1,2-polymerization of 1,3-butadiene with Cr(acac)3-alkylaluminum catalysts

The polymerization of butadiene (Bd) with chromium(III) acetylacetonato [Cr(acac)(3)] -trialkylaluminum (AIR(3)) or methylaluminoxane (MAO) catalysts was investigated for the synthesis of 1,a-poly(Bd). The polymerization of Ed was found to proceed with Cr(acac)(3)-AlR3 (R-Me, Et, i-Bu) catalysts to give poly(Bd) with a high 1,a-vinyl content, but highly isotactic 1,2-poly(Bd) was not synthesized. The Cr(acac)(3)-MAO catalyst gave a polymer consisting of low 1,2 units. The effects of the Al/Cr mole ratios on the polymerization of Bd with the Cr(acac)(3)-AlR3 catalysts were observed. With an increase of Al/Cr mole ratios, the isotactic (mm) content of the polymer increased but the 1,2-vinyl contents decreased. The effects of the aging time and temperatures of the catalysts on the polymerization of Ed with the Cr(acac)(3)-AlR3 catalysts were also observed, and the lower polymerization temperature and the prolonged aging time were favored to produce the 1,2-vinyl structure. (C) 2000 John Wiley & Sons, Inc.