Dl. Polis et Ki. Winey, KINK BANDS IN A LAMELLAR DIBLOCK COPOLYMER INDUCED BY LARGE-AMPLITUDEOSCILLATORY SHEAR, Macromolecules, 29(25), 1996, pp. 8180-8187
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.