For uncompatibilized blends, the relationship between particle size and composition is symmetric about the phase inversion composition; whereas, blends compatibilized with IA show an intense asymmetric behavior, i.e. SAN dispersed particles in a nylon 6 matrix are quite small, while nylon 6 particles in a SAN matrix are much larger and are elongated. On the other hand, the blends compatibilized with SANMA show a weak asymmetry. This asymmetry is seen for three nylon 6 materials of differing molecular weight.