Synthesis, Structure, and Reactions of Poly(ethylene oxide)/V₂O₅ Intercalative Nanocomposites

The intercalation of poly(ethylene oxide) (PEO) in layered V 2 O 5 xerogel and the structural and physicochemical characterization of the products is reported. The synthesis of PEO/V 2 O 5 nanocomposites is achieved by simply mixing aqueous solutions of PEO with aqueous V 2 O 5 gels followed by slow water evaporation. Several different phases of PEO/V 2 O 5 composites can be obtained by varying the component ratios. The interlayer distance of (PEO) x V 2 O 5 · n H 2 O varies from 13.2 Å, at x = 0.5, to 16.8 Å at x = 1.0, to 17.6 Å at 1 < x < 3, and to 18.3 Å at x ≥ 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 ≥ 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) x V 2 O 5 · n H 2 O intercalation compounds are water swellable and light-sensitive. UV irradiation causes dramatic changes in the electronic structure of V 2 O 5 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 V 4+ concentration in the layers and n-type charge transport. Lithium ion redox intercalation was performed on the PEO/V 2 O 5 composites by reaction with LiI. Variable-temperature 7 Li solid-state NMR studies of the Li/PEO/V 2 O 5 materials are reported.