On the Schroeder paradox for nonionogenic polymers

The well-known Schroeder paradox, i.e., the difference in the degrees of swelling of nonionogenic polymers occurring at equilibrium with liquid and vapor phases, has been discussed. A simple example has been presented, which illustrates the unavoidability of different degrees of swelling for a polymer brought into contact with vapor and liquid phases. A simple mechanism has been proposed for the excess swelling of a nonionogenic polymer immersed in a liquid phase, this mechanism being associated with the action of van der Waals and solvation forces at a polymer/solvent interface. The estimation of the contribution from the van der Waals interaction to the “excess” swelling has shown that the predicted values of the “excess” swelling agree with the data of real experiments.