Ultrahigh‐Molecular‐Weight Polyethylene by Using a Titanium Calix[4]arene Complex with High Thermal Stability under Polymerization Conditions

The new complex 25,27‐dipropyloxy‐26,28‐dioxocalix[4]arene titanium (IV) dichloride (1) was evaluated as an ethylene polymerization catalyst. Activation with methylalumoxane resulted in an active system producing ultrahigh‐molecular‐weight polyethylene. As expected for a Ziegler‐Natta catalyst, the polymerization reaction follows first‐order kinetics. The most striking feature of the catalytic system (1/MAO) is its remarkably high thermal stability. This peculiarity probably relies on the electronic stabilization of the metal center by the two coordinating propoxy groups. magnified image