Efficient synthesis of thermoplastic elastomeric amorphous ultra-high molecular weight atactic polypropylene (UHMWaPP)

Abstract

The selective and high-yielding synthesis of fully amorphous ultra-high molecular weight atactic polypropylene (UHMWaPP), with weight-average molecular weights (M_w) up to 2.0 MDa and narrow polydispersities is reported; permethylindenyl-phenoxy (PHENI*) titanium complexes immobilised on solid polymethylaluminoxane (sMAO) are remarkably efficient single-site catalysts for propylene polymerisation, with activities up to 12 000 kg_PP mol_Ti⁻¹ h⁻¹ bar⁻¹. UHMWaPP was found to be a high-performance thermoplastic elastomer, exhibiting an ultimate tensile strength of 1.08 MPa (at 184% strain), and remarkably high ductility, with a tensile strain at break of >1900%. Excellent elastic recovery is observed with a set value as low as 7% in stress–strain hysteresis experiments. The mechanical properties reported are compared with commercial olefinic thermoplastic elastomers, demonstrating the potential of this technology to compete with commercial copolymers and composites as an elastic homopolymer.