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Abstract  

Interactions of a series of polyethyleneglycols (PEG) in aqueous micellar solutions of sodium dodecylsulfate (SDS) were investigated through thermodynamic properties. Volumes, heat capacities and enthalpies of dilution were measured at 25°C. The resulting transfer properties of PEG are reflecting hydrophobic interactions which increase with the polymer length and the hydrophilic interactions occurring in the aqueous polar layer of the micelles. Typically heat capacities clearly evidence various structural changes taking place in the micellar solutions.

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Thermal analysis of aqueous micellar solutions

Study of some structural transitions and of solute-surfactant complexes

Journal of Thermal Analysis and Calorimetry
Authors: K. Ballerat-Busserolles, S. Rassinoux, G. Roux-Desgranges, and A. Roux

Abstract  

A micro differential temperature scanning calorimeter was used to characterize the structural changes between different types of micelles in aqueous solutions of ionic surfactants: anionic — sodium dodecylsulfate (SDS) — and cationic — hexadecyltrimethyl ammonium bromide (CTAB). Moreover, this technique allowed to confirm the existence of peculiar types of complexes between surfactants and selected solutes. In SDS solutions containing polyethylene glycols (PEG), the presence of complexes formed by small micelles adsorbed along the chains of the polymers was evidenced in the case of long enough polymer chains. In CTAB-phenol solutions, due to strong interactions between the polar heads of surfactant and phenol, molecular complexes of a composition of 1:1 molar ratio have been characterized. Depending on the ratio [phenol]/[CTAB], the rheological behaviour was found to change from fluid to viscoelastic and gel-like solutions, owing to the growth of elongated rod-like micelles. With entangled worm-like micelles, the important role of kinetics to reach the thermodynamic equilibria was shown.

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Abstract  

Th anionic micellar system of the sodium dodecylsulphate (SDS) with di-2-ethylhexylphosphoric acid (D2EHPA) chelating ligand reagent in acctate buffer solutions was studied. The influence of the concentration and the composition of the micellar system for strontium preconcentration was determined. Different pH values of solutions as well as different concentration ratios of the ligand to the surfactant were used.

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Journal of Thermal Analysis and Calorimetry
Authors: S. Papp, L. Kőrösi, B. Gool, T. Dederichs, P. Mela, M. Möller, and I. Dékány

Abstract  

Gold nanoparticles (Au NPs) were prepared by the reduction of HAuCl4 acid incorporated into the polar core of poly(styrene)-block-poly(2-vinylpyridine) (PS-b-P2VP) copolymer micelles dissolved in toluene. The formation of Au NPs was controlled using three reducing agents with different strengths: hydrazine (HA), triethylsilane (TES), and potassium triethylborohydride (PTB). The formation of Au NPs was followed by transmission electron microscopy, UV–Vis spectroscopy, isothermal titration calorimetry (ITC), and dynamic light scattering (DLS). It was found that the strength of the reducing agent determined both the size and the rate of formation of the Au NPs. The average diameters of the Au NPs prepared by reduction with HA, TES, and PTB were 1.7, 2.6, and 8 nm, respectively. The reduction of Au(III) was rapid with HA and PTB. TES proved to be a mild reducing agent for the synthesis of Au NPs. DLS measurements demonstrated swelling of the PS-b-P2VP micelles due to the incorporation of HAuCl4 and the reducing agents. The original micellar structure rearranged during the reduction with PTB. ITC measurements revealed that some chemical reactions besides Au NPs formation also occurred in the course of the reduction process. The enthalpy of formation of Au NPs in PS-b-P2VP micelles reduced by HA was determined.

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Abstract  

Template syntheses of mesoporous silicas have been carried out inside large pores of inorganic matrix. Portions of tetraethoxysilane and cetyltrimethylammonium bromide micellar solution were incorporated step-by-step inside pore volume of silica gel with large pore size. Synthesized materials were characterized using thermal analysis, adsorption-desorption of nitrogen and X-ray diffraction scattering.

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Abstract  

Surfactant enhanced non-classical extractions are presented and discussed. They include micellar enhanced ultrafiltration and cloud point extraction. The ideas of the processes are given and the main features are presented. They are compared to the classical solvent extraction. The fundamental of micellar solutions and their solubilisation abilities are also discussed.

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Thin-layer chromatography (TLC) of fifteen amino acids was performed using silica gel and alumina impregnated with micellar solutions of cetrimide and cetylpyridinium chloride as stationary phases and aqueous solutions of dextrose as mobile phases. TLC system comprising of silica gel impregnated with micellar solution of cetrimide (5.0 mM) as stationary phase and 40% ( w/v ) aqueous solution of dextrose as mobile phase was found the most favourable for the separation of amino acids. Impregnation of silica gel with the micellar solution of cetrimide brings about a substantial change in the mobility of lysine. Separation of lysine (ketogenic) from arginine (glucogenic) is important physiologically. Surface modification of silica gel on impregnation, as indicated by FTIR and SEM studies, was responsible for improved chromatographic performance. The effect on the separation of the presence in the sample of heavy metal cations, as impurities, was examined. Limits of detection for lysine and arginine were 0.17 μg and 0.12 μg, respectively. For validation, the stability of the mixture and the reproducibility of the chromatographic properties Δ R F , separation factor ( k ), and resolution ( R S ) were calculated. The proposed method is simple, rapid, and free from use of volatile organic solvents.

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. 6. Kimura , E , Hashimoto , H , Koike , T . Hydrolysis of lipophilic esters catalyzed by a zinc(ii) complex of a long alkyl-pendant macrocyclic tetraamine in micellar solution . J Am Chem Soc . 1996 ; 118 : 10963

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)00537-8 . 19. Han , MG , Cho , SK , Oh , SG , Im , SS . 2002 Preparation and characterization of polyaniline nanoparticles synthesized from DBSA micellar solution . Synth Met. 126 : 53 – 60 . 10.1016/S0379

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