Universal Relation for Effective Interaction between Polymer-Grafted Nanoparticles

Nitin K. Hansoge, Agam Gupta, Heather White, Andrea Giuntoli, Sinan Keten*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Understanding the interactions between polymer-grafted nanoparticles is imperative to predict the macroscale mechanical properties of the nanocomposites they form. Molecular dynamics simulations capture the interfacial effects of grafting on structure and mobility, but directly linking these features to macroscale constitutive relations for nanocomposites remains challenging. As a step toward addressing this challenge, we develop a computational framework to predict the effective pairwise interparticle interactions between polymer-grafted nanoparticles with different design parameters, that is, polymer chain length, grafting density, and polymer chemistry. Using coarse-grained molecular dynamics simulations, we evaluate the potential of mean force between two nanoparticles by varying their radial distance under uniaxial deformations, from which an effective interaction can be derived. We find that the repulsive part of the interaction can be expressed as an exponential repulsion term, whereas the attractive part is best captured using a sigmoidal form. The empirical constants of these equations depend linearly on the chain length and quadratically on the grafting density. To ensure that the finite rate of deformation does not affect our conclusions, we also take into account the strain rate dependence of the effective interaction, using a Cowper-Symonds model to extrapolate the zero-rate limit of our results. With the development of this interatomic potential between the nanoparticles, we propose a mesoscopic model for nanoparticle assemblies that circumvents the need to explicitly simulate polymer chains, significantly improving the computational efficiency by extending the spatiotemporal scales by 6-7 orders of magnitude.

Original languageEnglish (US)
Pages (from-to)3052-3064
Number of pages13
JournalMacromolecules
Volume54
Issue number7
DOIs
StatePublished - Apr 13 2021

ASJC Scopus subject areas

  • Organic Chemistry
  • Polymers and Plastics
  • Inorganic Chemistry
  • Materials Chemistry

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