Catalyzes the Conversion of Norbornene to Cyclic Polynorborene That Retains Stereochemistry upon Hydrogenation
This metallocyclopropylidene complex catalyzes the conversion of norbornene into cyclic polynorbornene with a high degree of stereoregularity that remains stable after hydrogenation. 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. Polynorbornene also often contributes to the production of personal protective equipment, shoe parts, and bumpers, as well as facilitates tire adhesion improvements. Available metallic catalysts frequently produce linear polynorbornene with lower glass transition temperatures, but they require several steps for their synthesis. Researchers at the University of Florida have developed an organometallic catalyst from molybdenum that converts norbornene into stereoregular, cyclic polynorbornene in only two steps. Additionally, synthesis of this catalyst involves the catalyst, itself, producing cyclic polynorbornene that maintains its high stereoregularity throughout the conventional hydrogenation processes.
Application
Organometallic catalyst that promotes highly-stereoregular polymerization of norbornene
Advantages
- Initiates the conversion of norbornene into cyclic polynorbornene, producing a polymer with significantly higher glass transition temperatures
- Forms a highly-stereoregular polymer, resulting in an ordered and more crystalline product
- Involves a shorter and more efficient procedure for catalyst synthesis, increasing efficiency of the overall conversion process
- Maintains polymer stereoregularity after hydrogenation, facilitating production of stereoregular hydrogenated cyclic polynorbornene
Technology
A two-step reaction between a terminal alkyne and a ligand with molybdenum as the metallic base forms this metallocyclopropylidene complex that actively catalyzes the polymerization of norbornene into cyclic polynorbornene. The conversion takes place through a ring expansion metathesis polymerization. Greater stereoregularity provides a more rigid and ordered crystalline structure for the polymer. The crystallinity results in increased glass transition temperatures. Since polymers with higher glass transition temperatures require more heating to change into a soft, rubbery state, the constructed cyclic polynorbornene retains greater structural integrity in heated conditions than its linear alternatives. After formation, the cyclic polynorbornene can undergo hydrogenation via standard H2/Pd/C procedures or tosylhydrazine decomposition all while maintaining its stereoregularity.
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