Interaction between acetylsalicylic acid and a cationic amphiphile model: An experimental approach using surface techniques

Mechanical and morphological effects of monolayers of octadecylamine upon aspirin adsorption are monitored by Langmuir isotherms measurements and Brewster angle microscopy. Aspirin induced a notable expansion of the corresponding isotherms and a concentration-dependence of the mechanical stability of the films as a consequence of the subtle balance between the solubility of the amine and the monolayer stabilization induced by the ion-pairs, as corroborated by Brewster Angle Microscopy images. The incorporation of the aspirin into the interface was confirmed by UV-vis reflection spectroscopy. Some comments on the feasibility of using aliphatic amines for drug delivery of anionic species are presented.