(CH3)(3)SIBR ALCL3 INDUCED CATIONIC POLYMERIZATION OF 1,3-PENTADIENE/

Cationic polymerizations of 1,3-pentadiene (PD) with AlCl3 in n-hexane were carried out in the absence and presence of trimethylsilyl bromid e (Me3SiBr or TMSBr). Structural evidence and proton trap experiment d emonstrate that in the TMSBr/AlCl3 induced polymerization the real ini tiating system is the combination of AlCl3 with HBr resulting from hyd rolysis of TMSBr by adventitious water existing in the system. The con version of the polymerization is greatly increased by adding TMSBr, bu t the introduction of TMSBr does not exert an effect on the formation of gel (crosslinked product). The molecular weight of the polymer prep ared by TMSBr/AlCl3 system shows a maximum in the range of [TMSBr]/[Al Cl3] = 1, and excessive TMSBr gives rise to a drop of the polymer mole cular weight. Kinetic data show that AlCl3 and TMSBr/AlCl3 induced pol ymerizations have the comparable polymerization rates.