Crystallization in oriented semicrystalline diblock copolymers

Crystallization in oriented diblock copolymers containing poly(ethylene) (PE) has been investigated using simultaneous small-angle and wide-angle X-ray scattering (SAXS/WAXS). The orientation of the crystallized PE stems was deduced from the orientation of peaks in the WAXS pattern with respect to those in the SAXS to be parallel to the lamellar interface for symmetric diblocks containing PE and either a rubbery or glassy amorphous block. For a symmetric diblock with a poly(vinylcyclohexane) block that is glassy at room temperature we observe diffuse scattering parallel to the meridian in the SAXS pattern that is consistent with lateral correlations between PE crystallites within the layers of semicrystalline PE. In contrast, in all the samples containing an amorphous component, PE crystallization occurred with no lateral positional correlations of crystallites. Crystallization in asymmetric diblocks with compositions f_PE = 0.35 and 0.46 was also investigated. It was found that a lamellar structure is the stable solid structure and that this melts epitaxially to a hexagonal-packed cylinder structure in the f_PE = 0.35 sample. For the f_PE = 0.46 sample that forms a perforated layer phase in the melt, chain-folded PE stems were found to be parallel to the lamellar interface, as for the symmetric diblocks.