THE ORDERED BICONTINUOUS DOUBLE-DIAMOND MORPHOLOGY IN DIBLOCK COPOLYMER HOMOPOLYMER BLENDS

The ordered bicontinuous double-diamond (OBDD) morphology was prepared in binary blends of poly(styrene-b-isoprene) or poly(styrene-b-butadiene) diblock copolymer (AB) and a homopolymer (hA). Previously reported observations of the OBDD morphology have been restricted to linear and star diblock copolymers. The ability to form the OBDD morphology was influenced by the homopolymer concentration, the homopolymer molecular weight, and the composition of the copolymer. The overall polystyrene (PS) volume fraction required for a polystyrene-rich OBDD morphology was approximately equivalent for the neat copolymers and the blend systems, namely, 64-67 vol % PS. If a diblock copolymer which forms the lamellar morphology was used in the blend, the homopolymer resides in the matrix region of the OBDD morphology. However, if a diblock copolymer with the cylindrical morphology was used to prepare the OBDD morphology in a blend, the homopolymer resides inside the channel regions. Attempts to prepare the OBDD blend morphology with homopolymer in the matrix region using a diblock copolymer with the cylindrical morphology failed; these blends underwent macrophase separation.