KINETICS OF END CROSS-LINKING IN DENSE POLYMER MELTS

The kinetics of the end crosslinking process in linear-polymer melts is studied using molecular-dynamics simulations. Starting from an equilibrated melt, tetrafunctional crosslinkers are attached randomly to a fraction x of the chain ends. The system is then allowed to evolve. When a free end comes within a short reaction radius r(x) from an unsaturated crosslinker, the chain ends are attached. Two cases can be distinguished. In the first, with a stoichiometric number (x(s) = 1/4) of crosslinkers present, the time dependence of such quantities as the number of free ends and the number of unsaturated crosslinkers decays as a power law in time t(-a) with a almost-equal-to 0.5. However, for x not-equal x(s), the decay is significantly faster.