SYNTHESIS AND ISOLATION OF OCTYLATED ASPHALTENE STANDARDS FOR CALIBRATION OF GPC COLUMNS AND DETERMINATION OF ASPHALTENE MOLECULAR-WEIGHTS

Seven fractions of octylated asphaltenes (OA) with average polydispersities equal to 1.13 +/- 0.01 (M(n) = 1500 to 12 300 daltons measured by v.p.o.-pyridine) were isolated by dialysis and used for the calibration of g.p.c. columns and measurement of asphaltene molecular weights. The v.p.o.-THF M(n) values of asphaltenes were reasonably predicted by the g.p.c. values. The slope of the graph of log M vs. t(r) (0.374) for octylated asphaltenes was similar to that for polystyrene standards (0.307). Thus, in spite of the structural differences between asphaltenes and polystyrene, the MW data predicted by polystyrene and OA calibrations were similar for the five samples examined.