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 tempera ture and the [TEMPO](o)/[H2O2](o) initial molar ratio, gamma(o)), were stud ied to optimize the reaction. It was observed that the higher the temperatu re, the higher the yield, with optimal yields noted for gamma(o) = 0.10 wit h high molecular weights and broad polydispersity indexes. In addition, the kinetics of radical polymerization showed a decrease (by one order of magn itude) of the macroradical concentration all along the reaction. The In [bu tadiene]/[butadiene], increased relative to time and behaved linearly after 90 min. Further, the concentration of free TEMPO was approximate to 1000 t imes lower than the initial concentration, in good agreement with the decol oring of the medium. Thus a quasi-living behavior of butadiene was noted fr om this system. Finally, the hydrolysis of these oligomers, either in the p resence of zinc or thermally by means of a thin-layer evaporator under vacu um allowed the production of telechelic hydroxy polybutadienes, the second technique enabling the obtaining of higher molecular weights by coupling an d the recovery of TEMPO. (C) 2000 John Wiley & Sons, Inc.