A two-state model for selective solubilization of benzene-limonene mixtures in sodium dihexyl sulfosuccinate microemulsions

When surfactants are used to solubilize oil, the oil to be solubilized is often a mixture of components with differing properties, for example, solubilization of drug molecules in microemulsion formulations, remediation of organic polluted aquifers using surfactants, and so forth. Previous research has demonstrated that selective solubilization of one organic component over the other may occur if the organic components are dissimilar. In this research, we investigated selective solubilization from benzene-limonene mixtures in Winsor type I and III microemulsion systems containing water, sodium di-n-hexyl sulfosuccinate, and NaCl. The effect of the oil phase composition and the electrolyte concentration on the selectivity was studied. It was found that the selectivity toward benzene was highest at low electrolyte and benzene concentrations, decreasing as the electrolyte or benzene concentration increased. The results are discussed on the basis of the two-state solubilization theory and by correlating the curvature of the surfactant film in the microemulsion with changes of the electrolyte concentration and the oil phase composition. A simple mathematical model is developed for the selectivity, which combines the two-state solubilization theory and the net-average curvature model of microemulsion solubilization to yield close agreement with the experimental data.     

Fractional sublimation of the β-diketone chelates of the lanthanide and related elements

Various β-diketone chelates of Sc(III), Y(III), Th(IV), U(IV). U(VI), Zr(IV) and the lanthanides have been prepared, characterized and investigated to determine if they were volatile and stable. The ligands employed were acetylacetone(AA), trifluoroacetylacetone(TFAA), hexafluoroacetylacetone(HFAA), and dipivaloyl-methane(DPM). The chelates were sublimed in a fractional vacuum sublimator and the recrystallization temperature zones recorded for individual chelates. None of the lanthanide acetylacetonates arc volatile but the Sc(III), Th(IV), U(IV) and dioxouranium(VI) acetylacetonates are thermally stable and quite volatile below 150° at 1 mm mercury pressure. The lanthanide, Sc(III), Y(III), and dioxouranium(VI) trifluoroacetylacetonates are volatile and can be vacuum-sublimed below 150°, but are thermally unstable; only the Th(IV) chelate is sufficiently stable to be quantitatively recovered by sublimation. The Sc(III), Y(III), Th(IV), and lanthanide hexafluoroacetylacetonates are thermally stable and easily sublimed below 125° in vacua or at atmospheric pressure. All the dipivaloylmethanates studied were thermally stable and volatile and could be quantitatively recovered by vacuum sublimation below 140°.The volatility of the HFAA and DPM lanthanide chelates increased with an increase in atomic weight (a decrease in ionic radii) of the lanthanides. The lack of volatility observed for the lanthanide AA and TFAA chelates is attributed to the fact that only hydrates of the chelates were formed, which decomposed at elevated temperatures in vacuo to form basic polymeric compounds.Separations are proposed for numerous binary mixtures of the β-diketone chelates of the lanthanide and related elements. Recrystallization temperature zones are given for the following binary mixtures which were quantitatively resolved by the fractional sublimation technique; 118-88° for Nd(DPM)₃ and 84-48° for Tm(DPM)₃; 72-49° for Sc(DPM) and 120-88° for Pr(DPM); 128-79° for La(DPM)₃ and 79-47° for Yb(DPM)₃; 70-47° for Th(TFAA)₄ and 116-96° for Gd(TFAA)₃; 52-42° for Th(HFAA)₄ and 120-80° for La(HFAA)₃.     

Moderate Deviations for Empirical Measures of Markov Chains: Upper Bounds

We obtain upper bounds for moderate deviations of empirical measures of Markov chains with general state space in the -topology under the minimal assumption of geometric ergodicity. The regeneration-split chain method and a result on projective systems are employed in the proof.     

Effect of introducing a cationic system into a thiol‐ene photopolymerizable formulation

Hybrid materials derived from a thiol‐ene and cationic polymerization were obtained from concomitant polymerization. The hybrid materials were cured by both photopolymerization and thermally induced polymerization. The kinetics of the photopolymerization were measured using time resolved‐IR and optical pyrometry. The nucleophilic character of the polysulfide obtained initially in the thiol‐ene polymerization inhibited the development of the cationic photoinitiated polymerization of epoxy monomers. Besides, the epoxide groups underwent a proton catalyzed addition reaction with the thiols to form new sulfides groups in the reaction mixture. It is proposed that the formed sulfides can terminate the growing polyether chains forming dormant species like trialkylsulfonium salts. These salts promote the thermal polymerization of the epoxy monomer in a post treatment, producing hard and transparent materials. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4829–4843, 2007