Predicting the change of MWD caused by interchange reactions during melt-mixing of linear and branched polycondensates (AB(2))

During mix melting of hyperbranched AB2- and linear CD-polycondensates distributive properties are changing by interchange reactions. Two mathematical modeling approaches are presented: (i) Simplified approach of monodisperse population of three-arm stars undergoing interchange reactions, both analytical and by Monte Carlo simulations, assuming interchange as subsequent scission and recombination of fragments. (ii) Full system of interchange and polycondensation/hydrolysis reactions with Monte Carlo simulations and kinetic model describing reactions of free groups (A, B, C, D) and bonds (AB, CD, BC, AD). MC simulations show that the final molecular weight and branching distribution is attained after 10% of reaction time. The change of structure, from few large fragments to more, smaller ones, is slower.