Controlled radical polymerization of 1,3-butadiene. II. Initiation by hydrogen peroxide and reversible termination by TEMPO

The radical polymerization of 1,3-butadiene initiated by hydrogen peroxide and controlled by TEMPO is presented. Various parameters (e.g., the temperature and the [TEMPO]o/[H2O2]o initial molar ratio, γo), were studied to optimize the reaction. It was observed that the higher the temperature, the higher the yield, with optimal yields noted for γo = 0.10 with high molecular weights and broad polydispersity indexes. In addition, the kinetics of radical polymerization showed a decrease (by one order of magnitude) of the macroradical concentration all along the reaction. The ln [butadiene]/[butadiene]o increased relative to time and behaved linearly after 90 min. Further, the concentration of free TEMPO was ≈1000 times lower than the initial concentration, in good agreement with the decoloring of the medium. Thus a quasi-living behavior of butadiene was noted from this system. Finally, the hydrolysis of these oligomers, either in the presence of zinc or thermally by means of a thin-layer evaporator under vacuum allowed the production of telechelic hydroxy polybutadienes, the second technique enabling the obtaining of higher molecular weights by coupling and the recovery of TEMPO.