Dumbbell kinetic theory for polymers in a combination of flow and external electric field.

Abstract

Combining Poiseuille flow with an external electric field is a demonstrated method to drive transverse migration in capillary electrophoresis. Despite both computational and experimental studies, a number of questions about how to best model polymers under these conditions remains. Attempts have been made to develop a kinetic theory for a bead-spring dumbbell model, but these have only been accurate at low electric field strength and have not captured the nonmonotonic relationship between migration and electric field strength. In this paper, we revisit the development of a kinetic theory for a bead-spring dumbbell in a combination of parabolic flow and an external electric field. The resultant theory yields a compact formula that predicts polymer concentration profiles that agree excellently with our Brownian dynamics simulations including the aforementioned nonmonotonic relationship. Furthermore, we compare our theoretical results to experimental data and find that our model nearly quantitatively predicts the position of the maximum in migration.