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Full-Text Articles in Physical Sciences and Mathematics
Effects Of Counterion Fluctuations In A Polyelectrolyte Brush, Christian Santangelo, A.W.C. Lau
Effects Of Counterion Fluctuations In A Polyelectrolyte Brush, Christian Santangelo, A.W.C. Lau
Christian Santangelo
We investigate the effect of counterion fluctuations in a single polyelectrolyte brush in the absence of added salt by systematically expanding the counterion free energy about Poisson-Boltzmann mean-field theory. We find that for strongly charged brushes, there is a collapse regime in which the brush height decreases with increasing charge on the polyelectrolyte chains. The transition to this collapsed regime is similar to the liquid-gas transition, which has a first-order line terminating at a critical point. We find that, for monovalent counterions, the transition is discontinuous in theta solvent, while for multivalent counterions, the transition is generally continuous. For collapsed …
Distribution Of Counterions Near Discretely Charged Planes And Rods, M. L. Henle, Christian Santangelo, D. M. Patel, P. A. Pincus
Distribution Of Counterions Near Discretely Charged Planes And Rods, M. L. Henle, Christian Santangelo, D. M. Patel, P. A. Pincus
Christian Santangelo
Realistic charged macromolecules are characterized by discrete (rather than homogeneous) charge distributions. We investigate the effects of surface charge discretization on the counterion distribution at the level of mean-field theory using a two-state model. Both planar and cylindrical geometries are considered; for the latter case, we compare our results to numerical solutions of the full Poisson-Boltzmann equation. We find that the discretization of the surface charge can cause enhanced localization of the counterions near the surface; for charged cylinders, counterion condensation can exceed Oosawa-Manning condensation.