ISOTHERMAL MORPHOLOGY DIAGRAMS FOR BINARY BLENDS OF DIBLOCK COPOLYMER AND HOMOPOLYMER

The equilibrium morphologies observed in over 130 diblock copolymer/homopolymer blends were summarized in two new types of isothermal morphology diagrams. Blends were prepared from homopolystyrene (hPS) and poly(styrene-b-isoprene) (SI) or poly(styrene-b-butadiene) (SB) diblock copolymer by slow solvent evaporation from a single-phase solution followed by annealing. The isothermal morphology diagrams distinguish the following morphological types: lamellae, the ordered bicontinuous double-diamond morphology, cylinders on a hexagonal lattice, spheres on a cubic lattice, disordered micelles of various shapes, and macrophase separation. The constant molecular weight morphology diagrams illustrated the dependence of the blend morphology on both the copolymer composition and the homopolymer concentration. This style of diagram showed that hPS exhibited a considerably higher solubility limit with a diblock copolymer when the majority component of the copolymer was PS. The constant copolymer composition diagrams emphasized the importance of the relative homopolymer molecular weight and the overall blend composition. These morphology diagrams provide a coherent means by which to present and predict the morphology types in binary blends of amorpbous diblock copolymer and homopolymer.