The molecular weight distribution (MWD) is derived for polymers generated by self-condensing vinyl polymerization (SCVP) of a monomer having a vinyl and an initiator group (“inimer”) in the presence of a multifunctional initiator. If the monomer is added slowly to the initiator solution (semi-batch process), this leads to hyperbranched polymers with a multifunctional core. If monomer and initiator are mixed simultaneously (batch process), even at vinyl group conversions as high as 99%, the total MWD consists of polymers which have grown via reactions between inimer molecules (i.e., the normal SCVP process) and those which have reacted with the initiator. Consequently, the weight distribution, w(M), is bimodal. However, the z-distribution, z(M), equivalent to the “GPC distribution”, w(log M) vs log M, is unimodal.

The molecular weight distribution and its moments for the hyperbranched polymer formed by the polycondensation of an AB2 type monomer with a multifunctional core moiety were derived rigorously by means of the kinetic method. The variations of several molecular parameters of the growing polymer during the reaction were estimated. The presence of a small amount of multifunctional core molecules, RB f , in the polycondensation system of AB2 type monomers is found to lead to a marked reduction in the polydispersity index of the final polymer. During the polymerization process, the molecular weight distribution first becomes broader with increasing conversion of A groups and then abruptly becomes considerably more narrow as the reaction approaches completion. The greater the number of functional groups in the core moiety, the narrower the final molecular weight distribution of the polymer.

The kinetic model of the self-condensing vinyl polymerization (SCVP) with nonequal molar concentrations of stimulus and monomer was developed in this work. The molecular size distribution function and other molecular parameters of the resulting hyperbranched polymers were derived. The feed ratio of stimulus to monomer significantly affects the molecular parameters of the products. The residual monomer and inimer in the reaction system have an important influence on the molecular parameters of the hyperbranched polymers obtained even at a high double-bond conversion. Similarly to the SCVP with nonequal reactivities and self-condensing vinyl copolymerization, the maximum of the degree of branching is 0.5 for the SCVP with nonequal molar concentrations of stimulus and monomer. In other words, when the molar ratio of stimulus to monomer approaches 0.627 and the vinyl conversion reaches 1, we can get the hyperbranched polymers with the highest degree of branching.

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