SMALL-ANGLE NEUTRON-SCATTERING STUDY OF END-LINKED GELS

Monomer concentration fluctuations in end-linked gels are investigated as a function of the swelling ratio with the help of small angle neut ron scattering. The signals scattered by the gels are compared to thos e of semidilute solutions of linear chains of the same concentration. It is shown that the gels scatter a signal at small angles much strong er than the equivalent solutions. Such a scattering excess is attribut ed to the presence of two types of heterogeneities in the gel. Two dif ferent types of behavior are observed: at intermediate values of the s cattering vector, q, the spectra exhibit a ''shoulder'' suggesting tha t ''starlike'' objects are present in the gel while at very small angl es, the scattering intensity, I(q), increases very strongly with q. In a log representation, the scattering intensity is roughly described b y approximately phiq-3. This scattering law at small values of q is in terpreted in terms of a distribution of starlike objects in space.