Effect of the extent of hydration on the motion of interlamellar water: A H-1 NMR study of the ion-exchanged layered hydrates Cd0.75PS3Na0.5(H2O)(y),y=1, 2

Hydrated Na ions have been ion-exchange intercalated into layered cadmium t hiophosphate to give Cd0.75PS3Na0.5(H2O)(y). Two Stable phases with y = 1 a nd 2 are obtained with lattice expansion 2.8 and 5.6 Angstrom, respectively . The former phase is formed from the y = 2 phase either by evacuation or h eating. The effect of the;extent of hydration on the motion of interlamella r water has been investigated by analyzing the dipolar Splittings observed in the H-1 NMR spectrum as the system transforms from the y = 2 phase to th e y = 2 phase. In the y = 2 phase the water molecules rotate about the inte rlamellar normal, C*, as well as about their (C) over right arrow(2) symmet ry axis. On formation of the y = 1 phase there is partial loss of rotationa l freedom; rotational motion about the (C) over right arrow(2) axis Of the interlamellar water is now no longer present. We propose a simple electrost atic model to explain these results.