Electrostatic interactions in dissipative particle dynamics—simulation of polyelectrolytes and anionic surfactants

Abstract

Electrostatic interactions have been incorporated in dissipative particle dynamics (DPD) simulation. The electrostatic field is solved locally on a grid. Within this formalism, local inhomogeneities in the electrostatic permittivity can be treated without any problem. Key issues like the screening of the potential near a charged surface and the Stillinger–Lovett moment conditions are satisfied. This implies that the method captures the essential features of electrostatic interaction. For the direct simulation of mixed surfactants near oil–water interfaces, or for the simulation of Coulombic polymer–surfactant interactions, this method has all the advantages of DPD over full atomistic molecular dynamics (MD). DPD has proven to be faster than MD by many orders of magnitude, depending on the precise scaling factor chosen for the simulation. This brings phenomena of microseconds in reach of routine simulation, while maintaining a fairly accurate representation of the structure of the molecules. As an example of this simulation tool, the interaction between a cationic polyelectrolyte and anionic surfactant is discussed. Without a surfactant, the polyelectrolyte shows a fractal dimensionality that is in line with the theoretical and experimental values cited in literature, it behaves as a fairly stiff rod, df∼1.1. When salt is replaced by anionic surfactant, the polymer wraps around one or more discrete surfactant micelles, in line with the current understanding of these systems, and scaling invariance in the correlation function is broken.

Prediction of Surfactants’ Properties using Multiscale Molecular Modeling Tools: A Review

“…Thus, different ways to implement electrostatics in DPD can be found in the literature. Direct resolution of the electrostatic field on a grid was proposed by Groot [79] and gave results on the interactions between charged polyelectrolytes and surfactants. Ewald method is an other way of calculation shown by Gonzalez et al [80], also used by Ibergay et al [81,82] for polyelectrolytes.…”

Advances in The Understanding of Nanomaterial–Biomembrane Interactions and Their Mathematical and Numerical Modeling

“…Groot proposed a method based on the local lattice grid to calculate the electrostatic force [101]. Based on this method, many studies have investigated the interac tion between the charged dendrimer and the membranes of different structures, such as the vesicle membrane [102,103].…”

Dissipative Particle Dynamics via Molecular Dynamics

“…Fluctuation-dissipation theory [2] then provides a relationship between the magnitude of the random and dissipative weight function magnitudes (w D (r) = [w R (r)] 2 ) and a relationship between σ, γ and T: σ 2 = 2γk B T. The claimed success and popularity of DPD lies in the use of a large time step -typically an order of magnitude greater than those used in MD -a consequence of the short ranged and soft nature of the conservative force law. Groot and other workers have also extended DPD to take electrostatic interactions into account [4,5]. DPD has been employed in a wide variety of cases including polymers [6 7], liquid crystals [8], biomolecules [9] and even cement [10].…”