resources, namely, lactose and ricinoleic acid from castor oil. Surface and thermodynamic properties at the air/water interface including critical micelle concentration (CMC), aggregation number (<N>), maximal densities (Γmax), minimal area per molecule (Amin), surface pressure at the CMC (ΠCMC) free energy of adsorption (ΔGad0), and free energy of micelle formation per mole of monomer unit (ΔGm0) were investigated. The results indicate that this particular glycolipid, because of branching in the hydrophobic chain, has a comparatively large Amin value and hence a very low CMC, aggregation number, and less free energy of micellization and adsorption at the air/water inter‐face than molecules with a straight hydrophobe, for example, n‐dodecyl‐β‐d‐maltoside. The effects of electrolytes (NaCl, KCl, CaCl2, and AlCl3) of the same ionic strength and of increasing ionic strength on the interfacial microenvironment of LOD were also investigated. For the same anion, Cl−, and the same ionic strength, different cations were found to have different effects on the CMC of LOD. With increasing ionic strength, different electrolytes were found to have different effects on the interfacially located, highly hydrated aqueous layer of the LOD micelle. The water structure‐making or‐breaking ability of different cations from the interfacial microenvironment of LOD was found to depend on the charge/radius ratio of the cations.