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 inhomogeneous viscous solvent converts the translational movement.
Highlights
The interaction between water and alcohol has been studied extensively.1–12 Because alcohol contains both hydrophilic and hydrophobic groups, mixing alcohol molecules in a water solvent generates complex networks of hydrogen bonds at the molecular scale
The plots for pure water show good agreement between the Brownian motion and the line calculated from the macroscopic viscosity
The experimental mean-square displacement (MSD) values are significantly higher than those calculated from the liquid viscosity, which shows less viscosity for the Brownian motion particles
Summary
The interaction between water and alcohol has been studied extensively. Because alcohol contains both hydrophilic and hydrophobic groups, mixing alcohol molecules in a water solvent generates complex networks of hydrogen bonds at the molecular scale. The interaction between water and alcohol has been studied extensively.1–12 Because alcohol contains both hydrophilic and hydrophobic groups, mixing alcohol molecules in a water solvent generates complex networks of hydrogen bonds at the molecular scale. There is still disagreement regarding mixing structures such as the existence of a clathrate-like component.3,8,9 These experiments were based on static and averaged measurements. The motion of polystyrene beads in a water-ethanol mixture was observed and the mobility or viscosity of the liquid was calculated. The shear viscosity of a water-ethanol bulk liquid is well known.. The shear viscosity of a water-ethanol bulk liquid is well known.24,25 These viscosity values are calculated by comparing the Stokes–Einstein equation (for microscopic viscosity) and bulk literature values (for macroscopic viscosity) The shear viscosity of a water-ethanol bulk liquid is well known. These viscosity values are calculated by comparing the Stokes–Einstein equation (for microscopic viscosity) and bulk literature values (for macroscopic viscosity)
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