Connecting nanoscale motion and rheology of gel-forming colloidal suspensions.
We report a combined x-ray photon correlation spectroscopy and rheometry study of moderately concentrated suspensions of silica colloids that form a gel on cooling. During gel formation, the suspensions acquire a shear modulus that increases with time, while the thermal motion of the colloids becomes localized over an increasingly restricted range. The nanometer-scale localization length characterizing this motion obeys an exact relationship with the shear modulus predicted theoretically from mode coupling calculations [K. S. Schweizer and G. Yatsenko, J. Chem. Phys. 127, 164505 (2007)]. This scaling thus demonstrates a direct quantitative connection between the microscopic dynamics and macroscopic rheology. It further indicates the importance of local structure over longer-range correlations in dictating the dynamical and mechanical properties of such gels.
Guo
Hongyu
H
Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA.
Ramakrishnan
S
S
Harden
James L
JL
Leheny
Robert L
RL
D001703:Biophysics / Q000379:methods; D003102:Colloids / Q000737:chemistry*; D005782:Gels; D053758:Nanoparticles / Q000737:chemistry; D036103:Nanotechnology / Q000379:methods*; D012212:Rheology / Q000379:methods; D033081:Shear Strength; D013696:Temperature
D003102:Colloids; D005782:Gels