Two-dimensional miscibility between a semifluorinated hydrocarbon and hydrogenated alcohols

The present work is aimed at investigating how semifluorinated alkanes (SFA) behave in 2D phase (Langmuir monolayers) mixed with fatty alcohols differing in hydrocarbon chain length. For our studies, F8H14 has been chosen as the representative of semifluorinated alkanes, and was mixed with homologous aliphatic alcohols (number of carbon atom in the alkyl chain, n = 12, 14 and 16). By changing systematically length of the hydrogenated chain (to be shorter, equal and longer than the hydrogenated part of the semifluorinated hydrocarbon), we expected to gain quantitative information regarding the miscibility of the investigated system. Our studies are based on the surface pressure–area (π/A) isotherms recorded with the Langmuir film balance. Our results show that the miscibility in the F8H14–alcohol systems depends both on the length of alkyl chain of the investigated alcohol and on surface pressure region. All the investigated systems were found to be immiscible at high surface pressures. When the alcohol chain length is smaller or equal to the hydrogenated part of the SFA, both components mix in low-pressure region; however, when the polimetylene part of the alcohol is longer, both components do not mix, independently on the surface pressure region.