Molecular Explanation for the Abnormal Flux of Material into a Hot Spot in Ester Monolayers

GALASSI, VANESA V.; DEL POPOLO, MARIO G.; FISCHER, THOMAS M.; WILKE, NATALIA

JOURNAL OF PHYSICAL CHEMISTRY B - (Print)

AMER CHEMICAL SOC

Año: 2017 vol. 121 p. 5621 - 5621

1520-6106

angmuir monolayers of certain surfactants show a negative derivative of thesurface pressure with respect to temperature. In these monolayers, a local temperature gradientleads to local yielding of the solid phase to a kinetically flowing liquid, so that the material flowstoward the hotter regions that act as sinks. The accumulation of material leads to the formationof nonequilibrium multilamellar bubbles of different sizes. Here we investigate the molecularfactors leading to such a peculiar behavior. First, we identify the required structural molecularmoieties, and second we vary the composition of the subphase in order to analyze its influence.We conclude that esters appear to be unique in two key aspects: they form monolayers whosecompression isotherms shift to lower areas as the temperature increases, and thus collapse into ahot spot; and they bind weakly to the aqueous subphase, i.e., water does not attach to themonolayer at the molecular level, but only supports it. Molecular sim