Abstract: | 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. © 2001 Society of Chemical Industry |