Liquid–liquid interfaces: Water–perfluoroalkanes and water–perfluoroalkylalkanes, experimental interfacial tensions and molecular simulation

Abstract

The liquid-liquid interfacial tension of water with four liquid perfluoroalkanes (perfluoropentane, perfluorohexane, perfluorooctane and perfluorononane) and four liquid perfluoroalkylalkanes (perfluorobutylpentane, perfluorobutylhexane, perfluorohexylhexane and perfluorohexyloctane) was measured as a function of temperature in the 273 K–340 K range. The studied perfluoroalkylalkanes cover a range of relative lengths of the hydrogenated and perfluorinated segments.This is the first time the liquid-liquid interfacial tension with water has been measured for these substances, which is surprising given their pharmaceutical and medical relevance. The new data thus fills an important gap in the literature.The organization and interactions of the liquid-liquid interfaces was further investigated using atomistic molecular dynamics simulations, providing structural and energetic information of the systems. The results demonstrate the contribution of the interaction between the water molecule and the dipole located at the center of the perfluoroalkylalkane molecules, which explains the lower interfacial tension of these solvents with water, relatively to alkanes and perfluoroalkanes. Ultimately, these findings will help to interpret the formation of nano-patterned molecular films of PFAA at the surface of water and of wet silicon wafers.