####################################################
# Prashant Mullick <pmullick@scs.uiuc.edu>
# requesting 2 days, at minimum=2 days
# beamline 33ID, "Phase Transitions in Temperature Sensitive Colloidal Suspensions"
####################################################
# top:/home/www/beamtime-requests/req00389.txt
# UNICAT Member Beam Time Request  #389
# created Mon Mar 17 10:55:29 CST 2003
####################################################

beamline:
	33ID

collaboration:
	Yes

collaborator+Pete:
	on

contact:
	pmullick@scs.uiuc.edu

days:
	2

description:
	Stimuli-responsive particles have potential applications in various areas like separation of bio-molecules, drug delivery and rheological property modifiers. Controlling particle size is key to these applications. In the case of temperature sensitive microgels, because the gel particles are composed of cross-linked polymer chains, the particle size is a function of temperature and solvent chemical potential. 
	
	In this study we propose to study the effect of this deswelling transition on the structure factor of hard core colloidal particles in a mixture with the microgel particles. The polymeric microgel particles in such a mixture are expected to behave as depletants that have a tunable particle size. The microgel particles do not adsorb onto the hard core particles and thus are capable of inducing depletion attractions between the particles. The strength and range of these depletion attractions will depend on the concentration and size of these microgel particles. Thus by tuning the size of the microgel particles, one can tune the range of the depletion attractions between the hard core particles leading to a rich variety of colloidal phase behavior. 
	
	Recent experiments at the 33ID beamline of the UNICAT facility at the APS conducted in February 2003, have shown that the structure factor of hard-core silica particles is affected by the presence of the microgel particles. Some amount of clustering of the hard core particles is observed as the microgel particle concentration is increased. Previous experiments have shown that the microgel particles themselves do not scatter X-rays in comparison with the silica particles. This allows us to probe the arrangement of only the silica particles as a function of increasing microgel concentration as we approach the gel boundary. The evolution of the structure factor in the liquid phase as we approach the gel boundary will provide insights into phase transitions from liquid to gel phases. We also propose to continue this study and explore the temperature phase space to observe the effects of deswelling of the microgel particles on the structure factor of the hard core silica spheres.
	
	The system that will be studied will include Stober silica coated with poly(N-isopropylacrylamide) (polyNIPAM) and microgel particles composed of polyNIPAM. The solvent in all samples will be 1 mM KCl.

equipment+required:
	We would like to use the SBUSAXS setup in this study.

experiment:
	Phase Transitions in Temperature Sensitive Colloidal Suspensions

foreign+nationals:
	Prashant Mullick

hazards:
	No known hazards.

minimumdays:
	2

name:
	Prashant Mullick

nonmembers:
	Dr. Jan Ilavsky
	Prof. Charles F. Zukoski

unacceptable+dates:
	All of June


#REMOTE_HOST: zukoski1.scs.uiuc.edu
#REMOTE_ADDR: 130.126.228.237
#CONTENT_LENGTH: 2875
#HTTP_REFERER: http://www.uni.aps.anl.gov/unireq.htm
#HTTP_USER_AGENT: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.0.2) Gecko/20021120 Netscape/7.01