A study of the hydration, sorption and diffusion for water and ethanol within polymer films prepared from aromatic polyamides (condensation of 4-4’-diaminodiphenylamino-2-sulfonate (DADPS) and 4-4’-diaminodiphenyloxide, taken in different ratios, with isophthaloylchloride) has been made. Knowledge of the factors controlling sorption and diffusion for water molecules as compared with alcohol molecules within polyamide films has stimulated the development of pervaporation (PV) membranes prepared from Na salt poly-4,4’-diphenylphthalamide-2,2’-disulfonic acid. The new PV membrane (Polar-2P) possesses the highest selectivity for water transport (alpha = 10(4)-10(5)) with dehydration of the water-organic mixtures (acetone, isopropanol, ethylacetate) and a high water flux (Q approximate to 0.5-1 kg/m(2) h at 30 mol% H2O). The high local concentration of C=O, the presence of sulfonic acid groups and organic cations on channel inlets and the inlet size are the factors regulating the high selectivity of water transport. The entrance of organic molecules such as isopropanol, acetone and ethylacetate into these channels becomes difficult due to the larger size of these molecules as compared with the inlet size.