Three-dimensional direct imaging of structural relaxation near the colloidal glass transition
Confocal microscopy was used to directly observe three-dimensional dynamics of particles in colloidal supercooled fluids and colloidal glasses. The fastest particles moved cooperatively; connected clusters of these mobile particles could be identified; and the cluster size distribution, structure, and dynamics were investigated. The characteristic cluster size grew markedly in the supercooled fluid as the glass transition was approached, in agreement with computer simulations; at the glass transition, however, there was a sudden drop in their size. The clusters of fast-moving particles were largest near the alpha-relaxation time scale for supercooled colloidal fluids, but were also present, albeit with a markedly different nature, at shorter beta-relaxation time scales, in both supercooled fluid and glass colloidal phases.
Weeks
ER
Department of Physics and Division of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA. Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104, USA. Department of Physics and Astro.
Crocker
JC
Levitt
AC
Schofield
A
Weitz
DA