Asphalt obtained from a refinery in Montreal was dissolved in toluene then fractionated in a preparative gel permeation chromatograph (prep.-GPC). Twenty-three fractions differing widely in molecular weights were collected and characterized by analytical GPC, viscometry, vapor pressure osmometry (VPO), element analyses, infrared spectroscopy (IR), and nuclear magnetic resonance spectroscopy (NMR). Similar studies were also carried out, for comparison purposes, on aliphatic and aromatic hydrocarbons to elucidate structure information on the different asphalt fractions.The GPC chromatograms of the fractions generally revealed narrow distributions indicating that their separation into different component groups has been reasonably well achieved. The number-average molecular weights fin of the fractions, as computed from their GPC chromatograms making use of the calibration curve prepared with polystyrene, polyoxypropylene glycol, and polyoxyethylene glycol, did not correspond to those obtained by the VPO technique. To overcome the problem, an alternate approach was developed whsreby anumber of calibration curves were tested for the asphalt fractions, and the one which yielded the f i n values closest to those found by VPO method was *any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming, and recording, or by any information storage and retrieval system, without permission in writing from the publisher. Downloaded by ["Queen's University Libraries, Kingston"] at 23:22 02 January 2015 608 KIET. BLANCHARD, AND MALHOTRA retained for the present study. fiW values could then be computed and related with [s] to calculate the Mark-Houwink constants K and a.Aliphatic hydrocarbons were found to obey the "Benoit theory" according to which the elution volume of solutes is controlled exclusively by their hydrodynamic volumes. Aromatic hydrocarbons, however, were found to diverge considerably from this theory. The asphalt fractions were found to dcviate somewhat from the Benoit theory but the extent to which this occurred was less than that observed with pure aromatic hydrocarbons.The GPC, IR, NMR, and elements analyses resuIts show that the aromaticity and the naphthenic carbon content of the fractions 5 to 9 in the intermediate molecular weight range are small while the paraffinic carbon content is maximum. Their unit sheet weight is 900 and is independent of their molecular weight. These appear to be made up of a number of unit sheets linked together rather than a single large pericondensed ring system.
