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Rheology is commonly used as a tool for analytics and quality control in latex technology. As soon as flow becomes essential for the structure measured in a scattering experiment we call it scattering from shear-ordered dispersions or rheologic scattering. In this paper it is shown that the structure of concentrated dispersions can with advantage be studied by scattering experiments. Theoretical and experimental aspects as well as examples of small-angle synchrotron x-ray and neutron scattering from colloidal dispersions, presented in the paper, are closely related to rheology.

In this paper we investigated the single particle dynamics in a colloidal crystal by means of video microscopy and digital imaging methods. To obtain the self term of the van Hove function Gs(x,τ) with a reasonable good statistical accuracy we analyzed up to two million particle displacements per time channel τ of Gs(x,τ), which corresponds to the analysis of 3000 video frames, each with approximately 1000 particles. It was found that the Gaussian approximation almost perfectly accounts for the experimental results, so that the time evolution of Gs(x,τ) can solely be described by the mean square displacement 〈x2(τ)〉. The measured mean square displacements were compared with the model of a Brownian particle bound in a harmonic potential [Physica A 157, 705 (1989)]. The experimental curves approach the plateau value 〈x2(τ→∞)〉 of the mean square displacement much slower than is predicted by the model. From the plateau value of the mean square displacement the Lindemann parameter was determined for various samples. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Dynamic and static light scattering is applied to concentrated suspensions of a new species of charged colloidal suspensions with a low refractive index. The polymer colloids which were obtained by polymerizing perfluorobutylacrylate could be index matched in a water/glycerol mixture. At volume fractions [uppercase_phi_synonym] greater than 0.22 a glass transition can be observed, which is manifested by the nondecaying components of the intermediate scattering functions. The intermediate scattering functions for a supercooled liquid sample and the predictions of the mode-coupling theory for the β relaxation are compared over a large Q range. By using an exponent parameter λ=0.76 a good agreement between theory and experiment can be obtained. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A dilute suspension of ordered polymer colloid particles was investigated by static and dynamic light scattering. The obtained results are compared with a Brownian dynamic (BD) simulation of a model system consisting of hard spheres interacting with an exponentially screened Coulomb potential. The long time properties of the self- and collective correlation functions are investigated in detail. The obtained mean squared displacement is best described by a stretched exponential model and the collective long time diffusion from the BD simulation can only be approximately described by a kinetic theory based on a hard sphere system. [ABSTRACT FROM AUTHOR]

The density of dependence of the static structure factor S(Q) of liquid-like ordered colloidal suspensions is investigated by light scattering techniques. We found that variation of the particle number density even by a factor of 8 produced only a modest change of the height of the first peak of S(Q). In order to obtain a consistent theoretical description of S(Q) at various particle number densities, the effective charge Z[ATOTHER]@B|[/ATOTHER]p of the particles and the Debye screening parameter κ* were calculated on the basis of the Poisson–Boltzmann–Cell (PBC) model and the Poisson–Boltzmann–Jellium (PBJ) model, respectively. The resulting Z*p and κ* values were used to calculate S(Q) via the rescaled mean spherical approximation (RMSA). It is found that a consistent description of the density dependence of S(Q) is possible with the PBC model. By contrast, the PBJ model predicts too weak a liquid-like order than observed experimentally. [ABSTRACT FROM AUTHOR]

Depolarized Rayleigh and Raman scattering from fluids is composed of orientational (OR), collision induced (CI), and cross (X) contributions. In order to investigate the influence of the interaction induced terms (CI and X) on allowed spectra (OR), C2H6, a molecule with a small ratio of the anisotropic part γ to the isotropic part α of the polarizability is considered. Both Rayleigh and ν3 Raman correlation functions were determined by molecular dynamics (MD) computer simulation and compared with experiment. The investigations extend over a wide range of densities (0.67ρc–2.85ρc, where ρc is the critical density, ρc=0.206 g/cm3). The different contributions to the time correlation functions (TCFs) were simulated within the frame of a first-order center–center dipole–induced-dipole polarizability model. The potential model used was a standard two-site Lennard-Jones potential. Details concerning partial OR, CI, and X correlation functions and second moments for Rayleigh and Raman scattering are presented. At the lower densities a large CI and a smaller X contribution to the total Rayleigh TCF is found. At higher densities the X and CI contributions increase but tend to cancel each other so that the OR contribution becomes more important. Concerning the Rayleigh second spectral moments an explanation of the minimum of the experimental second moment observed at intermediate densities and of the increase of the second moment with density for higher densities is presented. Both the Raman TCFs and second moments are essentially orientational due to the large polarizability anisotropy derivative γ′. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Computer simulations of the Rayleigh and Raman spectral time-correlation functions (TCFs) are reported for N2 at 323 K and densities ranging from 0.48 to 2.5 times the critical value. The results are compared with experiment. Particular attention is paid to the density dependence of the spectral intensity due to the correlated permanent polarizability and to the interaction-induced contributions to the polarizability. The partial cancellations that occur between various two-, three-, and four-body terms in the cross and collision induced (CI) parts of the spectral TCFs are evaluated. It is shown that these terms are significant in both the Raman and the Rayleigh spectra, but cancellation greatly reduces their net contribution at all densities studied. The weak but uncancelled TCFs that are associated with orientational correlations of the molecular polarizability anisotropies are shown to be a significant part of the high density Rayleigh TCFs. It is argued that the long-range nature of this TCF means that its simulated values are poorly known. [ABSTRACT FROM AUTHOR]