Thermal polymerization of methyl (meth)acrylate (MMA) was carried out using 2-cyanoprop-2-yl-1-dithionaphthalate (CPDN) and cumyl dithionaphthalenoate (CDN) as chain transfer agents. The kinetic study showed the existence of induction period and rate retardation, especially in the CDN mediated systems. The molecular weights of the polymers increased linearly with the monomer conversion, and the molecular weight distributions (M-w/M(n)s) of the polymers were relatively narrow up to high conversions. The maximum number-average molecular weights (M(w)s) reached to 351900 g/mol (M-w/M-n = 1.47) and 442 400 g/mol (M-w/M-n = 1.29) in the systems mediated by CPDN and CDN, respectively. Chain-extension reactions were also successfully carried out to obtain higher molecular weight PMMA and PMMA-block-polystyrene (PMMA-b-PSt) copolymer with controlled structure and narrow M-w/M-n. Thermal polymerization of methyl acrylate (MA) in the presence of CPDN, or benzyl (2-phenyl)-1-imidazolecarbodithioate (BPIC) also demonstrated "living"/controlled features with the experimented maximum molecular weight 312 500 g/mol (M-w/M-n = 1.57). The possible initiation mechanism of the thermal polymerization was discussed. (c) 2006 Elsevier Ltd. All rights reserved.