Structure and rheology of self-assembled aqueous suspensions of nanoparticles and wormlike micelles

Abhinanden Sambasivam, Subas Dhakal, Radhakrishna Sureshkumar

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

We present a systematic molecular dynamics (MD) simulation study of the structure and rheology of solutions consisting of cationic micelles and negatively charged nanoparticles (NPs) in the presence of a hydrotropic salt, namely, sodium salicylate. The addition of NPs to wormlike micelle (WLM) solutions results in the formation of electrostatically stabilised NP-micelle junctions, leading to a significant enhancement in the viscosity of the mixture due to effective lengthening of micelle clusters. A monotonic increase in zero-shear viscosity is observed as the NP volume fraction is increased. Branched micelles form at sufficiently large salt concentrations. Sliding motion of micelle branches along the contour of a wormlike chain provides an additional mechanism for stress relaxation. Hence, branch formation induces a non-monotonic variation in the solution viscosity as a function of the salt concentration. Reverse non-equilibrium MD simulations were performed to study the effect of uniform and steady shear flow on the viscosity of the WLM-NP mixtures. Beyond a critical shear rate, flow-induced anisotropy, which is quantified by an orientational order parameter, manifests as viscoelastic rheological behaviour. Specifically, at higher NP volume fractions and shear rates that exceed the inverse of a characteristic structure relaxation time, flow-alignment of the microstructure causes pronounced shear thinning.

Original languageEnglish (US)
Pages (from-to)1-9
Number of pages9
JournalMolecular Simulation
DOIs
StateAccepted/In press - Oct 21 2017

Keywords

  • molecular dynamics
  • nanoparticle
  • rheology
  • shear flow
  • Surfactant micelle

ASJC Scopus subject areas

  • Chemistry(all)
  • Information Systems
  • Modeling and Simulation
  • Chemical Engineering(all)
  • Materials Science(all)
  • Condensed Matter Physics

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