We study the form factor of thermoresponsive microgels based on poly(N-isopropylacrylamide) at high generalized volume fractions, ζ, where the particles must shrink or interpenetrate to fit into the available space. Small-angle neutron scattering with contrast matching techniques is used to determine the particle form factor. We find that the particle size is 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 is found to occur with little interpenetration. Noteworthily, the suspensions remain liquid-like for ζ larger than 1, emphasizing the importance of particle softness in determining suspension behavior.
Gasser U.; Hyatt J. S.; Lietor-Santos, J. J.; Herman E. S.; Lyon, L. A.; Fernandez-Nieves A., Form factor of pNIPAM microgels in overpacked states, J. Chem. Phys., 2014, 141(3), 034901.
American Institute of Physics