ISOTROPIC LIFSHITZ BEHAVIOR IN BLOCK COPOLYMER-HOMOPOLYMER BLENDS

A series of mixtures composed of a symmetric A-B diblock copolymer and a symmetric blend of A and B homopolymers was investigated by small-a ngle neutron scattering. Mean-field theory predicts that a line of lam ellar-disorder transitions with wave-vector instability q > 0 will me et a line of critical points with q = 0 in the three-component mixtur e at an isotropic Lifshitz point. Mean-field Lifshitz behavior (gamma = 1 and nu = 1/4) was observed in the disordered state at the anticipa ted composition to within 1 K of the phase transition.