CRYSTALLIZATION IN ORIENTED SEMICRYSTALLINE DIBLOCK COPOLYMERS

Crystallization in oriented diblock copolymers containing poly(ethylen e) (PE) has been investigated using simultaneous small-angle and wide- angle X-ray scattering (SAXS/WAXS). The orientation of the crystallize d PE stems was deduced from the orientation of peaks in the WAXS patte rn with respect to those in the SAXS to be parallel to the lamellar in terface for symmetric diblocks containing PE and either a rubbery or g lassy amorphous black. For a symmetric diblock with a poly(vinylcycloh exane) block that is glassy at room temperature we observe diffuse sca ttering parallel to the meridian in the SAXS pattern that is consisten t with lateral correlations between PE crystallites within the layers of semicrystalline PE. In contrast, in all the samples containing an a morphous component, PE crystallization occurred with no lateral positi onal correlations of crystallites. Crystallization in asymmetric diblo cks 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 i n the f(PE) = 0.35 sample. For the f(PE) = 0.46 sample that forms a pe rforated layer phase in the melt, chain-folded PE stems were found to be parallel to the lamellar interface, as for the symmetric diblocks.