Hydrodynamic studies of dilute pitch solutions: The shape and size of pitch molecules

The shape and size of pitch molecules were discussed through the measurements of the intrinsic viscosity [η] and the diffusion coefficient D of molecular weight fractionated petroleum pitches in dilute chloroform solutions, where [η] was measured by an Ubbelohde viscometer, and D by Northrup-McBain diaphragm cells. Hydrodynamical considerations on the [η] vs D relationship lead to a conclusion that pitch molecules examined are of 3-dimensional structure, the axial ratio being 1–3 under the oblate ellipsoid assumption, and their sizes being about 10 ~ 20 Å in equatorial diameter.