Homogeneous percolation versus arrested phase separation in attractively-driven nanoemulsion colloidal gels
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Doyle_Homogeneous percolation.pdf
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Author(s)
Helgeson, Matthew E.
Gao, Yongxiang
Lee, Jinkee
Godfrin, Michael
Tripathi, Anubhav
Bose, Arijit
Moran, Shannon E.
Doyle, Patrick S
Date Issued
February 2014
Journal
Soft Matter
Publisher
Royal Society of Chemistry
Citation
Helgeson, Matthew E. et al. “Homogeneous Percolation versus Arrested Phase Separation in Attractively-Driven Nanoemulsion Colloidal Gels.” Soft Matter 10.17 (2014): 3122.
Version
Author's final manuscript
Abstract
We elucidate mechanisms for colloidal gelation of attractive nanoemulsions depending on the volume fraction (ϕ) of the colloid. Combining detailed neutron scattering, cryo-transmission electron microscopy and rheological measurements, we demonstrate that gelation proceeds by either of two distinct pathways. For ϕ sufficiently lower than 0.23, gels exhibit homogeneous fractal microstructure, with a broad gel transition resulting from the formation and subsequent percolation of droplet–droplet clusters. In these cases, the gel point measured by rheology corresponds precisely to arrest of the fractal microstructure, and the nonlinear rheology of the gel is characterized by a single yielding process. By contrast, gelation for ϕ sufficiently higher than 0.23 is characterized by an abrupt transition from dispersed droplets to dense clusters with significant long-range correlations well-described by a model for phase separation. The latter phenomenon manifests itself as micron-scale “pores” within the droplet network, and the nonlinear rheology is characterized by a broad yielding transition. Our studies reinforce the similarity of nanoemulsions to solid particulates, and identify important qualitative differences between the microstructure and viscoelastic properties of colloidal gels formed by homogeneous percolation and those formed by phase separation.
MIT Department
Massachusetts Institute of Technology. Department of Chemistry
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DOI of Published Version
https://doi.org/10.1039/c3sm52951g
