Molecular aggregations in water–2-butoxyethanol mixtures by ultrasonic and Brillouin light-scattering measurements

Abstract

By means of ultrasonic and Brillouin light-scattering techniques, we have performed extensive measurements of the attenuation coefficient and sound velocity in 2-butoxyethanol aqueous solutions over a large temperature range. In the more concentrated solutions, the frequency dependence of these properties is well accounted for by a double relaxation time equation thus excluding contributions from concentration fluctuations. This finding, as well as the overall behavior as a function of concentration and temperature, suggests the presence of alcohol aggregates beyond a characteristic concentration-temperature line resembling a critical micelle concentration curve in micellar systems. The similarity between the ultrasonic behavior and the type observed in nonionic surfactant aqueous solutions, as well as indications from other experimental sources, strongly supports the possibility that butoxyethanol aggregates are micellelike structures.

Association and Microheterogeneity in Aqueous 2-Butoxyethanol Solutions

“…As noted in the Introduction, there have been a number of studies using light scattering − and SANS ,, experiments aimed at probing the existence and size of aggregates in BE–water solutions. The experimental size estimates are also based on the assumption of spherical aggregates, and in general, for comparable concentrations and temperatures, the radii reported are in qualitative accord with our estimates based on r cross .…”

“…We report a molecular dynamics simulation investigation of aqueous 2-butoxyethanol (BE, CH 3 –(CH 2 ) 3 –O–(CH 2 ) 2 –OH) solutions. BE–water solutions have been studied extensively by a variety of experimental methods, and many physical properties have been shown to undergo rather dramatic changes on variation of composition and temperature. ,− ,,− In particular, for BE–water solutions, densities, − refractive indices, surface tensions, − excess molar volumes, , ultrasonic speeds, , vapor pressures, heat capacities, ,, and excess thermodynamic properties ,,,− have been reported. We note that, in addition to the usual partial molar properties, Koga and co-workers ,,,, have obtained so-called “third and fourth derivative” quantities, which provide strong signals of unusual behavior in BE–water and other aqueous systems.…”

“…We note that, in addition to the usual partial molar properties, Koga and co-workers ,,,, have obtained so-called “third and fourth derivative” quantities, which provide strong signals of unusual behavior in BE–water and other aqueous systems. Also, the structure of BE–water systems has been directly probed by means of light scattering, − and small-angle neutron scattering (SANS) experiments. ,, In most of the studies cited above, some measured property of BE–water solutions is observed to change rapidly at some particular concentration, for example, at a BE mole fraction ( X BE ) in the neighborhood of 0.02 at 298 K. This feature has been widely associated with the formation of BE aggregates that have been described as micelle-like, or as pseudomicelles . However, from a microscopic perspective, much remains to be learnt about the formation and nature of the associated species in BE–water systems.…”

Aggregation phenomena in water-alcohol solutions. Thermodynamic and dynamic studies

“…Details of these experiments are reported elsewhere [7,8,12]. We found that the x, T, and co dependence of c and a in the three investigated solutions are qualitatively similar, but rather anomalous.…”

The effect of traces of hexyloxyethoxyethanol on the 2-butoxyethanol + water liquid-liquid coexistence curve

“…In particular, the phase diagram presents a lower critical solution temperature. Direct confirmation of the presence of micellar aggregates in this mixture has been obtained by light scattering [10][11][12] and, recently, by small-angle neutron scattering [ 13,14].…”