tereospecific polymerization of styrene was conducted in toluene using theMgCl_2/TiCl_4

NdCl_3/AlEt_3 catalyst. With increasing monomer concentration

the molecular weight of the products are increase while the polymer yield

the catalytic efficiency

and the isotacticity of the products are all first increased

reaching a maximun

and then decreased gradually. A maximum isotacticity of 98% of the products has been obtained. Results of DSC determinations show that an adequate content of atactic polystyrene(aPS) is favourable of the crystallization of isotactic polystyrene(iPS)

but the addition of more aPS linearly decreases the crystallinity of iPS because of the dilution effect. The content of polyethylene(PE) in blends of iPS/PE has no significant influence on the crystallinity of iPS while polycarbonate (PC)excerts a more complicate effect on the crystallinity of iPS in iPS/PC blends.