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Molecular weight distribution methods

The preceding discussions of the kinetics and molecular weight distributions in the step-growth polymerization of AB monomers are clearly exemplified by the esterification reactions of such monomers as glycolic acid or co-hydroxydecanoic acid. Therefore one method for polyester synthesis is the following ... [Pg.299]

The phenomena we discuss, phase separation and osmotic pressure, are developed with particular attention to their applications in polymer characterization. Phase separation can be used to fractionate poly disperse polymer specimens into samples in which the molecular weight distribution is more narrow. Osmostic pressure experiments can be used to provide absolute values for the number average molecular weight of a polymer. Alternative methods for both fractionation and molecular weight determination exist, but the methods discussed in this chapter occupy a place of prominence among the alternatives, both historically and in contemporary practice. [Pg.505]

The basic premise of this method is that the magnitude of the detector output, as measured by hj for a particular fraction, is proportional to the weight of that component in the sample. In this sense the chromatogram itself presents a kind of picture of the molecular weight distribution. The following column entries provide additional quantification of this distribution, however. [Pg.644]

A brief review has appeared covering the use of metal-free initiators in living anionic polymerizations of acrylates and a comparison with Du Font s group-transfer polymerization method (149). Tetrabutylammonium thiolates mn room temperature polymerizations to quantitative conversions yielding polymers of narrow molecular weight distributions in dipolar aprotic solvents. Block copolymers are accessible through sequential monomer additions (149—151) and interfacial polymerizations (152,153). [Pg.170]

In addition to this drive to look beyond manufacturing to specifications, new analytical methods such as molecular weight distribution, Mooney relaxation, and other measures of polymer processibiHty are being explored. [Pg.549]

NEW APPROACH TO INCREASING OF ROBUSTNESS FOR METHOD OF DETERMINATION OF MOLECULAR WEIGHT DISTRIBUTION IN DEXTRANS... [Pg.345]

The main problem of determination of molecular weight distribution (MWD) of dextrans (polysachaiides which ai e used as active substances for infusion medicines) is low robustness of the existing method. It means that obtained results are strongly dependent on controlled and uncontrolled pai ameters of chromatographic system standai d substances for calibration loading on columns etc. It has been shoved on practical examples. [Pg.345]

Determinarion of MW and MWD by SEC using commercial narrow molecular weight distribution polystyrene as calibration standards is an ASTM-D5296 standard method for polystyrene (11). However, no data on precision are included in the 1997 edition of the ASTM method. In the ASTM-D3536 method for gel-permeation chromatography from seven replicates, the M of a polystyrene is 263,000 30,000 (11.4%) for a single determination within the 95% confidence level (12). A relative standard deviation of 3.9% was reported for a cooperative determination of of polystyrene by SEC (7). In another cooperative study, a 11.3% relative standard deviation in M, of polystyrene by GPC was reported (13). [Pg.503]

ASTM D-5296-92, Standard Test Method for Molecular Weight Averages and Molecular Weight Distribution of Polystyrene by High Performance Size-Exclusion Chromatography. ASTM Annual Book of ASTM Standards, Vol.08.03, pp. 425-438. [Pg.529]


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Distribution weight

Molecular distribution

Molecular weight distribution

Molecular weight distribution methods above

Molecular weight distribution methods dynamic light scattering

Molecular weight distribution methods mass spectrometry

Molecular weight distribution methods membrane osmometry

Molecular weight distribution methods sedimentation equilibrium

Molecular weight distribution methods sedimentation velocity

Molecular weight distribution methods static light scattering

Molecular weight distribution methods ultracentrifugation

Molecular weight methods

Narrow molecular weight distribution methods

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