Investigation of organoboronates in metathesis polymerization

Molybdenum and ruthenium catalysis has been used to synthesize main-chain boronate ADMET polymers under bulk conditions; however, the long-term stability and solution characterization of these polymers are dramatically influenced by ligand-exchange reactions within the boronate moiety. Placing the boronate pendent to the main chain obviates this phenomenon as demonstrated in the ROMP polymerization of norbornene monomers with boronates both in exo and endo positions. The stereochemistry of the monomer influences both the rate of polymerization and the microstructure of the resulting polymer; these effects are more pronounced in the case of ruthenium catalysis. The thermal stability of these polymers also is dependent upon monomer stereochemistry.