Effect of tert‐Butyl Chloride on the Isoprene Polymerization with Neodymium Isopropoxide/Diisobutylaluminum Hydride and Neodymium Isopropoxide/Methylaluminoxane Catalysts

The effect of tert ‐butyl chloride ( t BuCl) as a third catalyst component on the isoprene polymerization with neodymium isopropoxide (Nd(O i Pr) 3 )/diisobutylaluminum hydride (Al( i Bu) 2 H) and Nd(O i Pr) 3 /methylaluminoxane(MAO) catalysts was examined in heptane at a fixed [Al]/[Nd] ratio of 30 and reaction temperatures of 30 and 60 °C. The Nd(O i Pr) 3 /Al( i Bu) 2 H catalyst was inactive without t BuCl, i.e., at [Cl]/[Nd] = 0, while it showed the highest activity under the conditions of [Cl]/[Nd] = 3.0 and an addition order of {Al( i Bu) 2 H + t BuCl} + Nd(O i Pr) 3 to yield polyisoprene with relatively low molecular weight ( M n ca. 5 × 10 4 ), broad MWD ( M w / M n ca. 5.4), and high cis ‐1,4 content (ca. 96%) at 30 °C. On the other hand, the Nd(O i Pr) 3 /MAO catalyst was effective at [Cl]/[Nd] = 0, and the most active at [Cl]/[Nd] = 1.0–1.5 with an addition order of {Nd(O i Pr) 3 + MAO} + t BuCl to afford polymer with high molecular weight ( M n ca. 8 × 10 5 ), fairly narrow MWD ( M w / M n ca. 1.6) and high cis ‐1,4 content (ca. 94%) at 30 °C. Thus, the novel Nd(O i Pr) 3 /MAO/ t BuCl system features high activity, high molecular weight, narrow MWD, and high cis ‐1,4 stereospecificity, as compared with the conventional Nd(O i Pr) 3 /Al( i Bu) 2 H/ t BuCl system. Effect of the [Cl]/[Nd] mole ratio on the cis ‐1,4 contents with Nd(O i Pr) 3 /Al( i Bu) 2 H/ t BuCl catalyst. Curve a: at 30 °C, 180 min; curve b: at 60 °C, 90 min. magnified image Effect of the [Cl]/[Nd] mole ratio on the cis ‐1,4 contents with Nd(O i Pr) 3 /Al( i Bu) 2 H/ t BuCl catalyst. Curve a: at 30 °C, 180 min; curve b: at 60 °C, 90 min.