Shear-induced orientation in well-exfoliated polystyrene/clay nanocomposites

Laura M.C. Dykes, John M. Torkelson, Wesley R. Burghardt*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


We report measurements of shear-induced particle orientation in highly exfoliated polystyrene/clay nanocomposites. Samples were prepared using an in situ polymerization technique, in which native clay is organically modified with a cationic surfactant that incoporporates a polymerizable vinylbenzyl moiety. Controlled radical polymerization was used during the synthesis to limit the molecular weight and polydispersity of the nanocomposite polymer matrix. Flow-induced orientation was measured in the flow-gradient plane of shear flow using synchrotron-based small-angle X-ray scattering. Despite the small rotational diffusivity expected for the clay particles, significant particle orientation was only observed at relatively high rates in steady shear or at high frequencies in large-amplitude oscillatory shear. Measurements of orientation upon flow cessation provided direct evidence of a structural relaxation process that was orders of magnitude faster than estimates of rotational Brownian motion. It is suggested that this fast relaxation arises from either relaxation of shear-induced distortion of partially flexible exfoliated clay sheets in a highly entangled nanoparticle network or coupling of particle and polymer dynamics.

Original languageEnglish (US)
Pages (from-to)1622-1630
Number of pages9
Issue number3
StatePublished - Feb 14 2012

ASJC Scopus subject areas

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


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