Linking single particle rearrangements to delayed collapse times in transient depletion gels (original) (raw)

Journal of Physics-condensed Matter - J PHYS-CONDENS MATTER, 2006

Abstract

Weak depletion gels with particle radii of ∼200–500 nm have been reported to display a time-dependent settling behaviour where an initially space spanning gel displays a catastrophic collapse after a characteristic period of time, defined as the delay time. Several experiments suggest that thermally activated particle rearrangements promote macroscopic gel coarsening, which ultimately triggers the rapid collapse. The delay time is found to be a sensitive function of the colloid volume fraction and polymer concentration. We have performed systematic experiments on the silica–decalin–polystyrene depletion system to explore how colloid volume fraction, polymer concentration, particle radius and ratio of polymer radius of gyration to particle radius influence the delayed collapse time of transient gels. We employ a recently developed activated barrier-hopping theory to make predictions of the timescales over which colloids can escape localized states as a function of system parameters. ...

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