Ternary mixture of a homopolymer blend and diblock copolymer studied near the Lifshitz composition by small-angle neutron scattering

A ternary mixture of two homopolymers and the corresponding diblock copolymer represents a good model system to study critical phenomena near the mean field predicted Lifshitz point. The structure factor of concentration fluctuations is in this regime of the phase diagram described by a formula which independently accounts for the peak-position q*, the scattering intensity at q*, S(q(*), and the forward scattering, S(0). The susceptibility, which is given by the maximum value of either S(0) or S(q*), shows markedly renormalized critical behavior with critical exponents significant larger than the 3d-Ising value relevant for simple binary blends.