0000000000422248
AUTHOR
A. Minore
FT-IR Investigation of the Urea State in AOT Reversed Micelles
Abstract FT-IR spectra of the urea/sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/CCl 4 system as a function of the urea-to-AOT molar ratio ( R urea ) at a fixed AOT concentration ([AOT]=0.1 mol·kg −1 ) have been recorded at 25°C. The experimental data are consistent with the hypothesis that at low R urea values urea is dispersed as monomers among the hydrophilic core of AOT reversed micelles, whereas at R urea >0.13 it is encapsulated as small molecular clusters. These clusters display some departures from the H-bonded structure of the pure solid urea attributable to their small size and to urea–AOT head group interactions. The stretching modes of AOT sulfonate groups are affected by the pr…
A simple method to prepare solid nanoparticles of water-soluble salts using water-in-oil microemulsions
A new and simple method to prepare solid nanoparticles of water-soluble salts using water-in-oil microemulsions is described. In particular, starting from water/sodium bis(2-ethylhexyl)sulfosuccinate/n-heptane microemulsions carrying inside the aqueous core of the reversed micelles some water-soluble salts [CaCl2, Na2HPO4, Cu(NO3)2], after evaporation of the volatile components (water and apolar organic solvent), the resulting inorganic salt/surfactant composites were found to be totally dispersible in pure n-heptane. The presence of nanoparticles in these resuspended composites was ascertained by transmission electron microscopy observation of samples obtained by gentle evaporation of the …
Calorimetric investigation of the precipitation of calcium monohydrogen phosphate in water/AOT/n-heptane microemulsions
Abstract The molar enthalpies of precipitation of calcium monohydrogen phosphate (CaHPO 4 ) in water/sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/ n -heptane microemulsions were measured at 25°C by a calorimetric technique as a function of the molar ratio R ( R = [water]/[AOT]) at a fixed AOT concentration. Calorimetric data indicate the formation of CaHPO 4 nanoparticles encapsulated in the aqueous core of the AOT reversed micelles displaying a slow growing process with time. Their energetic state is initially different from that in bulk water approaching the value in water at longer times. The observed growing process results to be completely inhibited by the presence of small amounts o…
FT-IR and dielectric study of water/AOT liquid crystals
Abstract In order to explore the influence of microwave radiation on highly viscous microheterogeneous systems, the evolution of structural and dynamical properties of the water/sodium bis(2-ethylhexyl) sulfosuccinate (AOT) liquid crystals as a function of the molar ratio R (R=[water]/[AOT]) has been investigated by FT-IR spectroscopy and time domain reflectometry. The study emphasises how the progressive hydration of the surfactant head groups is mainly responsible for the structural and dynamical evolution of water/AOT liquid crystals. In particular, it has been found that the state of water at lower R values is strongly perturbed, bulk-like water appears only at R>23 and the water/AOT in…