Understanding the role of grafted polystyrene chain conformation in assembly of magnetic nanoparticles

Abstract

Polystyrene-grafted iron oxide nanoparticles have been shown to phase separate into ordered morphologies of strings, well-dispersed particles, and spherical aggregates at low graft densities in polymer matrices. In this work, small-angle neutron scattering experiments are performed to reveal the role of grafted chain conformation on nanoparticle assemblies. We demonstrate that chains grafted at low densities follow Gaussian statistics at any dispersion states. These results suggest that grafted chains are not distorted but remain Gaussian when particles are aggregated into strings. Small-angle x-ray and neutron scattering results show that matrix chains do not influence the formation of strings, but have a significant impact on the size and internal structure of aggregated particles. We conclude that spherical aggregates of nanoparticles with low polymer graft densities are akin to interpenetrating networks in which free matrix chains bridge the fractals of particles and control the cluster density.

On the Colloidal Stability of PbS Quantum Dots Capped with Methylammonium Lead Iodide Ligands

“…Values of α close to 2 represent the fractal dimension D f of the CQD aggregates and suggest that branched aggregates are present in both solvents. 34 Their formation is probably induced by the ligand exchange. However, the overall size of these colloidal aggregates falls outside of the probed SAXS range.…”

Structure and Entanglement Factors on Dynamics of Polymer-Grafted Nanoparticles

“…Dynamics of nanoparticles is commonly used to resolve fundamental problems such as measuring the viscous properties of thin films, dynamics of free surfaces, and confined interfaces from the diffusion of particles, − or to explore the heterogeneous mechanical environments. , Since elastic properties are dependent on both the aggregation state of particles and the interactions between grafted and free matrix chains, particle relaxations can provide physical insight into the role of interfaces on mechanical properties. In composites with similar dispersion states, which were studied in transmission electron microscopy and small-angle X-ray scattering experiments, entropic interactions of grafted chains with different lengths of matrix chains were shown to be different . Subsequently, these interactions were modified by applying oscillatory shear flows .…”

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

“…In this study, particles with long grafted chains are examined to demonstrate long‐range ordering in monolayers. Particles that were shown to organize into strings and dispersed structures in solution and also in their composite forms are, herein, examined in their thin films at oil–air interfaces. It is important to note that the grafted layer of our particles is not dense or crosslinked to form uniform density of chains as in the particles assembled into ordered structures in monolayers .…”