Surface modification of sepiolite nanofibers with PEG based compounds to prepare polymer electrolytes

• In aqueous gels isolated sepiolite (Sep) fibers are coated with PEG ( Sep-PEG) and TPGS ( Sep-TPGS).
• Surface modification in Sep-PEG evolves with time, while Sep-TPGS remains stable for years.
• Only Sep-TPGS forms time stable suspensions in ethylene carbonate (EC)/PEG blends.
• Sep, and Sep-TPGS disperse well in electrolytes based on poly(ethylene oxide) (PEO) and EC.
• Sep-TPGS is a good candidate for the reinforcement of PEO/EC/Li salt based electrolytes.

The controlled surface modification of the fibrous clay mineral, sepiolite (Sep), with poly(ethylene glycol) (PEG) and Vitamin E tocopherol polyethylene glycol succinate (TPGS) is presented in this work. Sep, which has a rich surface reactivity because of the presence of silanol groups on its surface, is employed as nanofiller in clay polymer nanocomposites (CPN). It organizes itself into bundles of nanofibers which are difficult to separate from one another unless aqueous gels are prepared under very specific conditions. In the form of an aqueous gel, however, separation of the nanofibers and chemical modification of their surface can be easily done. Sets of very different organosepiolites (OSep) can be obtained in this way. In this work the resulting OSep are characterized in terms of mass incorporation and yields of reaction, specific surface, surface texture, surface water content and thermal stability. As the final purpose of these OSep is the mechanical reinforcement of poly(ethylene oxide) (PEO) based electrolytes highly loaded with ethylene carbonate (EC), blends with PEG or PEO and lithium triflate, with or without EC are prepared and the properties of the final materials are found to be strongly dependent on the type of OSep employed. In particular, examples on the fillers dispersion in the PEO nanocomposites and on their stability in dispersion of PEG/EC blends are described.

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