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

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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.