Crystal orientation within lamellae-forming block copolymers of semicrystalline poly(4-vinylpyridine)-b-poly(ε-caprolactone)

Crystal orientation and melting behavior within lamellae-forming block copolymers of poly(4-vinylpyridine)-b-poly(ε-caprolactone) (P4VP-PCL) under various nanoscale confinement have been examined. Three distinct confined spaces of 6, 8.8, and 11 nm were constructed upon varying the molar mass of diblock copolymers. For the large confined space, such as 11 nm with hard confinement and strong segregation, each PCL domain was found to accommodate perpendicularly oriented PCL crystallites. An altered confinement from 11 to 8.8 nm produced a transformation in crystallographic orientation, from perpendicular to parallel, indicating that the decrease in confined space retards the rate of crystal growth more significantly when the chain axis is parallel to the lamellar normal than when its is parallel to the lamellar surface. It was also observed that when the confined space is lower than 6 nm, the crystal orientation would be lost at deep undercoolings.