Brownian dynamics simulations of polyelectrolyte adsorption in shear flow: Effects of solvent quality and charge patterning

Abstract

We probe the effects of solvent quality and charge patterning on polyelectrolyte adsorption in shear flow using Brownian dynamics simulations with hydrodynamic interaction (HI). The polyelectrolyte is modeled as a freely jointed bead-rod chain, and electrostatic and non-electrostatic interactions are accounted for by using screened Coulombic and Lennard-Jones potentials, respectively. In the absence of flow, the conformation of a polyelectrolyte molecule adsorbed onto a uniformly charged surface changes from flat to globular with an increase in bead-bead attraction (hydrophobicity), consistent with prior experimental observations. In the presence of flow, migration due to bead-wall HI and, as a consequence, desorption decrease with an increase in bead-bead attraction, implying that flow-induced desorption is more difficult under poor-solvent conditions. When bead-bead non-electrostatic attraction is strong, desorption can be enhanced by increasing bead-bead electrostatic repulsion. Analogous to the effect of bead-surface electrostatic attraction, an increase in the strength of bead-surface non-electrostatic attraction reduces desorption. We also study the effect of shear flow on the adsorption of a polyelectrolyte molecule onto surfaces decorated with periodic arrays of charged patches. An increase in patch periodicity increases desorption even when the effective surface charge density is kept the same. The results of this work suggest mechanisms for controlling the desorption of polyelectrolyte molecules in shear flows.

Flow-induced conformational change of von Willebrand Factor multimer: Results from a molecular mechanics informed model

“…The BD simulation technique has been shown to be very efficient, especially for modeling long biopolymer chains under complex flow conditions [19][20][21][22]. Hydrodynamic interactions (HI) have been confirmed to play an important role in polymer dynamics [23][24][25][26][27].…”

Shear-induced dynamics of polymeric globules at adsorbing homogeneous and inhomogeneous surfaces

“…6, the rescaled velocity V /γz COM , measured along the adsorption transition line, decreases with decreasing interaction range σ W as a result of enhanced surface friction, while the extension in flow direction R S /2N , also measured along the transition line, increases strongly due to internal shear effects in the globule. This means that the inhomogeneous surface enhances unfolding of the FD polymer in shear flow but suppresses adsorption; in other words, the stretching of the chain, which by itself weakens entropic repulsion from the surface and therefore promotes adsorption [34], is overwhelmed by the weakened energetic attraction to the surface since the monomers are constantly pulled away from the surface binding sites [17,14].…”

“…When considering non-equilibrium effects, e.g. by inclusion of simple shear-flow [12][13][14], it has been shown that hydrodynamic interactions and the presence a e-mail: radtkem@physik.fu-berlin.de of a no-slip boundary is crucial and therefore has to be taken into account [15][16][17][18].…”

Polymer-induced phase separation in suspensions of bacteria

“…(b) E-mail: w.poon@ed.ac.uk be amphoteric, and display a minority of positive charges. At low enough ionicity, the negative polymer segments may adopt loopy configurations to contact the positive surface patches [6], leading to bridging and aggregation. Secondly, polyvalent cations can form salt bridges between negatively charged particles and polymer, once again allowing polymer-induced bridging [7].…”