Permeability of solutes through hydrated polymer membranes. Part II. Permeability of water soluble organic solutes

The diffusive permeabilities, P, of sodium chloride, urea, creatinine, secobarbital and bis‐hydroxyethyl terephthalate through water swollen polymer membranes were studied. The linear dependence of log P on the reciprocal of the volume fraction of water in the water swollen membrane, 1/H, (reported in Part I) was also found for those solutes investigated. The negative slope of the plot was found to increase with increasing size of solute. Ionic charge of the membrane phase was found to decrease the permeability of ionized solutes from values for neutral membranes and changes the permeability ratios of solutes. The permeability of highly ionized solutes, such as sodium chloride, are reduced by either positive or negative charge on the membrane phase; however, the permeability of weakly ionized organic solutes is affected mainly by membrane charge identical to the organic ions, and the effect of counter ions was found to be small.