Mobility of water and alcohols in a silica reinforced siloxane network

The water vapour permeability coefficient (P) of a silica reinforced siloxane network has been measured in the temperature range 5–45°C. P is independent of humidity and stretching of the material, but a plot of logP against reciprocal absolute temperature is non-linear, showing that the heat of permeation is negative and varies with temperature. This can be explained by the formation of water clusters. The transport of some alcohols has been studied in gravimetric sorption experiments. Amounts absorbed at equilibrium increase in the order methanol <2-propanol