Novel Highly Active Niobium Catalysts forRing Opening Metathesis Polymerization ofNorbornene

摘要

Ring-opening metathesis polymerization (ROMP) of norbornene catalyzed by niobium(V) N,NdialkylcarbamatesNb(O2CNR2)5, REt (1), Me (2) was studied in the presence of methylaluminoxane(MAO) as a cocatalyst. These novel catalytic systems resulted very active inchlorobenzene: 1 in the presence of methylaluminoxane catalyzes the ROMP of norbornenewith the highest activity (29 000 kg of polymer/mol of catalysthour) never reported up tonow for niobium catalysts. The high productivity appears particularly attractive consideringthat these precursors are rather cheap and easy tosynthesize and to handle. Polynorbornenes werecharacterized by FT-IR and NMR spectroscopiesand by DSC calorimetry. A new FT-IR methodfor the swift determination of the cis/trans contentof the polymer is presented.