8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P5.50Wed 711:10-14:00Rotational averaging-out the effects of gravity oncolloidal dispersionsDjamel el Masri, 1 Teun Vissers, 1 Stephane Badaire, 1 Johan Stiefelhagen, 1Hanumantha Rao Vutukuri, 1 Arnout Imhof, 1 and Alfons van Blaaderen 11 Soft Condensed Matter, Debye Institute for Nanomaterials Science, Princetonplein 5,OL 021 3584 CC, Utrecht, NetherlandsColloidal dispersions are often used as model systems to investigate a variety of phenomena incondensed matter physics, including crystallization, clustering/gelation, and the glass transition.However, when the gravitation length of individual colloids gets big or if the colloids form solidlikestructures, gravity plays an important role which may strongly alters particle trajectories, andconsequently influences or even prevents their structure formation. Here in this study, we report theeffects of gravity on structure formation in different systems: hard sphere fluid, long-rang chargedcolloidal crystal, oppositely charged colloidal gel, colloidal chains and colloidal gold platelets. Weuse a home-built rotating stage to average-out the effects of gravity and compare the results withsamples subject to normal gravity. In the case of a charged colloidal crystal, an unusual sequenceof dilute-Fluid/dilute-Crystal/dense-Fluid/dense-Crystal was observed throughout the suspensionunder gravity, related to the volume fraction dependence of the colloidal interactions. In the case ofan oppositely charged colloidal gel, the gel-like structure collapses under gravity, whereas withoutgravity, the gel completely transforms to crystallites that appear with random orientations.50