Polar (αp) and nonpolar (αn) parameters to characterize a variety of cellulosic and noncellulosic polymers have been developed from liquid chromatographic data on retention times for selected reference solutes in aqueous solutions. The above parameters give relative quantitative measures for the hydrogen bonding and nonpolar (hydrophobic) forces inherent in the chemical structure of the polymer molecule. Unique correlations are also shown to exist between the above parameters and Hansen's solubility parameters δh and δd for the polymers. These parameters and correlations offer significant guidelines for the choice of membrane material for reverse osmosis.