Gels made by radical copolymerization of monofunctional and difunctional monomer units in the presence of swelling medium will tend to be heterogeneous. A case in point is acrylamide copolymerized with N,N prime -methylene bis-acrylamide in water. As Weiss and Silberberg have shown, permeability can be used to characterize the distribution in space. In this paper, their earlier model is expanded and improved by considering specifically the permeability of each of the two phases and taking into account that each of these phases separately must have come into swelling equilibrium with the swelling medium, water. It is shown that only the length of the Kuhn statistical element remains as a free parameter in this model. The heterogeneity of the distribution lies in the nanometer range and reasonable agreement between the results obtainable from permeability and from viscoelasticity can be demonstrated. These results are consistent with the model for the polymerization process.
