Dynamics of aging soft matter

Condensed Matter lunchtime seminar

Dynamics of aging soft matter

  • Event time: 1:00pm
  • Event date: 12th February 2001
  • Speaker: Luca Cipelletti (Universit√© Montpellier II)
  • Location: Room 2511,

Event details

We use multispeckle dynamic light scattering to study the dynamics of aging soft materials. Results for gels formed by aggregating colloidal particles will be presented. Even though the gel is an elastic solid, the dynamic structure factor f(q,t) exhibits a nearly complete decay on long time scales, with an unusual form, f(q,t) ~ exp[-(t/tf)m], with m ~ 1.5 and with the relaxation time tf ~ q-1. A model for restructuring of the gel with aging correctly accounts for this behavior. Aging leads to a dramatic increase in the relaxation time; however all data can be scaled on a single master curve, with the relaxation time asymptotically growing linearly with age. This behavior is strikingly similar to that predicted for aging in disordered glassy systems, offering convincing proof of the universality of these concepts. I'll also present results on other soft materials, such as micellar polycrystals and concentrated emulsions, for which the same form of f(q,t) and the same tf ~ q-1 dependence are observed as for the gels, thus suggesting the generality of this behavior.
References:
[1] Aging of Colloidal Fractal Gels, webpage related to L.C.'s research at Harvard University
[2] Universal Aging Features in the Restructuring of Fractal Colloidal Gels, Phys. Rev. Lett. 84, 2275 (2000)

This is a weekly series of informal talks given primarily by members of the soft condensed matter and statistical mechanics groups, but is also open to members of other groups and external visitors. The aim of the series is to promote discussion and learning of various topics at a level suitable to the broad background of the group. Everyone is welcome to attend..

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