Molecular weight distribution determination

The comparison among these techniques is tabulated in Table 22.1. In summary, HdC is a separation technique with low selectivity however, the efficiency can be very high. Especially in PCHdC, high analysis speed can be achieved over a wide MW range. ThFFF performs best for the separation of high MW samples. SEC has an intermediate selectivity between FldC and ThFFF. Practicality makes SEC the most suitable method for the common MW range of synthetic polymers. SEC is by far the most commonly used technique for molecular weight distribution determinations. However, HdC is better for the fast analysis purpose. 

Two Streptomyces strains, S. badius and S. viridosporus, were found to be able to grow on kraft lignin (In-dulin ATR) as sole carbon source. The resulting APPL (Acid Precipitable Polymeric Lignin) was characterized by FTIR and elemental analysis for C, H and N, and was found to contain proteins in addition to a relatively demethoxylated lignin component. The proteins were further characterized by amino acid analysis, while the lignin component was separated by solvent extraction and its molecular weight distribution determined by HPSEC. 

The molecular weight distributions determined by an ASEC analysis... 

Figure 1. Molecular weight distribution (determined by Sepharose CL6B GPC) of lignosulfonate before (filled circles) and after (open circles) incubation with phenoloxidase.

Molecular Weight and Molecular-Weight Distribution Determination... 

Fig. 14.—Sectioning of the- Cellulose Fibers Having an Extended or Folded-chain Conformation and the Resulting Change in Molecular-weight Distribution Determined by Gel-permeation Chromatography, [(a) Before and (b) after sectioning. " ]...

Figure 1. Molecular weight distributions determined by GPC as a function of reaction time (t) for the SFR copolymerization of styrene/isoprene.

Stacy in 1985 was able to determine molecular weights of PPS by light scattering of solutions above 200 C and used the values to calibrate molecular weight distributions determined by gel permeation chromatography above 200°C. Heterogeneity index (M /M ) for PPS is near 1.7, less than the value of 2.0 expected of condensation polymers. The difference is the absence of a low molecular weight tail in PPS. 

TSiumber average molecular weight and molecular weight distribution determined by GPC using monodisperse polystyrene standards... 

The effect of EB on the molecular weight distribution (determined by gel permeation chromatography (6PC)) is shown in Fig.3 for catalyst PAR 3/4. The blmodal distribution. 

TFFF can be used for the separation and molecular-weight distribution determination of polymers in the molecular weight range lO -lO. As a tech-... 

Polymer molecular weights influence material properties and molecular weight distributions determine melt flow characteristics. 

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