Orientation and partitioning behavior of dilute rodlike polyelectrolyte suspensions within confined slit microchannels

In the confined space of narrow channels, the behavior of rodlike polyelectrolytes pertaining to anisotropic configuration effect is much different than in the bulk. Based on our previous study, we analyzed on the orientational order of rodlike polyelectrolyte in dilute suspensions under the action of the long-range colloidal interactions, which results in the concentration depletion near the solid surface. For the orientation of rodlike polyelectrolytes existing near the charged wall, the electrostatic repulsive interaction explicitly creates the preferential alignment of rod segments perpendicular to the surface, while the parallel alignment is favored without this interaction. The concentration-depleted layer thickness, in which the perpendicular orientation of the rods is predicted, increases either with decreased solution ionic strength or with increased surface potentials of the wall and the rod. The partition coefficient determined from the concentration profile presents the fact that the rod is more excluded by electrostatic and entropic effects with the increase of confining strength. It is evident that the presence of electrostatic interactions changes the partitioning behavior of rodlike polyelectrolyte suspension in the dilute limit.