Mark-Houwink relation, viscosity

In all the other solvents used, the intrinsic viscosities are smaller (possibly as a result of charge screening by electrolytes) cuid follow a single Mark-Houwink relation. This equation is found to be ... 

The intrinsic viscosity appears to depend on the molar mass according to the Mark-Houwink relation ... 

The Mark-Houwink relation for polypropylene in o-dichlorobenzene at 130°C was calibrated as follows. A series of sharp fractions of the polymer was obtained by fractionation, and the molecular weight of each fraction was determined by membrane osmometry in toluene at 90"C. The samples were then dissolved in o-dichlorobenzene at I30°C and their intrinsic viscosities ([ ]) were measured. The resulting data fitted an expression of the form... 

If a concentration-selective detector, such as a DRI, is connected on-line with the viscosity detector, the ratio of the two signals yields the intrinsic viscosity distribution of the polymer sample. In polymer characterization, the intrinsic viscosity can be a property just as important as the molecular-weight distribution. Furthermore, polymer intrinsic viscosity follows the Mark-Houwink relation to the molecular weight, M, where K and a are Mark-Houwink viscosity constants ... 

Solution characteristics of the polymer have been studied particularly in dimethylformamide that was made 0.1 V in anhydrous lithium bromide to suppress an apparent polyelectrolyte effect occasionally observed [16]. In this system the Mark-Houwink relation for the intrinsic viscosity at 90°C was found to be... 

Higher order moments can be defined, but they are less useful because they cannot be determined as accurately. Other measures of molecular weight include the peak value, Mp, which corresponds to the maximum in the distribution, and Af , determined from the intrinsic viscosity, [rj, using the Mark-Houwink relation (Chapter 3 herein) ... 

Complementary structural information can be obtained by the Mark-Houwink relation between viscosity and molecular weight (Eq. 4). 

There is no need to restrict the definitions to integer-order averages. Indeed the intrinsic viscosity of a polymer is related to the degree of polymerization through the Mark-Houwink relation [9]... 

For their characterization, alginates must first be purified and isolated under their sodium form. NMR spectroscopy ( H and C) is the most powerful technique to characterize the chemical composition and the microstructure of alginates [46 9]. Purified alginates, isolated under the sodium salt form, were also characterized by steric exclusion chromatography (SEC)with three detectors on line. For commercial products, molecular weights may range between 32 000 and 400 000. A further means of characterization is their intrinsic viscosity using the Mark-Houwink relation ... 

The limiting viscosity number depends on the polymer, solvent, and temperature, but imder a given set of conditions it is related to the molecular weight by the Mark-Houwink relation, [ >] = where K and a are constants and M is the molecular weight of the polymer. Tables of K and a are available for a large number of polymers and solvents (31,32). Excellent summaries of equations, techniques, and references relating to the viscosity of dilute polymer solutions are also available (33,34), as is information on dilute polymer solutions that are shear thinning (35). 

The variation of the intrinsic viscosity with the molecular weight has been established previously on a polyacrylamide of the same hydrolysis degree in a 20 g/l. NaCI solution (9). The results follow a Mark Houwink relation (fig. 13) ... 

Viscometric-average molar masses (M ) cannot be defined with the same rigor since they result from an empirical expression, the Mark-Houwink relation correlating the intrinsic viscosity (or limit index of viscosity) [r ] to the molar mass M of a nondispersed (isomolecular) fraction of a polymer sample. The way to establish the relation... 

The inherent viscosities of the poiyaniiine base samples were determined at 25°C using solutions (0.1 wt.%) prepared in 97% sulfuric acid. In addition, a number of polyaniline samples of different inherent viscosities were analyzed by size-exclusion chromatography in concentrated sulfuric acid. Since the conformation and stiffness of polyaniline in sulfuric acid has not yet been determined, it is not possible to make direct correlations between the viscosity and the molecular weight. Instead, upper and lower limits of the molecular weights were estimated from comparison with viscosities measured under identical conditions of nylon 6 and poly-para(phenylene terephthalamide) and the Mark-Houwink relations [42,43] for these polymers. 

The Mark-Houwink-Sakurada equation relates tire intrinsic viscosity to tire polymer weight ... 

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