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Handbook of Size Exclusion Chromatography and Related ...

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Figure 6 (A) Log-normal distribution curves <strong>of</strong> self-diffusion coefficients <strong>of</strong> the lignin<br />

fragments in some <strong>of</strong> the fractions, obtained by 1 H PFG NMR method. (B) Molar mass<br />

distribution curves for the fractions in Panel (A). (From Ref. 89.)<br />

performed for kraft lignins with different MMs. The results indicated that the<br />

apparent pK 0 is shifted to higher values by increasing MM because <strong>of</strong> an<br />

increase in the electrostatic attraction <strong>of</strong> the H þ -ions, which arise from a less<br />

curved surface. Predictions <strong>of</strong> dissociation behavior at temperatures close to<br />

those in the kraft processes (approx. 1608C) were performed. Under these<br />

conditions, the higher MM kraft lignin molecules never seemed to reach the<br />

point <strong>of</strong> complete dissociation.<br />

A non-solution technique, based on thermomechanical analysis <strong>of</strong> polymers<br />

(91), has also been presented <strong>and</strong> has been suggested to be used in studies <strong>of</strong><br />

polymeric matrix structures <strong>of</strong> wood <strong>and</strong> some <strong>of</strong> its derivatives. Molecular <strong>and</strong><br />

© 2004 by Marcel Dekker, Inc.

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