Ring-opening metathesis polymerization of norbornene catalyzed by substituted titanocene complexes

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The ring-opening metathesis polymerization (ROMP) of norbornene (NBE) with 11 substituted titanocene dichlorides and MeLi as catalysts was studied. The substituent effect showed that the catalytic activity was generally decreased as the substituents were introduced into the Cp ring. The more bulky the substituents, the lower the activity and the bis-substituted titanocene appeared to have an even lower catalytic activity. The molecular weight of polynorbornene (PNBE) also decreased as substituents are introduced on the Cp ring. But the molecular weight distribution and cis structure content have no significant differences compared with non-substituted titanocene complex as catalyst.