Surface viscosities and pressure-area isotherms of mixed monolayers of hexadecoxy ethanol with docosanoxy propanol and docosanoxy ethanol with hexadecoxy propanol at 25°C

Abstract

Surface pressure (π)-area ( A) and surface viscosity (μ)-π isotherms on water substrate of mixed monolayers of hexadecoxy ethanol (C 16H 33OC 2H 4OH) with docosanoxy propanol (C 22H 45OC 3H 6OH) and docosanoxy ethanol (C 22H 45OC 2H 4OH) with hexadecoxy propanol (C 16H 33OC 3H 6OH) were studied as a function of mole fraction at 25°C. The positive and negative deviations observed from additivity rule for molecular areas and fluidities (φ) for these systems and high negative excess free energies of mixing (Δ G E) suggested that the systems are nonideal and miscible. The data are indicative of intermolecular interaction between the two components. At high film pressures and at 1:1 molar ratio, the mixed monolayers exhibited higher stability which has been observed from area-composition curves and Δ G E values. μ 0, μ ∞, τ, Δ F, Δ F-Δ F 1, and w i-k (0.94 r i ) have been calculated for all the mixed monolayers studied. Nearly equal values of Δ F and w i-k (0.94 r i ) suggest that similar relaxation phenomena are involved in both pure and mixed monolayers. Δ F of mixed monolayers is found to be a weighted average of the pure constituents.