Ring-Opening Metathesis Polymerization of (Oxa)Norbornenes with Sulfonate, Sulfone, and Sulfoxide Sidechains

Sulfur-containing polymers are utilized in applications ranging from vulcanized rubbers to optical materials and proton conducting membranes. Typically, sulfur-containing polymers are synthesized via condensation methods. While ring-openining metathesis polymerization is a useful tool for polymerizing functional monomers, previous reports have shown difficulties incorporating sulfur-containing functional groups due to Ru-S interactions. In this work, we report the synthesis and polymerization of a number of poly(oxa)norobornenes containing sulfonate, sulfone, and sulfoxide sidechains. We demonstrate the effects of the identity of the bridge group, sidechain R groups, and substituent stereochemistry on polymerization rates, molecular weight distrubitons, and thermal properties. Interestingly, while the exo-norbornene phenyl sulfoxide monomer was effectively polymerized, the endo isomer resulted in exclusive single addition to the Ru catalyst due to sulfur chelation to the metal centre. This monomer could however be used for alternating copolymerization with other cyclic olefins.