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Synthesis of oligomeric models of coal derived materials for use with GPC calibration. Quarterly report, July-September 1983

Technical Report ·
OSTI ID:5649645

A series of model oligomers were used to calibrate a series of four high pressure gel permeation columns. Three types of model compounds used in the experiment were commercially prepared polystyrene polymers, a series of oligo(aryl ethers) prepared at our laboratory and a series of oligo(aryl methylenes) prepared at our laboratory. It was found that a nearly linear relationship exists between the logarithm of the molecular weight and the retention volumes using tetrahydrofuran solvent as long as the aryl groups in the oligomer were of the benzenoid type. Aryl oligomers containing more condensed ring systems such as naphthyl or phenanthryl moieties give too great a retention volume for their actual molecular weight. Tests with a few low molecular weight hydroxyl containing oligomers give too small a retention volume, indicating that hydrogen bonding with the solvent is occurring. Samples of relatively narrow molecular weight ranges of lignite-derived preasphaltenes and asphaltenes were also analyzed using the same system. In these experiments the samples were acetylated and their number average molecular weight values measured by vapor pressure osmometric means. In the range 2000 to 3000 g/mole, these samples fit the same calibration plot as the polystyrene and aryl-ether oligomers. Those asphaltenes with a high degree of aromatic condensation, particularly at low molecular weight, behaved in a fashion analogous to our more condensed models, i.e., the retention volumes were too large. We plan to investigate this phenomenon further by preparing some vinylnaphthalene, and vinylpyrene oligomers as calibration standards in our future work. 15 references, 3 figures, 5 tables.

Research Organization:
North Dakota Univ., Grand Forks (USA). Dept. of Chemistry
DOE Contract Number:
FG22-81PC40810
OSTI ID:
5649645
Report Number(s):
DOE/PC/40810-7; ON: DE84002050
Country of Publication:
United States
Language:
English