Novel telechelic 2-methyl-2-bromopropionate terminated polyurethane macroinitiator was synthesized and used further to polymerize methyl methacrylate to yield poly(methyl methacrylate)-block-polyurethane-block-poly(methyl methacrylate) triblock copolymers through atom transfer radical polymerization. Number-average molecular weight (M n ) was increased linearly with increasing polymerization time and conversion. Molecular weight distribution becomes narrower as the polymerization time increases and theoretical M n values of the tri-block copolymers were comparable to the experimental M n values. Structures of the macroinitiator and the tri-block copolymers were confirmed by 1 H NMR, 13 C NMR and FT-IR spectroscopic techniques. Mole percentage of poly(methyl methacrylate) in the triblock copolymers was calculated using 1 H NMR spectroscopy and was found to be comparable with the gel permeation chromatography results. Presence of two phases in the tri-block copolymers has been confirmed through differential scanning calorimetric studies.KEY WORDS: ATRP / Block Copolymers / Poly(methyl methacrylate) / Polyurethanes / Living anionic polymerization was first discovered by Szwarc, 1 where polymer chain propagation took place without chain breaking reactions such as chain transfer and chain termination. As a result polymers with defined molecular weight, narrow molecular weight distribution (MWD) and desired end groups were achieved through this method. But it requires stringent experimental conditions and highly pure monomers and solvents. On contrary, free radical polymerization is used widely to polymerize more than 70% of vinyl and acrylate monomers in industries but it has poor control over degree of polymerization, MWD and end functionalization during polymerization. In recent years, the idea of introducing livingness in free radical polymerization was proposed and it was termed as controlled radical polymerization (CRP).2 As the conversion increases M n also should increase linearly in any living polymerizations.2 In conventional radical polymerization there is no linear increase of molecular weight with the conversion.2 Hence in all CRP routes linear increase of molecular weight with conversion should takes place to show that they are following living polymerization mechanism.