Osmotic Equilibria for a Semi-Permeable Shell Immersed in a Solution of Polyionsстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:We study theoretically the osmotic equilibria for a shell immersed in a suspension of polyions (e.g.,
colloids, polyelectrolytes, etc.). The shell is treated as impermeable for polyions, but allowing free
diffusion of counterions that permeate inside the shell. From the solution of linearized Poisson–
Boltzmann equation, we obtain the distribution of a potential and concentration profiles for polyions
and counterions. We then obtain an explicit formula for the excess osmotic pressure of a polyion
solution exerted on the shell, which includes a quadratic term in order to provide a self-consistency
of a linear theory. As a result this pressure is larger than given by a concentration of polyions at the
outer shell boundary obtained within linearized theory. It is, however, always smaller than or equal
to the bulk osmotic pressure. This difference is attributed to a repulsive electrostatic disjoining
pressure due to an overlap of counterion clouds inside the shell. A comparison with molecular
dynamics simulations is provided and demonstrates that although the concentration profiles obtained
within a linear theory deviate from simulation data at large potential, the theoretical and simulation
pressures are in surprisingly good harmony.