Perpendicular deformation of a near-single-crystal triblock copolymer with a cylindrical morphology. 2. TEM

A poly(styrene-block-isoprene-block-styrene) (SIS) triblock copolymer with a polystyrene (PS) cylinder morphology was globally oriented via roll-casting. Transmission electron microscopy (TEM) was used to assess the quality of orientation. The roll-casting process produces films with near-single-crystal-like orientation. Large strain deformation was applied perpendicular to the cylinder axis and retained by irradiating the sample with high energy electrons. TEM of sections viewed parallel and perpendicular to the cylinder axis provided real space information on the deformed morphology. For views parallel to the cylinder axis, the initial hexagonal packing of the cylinders distorts into a faulted twinlike texture in which layers of cylinders are oriented at fixed angles with respect to the stretching direction (SD). These fault boundaries are separated by an average distance of about 0.1 mum at 180% deformation. Direct evidence for a chevron texture in which the cylinders kink and turn into the SD was observed at perpendicular incidence. Kink boundaries are separated by an average distance of about 5 mum at a strain df 180%. Optical transforms (OTs) of the TEM images as well as SAXS on deformed irradiated samples are used to directly connect the results to the dynamic SAXS described in a complementary paper.(1) A 3-D model of the deformed morphology summarizes the real space data self-consistently and provides the basis for an interpretation of the dynamic SAXS data.