An Evaluation of the Impact of SG1 Disproportionation and the Addition of Styrene in NMP of Methyl Methacrylate

A kinetic modeling study is presented for batch nitroxide mediated polymerization (NMP) of methyl methacrylate(MMA; nitroxide: N-tert-butyl-N-[1-diethylphosphono-(2,2-dimethylpropyl)] (SG1)). Arrhenius parameters for SG1 dis-proportionation (A 5 1.4 107Lmol21s21;Ea5 23 kJ mol21) are reported, based on homopolymerization data account-ing for unavoidable temperature variations with increasing time, that is, nonisothermicity. For low targeted chain lengths(TCLs  300), this nonisothermicity is also relevant for NM P of MMA with a small amount of styrene. Parameter tuningto copolymerization data confirms a penultimate monomer unit effect for activation (sa25 ka12/ka2256.7; 363 K;1: MMA; 2: styrene). To obtain, for a broad TCL range (up to 800), a dispersity well below 1.3 an initial styrene massfraction of ca. 10% is required. An interpretation of the comonomer incorporation is performed by calculating the frac-tions of activation-growth-deactivation cycles with a given amount of monomer units and the copolymer compositiondistribution.