Attractive interactions in dispersions of identical charged colloidal particles: a Monte Carlo simulation

Nanoparticle aggregation in the presence of a block copolymer

By employing dissipative particle dynamics simulations, we investigated the cooperative phase behavior of composites containing diblock copolymer molecules and nanoparticles. The nanoparticles and their aggregates are located either in the domains generated by each of the two kinds of segments of the block copolymer and/or at their interface. Various conditions, such as the interactions between nanoparticles, the interactions between them and the segments of the block copolymer, the interactions between the segments of the block copolymer, and the volume ratio of nanoparticles to block copolymer, have been changed to gather information about nanoparticle aggregation and block copolymer/nanoparticles morphology building. The dynamics of nanoparticles aggregation and the evolution of the morphology of the block copolymer have been followed. Our findings have identified two critical repulsive interactions regarding nanoparticle aggregation, one between nanoparticles and the other between the segments of the block copolymer and nanoparticles. Aggregates have been generated for repulsive interactions larger than the former critical value or smaller than the latter one.

Sedimentation in nano-colloidal dispersions: effects of collective interactions and particle charge

This is a review paper summarizing the progress of the development of colloidal sedimentation models for monodisperse, bidisperse, and polydisperse nanoparticle dispersions. This topic is of considerable interest because the sedimentation behavior of nanoparticles plays an important role in many practical systems, such as industrial coatings, optical products, ceramics, paints, dyes, and cosmetics. The limitations of various models are discussed. Multi-particle systems are highlighted, with a focus on the collective thermodynamic interactions resulting in the attractive depletion and repulsive structural forces. The effects of the particle concentration, particle charge, polydispersity in size, and electrolyte concentration on the sedimentation process are briefly summarized. Our contributions to this subject are reviewed.

Electrostatic surface interactions in mixtures of symmetric and asymmetric electrolytes: a Monte Carlo study

Canonical Monte Carlo simulations of the interaction between a uniformly charged spherical particle and a discretely charged planar surface in solutions of symmetric and asymmetric electrolytes were performed. To assess the nature of the interactions, the force exerted on the colloidal particle perpendicular to the planar surface was calculated. Attractive minima in the interaction force between the similarly charged surfaces reveal the occurrence of two phenomena: long-range attraction of electrostatic origin and short-range attraction due to depletion effects. The degree of electrostatic coupling determines the magnitude and range of like-charge attraction between the two surfaces.