Speaker
Dr
Urs Gasser Gasser
(Laboratory for Neutron Scattering, Paul Scherrer Institut)
Description
We study the form factor of soft, thermoresponsive microgels based on poly(N- isopropylacrylamide) at high effective volume fractions, where the particles must shrink or overlap to fit into the available space. Small-angle neutron scattering with contrast matching techniques is used to determine the particle form factor. The apparent particle size is found to be constant up to a volume fraction roughly between random close packing and space filling. Beyond this point, the particle size decreases with increasing particle concentration; this decrease approximately cor- responds to what is expected in the absence of microgel interpenetration. Noteworthy, we do not observe a glass transition, as the suspensions remain liquid-like even above space filling. In addition, shear thinning profiles do not map onto hard sphere behavior, confirming that particle softness is responsible for our observations.
Primary author
Dr
Urs Gasser Gasser
(Laboratory for Neutron Scattering, Paul Scherrer Institut)
Co-authors
Prof.
Alberto Fernandez-Nieves
(Georgia Institute of Technology)
Mrs
Emily S. Herman
(Georgia Institute of Technology)
Mr
John Hyatt
(Georgia Institute of Technology)
Dr
Juan-Jose Lietor-Santos
(Georgia Institute of Technology)
Prof.
L.A. Lyon
(Georgia Institute of Technolgy)
