Ginzburg Number of a Homopolymer–Diblock Copolymer Mixture Covering the 3D-Ising, Isotropic Lifshitz, and Brasovskiĭ Classes of Critical Universality

Abstract

The Ginzburg number Gi of deuterated poly(butadiene) (dPB) and poly(styrene) (PS) homopolymer blend of critical composition mixed with a dPB-PS symmetric diblock copolymer was determined from small angle neutron scattering. A 3 orders of magnitude change of Gi was determined between binary polymer blend and diblock copolymer melt. The strongest change of Gi is observed within the isotropic Lifshitz regime of critical universality occurring over a 3% range of diblock concentration and interpolates the corresponding Gi of the 3D-Ising and Brasovskii regimes. A Lifshitz critical point was not observed consistent with the proposed lower critical dimension d(LCP)=4.