Fractionation of woodmeal by prehydrolysis and thermal organosolv. Alkaline depolymerization, chemical functionality, and molecular weight distribution of recovered lignins and their fractions

1993 ◽  
Vol 71 (6) ◽  
pp. 779-789 ◽  
Author(s):  
Ronald W. Thring ◽  
Esteban Chornet ◽  
Ralph P. Overend
Keyword(s):  
Molecular Weight ◽  
Solvent Extraction ◽  
Phenolic Compounds ◽  
Nmr Spectroscopy ◽  
Elemental Composition ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Side Chain ◽  
Molecular Weight Fractions ◽  
C Nmr

Thermal organosolv glycol lignins and their fractions have been characterized by means of elemental composition, molecular weight distribution, and 1H and 13C NMR spectroscopy. Fractionation of each lignin by sequential solvent extraction produced fractions of increasing molecular weight and polydispersity. Structures in the highest molecular weight fractions were found to be linked by a high proportion of β-O-4 type bonds, whilst the lowest molecular weight fractions consisted of a high content of saturated aliphatic side-chain structures. A noticeable difference in the content of carbohydrate contaminants in both starting lignins indicated the formation of relatively stable lignin–carbohydrate complexes, especially in the lignin recovered from pretreated wood. In addition, depolymerization of the lignins and their fractions to monomeric compounds was explored using alkaline hydrolytic and nitrobenzene oxidative routes. The highest molecular weight fractions from each lignin were identified as the best candidates for production of useful monomeric phenolic compounds.

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.

scholarly journals Effects of Grinding Methods on Physicochemical Properties of Crude Polysaccharides from Phellinus baumii

2019 ◽  
Vol 78 ◽  
pp. 02004
Author(s):  
Tingting Li ◽  
Yan Yang ◽  
Linjun Chen ◽  
Wanling Yang
Keyword(s):  
Molecular Weight ◽  
Physicochemical Properties ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Raw264.7 Cells ◽  
Fruiting Bodies ◽  
Phellinus Baumii ◽  
Grinding Technique ◽  
Molecular Weight Fractions

The physicochemical properties of Phellinus baumii polysaccharides extracted from the fruiting bodies by different grinding methods were studied in this paper. Compared with ordinary grinding methods, superfine grinding technology exerts significantly higher yields of crude polysaccharides, polysaccharide contents and β-Glucan contents of six samples. HPSEC-MALLS- RI analysis shows the molecular weight distribution of P.baummii crude polysaccharides, which indicates superfine grinding technique generates higher molecular weight fractions and larger polydispersities. The 6 kinds of crude polysaccharides have obvious effects on NO generation of RAW264.7 cells, which indicated that crude polysaccharides from P.baumii may have some immune-enhancing effects. Meanwhile, CW30 and FP30 show the best immune enhancing effects. However, CW50 and CW70 exert weaker immune-enhancing effects compared with FP50 and FP70.

THE FRACTIONATION OF POLYTHENE

1961 ◽  
Vol 39 (10) ◽  
pp. 1888-1891 ◽  
Author(s):  
W. R. Blackmore ◽  
W. Alexander
Keyword(s):  
Molecular Weight ◽  
Distribution Function ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Negative Binomial ◽  
Average Molecular Weight ◽  
Weight Average Molecular Weight ◽  
Log Normal ◽  
Molecular Weight Fractions ◽  
Good Agreement

An apparatus is described for fractionating large quantities (400 g) of polythene into five roughly equal fractions using a fractional precipitation technique. Application of this method of fractionation to a linear polythene has shown that the width of the molecular-weight distribution of the successive fractions decreases as the fractionation proceeds. Consequently, the initial high-molecular-weight fractions require refractionation to produce equally narrow distributions in them as are found in later fractions. Good agreement is obtained with the experimentally determined values of the number-average and weight-average molecular weight for the parent polymer when the measured values of Mn and Mw for each fraction are used to calculate the values for the parent. The differential molecular-weight distribution function of the parent polymer was calculated on a Bendix G-15 computer from the data for the fractions by using the weight, number-average and weight-average molecular weight, measured for each fraction in conjunction with an assumed log-normal or negative binomial molecular-weight distribution function in each fraction.

Molecular Weight Distribution of Polystyrene and of Butadiene-Styrene Copolymers Prepared in Emulsion Systems

1970 ◽  
Vol 43 (6) ◽  
pp. 1424-1438
Author(s):  
C. A. Uraneck ◽  
J. E. Burleigh
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Homologous Series ◽  
Degree Of Branching ◽  
Styrene Copolymers ◽  
Divinyl Benzene ◽  
Emulsion Systems ◽  
Molecular Weight Fractions ◽  
Butadiene Styrene

Abstract Polystyrene and butadiene—styrene copolymers (SBR) were parepared in emulsion systems with a homologous series of commercial mercaptan modifiers. The molecular weight distribution (MWD) of the sets of polymers changed in a consistant manner when the regulating index of the mercaptan was relatively low. However the shape of the MWD curves appeared distorted in comparison to theoretical curves when the modifier depleted rapidly and when divinyl-benzene was present in the system. The divergence from the theoretical curve is attributed to a higher degree of branching in the high molecular weight fractions. Differences in MWD of SBR made with n- and tert-dodecyl mercaptans was marked. Notable differences were also found for SBR 1500 samples from the industry at random, but only slight differences were seen in a set of SBR 1503 samples. This study shows how the MWD of polymers prepared in emulsions can be varied simply by use of modifiers with different regulating indexes.

Reactions of silanes with bis(cyclopentadienyl)dialkylzirconium complexes

1991 ◽  
Vol 69 (2) ◽  
pp. 264-276 ◽  
Author(s):  
Ying Mu ◽  
Clare Aitken ◽  
Bruno Cote ◽  
John F. Harrod ◽  
Edmond Samuel
Keyword(s):  
Molecular Weight ◽  
Reaction Time ◽  
Nmr Spectroscopy ◽  
Key Words ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Active Catalyst ◽  
Systematic Comparison ◽  
H Nmr ◽  
Cyclic Polymer

A systematic comparison between the dimethylzirconocene (DMZ) and dimethyltitanocene (DMT) catalyzed dehydrocoupling of organosilanes is reported. The polymerization rates of primary silanes are about ten times faster for DMZ than for DMT, but the characteristics of the polymers produced are essentially identical. Variations of molecular weight and molecular weight distribution with varying monomer and reaction time, and the relative amounts of linear and cyclic polymer are also essentially the same for the two catalysts.Oligomerizations of phenylmethylsilane, diphenylsilane, and 1,2-diphenyldisilane are described. The compound Cp2Zr(SiPhMeH)(μ-H)2(SiPhMe2)ZrCp2 (1b) is isolated from the reaction of phenylmethylsilane with DMZ and its structure confirmed by crystallography and 1H-NMR spectroscopy. The compound Cp2Zr(Me)(μ-H)2(SiPh2H)ZrCp2 (1d) is isolated from the reaction of diphenylsilane with DMZ and its structure assigned by NMR spectroscopy. A number of other hydride bridged species are observed by 1H-NMR in the reactions of DMZ with phenylmethyl-, diphenyl-, and n-butylmethylsilanes and their structures are tentatively assigned. The implications of these observations on the mechanism of transformation of DMZ into active catalyst and our current views of the polymerisation mechanism are also discussed. Key words: silanes, dehydrocoupling, titanocene, zirconocene, polysilanes.

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