INQUISUR   21779
INSTITUTO DE QUIMICA DEL SUR
Unidad Ejecutora - UE
artículos
Título:
Bile salt structural effect on the thermodynamic properties of a catanionc mixed adsorbed monolayer
Autor/es:
1. MARCOS D. FERNÁNDEZ-LEYES; PAULA V. MESSINA; PABLO C. SCHULZ
Revista:
COLLOID AND POLYMER SCIENCE
Editorial:
SPRINGER
Referencias:
Lugar: Berlin; Año: 2011 vol. 289 p. 179 - 191
ISSN:
0303-402X
Resumen:
The interfacial effects of two bile salts (sodium deoxycholate (NaDC) and sodium dehydrocholate (NaDHC)) in a catanionic mixed adsorbed monolayer have been investigated at 25 °C. The surfactant interfacial composition, the interfacial orientation of the molecules and the energy changes are analysed to show a thermodynamic evidence of the hydrophobic BSs effect during its intercalation into interfacial adsorbed didodecyldimethyl ammonium bromide (DDAB) molecules. Both mixed systems (NaDC–DDAB and NaDHC–DDAB) have analogous adsorption efficiencies, which are similar from a pure DDAB monolayer and superior to that obtained for both bile salts molecules. Nevertheless, their adsorption effectiveness is different: NaDC causes an increment of Γ while NaDHC produces the opposite effect. The adsorption efficiency in surface tension reduction is due to the existence of interfacial synergistic interactions (confirmed by the analysis of βγ and ΔGad 0 values). Maximum synergistic interaction is seen for αBSs= 0.4. The hydrophobic steroid backbone of NaDHC molecule presents a deep interfacial penetration than NaDC. This fact causes a great disturbance of DDAB hydrocarbon tails and conduces to a large separation of molecules (high Am values) which explains the reduction of adsorption effectiveness (low Γm values)