Reactions of the adduct radical obtained by addition of the initiator-derived 2-carbomethoxy-2-propyl radical to methyl alpha-[(2-methyl-2carbomethoxy)propyl]acrylate (the unsaturated dimer of methyl methacrylate (MMAD)) have been monitored by electron paramagnetic resonance spectroscopy. Rate constants for addition of the 2-carbomethoxy-2-propyl radical to NMAD, mutual reactions between the adduct radicals, and reactions of the adduct radical and the 2-carbomethoxy-2-propyl radical, and beta-fragmentation of the adduct radical were evaluated by steady-state and non-steady-state kinetic analysis in tandem with computer modeling and simulations involving parameter optimization procedures. The resulting rate constants showed that addition and radical-radical reactions between low molecular weight radicals are suppressed due to the marked steric congestion of the carbon-carbon double bond and radical center, respectively, and that beta-fragmentation can compete with radical-radical reactions of the adduct radicals depending on the radical concentration. (C) 2003 Elsevier Science Ltd. All rights reserved.