Elastomeric Polypropylenes from Unbridged 2-Phenylindene Zirconocene Catalysts: Temperature Dependence of Crystallinity and Relaxation Properties

Abstract

The solid-state structure and physical behavior of an elastomeric polypropylene (PP1) synthesized with unbridged 2-phenylindene zirconocene catalyst were examined using solid-state 13C NMR spectroscopy, differential scanning calorimetry, wide-angle X-ray powder diffraction, and birefringence measurements of relaxation behavior. Extraction of these elastomeric polypropylenes with boiling ether and heptane yielded three fractions of different molecular weight and tacticity. The ether-soluble fraction is the lowest in isotactic pentad content and exhibits no detectable crystallinity. For the other fractions and the parent homopolymer, the degrees of crystallinity estimated from DSC and WAXD results are similar. The amount of the immobile phase determined by solid-state NMR, however, appears much higher than the degree of crystallinity. An increase in temperature from 20 to 80 °C results in a loss in the relative fraction of mobile and immobile phase as measured by solid-state NMR and a corresponding loss in ...