The free radical polymerization (FRP) is one of the most important processes used in polymer synthesis and presents several advantages, such as it is tolerant to impurities, applicable to most of monomers under mild reaction conditions, can be used in copolymerizations, among others. Despite presenting several advantages, this technique has some limitations related to the control of some important properties of the polymer, such as polydispersity, chain architecture and molecular weight. To overcome these limitations arose the living free radical polymerization (LFRP), capable of producing polymers with narrow molecular weight distributions and polydispersity close to unity. There are some techniques for controlled polymerization among those, the nitroxide mediated radical polymerization (NMRP) using TMEPO (2,2,6,6-tetramethyl-1-piperidinyloxy) as a control agent is one of the most effective, versatile, safe, cheap and simple. In this work bulk polymerization of styrene in the presence of sodium bicarbonate was performed, using TEMPO as controlling agent. Sodium bicarbonate was added to the reaction medium in order to understand its effect on the reaction kinetics. The reactions were performed in ampoules in a bath with fluid circulation. The synthesized material was characterized by gravimetric analysis.