Monolayer behavior of calix-4-resorcinarenes and their surfactant complexes

We describe within this paper a series of calix-4-resorcinarenes along with their complexes with tetraalkylammonium surfactants and their behavior in Langmuir monolayers. Calix‐4‐resorcinarenes were synthesized containing both undecyl and phenyl sidechains and then modified using Mannich reactions to incorporate neutral, cationic or anionic groups in the 2‐positions of the resorcinol unit. In the cases of resorcinarenes modified with four sulfonate groups, mixing with long chain dialkyl dimethyl ammonium surfactants led to the formation of 1:4 complexes. These various materials were spread as Langmuir monolayers and their behavior upon compression measured. Long chain substituted resorcinarenes gave more stable monolayers than their short chain analogues. The incorporation of long chain surfactants led to large increases in surface area, demonstrating that both resorcinarenes and surfactant are located at the water surface, except for one system where a bilayer structure is potentially formed.

► Anionic resorcinarenes and cationic surfactants form stable composite Langmuir films.
► Undecyl substituted resorcinarenes form more compact films than phenyl substituted.
► Both components of the composite are located at the air–water interface.
► Monolayers show side-by-side rather than head to head orientation of the counterions.