Characterization of anionic reverse micelles formulated on biobased solvents as replacing conventional nonpolar organic solvents

Abstract

Two reverse micelles (RMs) employing 1,4-bis-2-ethylhexylsulfosuccinate (AOT) and two biobased solvents, p-cymene (p-cym) or limonene (lim), have been formulated with the aim to obtain systems more environmentally friendly. Both RMs were studied by using different techniques such as dynamic light scattering (DLS) and 1H NMR. Additionally, spectroscopy techniques were used to obtain information such as critical micellar concentration and aggregation number of the system investigated. Our results show that both biobased solvents can be used to generate AOT RMs. Interestingly, even the maximum amount of water dispersed are similar for both RMs, and the sizes of the systems are not identical, being that the RMs are formulated in lim larger than in p-cym. Both the biobased solvent and RMs show interaction of the entrapped water and the interface; however, this interaction is different depending on the solvent employed to prepare the RMs. Thus, the interaction water-surfactant at the interface is weaker in p-cym/AOT than in lim/AOT RMs. We think that the different penetration of the external solvent to the interfacial region is the main reason for the facts observed. In this sense, the polarity of these biobased solvents could explain why the penetration of both biobased solvents is different, making the p-cym/AOT RMs less interactive and, therefore, with smaller droplets sizes values. In summary, the different capacities of these biobased solvents to penetrate into the AOT interface allow us to obtain a new interface with peculiar characteristics and therefore with diverse applications.