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Title: Kinetics of the glass transition of fragile soft colloidal suspensions
Authors: Saha, Debasish
Joshi, Yogesh M.
Bandyopadhyay, Ranjini
Issue Date: Dec-2015
Publisher: American Institute of Physics
Citation: Journal of Chemical Physics, 2015, Vol.143, p 214901
Abstract: Microscopic relaxation time scales are estimated from the autocorrelation functions obtained by dynamic light scattering experiments for Laponite suspensions with different concentrations (CL), added salt concentrations (CS), and temperatures (T). It has been shown in an earlier work [D. Saha, Y. M. Joshi, and R. Bandyopadhyay, Soft Matter 10, 3292 (2014)] that the evolutions of relaxation time scales of colloidal glasses can be compared with molecular glass formers by mapping the waiting time (tw) of the former with the inverse of thermodynamic temperature (1/T) of the latter. In this work, the fragility parameter D, which signifies the deviation from Arrhenius behavior, is obtained from fits to the time evolutions of the structural relaxation time scales. For the Laponite suspensions studied in this work, D is seen to be independent of CL and CS but is weakly dependent on T. Interestingly, the behavior of D corroborates the behavior of fragility in molecular glass formers with respect to equivalent variables. Furthermore, the stretching exponent β, which quantifies the width w of the spectrum of structural relaxation time scales, is seen to depend on tw. A hypothetical Kauzmann time tk, analogous to the Kauzmann temperature for molecular glasses, is defined as the time scale at which w diverges. Corresponding to the Vogel temperature defined for molecular glasses, a hypothetical Vogel time t∞α is also defined as the time at which the structural relaxation time diverges. Interestingly, a correlation is observed between tk and t∞α, which is remarkably similar to that known for fragile molecular glass formers. A coupling model that accounts for the tw-dependence of the stretching exponent is used to analyse and explain the observed correlation between tk and t∞α.
Description: Open Access
ISSN: 0021-9606
1089-7690 (Online)
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Copyright: 2015 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics
Appears in Collections:Research Papers (SCM)

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