Laminated TaS2/polymer nanocomposites through encapsulative precipitation of exfoliated layers

Several TaS2/polymer nanocomposites prepared through the encapsulative precipitation method are described. Namely, the encapsulation of poly(ethylene oxide) (PEO), polyethylene imine (PEI), and poly(vinylpyrrolidinone) (PVP) into TaS2 was examined in detail, and the nanocomposites were characterized by a wide variety of techniques. The nanocomposites disperse in water and are easily cast into free-standing films. The flexible metallic TaS2/ polymer nanocomposite films display bulk superconductivity. In addition, in this work the exfoliation properties of LixTaS2 were systematically explored, and it was found that material prepared from controlled lithiation with 0.2 equiv of LiBH4 exfoliates well in water and has high affinity for various polymers. The likely conformation of PEO molecules sandwiched between the TaS2 slabs was explored with analysis of the X-ray diffraction patterns of a highly oriented Li-x(PEO)(y),TaS2 nanocomposite films. The one-dimensional electron density maps, obtained for Li-x(PEOy,TaS2, can be explained with two sheets of PEO chains (bilayer) that adopt a conformation similar to that found in a type II PEO-HgCl2 complex. The chains are arranged with the -CH2- groups facing the TaS2 layers and the -O- atoms toward the center of the gallery, where the Li+ ions seem to be located. Solid state Li-7 NMR measurements indicate that Li-x(PEO),yTaS2 provides a more facile hopping environment for Li ions than pristine LixTaS2.