Synergistic Effects of Polypyrrole Nanotubes and Magnetite Nanoparticles in PEO-Based Composites for Solid Polymer...

A showcase study in which magnetic particles are investigated as a filler, mainly for the development of solid polymer electrolytes, is presented. The magnetic particles, in the form of polypyrrole (PPy) nanotubes, were decorated with different amounts of magnetite nanoparticles, which can be tuned through synthesis. The particles were dispersed in high molecular weight poly(ethylene oxide) blended with sodium carboxymethyl cellulose, preparing pellets and thin films. An external magnetic field was used to obtain anisotropic thin films, with the differences described in detail. After solid characterization, we show that, depending on the synthesis of composite particles and the fabrication methods of the pellets and films, we can alter various properties─magnetic (M_sat ∼ 30-60 emu/g), electric (σ_ionic ∼ 10^-7-10^-4 S/cm), and mechanical (G' ∼ 8-10 MPa). The presence of the filler improved the shear modulus (∼60 MPa), competing with dendrite propagation while offering improved thermal stability at elevated temperatures (80°C). Depending on the preparation and composition of the filler material, the ionic conductivity always improved with the presence of the PPy/Fe₃O₄, with a specific sample reaching ∼10^-4 S/cm at room temperature. The present work is a new strategy to improve the properties of solid polymer electrolytes and can pave the way for more efficient and more competitive magnetic composites used for energy storage.