Methylaluminoxane-activated neodymium chloride tributylphosphate catalyst for isoprene polymerization

The polymerization of isoprene was examined by using a novel binary catalyst system composed of neodymium chloride tributylphosphate (NdCl 3 ·3TBP) and methylaluminoxane (MAO). The NdCl 3 ·3TBP/MAO catalyst worked effectively in a low MAO level ([Al]/[Nd] = 50) to afford polymers with high molecular weight ( M n ∼10 5 ), narrow molecular weight distribution ( M w / M n = 1.4–1.6), and high cis -1,4 stereoregularity (> 96%). The catalytic activity increased with an increasing [Al]/[Nd] ratio from 30 to 100 and polymerization temperature from 0 to 50°C, while the M n of polymer decreased. The presence of free TBP resulted in low polymer yield. Polymerization solvent remarkably affected the polymerization behaviors; the polymerizations in aliphatic solvents (cyclohexane and hexane) gave polymer in higher yield than that in toluene. The M w / M n ratio of the producing polymer remained around 1.5 and the gel permeation chromatographic curve was always unimodal, indicating the presence of a single active site in the polymerization system. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131 , 40153.