Experimental and Theoretical Efforts to Identify the Microstructural Transition of Water to Acetonitrile‐Based Reverse Micelle through Binary Compositions of Polar Solvents

Abstract

AbstractThe present report was undertaken due to the scarcity of information regarding the microstructural transition from aqueous to acetonitrile (ACN)‐based non‐aqueous reverse micelles (RMs) stabilized by cationic didodecyldimethylammonium bromide (DDAB) and anionic sodium bis(2‐ethylhexyl) sulfosuccinate (AOT) in cyclohexane. The synergistic solubilization capacity of corresponding polar solvent at a fixed composition and the nature of conductance plots in these RMs were markedly varied along with the composition of binary solvents (water and ACN at pure or mixed states) and the surfactant charge types (DDAB and AOT). The structural alteration in these RMs through water‐ and ACN‐rich compositions were studied by FTIR, where the results were explained in terms of molecular states of water and ACN inside RMs. The differential binding affinity of both polar solvents with the two surfactants was shown using ab initio calculations. The subsequent appearance and disappearance of aqueous nano‐pool was verified from UV‐Vis technique using CoCl2. The lack of H‐bonding ability on going from aqueous to ACN‐based RMs was evidenced from the temperature‐dependent DLS study along with the absorption profiles of 7‐hydroxycoumarin. The results showed how the microstructures and H‐bonding interactions inside RMs are dramatically altered by simply changing polarity of the solvents or the surfactant charge‐types. This report could be useful to understand the formation mechanism of two class of RMs.