Synthesis of Liquid Polyisoprene with High cis-1,4 Unit Content and Narrow Molecular Weight Distribution Using Neodymium Phosphate Catalyst

Abstract

The polymerization of isoprene (Ip) initiated by a ternary catalytic system consisting of liquid Nd(P204)3 (Nd), Al(i-Bu)2H (Al), and CHCl3 (Cl) in cyclohexane was examined. The effects of order of addition and amount of Ip, Al, and Cl in the catalyst on the polymerization were evaluated. The molecular weight (Mn), molecular weight distribution (Mw/Mn), and microstructure of the polymer were characterized using size exclusion chromatography and multiangle light scattering, FT-IR, 1H NMR and 13C NMR analysis. The results indicate that the order of addition, i.e. Nd+Ip+Al+Cl and ratios of [Ip]/[Nd]=30, [Al]/[Nd]=20, and [Cl]/[Nd]=3 were essential for the optimized ternary catalyst system Nd(P204)3/Al(i-Bu)2H/CHCl3. The resulting liquid polyisoprene (LIR) has a high cis-1,4 unit content (>98%) and a narrow molecular weight distribution (Mw/Mn<1.2). The molecular weight of the polymer was precisely controlled.