Frank-Kasper σ and A-15 Phases Formed in Symmetry and Asymmetry Block Copolymer Blend System

Abstract

Frank Kasper (FK) σ and A15 phases were found in the blend system of asymmetric and symmetric polystyrene-b-poly(methyl acrylate) block copolymers. Bates and co-workers first discovered these complex particle packings in the blend system where the diblock copolymers with a constant chain length of one component which consists of corona chains and variable chain lengths being micelle core. It is significantly important to have discover the formation of these complex phases in different block copolymer systems and also from a different research group, which strongly supports the prediction that the FK and A15 packing. Such complex phases had been found in limited conditions with a low molecular weight BCP with high χ (strongly segregated system) and conformationally asymmetric BCP system (flexibility asymmetry between constituent blocks). Discovery of the FK and A15 phases in a high molecular weight diblock copolymer without high χ or conformational asymmetry indicates a universal phenomenon of the formation of the complex particle packing in a substantially wide range of polymers.