6533b86efe1ef96bd12cbed4

RESEARCH PRODUCT

Effect of core-forming molecules on molecular weight distribution and degree of branching in the synthesis of hyperbranched polymers

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The polydispersity index, the molecular weight distribution (MWD), and the degree of branching ( ) are calculated for hyperbranched polymers obtained in self-condensing vinyl polymerization of AB* monomers in the presence of a core-forming molecule (i.e. a multifunctional initiator, Bf*). Two cases are considered:  (a) batch polymerization, i.e., with all components mixed together; (b) semibatch polymerization, i.e., slow addition of the monomer to the core-forming molecule. The results obtained for the latter case are also valid for polycondensation of AB2 monomers. The presence of core-forming molecules leads to a considerable narrowing of the MWD's, the polydispersity index decreasing with increasing initiator functionality, f. In the batch process, we find w/ n ≈ 1 + n/f2 and in the semibatch mode w/ n ≈ 1 + 1/f. The degree of branching obtained in semibatch mode approaches = 2/3, which is higher than for the synthesis using a batch process with or without initiator. The polymers resulting from semiba...