Abstract  The aqueous solution properties and the micellar structure of two short-chain nonionic surfactants containing a hydrocarbon tail, 1,2-hexanediol (HD), and a perfluorinated tail, 3,3,4,4,5,5,6,6,6-nonafluoro-1,2-hexanediol(PFHD), have been compared by using various techniques such as pyrene fluorescence spectroscopy, vapor pressure osmometry,'tensiometry, and dye solubilization. The aggregational behavior of both systems in aqueous medium has been evidenced by the polarity decrease of the pyrene microenvironment with increasing surfactant concentration. The binding coefficient of pyrene with the aggregates was calculated by application of the phase-separation model to the pyrene fluorescence results. The aggregation numbers of the HD (N-H) and PFHD (N-PF) micelles have been evaluated by application of the phase-separation and the mass-action law models to the osmotic coefficients measurements. The N-H value (26 +/- 8), which is in good accordance with previous experimental results (30 +/- 10), is higher than N-PF (15 +/- I). Both compounds exhibit surface-active properties with a maximum surface tension lowering of 42 and 57 mN m(-1) for HD and its perfluorinated homologous compound, respectively. Their solubilizing power toward Orange OT was compared. Critical micelle concentrations (CMCs) have been determined in the temperature range 20-50 degrees C (30-50 degrees C for PFHD insoluble below 30 degrees C), and thermodynamic parameters such as standard enthalpy and entropy changes for micellization have been calculated.

Abstract  In this report, we introduce a new micelle modifier useful to alter selectivity in micellar electrokinetic capillary chromatography (MECC). 1,2-Hexanediol acts as a class I organic modifier in that its effects are on the sodium dodecyl sulfate (SDS) micellar rather than the surrounding aqueous phase. This characteristic allows 1,2-hexanediol to improve resolution when applied at concentrations as low as 20 mM (0.25% v/v) by altering the selectivity observed with SDS alone. The effects of 1,2-hexanediol on the critical micelle concentration of SDS, electroosmotic flow, electrophoretic mobility of the SDS micelle, and reproducibility are presented. 1,2-Hexanediol had little impact on the migration time window at concentrations below 100 mM. Changes in selectivity induced by 1,2-hexanediol for a large set of model compounds are presented. Analytes capable of forming hydrogen bonds tend to decrease their interactions with the micellar phase while nonhydrogen bonding analytes increase their interactions. The usefulness of 1,2-hexanediol was demonstrated by examining its effects on the separation of dansylated amino acids. Eighteen of twenty amino acids could be separated with a resolution greater than 1.6 within 1600 s using a combination of 1,2-hexanediol and isopropanol.

Abstract  The structure of iron oxide was controlled by regulating the hydrolytic polymerization of aquo iron complexes with organic polydentate ligands such as diols. Iron oxides were prepared by calcining the precursor polymers obtained from iron nitrate nonahydrate and diols. When the diols were 1,2-pentanediol, 1,2-hexanediol and 1,2-octanediol, alpha-Fe2O3 with corundum structure appeared exclusively or as the main crystalline phase, in spite of the amount of diol used and the calcination temperature. In the case of 1,2-decanediol and 1,2-dodecanediol, when five moles of the diols were used to one mole of iron nitrate and the calcination temperatures were below 400 degrees C, gamma-Fe2O3 with spinel structure appeared as the main phase and, when less than five moles of the diols were used, alpha-Fe2O3 appeared exclusively or as the main phase, irrespective of the calcination temperature. This tendency was also observed in thin films. Thus, a transparent magnetic film composed of gamma-Fe2O3 could be prepared by applying a benzene solution of the iron polymer, obtained with 5 equivalents of 1,2-decanediol, on quartz and calcining the gel him at 350 degrees C.