Mesoscopic simulations of polyelectrolyte electrophoresis in nanochannels

Mesoscale modelling of polyelectrolyte electrophoresis

The electrophoretic behaviour of flexible polyelectrolyte chains ranging from single monomers up to long fragments of hundred repeat units is studied by a mesoscopic simulation approach. Abstracting from the atomistic details of the polyelectrolyte and the fluid, a coarse-grained molecular dynamics model connected to a mesoscopic fluid described by the Lattice Boltzmann approach is used to investigate free-solution electrophoresis. Our study demonstrates the importance of hydrodynamic interactions for the electrophoretic motion of polyelectrolytes and quantifies the influence of surrounding io…

软层电荷分布对软纳米通道中Maxwell流体瞬态电渗流的影响

Impact of charge distribution of soft layers on transient electroosmotic flow of Maxwell fluids in soft nanochannels

本研究通过Laplace变换半解析求解了软纳米通道中Maxwell流体的瞬态电渗流，发现调整聚电解质层的电荷分布可有效控制电渗流的方向与强度，并引入临界数ks量化电渗流反转。

Polyelectrolytes in electric fields: Measuring the dynamical effective charge and effective friction

We use a coarse-grained molecular dynamics model to study the electrophoretic behaviour of flexible polyelectrolyte chains. We first characterize the static properties of the model with respect to the chain length, the polyelectrolyte concentration, additional salt and the influence of an applied external field. Next we investigate the dynamic behaviour in the oligomer range and compare to data obtained by two different experimental methods, namely capillary electrophoresis and PFG-NMR. We find excellent agreement of experiments and simulations when hydrodynamic interactions are accounted for …

Importance of hydrodynamic shielding for the dynamic behavior of short polyelectrolyte chains

The dynamic behavior of polyelectrolyte chains in the oligomer range is investigated with coarse-grained molecular dynamics simulation and compared to data obtained by two different experimental methods, namely capillary electrophoresis and electrophoresis NMR. We find excellent agreement of experiments and simulations when hydrodynamic interactions are accounted for in the simulations. We show that the electrophoretic mobility exhibits a maximum in the oligomer range and for the first time illustrate that this maximum is due to the hydrodynamical shielding between the chain monomers. Our find…

Ion size effect on electrostatic and electroosmotic properties in soft nanochannels with pH-dependent charge density

We report a theoretical study of ion size effect on various properties in a soft nanochannel with pH-dependent charge density. We develop a free energy based mean-field theory taking into account ion size as well as pH-dependence of charged polyelectrolyte layer grafted on a rigid surface in an electrolyte. The influence of ion size on properties in a soft nanochannel is evaluated by numerically calculating ion number densities and electrostatic potential. We demonstrate that unlike in point-like ions, for finite sizes of ions, a uniform distribution of chargeable sites within the polyelectrol…

Free Solution Electrophoresis of Homopolyelectrolytes

We investigate the behavior of single polyelectrolytes in multivalent salt solutions under the action of electric fields through computer simulations. The chain is unfolded in a strong electric field and aligned parallel to the field direction, and the chain size shows a sigmoidal transition. The unfolding electric field $E^*$ depends on the salt concentration and scales as $V^{-1/2}$ with $V$ being the ellipsoidal volume occupied by the chain. The magnitude of the electrophoretic mobility of chain drastically increases during the unfolding. The fact that $E^*$ depends on the chain length prov…

Salt-induced reentrant stability of polyion-decorated particles with tunable surface charge density

The electrostatic complexation between DOTAP-DOPC unilamellar liposomes and an oppositely charged polyelectrolyte (NaPA) has been investigated in a wide range of the liposome surface charge density. We systematically characterized the "reentrant condensation" and the charge inversion of polyelectrolyte-decorated liposomes by means of dynamic light scattering and electrophoresis. We explored the stability of this model polyelectrolyte/colloid system by fixing each time the charge of the bare liposomes and by changing two independent control parameters of the suspensions: the polyelectrolyte/col…

Unfolding Polyelectrolytes in Trivalent Salt Solutions Using DC Electric Fields: A Study by Langevin Dynamics Simulations

We study the behavior of single linear polyelectrolytes condensed by trivalent salt under the action of electric fields through computer simulations. The chain is unfolded when the strength of the electric field is stronger than a critical value. This critical electric field follows a scaling law against chain length and the exponent of the scaling law is $-0.77(1)$, smaller than the theoretical prediction, $-3ν/2$ [Netz, Phys. Rev. Lett. 90 (2003) 128104], and the one obtained by simulations in tetravalent salt solutions, $-0.453(3)$ [Hsiao and Wu, J. Phys. Chem. B 112 (2008) 13179]. It demon…