Synthesis, structure, and reactions of poly(ethylene oxide) V2O5 intercalative nanocomposites

The intercalation of poly(ethylene oxide) (PEG) in layered V2O5 xerogel and the structural and physicochemical characterization of the products is reported. The synthesis of PEO/V2O5 nanocomposites is achieved by simply mixing aqueous solutions of PEO with aqueous V2O5 gels followed by slow water evaporation. Several different phases of PEO/V2O5 composites can be obtained by varying the component ratios. The interlayer distance of (PEO)(x)V2O5 . nH(2)O varies from 13.2 Angstrom, at x = 0.5, to 16.8 Angstrom at x = 1.0, to 17.6 Angstrom at 1 < x < 3, and to 18.3 Angstrom at x greater than or equal to 3. One-dimensional electron density calculations based on X-ray diffraction data (perpendicular to layers) show that the composites contain a monolayer of PEO molecules when x < 1 and a bilayer when x greater than or equal to 1. The data suggest that the PEO chains are arranged side-by-side in a fully extended conformation between the layers forming corrugated mono- or bilayers. The (PEO)(2)V2O5 . H2O intercalation compounds are water swellable and light-sensitive. UV irradiation causes dramatic changes in the electronic structure of V2O5 and results in enhanced electrical conductivity and decreased solubility. The conductivity of the irradiated products decreases as the PEO content increases. The optical absorption spectra, electrical conductivity, thermoelectric power, magnetic susceptibility, and electron paramagnetic resonance spectra of the irradiated products are self-consistent and suggest an increased V4+ concentration in the layers and n-type charge transport. Lithium ion redox intercalation was performed on the PEO/V2O5 composites by reaction with LiI. Variable-temperature Li-7 solid-state NMR studies of the Li/PEO/V2O5 materials are reported.