Solid-state NMR Study Of Hydrated Poly(ethylene Oxide) And Complexes

Changes in phase structure of poly(ethylene oxide) (PEO) with the adsorption of water were studied by solid-state wide-line ¹H NMR. The crystallinity of pure PEO decreases with the increase of water content at room temperature. The bi-exponential feature of proton T₁ relaxation indicates that crystalline phase of PEO is destructed after the adsorption of water. The process of the adsorption of water was studied in-situ by time-resolved NMR.A series of PEO/LiCIO₄ complex samples with different molar ratios were studied systematically by solid-state high-resolution ¹³C and ⁷Li NMR spectroscopy. It was found that with the presence of a small amount of water (9% -16% by weight), the initial increase of LiCIO₄ gradually destroys crystals formed by PEO, while further increase of LiCIO₄ brings about the crystals formed by PEO and Li⁺. When the molar ratio of EO to LiCIO₄ is in the range of 6/1 to 8/1, the complex samples are complete amorphous. The ⁷Li NMR results indicate clearly that the existence of water hinders the formation of Li⁺ - PEO crystals.