je400597f_si_001.pdf (128.21 kB)

Effect of Polyoxyethylene Type Nonionic Surfactant and Polar Lipophilic Oil on Solubilization of Mixed Surfactant Microemulsion Systems

Download (128.21 kB)
journal contribution
posted on 18.02.2016 by Kaushik Kundu, Bidyut K. Paul
In the present report, the water solubilization capacity of water-in-oil microemulsion systems comprising mixed surfactants, that is, anionic sodium bis­(2-ethylhexyl) sulfosuccinate (AOT) and nonionic(s) [viz., polyoxyethylene (2) stearyl ether (Brij-72), polyoxyethylene (10) stearyl ether (Brij-76), polyoxyethylene (20) stearyl ether (Brij-78), polyoxyethylene (2) oleyl ether (Brij-92), polyoxyethylene (10) oleyl ether (Brij-97), and polyoxyethylene (20) oleyl ether (Brij-98)] was investigated in polar lipophilic oils [viz., ethyl myristate (EM), isopropyl myristate (IPM), and isopropyl palmitate (IPP)] with varying mole fractions of nonionic surfactant (Xnonionic) at a fixed surfactant concentration and 303 K. A maximum (i.e., synergism) in water solubilization (ω0,max) was observed at an optimal value of mole fraction of nonionic surfactant (Xnonionic,max). The solubilization efficiency parameter (SP*water) and the free energy of dissolution (ΔG0s) were evaluated for these mixed systems. All of the physicochemical parameters for solubilization (viz., ω0,max, Xnonionic,max, and SP*water) were found to be dependent on both nonionic surfactants and oils. A minimum in ΔG0s was observed at corresponding Xnonionic,max, where a maximum in SP*water was evidenced. The IPP-based system was found to be most efficient, whereas the EM-based system was least efficient. An attempt was made to correlate the interdependence of physicochemical (ω0,max or SP*water) and thermodynamic (ΔG0s) parameters.