Electrohydrodynamics of spherical polyampholyte-grafted nanoparticles: Multiscale simulations by coupling of molecular dynamics and lattice-boltzmann method

Abstract

We perform multiscale simulations based on the coupling of molecular dynamics and lattice-Boltzmann (LB) method to study the electrohydrodynamics of a polyampholyte-grafted spherical nanoparticle. The long-range hydrodynamic interactions are modeled by coupling the movement of particles to a LB fluid. Our results indicate that the netneutral soft particle moves with a nonzero mobility under applied electric fields. We systematically explore the effects of different parameters, including the chain length, grafting density, electric field, and charge sequence, on the structures of the polymer layer and the electrophoretic mobility of the soft particle. It shows that the mobility of nanoparticles has remarkable dependence on these parameters. We find that the When a charged colloidal particle is immersed in electrolyte solution, an electrical double layer (EDL) is formed close to the charged surface. The EDL consists of a thin ion layer tightly adsorbed to the surface (so-called Stern layer) and a diffuse layer where ions can move freely. If an external electric field is applied, the colloidal particle and its counterions can be induced to migrate in opposite directions. An electroosmotic flow (EOF) is generated around the particle, and the viscous friction primarily happens over the Debye length. The movement of charged components perturbs the solvent flow, which triggers complicated hydrodynamic interactions. The electrophoretic mobility is determined by the hydrodynamic interactions, electrostatic forces between charged species, and external electric field strength. For polymermodified soft colloids, the deformation of polymers induced by the electric field, monomer-monomer hydrodynamic interactions, and counterion shearing flow further complicated the analysis on experimental phenomena and theoretical derivation.Many physical mechanisms on microscopic levels involving the electrokinetics of charged soft particles still remain poorly understood. Computer simulation provides deeper

Transport of polymer-modified nanoparticles in nanochannels coated with polymers

“…7a). This is different from spherical polyelectrolyte or polyampholyte brushes, 25,26 which adopt signicantly extended conformation along the ow direction (or the direction of the electric eld). The enhancement of the electric eld causes the increase of the parallel component (Fig.…”

“…[18][19][20][21][22][23][24] Recently, electrophoresis of spherical colloids graed with charged polymers (such as polyelectrolytes and polyampholytes) was also studied by means of molecular dynamics (MD) simulations considering longranged hydrodynamic interactions based on lattice-Boltzmann method. 25,26 Nonzero electrophoresis mobility was observed for net-neutral particles. For graed polyampholytes, we found that the mobility of the net-neutral particles remarkably depends on the structures of the polymer layer.…”

“…For graed polyampholytes, we found that the mobility of the net-neutral particles remarkably depends on the structures of the polymer layer. 26 MD simulations provide insight into electrohydrodynamics for systems with polymer-modied surfaces. So far, most computational studies focus on the EOF through polymercoated channels.…”

“…For grafted polyampholytes, we found that the mobility of the net-neutral particles remarkably depends on the structures of the polymer layer. 26 …”

Formation of Ionomer Microparticles via Polyelectrolyte Complexation

“…Here, we briefly introduce the method, and interested readers are referred to our previous studies and other refs [ − ] for the details of the algorithm. In the LB method, the central quantity of the algorithm is f i ( x⃗ , t ), which is used to describe the solvent distribution at the lattice site x⃗ and time t .…”