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# SUbramanian Ramakrishnan <ramakris@scs.uiuc.edu>
# requesting 3 days, at minimum=1 days
# beamline 33ID, "Depletion Interactions in Attractive Systems"
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# top:/home/www/beamtime-requests/req00303.txt
# UNICAT Member Beam Time Request  #303
# created Sun Nov 03 11:14:39 CST 2002
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beamline:
	33ID

collaboration:
	Yes

collaborator+Pete:
	on

contact:
	ramakris@scs.uiuc.edu

days:
	3

description:
	Addition of Nonadsorbing polymer to a colloidal suspension can result in a gel or a crystal depending on the size and molecular weight of the polymer. THere is a wide interest in the academic and industrial community in studying the microstructure of the resulting suspension in such systems and to relate the microstructure to macroscopic properties such as viscosity and shear modulus. Small angle xray scattering provide an invaluable technique in getting to the microstructure for such systems.
	
	We have recently performed experiments on model hard sphere systems with nonadsorbing polymer for a variety of polymer molecular weights and concentrations and have investigated the resulting microstructure using USAXS. This study has resulted in a fundamental understanding of the physics of colloid-polymer mixtures and has provided an molecular level understanding of the interactions between the colloids which gives rise to the observed phase behavior.
	
	A number of industrial systems however involve spheres which are sticky. What would happen to such a system if polymers were added to it? THis would result in an additonal attraction which would be long ranged and hence would provide a means to control the phase behavior and rheology of such systems.
	
	We plan to study the phase behavior and microstructure of such attractive systems and would like to perform experiments on USAXS to get to the microstructure. THis would be the first kind of such experiments performed on these systems and would help in developing a basic theory to understand the underlying physics. The pioneering work of Shah and Zukoski in developing the technique for the hard sphere systems provides a strong basis on which these experiments will be planned and executed.
	
	References
	
	S. A. Shah and C. F. Zukoski : " Small angle scattering studies of colloid-polymer mixtures" to be submitted to Langmuir...

equipment+required:
	

experiment:
	Depletion Interactions in Attractive Systems

foreign+nationals:
	I am a Canadia Citizen

hazards:
	Silica spheres + Toluene

minimumdays:
	1

name:
	SUbramanian Ramakrishnan

nonmembers:
	NIST

unacceptable+dates:
	


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