Viscosimetry

Viscosity is a measure of the friction (resistance to mechanical movement) of a fluid. In the case of liquids, the viscosity of a solution is different from the pure solvent and is dependent on the nature and concentration of the solute. The following Staudinger equation (Tanford 1961 Clapp, Emerson, and Olness 1990 Stevenson 1994) allows to estimate molecular weights  

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The effect of Ca was assayed by viscosimetry in reaction mixtures containing 0.187 % pectin, buffered at pH 8.0, and ethylene diaminetetraacetic acid (EDTA) (0.005 M) or CaClj (0-0.02 M). 

Figure 1. Time-course of pectin lyase activity in cultures of F. oxysporum f. sp. radicis-tycopersici. Fungus was first grown on unrestricted glucose for three days, then the biomass was or shifted to restricted glucose and, after one day, to restricted galacturonic acid (1) or shifted to pectin (2). Enzyme activity was determined as increase in A235 nm (- -) and by viscosimetry (- -) and determined for 10 min.

Viscosimetry-right angle light-scattering detector.352... 

Recent advances have greatly decreased the difficulties raised by these cautionary points. In particular, on-line viscosimetry and multi-angle lightscattering make it possible to determine the molecular weight and viscosity of samples as a function of elution volume. With such detectors, effects of solute-column packing interactions become unimportant, since the properties of narrow fractions can be measured. These detectors will be discussed in greater detail below. 

We will summarize the results of a systematical study of these systems by phase titration, turbidimetry and viscosimetry, The concentration ranges were 0[Pg.134]

Kulicke, Clasen Viscosimetry of Polymers and Polyelectrolytes ISBN 3-540-40760-X... 

The laboratory technique for measuring viscosity is called viscometry (sometimes viscosimetry), and the device in the laboratory used to measure viscosity is called a viscometer (sometimes viscosimeter). 

To characterize dendrimers, analytical methods used in synthetic organic chemistry as well as in macromolecular chemistry can be applied. Mass spectrometry and NMR spectroscopy are especially useful tools to estimate purity and structural perfection. To get an idea of the size of dendrimers, direct visualization methods such as atomic force microscopy (AFM) and transmission electron microscopy (TEM), or indirect methods such as size exclusion chromatography (SEC) or viscosimetry, are valuable. Computer aided simulation also became a very useful tool not only for the simulation of the geometry of a distinct molecule, but also for the estimation of the dynamics in a dendritic system, especially concerning mobility, shape-persistence, and end-group disposition. 

The universal calibration, derived from GPC viscosimetry online coupling, has further confirmed the predicted molecular weights. Absolute verification of this calibration principle, which neglects differences in viscosity of molecules of equal molecular weight but with different architectures, is still underway [16]. 

Fig.2.16. Behavior of a polyelectrolyte in dilution viscosimetry in water (a) without, (b) with a low quantity and (c) with a higher quantity of a low-molecular-weight electrolyte (salt) which screens the electrostatic interactions...

Sufficiently concentrated polyamide solutions as needed for physical measurements (e.g., viscosimetry, opytical tests) must be prepared in two steps At first, synthesis of the polyamide by use of precipitation polymerization and secondly, dissolving the carefully washed and dried polymer in concentrated sulfuric acid. 

Measurements of osmotic pressure provide an absolute determination (without calibration) of the number-average molar mass. This is independent of the type of solvent for each solvent the extrapolation to zero concentration results in the same value H/c = RT/Mn. With viscosimetry the determination of M is not absolute dependent on the solvent and the temperature one finds a valne for the intrinsic viscosity, [rj], which is not unique but which has to be calibrated. 

The characteristic ratio of atactic polylferf.-butyl vinyl ketone) is determined from light scattering and viscosimetry measurements, and at 300 K in benzene the dipole moment ratio and its temperature coefficient are measured. Calculations of Ca and Da based on a two-state RIS model, with parameters independently derived from a previously developed semiempirical potential energy surface and from epimerization equilibrium measurements for dimeric and trimeric oligomers, are in excellent agreement with the experimental results. The predicted temperature coefficient is positive but lower in magnitude than that observed. 

With somewhat the same idea, Minoura [44] used the formation of a crown ether sandwich complex with K+ to force the association of helical dimers of C-terminal modified poly-benzylglutamate (52). Although no structural data were provided, he observed by viscosimetry the reversible formation of a K+ sandwich complex with two 15-crown-5 modified peptides. 

One of the few processable polymers capable of doping to respectable conductivity is poly(phenylene sulfide). Stacey 339 has reported GPC studies of this polymer, using an instrument operating at 210 °C with 1-chloronaphthalene as solvent and detection by viscosimetry. Samples tested were found to be of high molecular weight with Mw in the range 20 to 80,000 and Mw/Mn typically less than 1.7. 

In this work both the prepolymers and the block copolymers were prepared in bulk and, therefore, it is not surprising that a large amount of homopolymer was obtained74,75. The subsequent characterization of the products was carried out, after a selective solvent extraction process, using NMR, IR, osmometry, viscosimetry and GPC. 

Finally, the endo-/ -l,4-glucanase (Cx) can be assayed using amorphous cellulose, cellodextrins, or water-soluble derivatives by determination of the reducing sugars released or by viscosimetry. It is generally accepted that the release of reducing sugars is not a typical measure for the random action of endocellulases. 

Dimova, Rumiana, Motion of Particles Attached to Giant Vesicles Falling Ball Viscosimetry and Elasticity Measurements on Lipid Membranes, 6, 221. 

Lohmander U (1964) Non-Newtonian flow of dilute macromolecular solutions studied by capillary viscosimetry. Macromol Chem 72(1) 159-173 Maugin GA (1999) Thermomechanics of nonlinear irreversible processes. World Scientific, Singapore... 

The effect of divalent ions such as SO4 " has been studied either by electric permittivity techniques, or by viscosimetry. It was experimentally observed that the dielectric increment is larger than in the presence of monovalent ions. In the presence of the bivalent counterions there are two opposite effects. From one hand, the bivalent ions tend to increase the dielectric increment through a charge effect, while from the other hand the observed reduction of the viscosity proves that in the presence of SO4 - the polyions contract76). 

Various hydrodynamic studies of proteins, for example viscosimetry and diffusion, have shown that proteins behave in solution as fairly compact and symmetric particles. In time, equations were developed to describe the overall size and shape of proteins in terms of ellipsoids of revolution. Two basic types of ellipsoids of revolution, the prolate and oblate, are used to depict the approximate three-dimensional shapes of protein molecules. These are shown in Figure 4.12. Each ellipsoid of revolution may also be described by an axial ratio, that is, the ratio of the short axis to the long axis. A spherical protein molecule has an axial ratio of 1 1, whereas an asymmetric molecule, such as fibrinogen, may have an axial ratio of 1 10. 

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