Ca2+- and Mg2+-induced molecular interactions in a dehydrocholic acid/didodecyldimethylammonium bromide mixed monolayer
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- Messina, P.V., Ruso, J.M., Prieto, G. et al. Colloid Polym Sci (2010) 288: 449. doi:10.1007/s00396-009-2170-5
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The aim of this article is the evaluation of Ca2+ and Mg2+ subphases presence effect on mixed monolayers composed by dehydrocholic acid (HDHC) and didodecyldimethylammonium bromide (DDAB). The monolayer stability was analyzed by the evaluation of thermodynamic parameters, ΔGmixE and α. At all calcium ion-tested concentration, the mixed systems XHDHC = 0.6 and 0.8 at π = 30 mJ m−2 were always the most favored proportions. The XHDHC = 0.6 system was also stable in magnesium presence, and the XHDHC = 0.2-mixed monolayer went through a stable to an unstable state as the content of Ca2+ or Mg2+ augment. Finally, the XHDHC = 0.4 monolayer showed a particular behavior, i.e., remained stable at low cation concentration, unstable at intermediate concentration and stable again at high concentration. The effect was similar at Mg2+ presence.