Synthesis of ultra-high molecular weight polystyrene with rare earth-magnesium alkyl catalyst system: general features of bulk polymerization

Bulk polymerization of styrene (St) with an in-situ-activated Ziegler-catalyst containing neodymium 2-ethylhexyl phosphonate [Nd(P204)3], magnesium–aluminum alkyls and hexamethyl phosphoramide (HMPA) was studied. The new rare-earth catalyst exhibited high activity for polymerization of styrene, and its catalytic efficiency reached 14 730 g PSt/g Nd. The influence of reaction parameters, such as Mg/Nd, Mg/Al, St/Nd molar ratios, temperature, etc, on the catalyst performance was examined in detail. The molecular weight of the resulting polystyrene is ultra-high (MW = 40 × 104 ∼ 120 × 104 g mol−1) and the distribution of molecular weight is broad (MW/Mn = 2.1 ∼ 2.8). The microstructure of the polystyrene was characterized by IR and 13C NMR spectroscopies and found to be atactic.