Adsorption and Disjoining Pressure Isotherms of Confined Polymers Using Dissipative Particle Dynamics

Abstract

The adsorption and disjoining pressure isotherms of polymers confined by planar walls are obtained using Monte Carlo (MC) simulations in the Grand Canonical (GC) ensemble in combination with the mesoscopic technique known as dissipative particle dynamics (DPD). Two models of effective potentials for the confining surfaces are used: one with both an attractive and a repulsive term and one with a purely repulsive term. As for the polymer, seven-bead linear model of polyethylene glycol (PEG) dissolved in water is used. The results indicate remarkably good agreement between the trends shown by our adsorption isotherms and those obtained from experiments of PEG on oxide surfaces. Additionally, the disjoining pressure isotherm of water shows oscillations, while those of PEG display the same trend for both wall models. Moreover, it is found that the disjoining pressure isotherms are in qualitative agreement with those from experiments on confined linear polymers.

Mesoscopic modeling of structural and thermodynamic properties of fluids confined by rough surfaces

“…In this section we present an overview of the formulation and implementation of the MC method (using the Metropolis algorithm 53 ) in the Grand Canonical ensemble (at fixed chemical potential, volume and temperature) for the DPD model (GCMC-DPD) to simulate fluids confined by structured surfaces, on the mesoscopic scale. This methodology has been applied successfully by one of us (AGG) to study polymers, polyelectrolytes and colloids, among other systems.…”

Structure of a Thermoset Polymer near an Alumina Substrate as Studied by Dissipative Particle Dynamics

“…We perform this matching for a is by using a quantity called the surface excess Γ. 33 The surface excess quantifies to what extent a bead type is adsorbed at the interface. In this way the relative adsorptions of different beads are characterized.…”

A Model for the Stability of a TiO2 Dispersion

“…For the particular case shown in Figure 6, polystyrene was chosen as a generic latex particle. The case of water soluble, adsorbed polymers such as PEG has been discussed in [12]. As a final word on the rdf shown in Figures 4-6, one notices that the second peak is always weak.…”

“…It has been shown before how, for example, molecular dynamics simulations are very helpful in understanding and predicting the behavior of polymers of industrial interest in different solvents [11]. Also, molecular simulation can be a powerful tool in the design of new molecules with certain tailored functionality [12]. The primordial interest here is the calculation of structural properties of a system like that depicted in Figure 1.…”

“…The effect of the TiO 2 pigment coating can be investigated also by means of the Hamaker constant [14]. Doing so is important for the particular application of the dispersion one has in mind, for example, in paints, to graft certain kinds of dispersants on the pigment surfaces so that the paints are more stable [12], or to ensure the whiteness of the paint [15], to name just some examples. This can be accomplished through an appropriate combination of the Hamaker constants for the pigment-solvent ( 12 ), with the coating substances, also for the particular solvent chosen ( 13 , 14 , etc.…”