This is the first report on the catalytic room temperature free-radical polymerization of vinyl monomers, namely styrene (STY) and methyl methacrylate (MMA) using Co(II)TPP(Py) and aerial oxygen as a catalyst and a co-catalyst, respectively. The mechanism of polymerization has been investigated using H-1 NMR, differential scanning calorimeter (DSC), thermogravimetric (TGA) and gel permeation chromatography (GPC) analysis and a, radical pathway for the polymer formation is proposed. The rate of polymerization for the synthesis of active polymers of STY is higher than that of MMA, which has also been supported by computational studies. The active polymer, polystyrene (PS)-poly(styrene peroxide) (PSP) was also used for the synthesis of another block copolymer, PS-b-PMMA, by reacting PS-PSP with MMA. The mechanism of block copolymerization is discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.