A kinetic approach to multifunctional polymerization with cyclization

A kinetic model for the step growth polymerization of multifunctional monomers RAf valid up to the gel point has been presented which accounts for the intramolecular reactions. From the Jacobson‐Stockmeyer equation, the average rats constant for this step has been derived and is found to be chain length dependent. A computation scheme has been evolved by which the molecular weight distribution of the linear, branched as well as cyclized polymer can be determined up to the gel point. It is found that even though the molecular weight distribution of cyclic oligomers is little affected for the range of the values of the intramolecular rate constant (kc) studied, the average chain length μn and the polydispersity index p of the polymer formed are extremely sensitive to kc near the gel point. Numerical computations confirm that as the gel point is approached, larger polymer chains are formed which have a higher tendency to react intramolecularly. However, even at high conversions the number of the cyclic rings per polymer chain remains small, which is consistent with experimentally observed results.