ACYCLIC DIENE METATHESIS (ADMET) POLYMERIZATION

The synthesis of the first high molecular weight polymers by acyclic diene metathesis (AD-MET) polymerization is reported, using a catalyst free of Lewis acids. Previous attempts, most recently in our laboratory and in several other laboratories over the past 20 years, had proven to be unsuccessful. 1,9-Decadiene has been converted to poly(octenylene), and 1,5-hexadiene has been converted to exclusively 1,4-polybutadiene by this procedure. The metathesis polymerization reaction is quantitative at or near room temperature and yields only polymer and ethylene as a byproduct. No other products are observed. Poly-(octenylene) exhibits a minimum weight-average molecular weight of 108 000 and is more than 90% trans in its stereochemistry. Exclusively 1,4-polybutadiene is of a minimum weight-average molecular weight of 28 000 and is more than 70% trans in its stereochemistry. The stereochemistry appears to be controlled thermodynamically due to the equilibrium nature of the polymerization, and this stereochemical feature distinguishes ADMET polymerization from ring-opening metathesis polymerization (ROMP).