The evolution of kink bands and kink band boundaries in a prealigned poly(s
tyrene-b-ethylene propylene) lamellar diblock copolymer was investigated by
applying steady shear at strains in the range of 1-10 strain units. Bounda
ry morphologies were characterized using transmission electron microscopy.
As the shear strain increases, both the kink bands and the lamellae within
the kink bands rotate continuously toward the shearing direction, leading t
o a decrease in the tilt boundary angle and the kink band boundary angle. S
imultaneously, the nature of the kink band boundary transforms. The chevron
boundaries present at low strains, and thus large tilt angles, become omeg
a boundaries as the strain increases to similar to 3 strain units. At highe
r strains (similar to 5 strain units), the tilt angle further decreases, an
d the omega boundaries start to break, preferentially in the PS microdomain
s. Delamination of the PS microdomains was also observed at the highest str
ain amplitude (10 strain units), which was associated with the limited exte
nt of entanglement across the PS microdomains.