Scaling approach to dilferential swelling of polymer solutions and gels

The failure of the classical theories for swollen polymer networks was clearly demonstrated by recent differential swelling experiments of Gee, Eichinger and McKenna. We introduce a weaker form of the additivity assumption based on the separation of the gel into “solid"-like and “liquid"-like components. Using simple scaling arguments and the assumption that the effective solvent quality for a crosslinked polymer system is worse than for its uncrosslinked counterpart, we predict a similar anomaly of the swelling activity parameter (dilation modulus) in osmotic deswelling experiments in the semi-dilute range of concentration. The relevance to Eichinger's and McKenna's experiments on concentrated systems is discussed