PARTITIONING INVERSION OF A BIMODAL POLYMER-SOLUTION IN CONFINED GEOMETRIES

The partitioning of solvated polymer molecules with a bimodal molecular weight distribution between a confined geometry such as a porous medium and an external free volume has been investigated. Applying the results of renormalization group theory, we derive the chemical potentials in the interior and exterior of the pore for each fraction of the polymer in equilibrium. It was found that, as the concentration of the high molar mass macromolecule exceeds the overlap concentration in the exterior, the low molar mass fraction is driven into the restricted pore channels, while the high molar mass fraction remains outside. We note that this segregation effect could in principle be used to recover a low molar mass fraction in high purity from a mixture. The implication of this finding with respect to size-exclusion chromatography is also briefly mentioned.