Diffusiophoresis of a polyelectrolyte in a salt concentration gradient

Abstract

The diffusiophoresis of a polyelectrolyte subject to an applied salt concentration gradient is modeled theoretically. The entirely porous type of particle is capable of simulating entities such as DNA, protein, and synthetic polymeric particles. The dependence of the diffusiophoretic behavior of the polyelectrolyte on its physical properties, and the types of ionic species and their bulk concentrations are discussed in detail. We show that in addition to the effects coming from the polarization of double layer and the difference in the ionic diffusivities, the polarization of the condensed counterions inside the polyelectrolyte might also be significant. The last effect, which has not been reported previously, reduces both the electric force and the hydrodynamic force acting on the polyelectrolyte. Both the direction and the magnitude of the diffusiophoretic velocity of the polyelectrolyte are found to highly depend upon its physical properties. These results provide valuable references for applications such as DNA sequencing and catalytic nano- or micromotors.

Influence of double-layer polarization and chemiosmosis on the diffusiophoresis of a non-spherical polyelectrolyte

“…However, as Q fix is raised from 10 to 70, although type II DLP is further enhanced, type I DLP almost vanishes, as reflected by a small E Ã DLP inside the PE. This phenomenon was also observed by Liu et al [32]. As seen in Fig.…”

“…On the other hand, if Q fix is large, l ⁄ has both a local maximum and a local minimum, and the larger the Q fix the more apparent the presence of these local extrema. The presence of those local extrema in l ⁄ results from the competition of the effects of DLP, counterion condensation, and chemiosmotic retardation flow, discussed by Liu et al [32] for a spherical PE. Due to the nonspherical shape of a PE in our case, the associated phenomena are more complicated.…”

“…Typical example of PEs includes polypeptides and DNA molecules. A phenomenon specific to PEs is counterion condensation (CC) occurring when their charge density exceeds a critical level [32]. CC has the effect of reducing the effective charge of a PE, yielding interesting phenomena such as DNA condensation [33][34][35] and RNA folding [36,37].…”

“…Zhang et al [51], for example, considered the diffusiophoresis of a soft spherical particle in a spherical cavity. Liu et al [32] modeled the diffusiophoresis of a polyelectrolyte. They showed that the diffusiophoretic behavior of a soft particle can differ significantly from that of a rigid one.…”

Influence of polyelectrolyte shape on its sedimentation behavior: effect of relaxation electric field

“…8 The strength of the local electric eld arising from the movement of a PE as well as its effective charge density are evaluated so that its behavior can be explained both qualitatively and quantitatively. 10…”