Orientation and Motion of Interlamellar Water:  An Infrared and NMR Investigation of Water in the Galleries of Layered Cd_0.75PS₃K_0.5(H₂O)_y

Abstract

The motion of water in the galleries of layered Cd0.75PS3K0.5(H2O)1.2, prepared by the ion-exchange intercalation of hydrated potassium ions into CdPS3, have been investigated using a combination of orientation dependent NMR and infrared (IR) spectroscopies as a function of temperature. Within the galleries of the intercalated compound the potassium ions are displaced toward the layers and are immobile, while the water molecules form monolayer-thick two-dimensional islands. Two types of interlamellar water are distinguishable by both NMR and IR spectroscopy. A loosely bound isotropically tumbling water which is easily lost on mild evacuation and a more tightly bound water with restricted degrees of rotational freedom. The angular dependence of the NMR and IR spectral features of the latter indicate that their C⃗ 2 symmetry axis is at a fixed orientation with respect to the interlamellar normal and rotate rapidly about it. In analogy with bulk aqueous solutions these two types of interlamellar water may be considered as two-dimensional solventlike water and water coordinated to the potassium ion forming part of its hydration shell. A remarkable feature of the water in the galleries of Cd0.75PS3K0.5(H2O)1.2 is the extremely slow rate of exchange (τ ≫ 10-5 s) between the two-dimensional solventlike water and the coordinated water, in direct contrast to the rapid exchange observed for K ions in bulk aqueous solutions. The present experimental results provide the first observation of the effect of confinement on solvation shell exchange. It is suggested that the slowing down could be the effect of confinement in two dimension which would strongly inhibit any mechanism involving transition or intermediate states which require an expansion of the coordination shell around the potassium ion.

Li ion transport in an intercalated polymer electrolyte

“…5 Complete ion-exchange intercalation was ascertained by the absence of the host 00l reflections and the appearance of new 00l reflections with lattice spacing, 9.4 Å. 4 The intercalation of PEO in Cd 0.75 PS 3 Li 0.5 (H 2 O) 2 was carried out by refluxing the lithium-ion-exchanged intercalation compound Cd 0.75 PS 3 Li 0.5 (H 2 O) 2 with a methanolic solution of PEO ͓molecular weight (M w )ϭ6ϫ10 5 ] following the procedure reported in Ref. 5:…”

“…These compounds also serve as model systems for understanding the effect of confinement on properties of the guest in relation to those in the bulk. 3,4 Here we focus on a polymer electrolyte, Lipolyethylene-oxide ͑Li-PEO͒, confined by intercalation within the galleries of an inorganic layered host CdPS 3 . 5 The Li-PEO CdPS 3 -based intercalated polymer electrolyte Cd 0.75 PS 3 Li 0.5 (PEO) has been characterized previously 5 and a detailed study of the conductivity and dielectric properties reported.…”

Starre Lipidmembranen und Nanometerlücken – Motive zur Gestaltung molekularer Landschaften

“…Die Lage und Aufspaltung der Pake‐Dublettsignale änderte sich nicht mit der Temperatur, und der Austausch zwischen den frei beweglichen und fest gebundenen Molekülen war mindestens 10 6 ‐mal langsamer als im Volumenwasser. Die starre Umgebung der Wassermonoschichten verhinderte offensichtlich die Erweiterung der Hydrathülle und verlangsamte damit Austauschreaktionen 116…”

Enhanced electrical and electrochemical properties of PMMA–clay nanocomposite gel polymer electrolytes

“…These compounds also serve as model systems for understanding the effect of confinement of the guest on properties in relation to those in bulk [13,14]. Among the most commonly used inorganic layered host, montmorillonite is a favored choice in view of its special features of high aspect ratio (∼1000), high cationexchange capacity (CEC ∼80 meq/100 g), large specific surface area (∼31.82 m 2 g −1 ), appropriate interlayer charge (∼0.55) and length scale (clay channel width = 16 Å).…”