Interacting Polyelectrolyte Brushes Grafted in Two Bilayers: Molecular Dynamics Simulations

Nourdine Hadrioui

doi:10.11648/j.ajpa.20160402.11

Abstract

Using molecular dynamics simulations, we study interacting polyelectrolyte brushes that are grafted to two parallel surfaces (quasi-Planar Membrane). The interactions between brushes are important, for instance, in stabilization of dispersions against flocculation. We simulate the relative shear motion of both neutral and polyelectrolyte end-grafted polymer brushes. The flexible neutral polymer brush is treated as a bead-spring model, and the polyelectrolyte brush is treated the same way except that each bead is charged and there are counter ions present to neutralize the charge. We investigate the friction coefficient, monomer density, and brush penetration for the two kinds of brushes with both the same grafting density and the same normal force under good solvent conditions.

Highlights

Adhesion of membranes and vesicles has attracted considerable experimental and theoretical interest because of its prime importance to many bio-cellular processes [1, 2]
From our molecular dynamics simulation results, the friction coefficient between neutral polymer brushes is much larger than the value between two charged brushes under same grafting density and surface separation
When the wall separation distance D was decreased, the normal force and shear force on the wall increased for both neutral and charged brushes. This result comes from stronger interactions between beads in the system because decreasing the surface separation distance D results in an increase in the global monomer density of the polymer brushes, which can be seen in figure (12), and the counterion density

Summary

Introduction

Adhesion of membranes and vesicles has attracted considerable experimental and theoretical interest because of its prime importance to many bio-cellular processes [1, 2]. Iii) Lock-and key adhesion where the bridges consist of two different stickers forming a ligandreceptor type bond. This case represents an asymmetric adhesion due to the lack of symmetry between the ligand and receptor. Mutual repulsion between polymer segments and Nourdine Hadrioui et al.: Interacting Polyelectrolyte Brushes Grafted in Two Bilayers: Molecular Dynamics Simulations electrostatic forces between charged monomers and counter ions strongly influence the conformation of the polyelectrolyte brush [8, 9]. The normal force and shear force have been well studied experimentally by the surface force apparatus (SFA) both on neutral polymer brush membranes and polyelectrolyte brush membranes.

Simulation Details

Results and Discussion

Conclusion