  The physico-chemistry of surfactants (amphiphilic surface active agents) is
often used to control the dynamics of viscous drops and bubbles. Surfactant
sorption kinetics has been shown to play a critical role in the deformation of
drops in extensional and shear flows, yet to the best of our knowledge these
kinetics effects on a viscous drop in an electric fieldhave not been accounted
for. In this paper we numerically investigate the effects of sorption kinetics
on a surfactant-covered viscous drop in an electric field. Over a range of
electric conductivity and permittivity ratios between the interior and exterior
fluids, we focus on the dependence of deformation and flow on the transfer
parameter $J$, and Biot number $\text{Bi}$ that characterize the extent of
surfactant exchange between the drop surface and the bulk. Our findings suggest
solubility affects the electrohydrodynamics of a viscous drop in distinct ways
as we identify parameter regions where (1) surfactant solubility may alter both
the drop deformation and circulation of fluid around a drop, and (2) surfactant
solubility affects mainly the flow and not the deformation.
