Oriented association of multiwall carbon nanotubes upon efficient epitaxial organization of polyfluorene

Upon the epitaxial crystallization of poly(9,9-di-n-octyl-2,7-fluorene) from prior smectic organization, originally dispersed carbon nanotubes were found to be segregated into noncrystalline regions in between stacked crystalline lamellae. Arrays of oriented nanotube bundles subsequently resulted upon the establishment of regular lamellar stacking. Dependent on the domain sizes of resultant composite crystals, these intercalated nanotube bundles continuously extended for several micrometers in a slightly wavy manner. When the stacking of crystalline lamellae of polymer matrix is less efficient, the separation between neighboring bundles become wider and less uniform. Upon the increase of the extent of undercooling, the lamellar stacking effectively arrested the migration of carbon nanotubes, and the decline of both bundles diameter and waviness was observed. Accordingly the stacking of crystalline lamellae emerges to serve as an adjustable template for organizing carbon nanotubes within thin film of conjugated polymers. The dispersion of carbon nanotubes within smectic phase modifies the ultraviolet absorption spectrum and also the packing symmetry of later developed crystal structure. The inevitably involved irregularity of backbone distortion manifests the prevalence of the favored attractive interactions between nanotubes and fluorene backbones, which is viewed to render the self-aggregation of nanotubes at domain boundaries less favorable.