The structure of water and methanol in p-dioxane as determined by microwave dielectric spectroscopy

Dielectric measurements were performed on water–p-dioxane and methanol–p-dioxane mixtures using time domain reflectometry over the frequency range 0.1–10 GHz. In the case of water–p-dioxane mixtures, the relaxation strength normalized by the number of water molecules per unit volume is independent of the molar fraction of water xW if xW<0.83. There are no ordered micellelike clusters in the mixture. On the other hand, if xW is larger than 0.83, the normalized strength increases linearly with xW. The clusters of pure water which appear in this region are cyclic and consist of six molecules. In the case of methanol–p-dioxane, the normalized strength is independent of xM for xM<0.66 and increases linearly with xM for xM>0.66. However, the relaxation time of pure methanol is too large for clusters consisting of three molecules. It is suggested that the chainlike clusters form network structures.