MECHANISM OF CONTROLLED LIVING RADICAL POLYMERIZATION OF STYRENE IN THE PRESENCE OF NITROXYL RADICALS - KINETICS AND SIMULATIONS/

The polymerization of styrene in the presence of a stable radical, TEM PO (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 prop osed. In order to simulate the experimental data properly, it was nece ssary to include thermal self-initiation, transfer, and irreversible d ecomposition of intermediate alkoxyamines in addition to the reversibl e cleavage of the TEMPO-polymeric radical adduct. This model, combined with the values of the rate constants of propagation (k(p)), terminat ion (k(t)), transfer (k(trm)), and alkoxyamines decomposition (k(decom p)), was then employed to estimate the kinetic and thermodynamic param eters for the exchange between dormant and active species. The equilib rium constant, K, was estimated to be approximately 10(-11) mol . L(-1 ) the deactivation rate constant, k(d) = 8 x 10(7) mol(-1). L . s(-1), and the activation rate constant, k(a) = 8 x 10(-4) s(-1), for bulk s tyrene polymerization at 120 degrees C.