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The polymerization of styrene in the presence of a stable radical, TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy), has been simulated using a Predici simulations package. On the basis of the experimental data, a kinetic model for the TEMPO-mediated polymerization of styrene is proposed. In order to simulate the experimental data properly, it was necessary to include thermal self-initiation, transfer, and irreversible decomposition of intermediate alkoxyamines in addition to the reversible cleavage of the TEMPO-polymeric radical adduct. This model, combined with the values of the rate constants of propagation (k p), termination (k t), transfer (k trm), and alkoxyamines decomposition (k decomp), was then employed to estimate the kinetic and thermodynamic parameters for the exchange between dormant and active species. The equilibrium constant, K, was estimated to be approximately 10-11 mol·L-1, the deactivation rate constant, k d = 8 × 107 mol-1·L·s-1, and the activation rate constant, k a = 8 × 10-4 s-1, for bulk styrene polymerization at 120 °C.

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Radical polymerizations cannot truly be ‘living’ because of the inevitable termination between growing radicals. However, relatively good control of molecular weights, polydispersities and terminal functionalities can be achieved by using either unimolecular or bimolecular exchange between growing radicals and dormant chains. The dormant chains can be in the form of either covalent species or organometallic compounds. Some systems based on alkoxyamines, organochromium compounds, organoaluminum compounds and alkyl iodides were studied and are discussed in detail.