Polyether-grafted nanoparticle nanocomposites

Polyethers, in particular poly(ethylene oxide) (PEO), are useful as polymer electrolytes for lithium ion batteries. However, ionic conductivity, especially at room temperature, remains too low. Adding ceramic (e.g., silica) nanoparticles (NPs) to PEO can enhance ionic conductivity, but the NPs aggregate over time under the dynamic environment in a battery cell, spoiling properties. Polymer brushes can be grafted to NP surfaces to stabilize the dispersion, but polyether brushes have largely been restricted to PEO via a graft-to approach, limiting both brush chemistry and conformation. Here, we present our recent work in the surface-initiated polymerization of epoxides to form polyether brushes of varying chemistry on silica NPs. Initiators are grafted to the surface via simple silane chemistry and grafting density is controlled. Polymerizations are done from the surface using various epoxides (e.g., epichlorohydrin (ECH), propylene oxide, etc.) to control brush chemistry. The brush grafted NPs were characterized via FTIR and NMR spectroscopy, TGA, and DLS. Nanocomposites were prepared of PECH-grafted NPs in PEO (χ < 0) and PECH matrices at various molecular weights and dispersion characterized via electron microscopy. Finally, ionic conductivity of the composites was measured at various LiTFSI salt loadings. Ultimately, we present a facile method to controllably produce polyether brushes on NP surfaces.