catalytic properties in chemical and enzymatic reactions (3).
The interface polarity of benzyl-n-hexadecyldimethylammon-Thus, information about the aggregation behavior of differium chloride (BHDC) cationic reversed micelles in benzene was ent surfactants and the knowledge of the properties of their studied and compared with those of the anionic systems of sodium microenvironment, such as the local polarities, are essential 1,4-bis-2-ethylhexylsulfosuccinate (AOT) in benzene and hexane. to understand the mechanisms of those reactions.
The nonionic reversed micelles of the poly(oxyethylene) n dodecyl
One of the main interest on the reverse micelles is based ethers type surfactants Brij 30 in benzene, cyclohexane, and decane on their ability of dissolving water in their core. This proand C 12 E 5 in hexane, heptane, and decane were also investigated.
vides a unique opportunity when using ionic surfactants, to 1-Methyl-8-oxyquinolinium betaine (QB) was used as optical study the properties of water aggregates close to the ionic
probe. The influence of surfactant concentration and W Γ
[H 2 O]/
[surfactant] were analyzed as a function of the absorption bands center (head polar groups and the corresponding counterions shifts in the visible, B 1 , and in the UV, B 2 , and the absorbances of the surfactant) without the interface due to large quantities ratio of these bands. At W Γ
0 the polarity sensed in the micelle of bulk water (4).
interfaces of AOT-hexane and AOT-benzene is entirely similar
In a previous work (5), we reported a study of the micropowhile for BHDC-benzene is quite smaller. The detected interaclarity of sodium 1,4-bis-2-ethylhexylsulfosuccinate (AOT) retion between the QB and BHDC may favor the entrance of QB verse micelles in hexane sensed through the UV-visible abinto the oil side of the micelle interface thus sensing a less polar sorption spectra of 1-methyl-8-oxyquinolinium betaine (QB).
environment. At W Β§ 10 once the polar heads of the surfactants
When using probe molecules, ideally, one expects the probe are completed hydrated, the anionic as well as the cationic surfacnot to perturb significantly the system that is to be measured tants show the same behavior. The polarity of Brij 30 and C 12 E 5 but, having the proper location within the aggregate, it should in the aliphatic hydrocarbons is comparable. However at W Γ
0 be sensitive enough to relevant changes in the system to be their micropolarity is higher than that of AOT-hexane, showing that the formation of hydrogen bond between QB and the free able to provide meaningful information. QB may be considered OH groups of these surfactants is the major factor affecting the one of the smallest organic optical probes used for the investimicroenvironment. In all the studied systems even at the maxigation of reverse micellar systems and it is assumed it does mum possible W, the polarity sensed by QB never reaches the not perturb the system under study. The absorption spectra value of pure water, that is, never reaches the bulk water phase analysis of QB in pure solvents have permitted to explain the prevailing in the micellar core.