Physicochemical Studies of Alkali Lignins: Ii. Ultracentrifugal Sedimentation Analysis

Abstract

Ultrace~ltrifugal seditnentation of alkali lignin fractions revealed marked boundary spreading a t low and high centrifugal fields. An analysis of the gradient diagrams indicated a wide distribution of sedimentation coefficients ranging from 0.5 to over 400X10-13 second. There was only a small decrease in the polydispersity on subfractionation. The distributions were continuous with a single peak and positive skewness. A linear relationship was found between the intrinsic viscosity and the standard deviation of the weight-average sedimentation coefficient. The sedimentation coefficient based on the movement of the maximum ordinate a t a field of 11.5X103 g was several times greater than the corresponding coefficient for the same fraction a t 200X103g. A qualitative interpretation of this phenomenon is given in terms of the Fasen and the Archibald solution to the Lamm equation.

Degradation of insoluble lignin by chlorine monoxide

“…The abundance of fractions then decreases with increasing molecular weight. This was the very pattern found some years ago by Gupta et al (1960) on examining a number of fractions of soda lignin by ultracentrifugal sedimentation. It is also the pattern of molecular weight distribution that we have found on chromatographing chlorolignins on Styragel (Figure 3).…”

“…As long ago as 1952, Schuerch proposed for lignin-inwood the architecture of a three-dimensional network polymer because he could not otherwise explain its insolubility in good solvents. Since then, Gupta et al (1960) have pointed out that such an architecture would account for the molecular weight distribution of isolated lignins. Later, starting with the assumption that wood lignin is cross-linked gel, and using different aspects of the theories of synthetic gel formation (Flory, 1953), Szabo and Goring (1968) and Bolker and Brenner (1970) were able to duplicate by calculation the molecular weight/yield relationship of kraft, sulfite, and dioxane lignins.…”

Physicochemical Studies of Alkali Lignins. I. Preparation and Properties of Fractions

“…Fischer and co-workers (18) while studying alkaline oxidation of lignin were able to precipitate lignin with barium and separated it into readily soluble a n d slightly soluble fractions. Fractionation with Ba++ is not particularly selective and the fractions had a wide polydispersity as discussed in the following paper of the present s e r i e s (25). Perhaps the polydispersity contributes to the solubility of the initial high molecular weight fractions with Ba++ a s precipitant, assuming t h a t the low molecular weight molecules peptize or disperse the high n~olecular weight material.…”

“…and visible absorption, methoxyl content, neutralization equivalent, electrophoresis, viscosity, and X-ray diffraction are reported. Succeeding papers (25,26) will deal with ultracentrifugal sedimentation analysis and the size and shape of the macromolecule.…”

Analise da unidade de recuperação do licor negro de eucalipto no processo "Kraft", avaliando alternativas de processamento

“…• sooc (Alen, Patja e Sjostrom, 1979); (Whalen. 1975); (Gupta e Goring. 1960); (K.ringstad e Morck, 1983); (Sarkanen et al, 1981 ); (Obiaga e Wayman, 1983) e (Lindstrom, 1979).…”