Static scattering behavior

When a metallic particle is small compared with the illuminating wavelength, the variation of the electric field can be ignored, and the scattering behaviors can be described under the quasi-static approximation. Consider a smaller metallic sphere with radius a and a A placed in a uniform static electric field E — EqZ. The field potentials inside and outside the sphere, < ). and, are written by... 

These results confirm the observation that polyelectrolyte aqueous solutions show two separate decay modes in the autocorrelation function and support our contention that ionic polymer systems generally behave similarly in polar solvents [23], To support this, it may be added that similar dynamic scattering behavior was recently reported for another type of ionomer, polyurethane ionomer, dissolved in a polar solvent, dimethylacetamide (e = 38) [92], Finally, it should be stressed that the explanation given above for light scattering (both static and dynamic) behavior of salt-free polyelectrolytes is based on the major role of intermolecular electrostatic interactions in causing characteristic behavior. No intramolecular interactions are explicitly included to explain the behavior. This is in accord with our contention that much of the polyelectrolyte behavior, especially structure-related aspects, is determined by intermolecular interactions [23]. 

We have investigated various aspects of the microphase separation transition of diblock copolymers P(S-b-B) by small angle x-ray scattering. The temperature dependence of the scattering behavior of P(S-b-B) agrees well with recent theories. It shows a distinct deviation from mean field behavior in the vicinity of Tmst, which may be explained by the influence of thermally induced fluctuations. Static pressure dependent behavior on the other hand seems to be in accordance with the temperature experiments and it seems possible for instance to use a... 

The defining property of a structural glass transition is an increase of the structural relaxation time by more than 14 orders in magnitude without the development of any long-range ordered structure.1 Both the static structure and the relaxation behavior of the static structure can be accessed by scattering experiments and they can be calculated from simulations. The collective structure factor of a polymer melt, where one sums over all scattering centers M in the system... 

The development of various techniques has led to important advances. The possibility to measure intermolecular and intercolloidal forces directly represents a qualitative change from the indirect way such forces had been inferred in the past from aggregation kinetics or from bulk properties such as the compressibility (deduced from small angle scattering) or phase behavior. Both static (i.e., equilibrium) and dynamic (e.g., viscous) forces can now be directly measured, providing information not only on the fundamental interactions in liquids but also on the structure... 

We have focused on only the static (i.e., the time-averaged) measurements of intensities so far. However, one can also obtain the dynamic structure factor (i.e., as a function of time) from scattering experiments. The dynamic structure factor can then be used as a probe of the rheological behavior of the dispersions discussed in Chapter 4. 

Chapter D gives details on the common evaluation and interpretation of scattering experiments. Many experimental results are discussed in comparison with the behavior predicted by theory. This will show how much of this behavior can already be described by the cascade branching theory in spite of its obvious limitations. Furthermore, the great advantage of a combined measurement of both the static and dynamic LS is shown. 

High-pressure static and dynamic light scattering were used to closely examine the behavior of block copolymers of poly(vinyl acetate) (PVAc) and poly(l,l,2,2-tetrahydroperfluoroalkyl acrylate (PTAN) as a function of C02 density (Buhler et al., 1998). The phase diagram for PVAc-6-TAN shows three distinct phases as a function of polymer concentration and C02 density at a fixed temperature of 45 °C (see Figure 9.1). The block copolymer forms a precipitated phase at low C02 densities, spherical micelles at intermediate C02 densities, and unimers, or free polymer chains in solution, at high densities. The micelles-to-unimer transition was found to be very... 

Compared to binary mixtures of low molecular fluids, the critical behavior of polymer blends has been much less explored so far. However, a number of interesting static and dynamic critical phenomena in polymer blends attract increasing attention [4, 5], Neutron, X-ray, and static light scattering experiments belong to the major techniques for characterizing the static properties of polymer blends. Photon correlation spectroscopy (PCS) has traditionally been the method of choice for the investigation of the dynamics of critical [6-9] and noncritical [10-12] polymer blends. 

In the present study, we have made X-ray diffraction, neutron diffraction with isotopic substitution, and quasi-elastic neutron scattering measurements on highly concentrated aqueous solutions of lithium halides in a wide temperature range from room temperature to below glass transition temperature, from which the microscopic behaviors of the static structure and dynamic properties of the solutions are revealed with lowering temperature. The results obtained are discussed in connection with ice nucleation, anisotropic motion of water, crystallization, and the partial recovery of hydrogen bonds. 

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