Diffusiophoresis of a pH-regulated toroidal polyelectrolyte in a solution containing multiple ionic species.

Extending previous analysis for the diffusiophoresis of a toroidal PE having a fixed charge density, we consider the case where it is pH-regulated and the liquid phase contains multiple ionic species so that the underlying assumptions are more realistic. The diffusiophoretic behaviors of the toroidal PE considered under various conditions are examined by varying its functional group density, size, and softness, and the solution pH and bulk salt concentration. We show that the behavior of a toroidal PE can be different both quantitatively and qualitatively from the corresponding spherical PE. The effective charge of the present PE is also different both quantitatively and qualitatively from the corresponding PE having fixed charge density. In particular, both the magnitude and the direction of diffusiophoretic velocity depend highly on the conditions assumed, implying that an efficient separation process can be designed. A three-dimensional velocity-pH-Debye length plot is constructed for that purpose.