Rheological spectroscopy of concentrated colloidal dispersions

A new instrument, the virtual gap rheometer (VGR) for the determination of dynamic shear moduli (and mechanical relaxation spectra therefrom) at frequencies above 100 Hz is described. Several features of the VGR which make it particularly suited to the study of concentrated viscoelastic colloidal dispersions are discussed. The underlying theory is presented and the instrument's operation illustrated with results obtained on aqueous dispersions of a model clay colloid