Reply to Gordon and Judd

Abstract

ALTHOUGH expressions similar to that of Flory¹ have been derived by several authors for the size distribution in branched polymers it has been assumed, implicitly or explicitly, in such derivations that the conversion α equals the probability that a functional group chosen at random has reacted. We have shown that, because functional groups never occur singly after their mutual condensation, but always in pairs, the choice between a “reacted” and an unreacted functional group is not meaningful. Our choice must lie between unreacted groups and reacted pairs. Flory's incorrect use of α in this respect led immediately to a divergence at α=1/(f−1) in his expression for the size distribution. This led Flory, and subsequently many other investigators, to the belief that this divergence corresponded to the gel point. It is hardly surprising that others with the same assumption derived the same result as Flory.