Styrene polymerization with Ni-Calix[4]arene diphosphine complexes activated by MAO

Neutral and cationic Ni(II) chelate complexes based on two calix[4]arene-derived diphosphines, namely cone -11,23-bis(diphenylphosphino)-25,26,27,28-tetrapropoxy-calix[4]arene ( L 1 ) and cone -5,17-dibromo-11,23-bis(diphenylphosphino)-25,26,27,28-tetrapropoxy-calix[4]arene ( L 2 ), have been assessed in the polymerization of styrene using MAO as activator.The experiments were carried out in the temperature range 25°C - 80°C and applying different Al/Ni ratios. For each complex, the resulting polystyrene exhibited a bimodal molar mass distribution, thus reflecting the existence of at least two different polymerization pathways. The runs led mainly to isotactic polystyrenes with characteristic glass transition and degradation temperatures of polystyrene resins. These temperatures were found to depend on the proportion of low molecular weight polystyrene.