Isotropic Lifshitz Behavior in Block Copolymer-Homopolymer Blends

Abstract

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-angle neutron scattering. Mean-field theory predicts that a line of lamellar-disorder transitions with wave-vector instability $q^{*}>0\mathrm{}$ will meet a line of critical points with $q^{*}=0\mathrm{}$ in the three-component mixture at an isotropic Lifshitz point. Mean-field Lifshitz behavior ($\gamma =1\mathrm{}$ and $\nu =\frac{1}{4}$) was observed in the disordered state at the anticipated composition to within 1 K of the phase transition.