Using a modified definition, the average degree of branching,, the fraction of branchpoints,, as well as the fractions of various structural units are calculated as a function of conversion of double bonds for hyperbranched polymers formed by self-condensing vinyl polymerization (SCVP) of monomers (or “inimers”) with the general structure AB*, where A is a vinyl group and B* is an initiating group. The results are compared to those for the polycondensation of AB 2 -type monomers. At full conversion, is somewhat smaller for SCVP ( ∞ ≈ 0.465) than for AB 2 systems ( ∞ = 0.5). There are two kinds of linear groups in SCVP whereas there is only one kind in AB 2 systems. Since there are two different active centers in SCVP, i.e., initiating B* and propagating A* centers, the effect of nonequal reactivities on is also discussed. At a reactivity ratio of the two kinds of active centers, r = k A /k B ≈ 2.59, a maximum value of ∞ = 0.5 is reached. For the limiting case r << 1, a linear polymer resembling a polycondensate will be formed whereas for r >> 1 a weakly branched vinyl polymer is expected. NMR experiments allow for the determination of reactivity ratio r .
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Yan et al. (1997) studied this question.