Viscosity light scattering

The association states of the benzylic- and allylic-lithium active centers have been studied by viscosity, light scattering and cryoscopy (Table 2). The majority of results indicate that the dimeric state of association is present for these active centers at the concentrations appropriate for polymerization (10-3 to 10-4 M). 

Example. A tailings stream from the hot-water flotation process (oil sands) contains 27 % (mass) solids. Estimate the suspension viscosity. Light-scattering analysis indicates that the particles are finely divided and anisotropic with a 10 Tm major dimension and a 0.5 pm minor dimension. Using Eq. 

Polymer molecules in solution can be found in many different geometric conformations, and there exist a variety of experimental methods (e.g., viscosity, light scattering, optical rotation) for obtaining information about these conformations. In this experiment, the measurement of optical rotation will be used to study a special type of conformational change that occurs in many polypeptides. 

Size-exclusion chromatography (SEC) has become the technique of choice in measuring the molar-mass distributions of polymers that are soluble in easily handled solvents (Dawkins, 1989). The technique as widely practised is not an absolute method and a typical SEC system must be calibrated using chemically identical polymers of known molar mass with a narrow distribution unless a combined detector system (viscosity, light scattering and refractive index) is employed. 

The conformational properties of polymer chains [1-4] are usually determined in dilute solutions of the polymers. Viscosity, light scattering, small-angle x-ray scattering, and osmotic pressure, are the main types of measurements made in solution. 

Three time-dependent property relationships have thus far been derived for a gelation system. These are for viscosity, light scattering, and refractive index. It should be noted that these relationships have been derived to the gel point. Past gelation, other processes related to the aging, or postgelation reactions, occur that are not treated by these formalisms. The three relationships are summarized in Table 1. 

Millaud and co-workers (12) have examined several of these polymers, particularly the polymer from 2-methyl-l,4-phenylenediamine and terephthaldehyde, for viscosity-light scattering molecular weight relationships, persistence length, light absorption spectra, and the formation of lyotropic solutions in sulfuric acid. 

Exchangeable cation Neutron scattering" X-ray scattering" Electron microscopy Viscosity Light scattering Chloride exclusion ... 

Turbidity titration Viscosity, light scattering, FT-IR Chemical degradation, NMR, chromatography... 

Various methods have been nsed to investigate interactions between polymers. Measurements of turbidity, pH, p, and ionic strength - " as a function of weight ratio of polymer in the media, viscosity, light scattering, infrared spectroscopy, nuclear magnetic resonance (NMR), thermal analysis, and powder x-ray diffraction were employed to evaluate interpolymer complexation. 

From viscosity, light scattering, and critical concentration data in H2SO4 and in N, N-dimethylacetamide (DMAc)/3% LiCl, they concluded that in the latter solvent poly(p-benzamide) is not molecularly dispersed but rather occurs as supramolecular aggregates composed likely of seven polymer chains with a side-by-side shift of one-fourth of the molecular length. Since the... 

Information regarding the shape of protein molecules may be obtained from measurements of viscosity, light scattering or streaming birefringence, aided by electron microscopy and X-ray diffraction analysis. This last technique is specially valuable since it can be used to provide not merely the overall shape of a protein molecule but also a detailed picture of its molecular architecture. 

The experimental methods used for the study of thermodynamic parameters such as Xi and 0 of a polymer in dilute solutions are numerous. Among them are intrinsic viscosity, light scattering, diffusion, sedimentation, vapor pressure, and phase equilibrium. Here we discuss vapor pressure and phase equilibrium, leaving the other methods for later chapters. 

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