Molecular and Thermal Characterization of a Nearly Perfect Isotactic Poly(propylene)

Abstract

The structure formation upon cooling of the quiescent melt of a nearly defect‐free isotactic poly(propylene) (iPP) homopolymer is investigated in this study. This iPP, having a molecular weight of 1 × 106 g mol−1 and a narrow molecular weight distribution, has been produced with a C2 symmetric hafnocene complex. Information about the crystallization kinetics is collected in a broad range of cooling rates. Standard differential scanning calorimetry is used for cooling rates in the range 3–100 °C min−1 and FSC is employed to analyze the solidification process at cooling rates larger than 100 °C s−1. The near absence of regio‐ and stereo‐defects allows this iPP to crystallize at significantly high temperatures and to form crystals at cooling rates higher than commonly observed for standard Ziegler–Natta iPP. The data reveal that the iPP homopolymer with close‐to‐perfect stereo‐regularity form crystals at high cooling rates as, e.g., α‐nucleated iPP. The defect‐free polymer chain allows the formation of relatively thick lamellar crystals which resulted in a relatively high tensile modulus of 2088 ± 8 MPa. image