Microphase-separated diblock copolymers have been known since 1970 to exhibit three principal morphologies. These morphologies depend on the composition of the copolymer and include dispersed spheres of the minor component on either a BCC or FCC lattice, dispersed cylinders of the minor component on a hexagonal lattice, or alternating lamellae. Recent microstructural studies of starblock and diblock copolymers have shown that an ordered bicontinuous morphology is observed between the lamellar and cylindrical regimes. This microstructure is currently referred to as the ordered bicontinuous double-diamond (OBDD) morphology and is an example of the Pn3m space group. In poly(styrene-b-isoprene) (SI) diblock copolymers, it exists at approximately 62-66 vol% polystyrene (PS). Efforts aimed at producing this morphology by blending a copolymer with various PS homopolymers have also been successful, when the blend composition is 65-67 vol% PS and the molecular weight of the hompolymer (Mhps) is less than that of the styrene block in the copolymer (Ms). In this work, we have used transmission electron microscopy to elucidate some additional factors responsible for development of the OBDD and other bicontinuous morphologies.
Various Factors Affecting Molecular Weight Jump Reaction of cis-1, 4-Polybutadiene