Cylindrically Confined Diblock Copolymers

Lamella-, cylinder-, and sphere-forming block copolymers (BCPs) of polystyrene-b-polybutadiene (PS-b-PBD) were drawn into the pores of anodized aluminum oxide (AAO) membranes in the melt by capillary forces. After thermal annealing, the nanorods of the BCP were removed by dissolution of the AAO with a weak acid, and transmission electron microscopy (TEM) was used to investigate the resultant morphologies of the confined BCPs. The diameters of the pores in the AAO and the molecular weight of the block copolymers were varied to investigate the effect of confinement on the microphase separation of the BCP. Concentric cylinders were observed for the lamella-forming BCPs under 2D confinement, and deviations of the lamella repeat period were measured as a function of AAO pore diameter. In addition, torus-like morphologies were observed as the degree of confinement increased. For the bulk cylinder-forming BCPs, a rich variety of morphologies, not seen in the bulk, were observed that included stacked torus-like m...