KINK BANDS IN A LAMELLAR DIBLOCK COPOLYMER INDUCED BY LARGE-AMPLITUDEOSCILLATORY SHEAR

Recent studies have induced a biaxial texture in lamellae-forming poly (styrene-b-ethylene propylene) diblock copolymers by applying large am plitude oscillatory shear. According to small-angle X-ray scattering, this bia-dal texture consists of ''parallel'' lamellae (normal to lame llae aligned perpendicular to the shearing surfaces) and ''transverse' ' lamellae (normal to lamellae aligned parallel to the shearing direct ion). This study determines the arrangement of these two populations o f lamellae by using field emission scanning electron microscopy to exa mine the microstructure and superstructure. The transverse lamellae ar e separated from the parallel lamellae by sets of parallel wall defect s which have two characteristic orientations. This parallel-transverse biaxial morphology shows an astonishing resemblance to that of kink b ands. The formation of kink bands suggests that the transverse lamella e could be the result of buckling in the parallel lamellae. Relaxation of the kink band superstructure during quiescent annealing occurs pri marily by lamellae tilting, rather than twisting, and produces a varie ty of defect structures.