Molecular dynamics simulations of end-grafted centipede-like polymers with stiff charged side chains

Abstract

We use molecular dynamics simulations to investigate centipede-like polymers with stiff charged side chains, end-grafted to a planar wall. The effect of the grafting density and the Bjerrum length on the conformational behaviour of the brush is examined in detail. In addition, we make a comparison of centipede-like polyelectrolyte (CPE) brushes with neutral centipede-like polymer (NCP) and linear polyelectrolyte (LPE) brushes. At weak electrostatic interaction, the main chains of the CPE chains adopt a strongly stretched conformation, and the monomer density profiles of side chains exhibit a clear oscillatory behaviour. With increasing Bjerrum length, the CPE brush undergoes a collapse transition. Compared to the CPE brushes, the counterion condensation effect is stronger for the LPE brushes, regardless of whether the electrostatic interaction is weak or strong and of whether the grafting density is low or high. Additionally, it is shown that the architecture of the grafted chains makes a weak contribution to the counterion condensation at strong electrostatic interaction. We also find that the electrostatic repulsion between charged side chains can enhance the stiffness of the main chains and thus limit the range of movement of the free-end monomers.

Electrophoresis of Bottle‐Brush Polyelectrolytes in an Attractive Nanochannel

“…The model potentials used in the paper are analogous to those described in our recent works 39, 45. The short/range interaction between any two particles is modeled by the truncated‐shifted Lennard‐Jones (LJ) potential where ε LJ is the well depth, σ the particle diameter chosen to be the same irrespective of the particle type, and r sc is the cutoff distance beyond which the LJ interaction is ignored.…”

Effects of chain stiffness and salt concentration on responses of polyelectrolyte brushes under external electric field

“…More details on the model potentials used in the paper have been described by Ouyang et al 16 and our group. 17,31 Initially, cations and anions are randomly dispersed within the simulation box. Polyelectrolyte chains stretch normal to the grafting surface.…”

“…[27][28][29] It was found that unlike flexible polyelectrolyte brushes, the force between stiff brushes not only arises from the osmotic stress of compressed counterions within the brush but also from the work required to bend the rigid chains. 27 We have also investigated the self-assembly of surfactants and bottle-brush polyelectrolytes with varying backbone stiffness, 30 and the conformational behavior of grafted bottle-brush polyelectrolytes with stiff side chains 31 and flexible ones. 32 Our results demonstrated that the change of backbone stiffness leads to different aggregate morphologies.…”

Polymer brushes and their possible applications in artificial cilia research

“…The ionic strength (20) is controlled to directly affect the electrostatic repulsion and steric effects of the polymer brush, and then the inner osmotic pressure and elasticity of molecular chain structure are affected immediately to alter the morphology of brushes. It has been demonstrated that the response of ionic strength-responsive polymer brushes is influenced by the concentration of salt (21), ionic radius (22) and the structure of the molecular chain (23). Currently, polymer brushes are primarily used for surface modification, including alterations in wettability, permeability, absorbability and adhesion in other materials due to its unique topological structure (24).…”