INVESTIGADORES
PALMA Santiago Daniel
artículos
Título:
Surface phase behavior and domain topography of ascorbylpalmitate monolayers
Autor/es:
BENEDINI LUCIANO; FANANI, LAURA; MAGGIO, BRUNO; WILKE, NATALIA; MESSINA PAULA; PALMA S; SCHULZ P
Revista:
LANGMUIR
Editorial:
AMER CHEMICAL SOC
Referencias:
Año: 2011 vol. 27 p. 10914 - 10919
ISSN:
0743-7463
Resumen:
Ascorbyl palmitate (ASC16) is a molecule of
potential pharmacological interest due to its antioxidant properties
and amphiphilic nature. The surface behavior of ASC16 was
studied using Langmuir monolayers and Brewster angle microscopy.
This molecule formed stable monolayers at room temperature
that showed phase transition from a liquid-expanded to
liquid-condensed or crystalline phase, depending on the subphase
conditions. Using a theoretical approach, we were able to explain
the behavior of the ASC16 film at different bulk pH values and salt
conditions based on the surface pH and the dissociation fraction
of the film. Both condensed phases corresponded to highly packed
conditions with the crystalline phase occurring at a low charge
density, showing molecular tilting and preferential growth at
characteristic angles, while the liquid-condensed phase formed in highly charged surfaces revealed small flowerlike domains
probably as a consequence of internal dipole repulsion. A smaller perpendicular dipole moment was observed for the crystalline than
the liquid-condensed phase which may explain the domain features. In conclusion, ASC16 showed a complex surface behavior that
was highly sensitive to subphase conditions.