Characterization of autohydrolysis aspen (P. tremuloides) lignins. Part 1. Composition and molecular weight distribution of extracted autohydrolysis lignin

1979 ◽  
Vol 57 (10) ◽  
pp. 1141-1149 ◽  
Author(s):  
Miranda G. S. Chua ◽  
Morris Wayman
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Blocking Agent ◽  
Low Molecular Weight ◽  
Aspen Wood ◽  
Milled Wood Lignin ◽  
Carbonium Ions ◽  
Distribution Studies

Extractive-free aspen wood meal was subjected to autohydrolysis at 195 °C for 5 min to 2 h, and the lignin extracted with 90% dioxane. Extracted autohydrolysis lignin was found to be higher in carbon but lower in hydrogen and oxygen content than aspen milled wood lignin. The methoxyl content was also lower than the reference lignin. These differences have been attributed to condensation and incorporation into the lignin of non-lignin components. A lignin extractability curve with a maximum delignification at autohydrolysis time of 30–40 min was found. From molecular weight distribution studies the ratio of high molecular weight to low molecular weight materials varied for the different extracted lignins and reached a maximum at autohydrolysis time of 40 min. A mechanism of depolymerization/repolymerization of the lignin via carbonium ions has been proposed. p-Hydroxybenzoic acid is postulated as contributing to the extractability of aspen lignin by acting as a blocking agent.

Characterization of autohydrolysis aspen (P. tremuloides) lignins. Part 2. Alkaline nitrobenzene oxidation studies of extracted autohydrolysis lignin

1979 ◽  
Vol 57 (19) ◽  
pp. 2599-2602 ◽  
Author(s):  
Morris Wayman ◽  
Miranda G. S. Chua
Keyword(s):  
Molecular Weight ◽  
Molar Ratio ◽  
Low Molecular Weight ◽  
Aspen Wood ◽  
Milled Wood Lignin ◽  
Wood Meal ◽  
Nitrobenzene Oxidation ◽  
Carbon Carbon Bonds ◽  
Degree Of Condensation

Alkaline nitrobenzene oxidation of the lignins extracted from extractive-free aspen wood meal after autohydrolysis at 195 °C for periods varying from 5 min to 2 h indicated that these lignins were structurally more condensed in terms of an increase in new carbon–carbon bonds than aspen milled wood lignin. The degree of condensation generally increased with longer autohydrolysis times. It is postulated that condensation involved materials from both the carbohydrate and lignin components of the wood which were generated during the autohydrolysis. The molar ratio of syringaldehyde to vanillin of extracted lignin on oxidation was observed to decrease with increasing autohydrolysis time. It is suggested that syringyl units are preferentially extracted as low molecular weight material.

A Progress in Development and Application of Size Exclusion Chromatograph/Multi-Angle Laser Light Scattering

2014 ◽  
Vol 936 ◽  
pp. 1597-1602
Author(s):  
Xue Yang ◽  
Ze Quan Liu ◽  
Qiang Zhang
Keyword(s):  
Molecular Weight ◽  
Light Scattering ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Laser Light ◽  
Laser Light Scattering ◽  
Size Exclusion

This paper reveals the development and significance of size exclusion chromatograph/multi-angle laser light scattering(SEC-MALLS) for determination of the molecular weight and characterization of the molecular weight distribution. This technque has been applied in many aspects, such as biology, polymer and carboxylate surfactant. It has made a big contribution to study the property of macromolecular substances.

Characterization of Elution Chromatography Fractions from CIS-Polybutadiene by GPC

1970 ◽  
Vol 43 (6) ◽  
pp. 1439-1450 ◽  
Author(s):  
W. V. Smith ◽  
S. Thiruvengada
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Low Molecular Weight ◽  
Molecular Weight Distributions ◽  
Weight Distributions ◽  
Log Normal ◽  
Analytical Fractionation ◽  
Molecular Weight Fractions ◽  
Elution Chromatography

Abstract A preparative fractionation of about 23 g of a commercial cis-polybutadiene rubber is described. The method employed was a solvent elution chromatographic method with very little temperature gradient. The molecular weight distributions of the fractions obtained were determined by an analytical fractionation of 20 mg of polymer. The method was similar to the preparative fractionation and involved solvent elution chromatography. The fractions obtained were assayed for quantity, molecular weight, and molecular weight distribution by GPC. The low molecular weight fractions of the preparative fractionation had molecular weight distributions which could be closely approximated by two log normal distributions, the low molecular weight component having the narrower width. The ratio of weight to number average molecular weight was found to be about 1.1 for these samples. The higher molecular weight fractions could also be approximated by two log normal distributions; however, in these fractions the low molecular weight component had a very broad distribution but constituted only a small portion of the sample. The widths of the GPC curves of the fractions correlate satisfactorily with the molecular weight distributions found by the analytical refractionations. The GPC width is a sensitive criterion of the width of the molecular weight distribution even when only two columns are used. It is felt that the analytical fractionation procedure presented gives more detailed information on the molecular weight distribution than is easily obtainable from an ordinary GPC curve.

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