This metallocyclopropylidene complex catalyzes the conversion of norbornene into cyclic polynorbornene with a high degree of stereoregularity. Polynorbornene, the polymerized form of the norbornene hydrocarbon, serves many purposes in the rubber industry, is beneficial in the fabrication of anti-vibration materials, and has particular use in the railway, construction, and industrial sectors. It often contributes to the formation of personal protective equipment, shoe parts, and bumpers, and can improve adhesion in the tires of cars and toys. Available metallic catalysts frequently produce linear polynorbornene with lower glass transition temperatures and the catalysts require several steps for formation. Researchers at the University of Florida have developed an organometallic catalyst from molybdenum that converts norbornene into stereoregular, cyclic polynorbornene. The synthesis of this catalyst involves only two steps and the catalyst itself produces cyclic polynorbornene with high stereoregularity.
Organometallic catalyst that promotes highly-stereoregular polymerization of norbornene
This metallocyclopropylidene complex actively catalyzes the polymerization of norbornene into cyclic polynorbornene. The conversion takes place through a ring expansion metathesis polymerization, involving the exchange of ions to construct the stereoregular polymer. Greater stereoregularity enables the polymer to maintain a more rigid and ordered crystalline structure. This crystallinity results in increased glass transition temperatures. Polymers with higher glass transition temperatures require more heating to change into a soft, rubbery state, thus the constructed cyclic polynorbornene retains greater structural integrity in heated conditions than its linear alternatives. The metallocyclopropylidene complex forms from a two-step reaction between a terminal alkyne and a ligand, using molybdenum as the metallic base.