Surface potentials of mixed monolayers of n-long chain alcohols and n-alkoxy ethanols

Abstract

The surface potentials (ΔV) of the mixed monolayers of n-long chain alcohols (C_n - OH) and n-alkoxy ethanols (C_n - OCH₂CH₂OH) (where n = 16, 18, 20, and 22) have been measured at 25°C by the ionizing electrode method and the results have been represented in the form of ΔV - π, ΔV - A, µ_⊥ - A and π - A isotherms. The effect of chain length and polarity on the intermolecular interaction and the packing characteristics in the mixed monolayer state has been investigated. All the mixtures were found to be homogeneous; however, the simple mixture law was not found to be applicable to them. The mixtures, such as C₁₆ - OH + C₁₆- OC₂H₄OH gave ΔV, µ_⊥ and the I_c à LS or S transition pressure values, which were nearly the mean of those obtained for the pure components. But where the chain length or the polar group of the compounds was different, the ΔV, µ_⊥, and the L_c → LS or S pressure values were appreciably lower than the mean values, indicating stronger intermolecular interactions. The mixed film of C₁₆ - OH and C₂₂ - OC₂H₄OH showed two phase transitions in the condensed region.