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 pres ented for different polymer and cross link concentrations. The gels are ana lyzed in connection with their elastic properties. For less than 11% of pol ymer concentration and for small cross link contents c(x), it was found tha t the gels are no more heterogeneous than the solutions. This corresponds t o the range of c(x) where the elastic modulus increases with c(x). For larg er cross link contents when the elastic modulus decreases if c(x) increases , the sample appears to be strongly heterogeneous with a large size distrib ution of the inhomogeneities. The results are compared with the recent mode l of Oshmyan and Benguigui of the elastic properties of the polyacrylamide gels. Thus a relation can be proposed between the observation of the inhomo geneities by scattering and the mechanical properties.