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DTSTAMP:20260728T120427Z
LAST-MODIFIED:20121116T203436Z
DTSTART:20100917T160000Z
DTEND:20100917T170000Z
UID:event672@bu.edu
URL:http://physics.bu.edu/internal/events/show/672
SUMMARY:Universal Gelation of Particles with Short-ranged Attraction
DESCRIPTION:Featuring Peter Lu\, Harvard University\nHosted by: Ophelia Tsu
	i\n\nPart of the Biophysics/Condensed Matter Seminar Series.\n\nAbstract:\n
	Nanoscale or colloidal particles are exceptionally important in many realms
	 of science and technology. They can dramatically change the properties of 
	materials\, imparting solid-like behavior to a wide variety of complex flui
	ds\, from yoghurt to cast ceramics. This behavior arises when particles agg
	regate to form mesoscopic clusters and networks. The essential component le
	ading to aggregation is an interparticle attraction\, which can be generate
	d by many physical and chemical mechanisms. In the limit of irreversible ag
	gregation\, infinitely strong interparticle bonds lead to diffusion-limited
	 cluster aggregation (DLCA)\, long-understood as a purely kinetic phenomeno
	n\, which can form solid-like gels at arbitrarily low particle density. Far
	 more important technologically are systems with weaker attractions\, where
	 gel formation requires higher colloid densities. Numerous scenarios for ge
	lation have been proposed\, including DLCA\, kinetic or dynamic arrest\, ph
	ase separation\, percolation\, and jamming. No consensus has emerged\, and 
	despite its ubiquity and significance\, gelation is far from understood; ev
	en the location of the gelation phase boundary is not agreed upon. I will s
	how that gelation of spherical particles with isotropic short-ranged attrac
	tions is initiated by spinodal decomposition; this thermodynamic instabilit
	y triggers the formation of density fluctuations\, leading to spanning clus
	ters that dynamically arrest to create a gel. This simple picture of gelati
	on does not depend on microscopic system-specific details\, and should thus
	 apply broadly to any short-ranged attractive particle system. Our results 
	suggest that gelation\, often previously considered a purely kinetic phenom
	enon\, is in fact a direct consequence of equilibrium liquid-gas phase sepa
	ration.
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
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