Flow rates of polymer solutions through porous disks as a function of solute. I. method

A method for studying the thickness of adsorbed polymer films, based on the reduction in effective cross section for liquid flow caused by the deposition of such a film on the interior of a capillary, is described. A sintered disk is used instead of a single capillary to raise the flow rate to an easily measured level, to avoid the difficulties of obtaining or fabricating the extremely fine capillaries which would be required, and to eliminate the extreme precautions needed to prevent plugging of a single capillary. Techniques for characterizing the sintered disks are presented. When applied to benzene solutions of stearic acid and of polystyrene, film thicknesses of 30 and 312 A., respectively, were obtained. This is in good agreement with present knowledge of fatty acid adsorption, and suggests that the polymer is adsorbed in a highly extended configuration. The application of this method to solutions of poly(vinyl acetate), poly(methyl methacrylate), and polystyrene in several solvents at various temperatures is described in a following paper.