The Influence of Humidity on the Structure of MoS_2(PEO)_(1.3) Nanocomposites

摘要

Layered nanocomposites of molybdenum disulfide (MoS_2) and poly (ethylene oxide) (PEO) were studied using x-ray diffraction of powder and oriented thin film samples. Thermal gravimetric analysis provided information on the composition of the material. The effects of the molecular weight of PEO and the atmospheric relative humidity on the structure were also investigated. A basal plane spacing of 14.3 A. corresponding to an expansion of 8.1 A between MoS2 layers, was found for dry samples, in agreement with the literature. At about 30% humidity, the expansion increases to 10.6A. This increase corresponds approximately to the thickness of one monolayer of water. The spacing is constant until around 80% humidity, when the expansion begins to increase again, reaching up to 25 A near 100% humidity. X-ray coherence lengths in the direction perpendicular to the planes averaged 13, 7 and 2 MoS_2 layers for the dry, 58% humid and nearly 100% humid samples, respectively.