Homogeneous and inhomogenous polyacrylamide gels as observed by small angle neutron scattering:: A connection with elastic properties

Small angle neutron scattering of polyacrylamide solutions and gels is presented for different polymer and cross link concentrations. The gels are analyzed in connection with their elastic properties. For less than 11% of polymer concentration and for small cross link contents c(x), it was found that the gels are no more heterogeneous than the solutions. This corresponds to the range of c(x) where the elastic modulus increases with c(x). For larger cross link contents when the elastic modulus decreases if c(x) increases, the sample appears to be strongly heterogeneous with a large size distribution of the inhomogeneities. The results are compared with the recent model of Oshmyan and Benguigui of the elastic properties of the polyacrylamide gels. Thus a relation can be proposed between the observation of the inhomogeneities by scattering and the mechanical properties.