Water vapor transport in a series of polyarylates

Water vapor sorption and transport properties are presented for a series of polyarylates. The effect of making various structural changes in the polym er backbone has been studied, by comparing the transport properties to thos e of the base polymer bisphenol A isophthalate. All the polymers exhibit an upturn in the sorption isotherm at moderate to high activities, which in m ost cases is caused by plasticization of the polymer by water vapor. The re sponse of water vapor to the structural changes is compared to that of the permanent gases reported previously for these materials. A good correlation is established between the diffusion and permeability coefficients and the fractional free volume. A similar behavior is seen in gases. However, the solubility coefficient, which decreases with increase in the fractional fre e volume, shows an opposite effect. Water vapor has the ability to hydrogen bond with itself and interact strongly with the polymer. In the case of so lubility, the water vapor-polymer interaction plays an important role and o verrides the effect of the: increase in fractional free volume. The structu ral changes described here have similar effects on the permeation of water in a series of polysulfones reported earlier, as seen here for the polyaryl ates. (C) 2001 Elsevier Science B.V. All rights reserved.