Ordering in Surfactant Foam Films Transferred onto Hydrophilic and Hydrophobic Substrates

Foam films have been formed by aqueous dodecyldimethylphosphine oxide (C₁₂DMPO) and aqueous hexadecyltrimethylammonium bromide (C₁₆TAB) solutions and drained. The surfactant films were transferred onto hydrophilic and hydrophobic substrates at five different drainage times. Angle-resolved X-ray photoelectron spectroscopy and metastable induced electron spectroscopy were used for investigation of the thickness and orientation of the surfactant molecules in the transferred foam film. Of the four combinations only the drained film formed by C₁₆TAB transferred onto hydrophobic surfaces shows a strong degree of orientation of the surfactant molecules in the transferred film. The other three combinations do not show a preferred orientation of the surfactant molecules in the foam film. The phenomenon is discussed based on the interaction of the molecules within the films and the interaction of the formed films with the substrates.