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The frequency-dependent behavior of the storage modulus G′ and loss modulus G″ has been measured for an ordered latex at different volume fractions. From these measurements the volume fraction dependency of the static shear modulus was obtained. The theoretical static shear modulus has been deduced from a stress tensor expression which only takes into account the electrostatic pair interactions between nearest neighbors. The electrostatic pair interaction is modeled adequately to account for the multiparticle environment of a particle and for high surface charges. The interactions are described by the linear superposition approximation for the pair interaction energy between two particles given by Bell et al. [J. Colloid Interface Sci. 33, 335 (1970)]. The apparent surface potential and the effective Debije screening length used in this expression are determined from the electrostatic potential which is numerically determined from the Poisson–Boltzmann equation in a spherical cell. The theoretical model is also compared with measurements of several other investigators. Most of the experimental data can be scaled to a single mastercurve resulting from the proposed theoretical model.

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The shear viscosity of a latex which is ordered at rest is studied as a function of the shear rate and volume fraction. At low shear rates and for moderate to high volume fractions, the flow curves show dynamic yield behavior which disappears below a volume fraction of 8%. At high shear rates, the onset to the high shear rate plateau of the viscosity can be observed. A new model for the shear viscosity for lattices at high volume fractions is described. This model is based upon theories for the shear viscosity of dilute lattices of Blachford et al. ͓J. Phys. Chem. 73, 1062 ͑1969͔͒ and Russel ͓J. Fluid Mech. 85, 673 ͑1978͔͒. In terms of this model, the ordered latex is broken down under shear flow into ordered domains suspended in a disordered fluid. The larger the shear rate, the smaller the volume fraction of ordered domains. The experimental results can be described reasonably well with the model discussed here. ͓S1063-651X͑97͒12808-2͔ PACS number͑s͒: 82.70.Ϫy

The linear viscoelastic behavior of an ordering polystyrene latex during steady shear flow has been investigated. In this study a home-made instrument has been used that superimposes a small-amplitude oscillatory shear orthogonal onto the steady shear flow. The measurements can be interpreted as due to the coexistence of two phases under flow. For increasing shear rate the ordered ͑or solidlike͒ phase melts away until the suspension becomes completely disordered ͑or fluidlike͒. A model is presented in which the fluid is conceived as a viscoelastic matrix containing spherical viscoelastic domains. The model predicts a similar linear viscoelastic behavior of sheared lattices as found experimentally. The resulting parameters give information about the microstructure of the dispersion under shear flow. ͓S1063-651X͑98͒15002-X͔ PACS number͑s͒: 83.50.Fc