Brownian motion probe for water-ethanol inhomogeneous mixtures

Abstract

Brownian motion provides information regarding the microscopic geometry and motion of molecules, insofar as it occurs as a result of molecular collisions with a colloid particle. We found that the mobility of polystyrene beads from the Brownian motion in a water-ethanol mixture is larger than that predicted from the liquid shear viscosity. This indicates that mixing water and ethanol is inhomogeneous in micron-sized probe beads. The discrepancy between the mobility of Brownian motion and liquid mobility can be explained by the way the rotation of the beads in an inhomoge-

An atomistic explanation of the ethanol–water azeotrope

“…The energy balance thus drives the system away from a homogeneous ideal solution towards separate phases. The microscopic bulk structure of ethanol–water mixtures has been studied by many techniques, including neutron diffraction, 7–9 X-ray absorption, 4 Brownian motion probes, 10 and mass spectroscopy, 11,12 as well as computationally by molecular dynamics 13–15 and quantum mechanics/molecular mechanics 16 techniques. While the results differ in details, most studies agree that the two components tend to form cluster-like structures in the mixture.…”

Variations of the Hydrogen Bonding and Hydrogen-Bonded Network in Ethanol–Water Mixtures on Cooling

“…Mixtures of water and alcohols show significant deviations relative to the ideal solutions in terms of various thermodynamic properties, e.g., self-diffusion coefficient, shear viscosity, excess volume, excess enthalpy, compressibility, and sound attenuation coefficient. − In most cases, the nonideal behavior is manifest in the low-alcohol-concentration region, by showing minima or maxima of a given property. − ,− The perturbation of the local and global structure of the hydrogen-bond network is now commonly accepted to be the reason behind these anomalous properties . Despite considerable effort in both experiment and theory, significant disagreement remains regarding the microscopic details of this effect. ,− Different models for the structure of alcohol–water liquid mixtures have been proposed to address the anomalous behavior, such as the enhancement of the water hydrogen-bonding network around the alcohol hydrophobic groups − and microscopic immiscibility or clustering. − …”

Local Immiscibility Control on Shape and Size of Nano-objects in the Solvo-Thermal Process: Implications for Ferroelectric Nanoparticles

“…These clusters are not a static feature of the solvents, and therefore, a precise definition of their size cannot be assigned. Such a dynamic nature has been probed through the Brownian motion of polysterene beads in water–ethanol mixtures …”