Morphological reorientation by extensional flow deformation of a triblock copolymer styrene–isoprene–styrene

An oriented morphology has been generated by shear aligning a triblock copolymer SIS below its order–disorder transition (ODT) temperature. Elongational flow deformation was conducted on a polystyrene-block–polyisoprene-block–polystyrene (SIS) triblock copolymer having soft spherical microdomains composed of polyisoprene block chains in a hard matrix of polystyrene block chains with extensional rheometer (RME). The triblock copolymer has an equilibrium microphase-separated morphology of spheres (body centered cubic, BCC) of polystyrene in a polyisoprene matrix. The evolving structure was investigated with rheology, transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). The structure related to various condition of elongational flow deformation has been determined from SAXS patterns by considering separately changes in the single particle scattering, which influence the scattering patterns. The TEM and SAXS data of the film samples show that the spherical PS-domain was deformed and reoriented along the direction of elongation. It was found that the spheres microdomains are transformed into cylinder microstructures with short-range order.