Synchrotron Small‐Angle X‐Ray Scattering Studies on Flow‐Induced Gyroid to Cylinder Transition in an Elastomeric SBS Triblock Copolymer

Abstract We report elongational flow‐induced morphological transition from double gyroid (DG) to hexagonal cylinders in polystyrene‐block‐polybutadiene‐block‐polystyrene triblock copolymer (SBS). First, the SBS sample was fully annealed at 190°C for 24 hr to prepare a DG structure. Then the sample was subjected to planar elongational flow at 190°C for 24 hr. Two‐dimensional, small‐angle x‐ray scattering (2d‐SAXS) measurements revealed that the DG structure transformed into uniaxially aligned cylinders with hexagonally close packing upon imposing the flow, where a (101¯0) plane of the hexagonally packed cylinders was preferentially aligned parallel to the substrate.