Oriented Microstructures of Crystalline-Crystalline Block Copolymers Induced by Epitaxy and Competitive and Confined Crystallization

Polyethylene-block-syndiotactic polypropylene (PE-block-sPP) crystalline-crystalline block copolymers with different block lengths have been synthesized with a stereospecific living organometallic catalyst. Samples of PE-block-sPP have been epitaxially crystallized onto crystals of p-terphenyl (3Ph) to achieve a control over the crystallization of both blocks and study the dependence of the thin film morphology on the sequential crystallization of the two blocks by cooling from the melt. The epitaxial crystallization generates oriented overgrowth of both crystals of sPP and PE, with a highly ordered single orientation of sPP lamellae and a double orientation of PE lamellae onto the (001) face of 3Ph. The final morphology depends on which polymer block crystallizes first, a sequence that depends on the block copolymer composition and block lengths. Ordered nanostructures with alternating lamellar domains are obtained and oriented by the lamellae that crystallize first.