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

Abstract

AbstractThe effect of tert‐butyl chloride (tBuCl) as a third catalyst component on the isoprene polymerization with neodymium isopropoxide (Nd(OiPr)3)/diisobutylaluminum hydride (Al(iBu)2H) and Nd(OiPr)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(OiPr)3/Al(iBu)2H catalyst was inactive without tBuCl, 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(iBu)2H + tBuCl} + Nd(OiPr)3 to yield polyisoprene with relatively low molecular weight (Mn ca. 5 × 104), broad MWD (Mw/Mn ca. 5.4), and high cis‐1,4 content (ca. 96%) at 30 °C. On the other hand, the Nd(OiPr)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(OiPr)3 + MAO} + tBuCl to afford polymer with high molecular weight (Mn ca. 8 × 105), fairly narrow MWD (Mw/Mn ca. 1.6) and high cis‐1,4 content (ca. 94%) at 30 °C. Thus, the novel Nd(OiPr)3/MAO/tBuCl system features high activity, high molecular weight, narrow MWD, and high cis‐1,4 stereospecificity, as compared with the conventional Nd(OiPr)3/Al(iBu)2H/tBuCl system. Effect of the [Cl]/[Nd] mole ratio on the cis‐1,4 contents with Nd(OiPr)3/Al(iBu)2H/tBuCl catalyst. Curve a: at 30 °C, 180 min; curve b: at 60 °C, 90 min.magnified imageEffect of the [Cl]/[Nd] mole ratio on the cis‐1,4 contents with Nd(OiPr)3/Al(iBu)2H/tBuCl catalyst. Curve a: at 30 °C, 180 min; curve b: at 60 °C, 90 min.