Perpendicular deformation of a near-single-crystal triblock copolymer witha 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-casti ng. Transmission electron microscopy (TEM) was used to assess the quality o f orientation. The roll-casting process produces films with near-single-cry stal-like orientation. Large strain deformation was applied perpendicular t o the cylinder axis and retained by irradiating the sample with high energy electrons. TEM of sections viewed parallel and perpendicular to the cylind er axis provided real space information on the deformed morphology. For vie ws parallel to the cylinder axis, the initial hexagonal packing of the cyli nders 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 incidenc e. 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 p rovides the basis for an interpretation of the dynamic SAXS data.