Polynorbornene-Based Polyelectrolytes With Covalently Attached Metallacarboranes: Synthesis, Characterization, And Lithium-Ion Mobility

Metallacarborane clusters, such as COSAN, belong to surface-active and low-coordinating nanosized anions. Therefore, they have been used as separate building blocks in self- and co-assembly. As a step forward, we synthesized via ringopening metathesis polymerization a novel polyelectrolyte, poly(norbornene-COSAN), PNC, with metallacarborane anions covalently attached to a polynorbornene backbone. The resulting PNC, with the degree of polymerization around 120, is soluble in polar organic solvents, and it can be deposited on a substrate as separate polymer chains or as multichain aggregates, with the bundle-of-fibril patterning. PNC is miscible with polyethylene oxide (PEO), forming the PNC/PEO composite. As shown by solidstate nuclear magnetic resonance spectroscopy, Li+ counterions are firmly coordinated in the PNC matrix, exhibiting rather restricted dynamics. In contrast, the mixing of PNC with PEO leads to a substantial increase of Li+ dynamics. As the result, the mobility of Li+ in the PNC/PEO composite remains almost unrestrained, which makes the COSAN-containing polyelectrolytes promising candidates for ion-conducting materials.