Modeling of nitroxide-mediated semibatch radical polymerization

A mechanistic model is developed for high-temperature (138 degrees C) styrene semibatch thermally and conventionally initiated FRP, as well as NMP with a two-component initiating system (tert-butyl peroxyacetate, 4-hydroxy-TEMPO). The model, using kinetic coefficients from literature, provides a good representation of the FRP experimental results. Implementation of a gel effect correlation to represent the change in the diffusion- controlled termination rate coefficient with conversion improves the fit to the thermally initiated system, but is not required to represent the production of low molecular weight material ((M) over bar (n) < 10 000 Dalton) by conventionally initiated FRP or NMP. The low initiator efficiency found in NMP is well explained by a reaction network involving combination of free nitroxide with methyl radicals formed from initiator decomposition.