Branching frequencies have been determined by dilute solution measurements through evaluation of the radius of gyration, either directly by light scattering or indirectly through the intrinsic viscosity. A third possibility is presented by the decrease in the second virial coefficient, A2, with branching. Through use of a semi‐empirical relation between A2 and [η], it is shown that a reasonable approximation over a wide range of branching frequencies should be furnished by: where the quantities designated by an asterisk refer to the branched polymer, and the corresponding unmarked quantities to a linear polymer having the same molecular weight. The validity of the approximate relation between A2 and branching is confirmed using the data of Thurmond and Zimm for linear and branched polystyrene, and using data for linear and branched polyethylene presented here. This procedure should prove useful inasmuch as the molecular weight of a branched polymer must be determined by an absolute method, and the branching frequency can be estimated through the A /A2 ratio from these same data.
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Krigbaum et al. (1958) studied this question.