3,707 research outputs found
Electrolytes at spherical dielectric interfaces
A variational theory is developed and applied to study the properties of dielectric spheres immersed in a symmetric electrolyte solution. In the limit that the radius of the sphere becomes much larger than the Debye screening length, the system reduces to that of a planar dielectric interface. For this case, the excess surface tension obtained by the variational theory reduces to the Onsager-Samaras [J. Chem. Phys. 2, 528 (1934)] limiting law at low electrolyte concentrations. As the radius of the dielectric sphere decreases, the excess surface tension also decreases. The implications of this work to protein-salt interactions and the salting out of proteins are discussed
Diffusion of a sphere in a dilute solution of polymer coils
We calculate the short time and the long time diffusion coefficient of a
spherical tracer particle in a polymer solution in the low density limit by
solving the Smoluchowski equation for a two-particle system and applying a
generalized Einstein relation (fluctuation dissipation theorem). The tracer
particle as well as the polymer coils are idealized as hard spheres with a
no-slip boundary condition for the solvent but the hydrodynamic radius of the
polymer coils is allowed to be smaller than the direct-interaction radius. We
take hydrodynamic interactions up to 11th order in the particle distance into
account. For the limit of small polymers, the expected generalized
Stokes-Einstein relation is found. The long time diffusion coefficient also
roughly obeys the generalized Stokes-Einstein relation for larger polymers
whereas the short time coefficient does not. We find good qualitative and
quantitative agreement to experiments.Comment: 9 Pages, 6 Figures, J. Chem. Phys. (in print
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