Syndiospecific Polymerization of Styrene Using Half-Titanocene Catalyst Govalently Supported on MgCl2/AlEt_n(OEO)_(3-n)

摘要

The novel half-titanocene catalyst bearing reactive functional amino group, η~5-pentamethylcyclopentadienyltri(p-amino-phenoxyl) titanium [Cp~*Ti(p-OC6H4NH2)3], was easily synthesized by the reaction of η~5-pentamethylcyclopentadienyltrichloride titanium (Cp~*TiCl3) with p-amino phenol in the presence of triethyl amine (NEt3). Cp~*Ti(p-OC6H4NH2)3 covalently anchored on MgCl2/AlEt_n(OEt)_(3-n) support obtained from the reaction of triethylaluminium (AlEt3) with the adduct of magnesium chloride (MgCl2) and ethanol (EtOH), has been investigated and used to catalyze syndiospecific polymerization of styrene. Influences of the support structure, cocatalyst, and the molar ratio of Al in methylaluminoxane (MAO) and Ti (Al_(MAO)/Ti) on catalytic activity, syndiotacticity and molecular weight of the resultant polystyrene were investigated. Compared with the corresponding Cp~*Ti(p-OC6H4NH2)3 homogeneous catalyst, a considerable increase in activity and molecular weight of syndiotactic polystyrene (sPS) was observed for the Cp~*Ti(p-OC6H4NH2)3-MgCl2/AlEt_n(OEt)_(3-n) supported catalyst even at a relatively low Al_(MAO)/Ti ratio of 50, and the kinetics of polymerization was stable during the reaction process.