Molecular Explanation for the Abnormal Flux of Material into a Hot Spot in Ester Monolayers
| Autor: | Vanesa Viviana Galassi, Thomas M. Fischer, Mario G. Del Pópolo, Natalia Wilke |
|---|---|
| Jazyk: | angličtina |
| Předmět: |
Langmuir
Stereochemistry Ciencias Físicas Non-equilibrium thermodynamics Hot spot (veterinary medicine) 02 engineering and technology Surface pressure 01 natural sciences Phase (matter) 0103 physical sciences Monolayer Materials Chemistry NEGATIVE PYROBARIC COEFICIENT Physical and Theoretical Chemistry NEGATIVE THERMAL EXPANSIVITY Aqueous solution 010304 chemical physics ESTERS THIN FILMS ABNORMAL THERMAL BEHAVIOR Chemistry 021001 nanoscience & nanotechnology Surfaces Coatings and Films Astronomía Temperature gradient 13. Climate action Chemical physics 0210 nano-technology CIENCIAS NATURALES Y EXACTAS |
| Zdroj: | The Journal of Physical Chemistry B |
| ISSN: | 1520-5207 1520-6106 |
| DOI: | 10.1021/acs.jpcb.7b00949 |
| Popis: | Langmuir monolayers of certain surfactants show a negative derivative of the surface pressure with respect to temperature. In these monolayers, a local temperature gradient leads to local yielding of the solid phase to a kinetically flowing liquid, so that the material flows toward the hotter regions that act as sinks. The accumulation of material leads to the formation of nonequilibrium multilamellar bubbles of different sizes. Here we investigate the molecular factors leading to such a peculiar behavior. First, we identify the required structural molecular moieties, 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 whose compression isotherms shift to lower areas as the temperature increases, and thus collapse into a hot spot; and they bind weakly to the aqueous subphase, i.e., water does not attach to the monolayer at the molecular level, but only supports it. Molecular simulations for a selected system confirm and help explain the observed behavior: surfactant molecules form a weak hydrogen bonding network, which is disrupted upon heating, and also the molecular tilting changes with temperature, leading to changes in the film density. Fil: Galassi, Vanesa Viviana. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentina Fil: del Popolo, Mario Gabriel. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentina Fil: Fischer, Thomas M.. University of Bayreuth; Alemania Fil: Wilke, Natalia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Química Biológica de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Centro de Investigaciones en Química Biológica de Córdoba; Argentina |
| Databáze: | OpenAIRE |
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