2015 Volume 15 Issue 7 Pages 289-296
The counterion distribution of cationic surfactants at aqueous solution/air interface and the structure of oil soluble alcohols at hexane solution/water interface were examined by means of the synchrotron X ray analysis, from which the adsorbed films were suggested to often have heterogeneous structure. From the X-ray Absorption Fine Structure (XAFS) analysis of the adsorbed films of dodecyl- (DTAB) and hexadecyltrimethylammonium bromide (HTAB) and 1-decyl-3-methylimidazolium bromide (DeMIMBr), it was revealed that in all cases there exist two kinds of hydrated bromide ions in the adsorbed films; fully hydrated ones by six water molecules (free) and partially dehydrated ones but bound to surfactant head group (bound). The dependence of the ratio of bound Br to the free ones on the surface density was examined. From the X ray reflection analysis of the adsorbed films of 1H,1H,2H,2H-perfluorodecanol (FC10OH) and 1H,1H,10H,10H-perfluorodecane-1,10-diol (FC10diol), it was clarified that for FC10OH the condensed monolayer has a two dimensional solid-like structure and the expanded monolayer was not homogenous but heterogeneous with small condensed domains and for FC10diol, the films transformed their structure from the flat condensed monolayer anchored by two OH groups to the condensed multilayer. Furthermore the film structure of FC10OH and FC10diol mixture was also examined.
