| Abstract: | An attempt has been made to prepare a high molecular weight isotactic polybutene-1 from cis- or trans-butene-2. Polymerization of butene-2 did not occur due to the steric effect of the substituents. In the presence of TiCl3–Al(C2H5)3 catalyst, however, both butene-2 monomers were found to polymerize at a slower rate than butene-1 and to give polymers consisting of the repeating unit of butene-1. From the gas chromatographic determination of the isomer distribution of the butenes recovered after the polymerization, it was found that the butenes isomerized, in the presence of the catalyst system containing TiCl3, to approach the thermodynamic equilibrium mixture of butene-1, cis-butene-2, and trans-butene-2. It was also found that the rates of polymerization of butene-2 for the catalyst systems used were proportional to the isomerization rates. These results show that butene-2 isomerizes first to butene-1 which has less steric hindrance and then polymerizes as butene-1, through ordinary vinyl polymerization by a coordinated anionic mechanism. This type of polymerization was observed in some other linear β-olefins such as n-pentene-2 and n-hexene-2. |
