Joël Lelièvre

Redox-switched amphiphilic ionic liquid behavior in aqueous solution.

A new redox amphiphilic ionic liquid (AIL) containing ferrocene as a redox-active group was synthesized, 1-(11-ferrocenylundecyl)-3-methylimidazolium bromide (Fc11MIm+). Adsorption and aggregation of both reduced and oxidized forms of this ferrocenated AIL in aqueous solution were studied by surface tension measurements. The micellization was favored for the reduced ferrocenated AIL (Fc11MIm+) as compared with the oxidized ferrocenated AIL (Fc+11MIm+). Minimum areas at the air/aqueous solution interface were identical whereas limiting surface tensions were slightly different. This corroborated the formation of an expanded monolayer of redox active AIL at the interface. The electrochemical behavior of redox active AIL was investigated. The electrochemical responses of Fc11MIm+ aqueous solution interestingly differed, depending on its concentration. Below the cmc, the electrochemical reaction was dominated by ferrocenated AIL adsorbed onto the electrode surface; then above the cmc, it was controlled by the Fc11MIm+ diffusing to the electrode. For the latter, the electrochemical mechanism was suggested to couple with the disruption reaction of the reduced form micelles.

Modification of the order of reaction and reaction rate of nucleophilic aromatic substitution in micellar solutions

The rate of formation of 2,4,6-trinitrodiphenylamine following the attack of aniline on 1-methoxy-2,4,6-trinitrobenzene has been studied in micellar media. The partial order with reference to the nucleophilic reagent (aniline) is unity in solutions of cationic detergents (positive micelles) and 3/2 in water or solutions of anionic detergents. For such reactions there are two main steps in the reaction scheme: first, the formation of an adduct between reagents, favoured by the effect of local higher concentration in the two kinds of micellar solutions and secondly, ejection of a proton from the adduct formed. The latter reaction is catalysed largely by positive micelles and in this case the kinetics are not limited by the deprotonation step. On the other hand, negative micelles inhibit the ejection of a proton and this opposes, in part, the effect of higher local concentrations.

A kinetic study of the formation and dissociation of the Meisenheimer complex formed between 1,3,5-trinitrobenzene and the hydroxide ion in micellar dodecyltrimethylammonium bromide solution

The rates of formation and dissociation of the thermoaddition complex of 1,3,5-trinitrobenzene with OH– has been investigated in micellar solutions of dodecyltrimethylammonium bromide (DTABr) using a stopped-flow spectrometer. We have observed and measured three processes which proceed under different conditions of acidity: (a) formation of the σ complex, (b) spontaneous (equilibrium) dissociation in less basic solutions and (c) dissociation via proton attack in acid solutions. These processes are influenced by the background KBr electrolyte. The interphase potential Δϕ=ϕm–ϕw, depicted in the pseudophase model, allows us to explain the variations of the rate constants.

New pseudo-stationary phases for electrokinetic capillary chromatography. Complexes between bovine serum albumin and sodium dodecyl sulfate.

The complexes formed between a protein (bovine serum albumin, BSA) and a surfactant (sodium dodecyl sulfate, SDS) were studied as separation carriers in electrokinetic chromatography. Selectivities different from those with either SDS or BSA alone in the background electrolyte (BGE) were obtained. Separation performances were demonstrated to be closely related to the type of complex formed, as predicted by the isotherm curve of SDS on BSA. For each composition of background electrolyte, capacity factors and resolutions were calculated. We compared the results with these complexes to electropherograms using BGE containing either BSA or SDS alone. The separation of a mixture of phenols indicate that some compositions of the BSA-SDS complexes are efficient selectors.