Dl. Polis et Ki. Winey, CONTROLLING KINK BAND MORPHOLOGY IN BLOCK-COPOLYMERS - THRESHOLD CRITERIA AND STABILITY, Macromolecules, 31(11), 1998, pp. 3617-3625
The initiation, structure, and dynamics of defects control both the st
ructure and physical properties of materials. In this work, kink band
defects are systematically introduced into a lamellar poly(styrene-b-e
thylene propylene) diblock copolymer by applying various rates and tot
al strains of steady shear. However, kink bands are only produced when
the shear strain exceeds a critical value. The mere existence of kink
bands implies the presence of a preferential slip plane parallel to t
he lamellae, which we estimate exists within the polystyrene microdoma
ins. Furthermore, our results regarding the dependence of kink band ge
ometry on shear rate and strain suggest that these defects are formed
by the rotation of lamellae. Based on a rotation mechanism, the charac
teristic size of the kink bands and their spatial distribution, it app
ears that preexisting defects initiate kink bands. Insights gained fro
m steady-shear-induced kink bands are extended to oscillatory shear al
ignment of this high molecular weight diblock copolymer, allowing us t
o circumvent a previously reported shear-stabilized parallel-transvers
e biaxial texture.