Ordering Polymer‐Grafted Nanoparticles at Oil–Air Interfaces under Magnetic Fields

Abstract

Polymer‐grafted magnetic nanoparticles at oil–air interfaces are examined to reveal the role of chain length and anisotropy on particle packing order in thin films. It is found that particles grafted with intermediate chain lengths and sparse grafting densities exhibit enhanced packing order with increasing magnetic field strength. Voronoi tessellation results present an increase in the cell area distribution of these samples, suggesting that chain conformations are affected. For the longest graft length, particles become more disordered under magnetic fields. It is proposed that fluctuations in the bridged chains rearrange particles into less ordered packing with field application and the mechanism of packing order differs for varying graft chain lengths. Grafting anisotropy is found to determine the spatial nanoparticle organization in assembled monolayers.

Interfacial behavior of core–shell composite nanoparticles under compression and shear: Influence of polymer shell thickness

“…While most studies synthesize composite particles via chemical grafting methods, [8,13,24] few studies consider the foam stabilizing potential of composite nanoparticles formed by physical adsorption, a method that is more amenable to process scale-up.…”

“…[7,[17][18][19][20][21] For particle-laden interfaces, the surface shear moduli has been shown to undergo a liquid-to-solid transition with increasing surface pressure, [7,22] where the magnitude of the interfacial viscoelastic moduli was found to be determined locally by the degree of restricted particle motion that is dictated by both the particle-particle interaction strength and severity of caging caused by the local microstructure. [23] Researchers have synthesized core-shell composite particles via chemical grafting methods [2,8,13,24] but less is known about the interfacial behavior of core-shell nanoparticles formed via physical adsorption. The physical adsorption method is attractive as it can be easily scaled, however, the polymer binds to the nanoparticle via multiple contacts to form an expanded polymer shell typically of loops and tails orientation, therefore the arrangement and polymer coverage may not be uniform.…”

Solution Rheology of Poly(acrylic acid)-Grafted Silica Nanoparticles

“…Grafting polymers onto nanoparticles is a widely recognized strategy to control particle interactions, dispersion, and assemblies in polymer matrices and matrix-free systems. − Most of the studied problems focus on controlling the dispersion state of nanoparticles and entanglement states as grafting characteristics (i.e., grafting density and grafted chain length) determine the mixing, free volume, packing, and organization of grafted particles. − These structural and conformational properties of grafted systems govern solute transport and rheological behavior of nanocomposites and thin films. − Polyelectrolyte-grafted nanoparticles are quite complex as the electrostatic interactions control the solubility and flexibility of brushes. Polyelectrolyte brushes possess profoundly different properties compared with neutral brushes.…”