Number- and Weight-Average Molecular Weights for Some Proanthocyanidin Polymers (Condensed Tannins)

The number-average molecular weights (Mn) and weight-average molecular weights (Mw) for proanthocyanidin polymers (condensed tannins) have been measured by vapour pressure osmometry and low-angle laser light-scattering measurements in methanol. These confirm earlier findings (based on gel permeation chromatography of the peracetate derivatives of these polymers) that they are polydisperse. The results also indicate that the incidence of branching in the polymer chains increases as the average chain length increases.