The effect of concentration on the distribution of macromolecules between solution inside the pores and outside the porous medium after mixing of polymer solution with the medium was investigated. Experimental measurements were carried out for polystyrene standards in a thermodynamically good solvent-tetra-hydrofuran, and in a mixed theta solvent tetrahydro-furan-methanol. The results of measurements, particularly in the theta solvent, suggested a considerable effect of secondary non-exclusion interactions. A comparison between the distribution coefficients calculated theoretically using various models and those determined experimentally revealed a considerable discrepancy. It is obvious that the reported theoretical models of concentration dependence of the distribution coefficients under stationary conditions do not adequately reflect the real situation. The individual likely causes of this discrepancy have been critically discussed.
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