Dynamics in physisorbed monolayers of 5-alkoxy-isophthalic acid derivatives at the liquid/solid interface investigated by scanning tunneling microscopy

Monolayers of isophthalic acid derivatives at the liquid/solid interface ha ve been studied with scanning tunneling microscopy (STM). We have investiga ted the dynamics related to the phenomenon of solvent co-deposition, which was previously observed by our research group when using octan-1-ol or unde can-1-ol as solvents for 5-alkoxyisophthalic acid derivatives. This solvent co-deposition has now been visualized in real-time (two frames per second) for the first time. Dynamics of individual molecules were investigated in mixtures of semi-fluorinated molecules with video-STM. The specific contras t arising from fluorine atoms in STM images allows us to use this functiona lity as a probe to analyze the data obtained for the mixtures under investi gation. Upon imaging the same region of a monolayer for a period of time we observed that non-fluorinated molecules progressively substitute the fluor inated molecules. These findings illustrate the metastable equilibrium that exists at the liquid/solid interface, between the physisorbed molecules an d the supernatant solution.