Effect of Complementary Hydrogen Bonding Additives in Subphase on the Structure and Properties of the 2-Amino-4,6-dioctadecylamino-1,3,5-triazine Amphiphile at the Air-Water Interface: Studies by Ultraviolet-Visible Absorption Spectroscopy and Brewster Angle Microscopy

The present work is focused on the effects of hydrogen bonding on the 2-D properties of aminotriazine amphiphile 1 (2C18TAZ) by incorporating different complementary hydrogen bonding components in the subphase. The structural organization of 1 at the air-water interface in the presence of barbituric acid (BA), barbital (BT), andcyanuricacid (CA)wasexaminedbysurfacepressure-area isothermmeasurements, Ultraviolet-visible (UV-vis) absorption spectroscopy, andBrewster anglemicroscopy. UV-vis absorption spectra reveal that amphiphile 1 forms an irreversible monolayer at the air-water interface due to its “auto assembly”. The binding of BA molecules to a 2C18TAZ monolayer can be detected by UV spectra at BA subphase concentrations as low as 0.01 mM. Different complementary hydrogen bonding additives in the subphase have different effects on the monolayer structure and properties of 1, which are likely due to the different structures of hydrogen bonding additives at the air-water interface. The effects of organic solvents in the subphase was also investigated. The strong solvating ability of dimethyl sulfoxide (DMSO) destroyed the hydrogen bonding network whereas dioxane enhanced the hydrogen bonding between 1 and its hydrogen bonding complements.