Isospecific Polymerization of Vinylcyclohexane by Zirconium Complexes of Salan Ligands

Abstract

The polymerization of vinylcyclohexane by C2-symmetric dibenzylzirconium complexes of nonchiral and chiral Salan ligands that feature electron-withdrawing halo or alkyl substituents is reported. The catalysts containing the electron-withdrawing groups exhibited ultrahigh activities. In contrast to polymerization of less hindered α-olefins, highly isotactic poly(vinylcyclohexane) were obtained from all Salan complexes studied. This indicates that the isospecificity is not derived from the bulkiness of the phenolate substituents. Characterization of the polymers by differential scanning calorimetry and by X-ray powder diffraction reveals the formation of similarly crystalline polymers regardless of the nature of Salan catalysts. DSC measurements indicates that these polymers act as effective nucleation agents for polypropylene.