Kinetics of End Crosslinking in Dense Polymer Melts

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Abstract
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 rx from an unsaturated crosslinker, the chain ends are attached. Two cases can be distinguished. In the first, with a stoichiometric number (xs = 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 α ≈ 0.5. However, for x ≠ xs, the decay is significantly faster.