Comparison of Number—Average Molecular Weights Calculated by GPC and Membrane Osmometry

1973 ◽  
Vol 46 (1) ◽  
pp. 115-126
Author(s):  
M. R. Ambler ◽  
R. D. Mate
Keyword(s):  
Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Appreciable Amount ◽  
Diffusion Limit ◽  
Low Molecular Weight ◽  
Molecular Weights ◽  
True Value ◽  
Usual Manner ◽  
Gel Permeation ◽  
Polymer Species

Abstract Data are presented which show that when a polymer contains an appreciable amount of low molecular weight species below the diffusion limit of the osmometer membrane, the osmotic molecular weight, Mn, is generally higher than the Mn calculated from gel-permeation chromatography (GPC). Experiments were performed on samples of poly(vinylchloride) (PVC) and high-cis poly (butadiene) polymers. Osmotic data were obtained in the usual manner, while GPC data were obtained using the universal calibration approach. It was found that when all polymer species below approximately 10,000 molecular weight were excluded from the calculation of Mn by GPC, agreement in Mn was obtained between membrane osmometry and GPC. The data obtained suggest that the choice of Mn as measured by membrane osmometry in the calibration of the GPC should not be done casually, as the measured Mn may not reflect the “true” value of that sample, especially when the polymer sample contains an appreciable amount of low molecular weight material.

Molecular Weight Measurements of Low Molecular Weight Heparins by Gel Permeation Chromatography

1997 ◽  
Vol 77 (04) ◽  
pp. 668-674 ◽  
Author(s):  
B Mulloy ◽  
C Gee ◽  
S F Wheeler ◽  
R Wait ◽  
E Gray ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Low Molecular Weight Heparin ◽  
High Performance ◽  
Gel Permeation Chromatography ◽  
Low Molecular Weight ◽  
Low Molecular Weight Heparins ◽  
Molecular Weights ◽  
Calibration Table ◽  
Gel Permeation ◽  
Degraded Material

SummaryThe molecular weight profiles of low molecular weight heparin samples have been measured by high-performance gel permeation chromatography using as calibrant the heparinase-degraded material (90/686) now established as the 1st International Reference Preparation (IRP) Low Molecular Weight Heparin for Molecular Weight Calibration. Use of the calibrant as a broad molecular weight standard is described and a calibration table provided based on data collected over several years in one laboratory.In order to confirm the assignment of degree of polymerisation to resolved oligosaccharide peaks in the calibrant, molecular weights of oligosaccharides fractionated from the 1st IRP were independently determined by fast atom bombardment mass spectrometry (FAB MS).The molecular weight distributions of commercial low molecular weight heparins have been characterized. Measurements of molecular weight parameters of heparin molecular weight standards from several sources provide comparisons between the molecular weight scales of this and other studies.

Structural studies of oligosilanes produced by catalytic dehydrogenative coupling of primary organosilanes

1987 ◽  
Vol 65 (8) ◽  
pp. 1804-1809 ◽  
Author(s):  
C. Aitken ◽  
J. F. Harrod ◽  
U. S. Gill
Keyword(s):  
Molecular Weight ◽  
Nuclear Magnetic Resonance ◽  
Gel Permeation Chromatography ◽  
Structural Studies ◽  
Molecular Weights ◽  
Molecular Weight Distributions ◽  
Dehydrogenative Coupling ◽  
Weight Distributions ◽  
Gel Permeation ◽  
End Groups

The structures of some poly(organosilylenes), [Formula: see text] (R = Ph, p-tolyl, n-hexyl, and benzyl), produced by catalytic dehydrogenative coupling of primary silanes have been studied by infrared, nuclear magnetic resonance, and mass spectroscopies. These results, combined with data on molecular weights and molecular weight distributions from vapour pressure osmometry and gel permeation chromatography, lead to the conclusion that the polymers are linear and have SiH2R end groups. The polymers all have degrees of polymerization of ca. 10 and very narrow molecular weight dipersions. Some possible features of the mechanism that gives rise to this behaviour are discussed.

scholarly journals Fractionation of lignosulphonates released during the early stages of delignification

1983 ◽  
Vol 61 (2) ◽  
pp. 416-420 ◽  
Author(s):  
Norman G. Lewis ◽  
David A. I. Goring ◽  
Alfred Wong
Keyword(s):  
Molecular Weight ◽  
High Performance ◽  
Black Spruce ◽  
Gel Permeation Chromatography ◽  
Bimodal Distribution ◽  
High Yield ◽  
Low Molecular Weight ◽  
Lower Yield ◽  
Spruce Wood ◽  
Gel Permeation

High-yield spent bisulphite liquor (HY-SBL) from sulphonated black spruce wood (Piceamariana) was fractionated by gel permeation chromatography (GPC) and by high-performance liquid chromatography (HPLC). The GPC fractionation gave a wide bimodal distribution, whereas with HPLC, a more detailed resolution was seen with the bulk of the fraction giving several clearly defined peaks. The paucidisperse material was further concentrated by a bulk fractionation of the crude SBL which included complexing the lignosulphonates with dicyclohexylamine. The isolated paucidisperse material was found to be dialyzable and to constitute 90% of the lignosulphonate in the sample of SBL. If the bisulphite pulp obtained was recooked in fresh acid sulphite liquor to a lower yield, most of the lignosulphonate dissolved was widely polydisperse with no indication of the discrete components resolvable by HPLC. However, 25% of the lignin made soluble was in the form of the paucidisperse fractions. In all, we were able to obtain about 50% of the lignin in spruce wood as a relatively low molecular weight lignosulphonate resolvable into discrete fractions by HPLC.

Gel Permeation Chromatography of Natural Rubber

1972 ◽  
Vol 45 (1) ◽  
pp. 346-358 ◽  
Author(s):  
A. Subramaniam
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Weight Distribution ◽  
Hevea Brasiliensis ◽  
Distribution Curve ◽  
Gel Permeation Chromatography ◽  
Bimodal Distribution ◽  
Fractional Precipitation ◽  
Molecular Weights ◽  
Gel Permeation

Abstract The Waters Model 200 Gel Permeation Chromatograph has been used to study the molecular weight distribution of natural rubber. The cumulative weight distribution curve of synthetic cis-polyisoprene from the GPC method showed fair agreement with the distribution obtained by fractional precipitation. For natural rubber the agreement was not so good. Natural rubber samples from six clones of Hevea Brasiliensis were examined with the GPC. Differences were observed in their distributions. Five clones showed a distinct bimodal distribution. The weight and number average molecular weights from the GPC were found to be too low. Some possible reasons for this have been suggested.

Characterization of LARCTM-CPI 2 poly(amide acid) aging by gel permeation chromatography/differential viscometry

1995 ◽  
Vol 7 (1) ◽  
pp. 55-68 ◽  
Author(s):  
E J Siochi ◽  
S J Havens ◽  
P R Young ◽  
P M Hergenrother
Keyword(s):  
Molecular Weight ◽  
Fourier Transform ◽  
Infrared Spectroscopy ◽  
Gel Permeation Chromatography ◽  
Concentrated Solutions ◽  
Solution Property ◽  
Molecular Weights ◽  
Gel Permeation ◽  
Property Changes

A controlled-molecular-weight LARCr'-CPI 2 poly(amide acid) was synthesized to investigate solution property changes that result from aging'Both dilute and concentrated solutions were aged at five temperatures and periodically analysed over a 33 d period. Various molecular weight parameters were obtained by gel permeation chromatography in combination with differential viscometry. Chemical changes were also followed by Fourier transform infrared spectroscopy. The temperatures used allowed the calculation of the energy of activation associated with changes in weight and number average molecular weights.

Influence of Thermal Treatment on the Molecular Weights of Polyhydroxyalkanoate Containing 3-Hydroxyhexanoate

2013 ◽  
Vol 812 ◽  
pp. 250-253 ◽  
Author(s):  
Yoga Sugama Salim ◽  
Chin Han Chan ◽  
Kumar Sudesh ◽  
Seng Neon Gan
Keyword(s):  
Molecular Weight ◽  
Thermal Treatment ◽  
Gel Permeation Chromatography ◽  
Polymer Processing ◽  
Polymer Chains ◽  
Molecular Weights ◽  
Gel Permeation ◽  
Ftir Spectrometer ◽  
Major Reduction ◽  
End Group

With blooming interests in the research of biodegradable polyesters produced from microorganisms as well as polymer processing and technology, this study is intended to reveal the influence of thermal treatment on the molecular weight of poly (3-hydroxybutyrate-co-3 mol% 3-hydroxyhexanoate)/P(3HB-co-3 mol% 3HHx), a copolymer of polyhydroxyalkanoates (PHA). P(3HB-co-3 mol% 3HHx) was thermally treated using Differential Scanning Calorimeter and analyzed using Gel Permeation Chromatography and Attenuated Total Reflectance-Fourier transform infrared (ATR-FTIR) spectrometer. Results from gel permeation chromatography suggest a major reduction of molecular weight up to 50 % when P(3HB-co-3 mol% 3HHx) is exposed to 180 °C for 30 mins. The half-time degradation of P(3HB-co-3 mol% 3HHx) treated at 170 °C and 180 °C is 14.1 and 9.9 mins, respectively. FTIR spectroscopy shows an increase absorbance intensity of P(3HB-co-3 mol% 3HHx) after thermal treatment, indicating a formation of more alkenyl and carboxylic end-group in polymer chains due to random chain scissions.

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