Molecular Dynamics Simulation of Nanoparticle Self-Assembly at a Liquid−Liquid Interface

Abstract

We have used molecular dynamics simulations to investigate the in situ self-assembly of modified hydrocarbon nanoparticles (mean diameter of 1.2 nm) at a water-trichloroethylene (TCE) interface. The nanoparticles were first distributed randomly in the water phase. The MD simulation shows the in situ formation of nanoparticle clusters and the migration of both single particles and clusters from the water phase to the trichloroethylene phase, possibly due to the hydrophobic nature of the nanoparticles. Eventually, the single nanoparticles or clusters equilibrate at the water-TCE interface, and the surrounding liquid molecules pack randomly when in contact with the nanoparticle surfaces. In addition, the simulations show that the water-TCE interfacial thickness analyzed from density profiles is influenced by the presence of nanoparticles either near or in contact with the interface but is independent of the number of nanoparticles present. The nanoparticles, water molecules, and TCE molecules all exhibit diffusion anisotropy.

Synthesis of polystyrene–silica composite particles via one-step nanoparticle-stabilized emulsion polymerization

“…In contrast to the dispersion polymerization in which the polystyrene monomers are dissolved in alcohols, the emulsion polymerization here contains distinguished liquid-liquid interfaces due to the immiscibility between the monomers and the aqueous continuous phase. Thus the nanoparticles, even in the absence of electrostatic interactions, are thermodynamically favorable to self-assemble and remain at the liquid-liquid interfaces, following the same argument in sold-stabilized emulsions [37][38][39][40][41][42]. At the initial stage of polymerization, the nanoparticles provide stability to the monomer droplets.…”

“…In the latter case, the initiator molecules or residues adsorb onto the silica nanoparticle surfaces after initiation [22] thus the silica nanoparticles function as the surface-active initiator residue in that polymerization. This is our first attempt of applying the concept of solid-stabilized emulsions in polymerization, after studying the fundamentals of solid-stabilized emulsions [40][41][42], utilizing them as templates to investigate the dynamics of particles [43][44][45], and developing microrheology at liquid-liquid interfaces [46,47]. Such application may open new avenues of synthesizing advanced materials utilizing the concept of solid-stabilized emulsions.…”

Comparison of the capillary wave method and pressure tensor route for calculation of interfacial tension in molecular dynamics simulations

“…Accurate and precise calculation of surface tension is becoming increasingly important in molecular models, particularly as they are used to examine nanoscale capillary phenomena. Molecular dynamics (MD) simulations provide a unique tool for such studies, allowing for a molecular‐resolution view of the interface and its dynamics . Surface tension is also a useful quantity for evaluating the adequacy of molecule‐specific force fields and the mechanisms behind particle‐interface interactions .…”

Molecular simulation of nanoparticle diffusion at fluid interfaces

“…Previous simulations have addressed the stability of nanoparticles at interfaces [13][14][15][16][17], interactions between nanoparticles [18], orientational behaviour of anisotropic nanoparticles [17,19], and the self-assembly of nanoparticles at fluid interfaces [20,21]. These simulations have largely focused on the static properties of nanoparticles at interfaces, while only recently has simulation be turned to the dynamic properties of nanoparticles at liquid interfaces [22].…”