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-catal yst containing neodymium 2-ethylhexyl phosphonate [Nd(P-204)(3)], magnesium -aluminum alkyls ((MgBu2AlEt3)-Al-n)and hexamethyl phosphoramide (HMPA) was studied. The new rare-earth catalyst exhibited high activity for polymeriz ation of styrene, and its catalytic efficiency reached 14730 g PSt/g Nd. Th e influence of reaction parameters, such as Mg/Nd, Mg/Al, St/Nd molar ratio s, temperature, etc, on the catalyst performance was examined in detail. Th e molecular weight of the resulting polystyrene is ultra-high (M-W = 40 x 1 0(4) similar to 120 x 10(4) g mol(-1)) and the distribution of molecular we ight is broad (M-W/M-n = 2.1 similar to 2.8). The microstructure of the pol ystyrene was characterized by IR and C-13 NMR spectroscopies and found to b e atactic. (C) 2001 Society of Chemical Industry.