Electroconductivity measurements in the solutions of catalytic systems
based on metallocene complexes and various activators
Polimery 2001, No 6, 393
SummaryElectroconductivity (χ) was studied in 10-1 to 10-7 M bent-sandwich and ansa-metallocene (Cp2 MX2, Me2SiInd2MX2, Me2SiCp2MX2, Me2SiCp-t-BuMX2, Me2Si(2-MeInd)2MX2, (2-PhInd)2MC12, EtInd2ZrCl2 and ((cyclo-C6H11)2Cp)2ZrC12; M = Ti, Zr; X = Cl, Me) solutions (toluene, dimethylene chloride as varying polarity solvents) of homogeneous Ziegler-Natta catalyst systems derived in situ from the metallocene precursors and an arganoaluminum compound (AlEt3, AlEt2Cl, Al-i-Bu3), polymethylaluminoxane (MAO) or perfluarophenyl borate (Ph3CB(C6F5)4, Me2PhHNB(C6F5)4) as cocatalyst in relation to metallocene/activator ratio over a wide metallocene concentration range and in the absence or presence of an α-olefin. The specific electroconductivity of the reaction produet solution was almost always higher than the sum of the electroconductivities of the individual component solutions measured under comparable conditions (Table 1). Apparent dissociation degrees and charge d species equilibrium concentrations were evaluated (Tables 2, 3). The time profiles of electroconductivities and polymerization rates measured simultaneously were found to follow analogously descending courses (Figs. 3, 4). Low ar very low metallocene concentration (10-5-10-7 M), perfluarophenyl borate as activator, and sometimes also the α-olefin (propylene, hexene) added were found to enhance the electroconductivity (Table 1), i.e., to favor the formation of charged species.