A Pathway Toward Sub‐10 nm Surface Nanostructures Utilizing Block Copolymer Crystallization Control

Abstract It is elucidated how crystallization can be used to create lateral surface nanostructures in a size regime toward sub‐10 nm using molecular self‐assembly of short chain crystallizable block copolymers (BCP) and assist in overcoming the high‐χ barrier for microphase separation. In this work, an amphiphilic double‐crystalline polyethylene‐b‐polyethylene oxide (PE‐b‐PEO) block co‐oligomer is used. A crystallization mechanism of the short‐chain BCP in combination with neutral wetting of the functionalized substrate surface that permits to form edge‐on, extended chain crystal lamellae with enhanced thermodynamic stability. In situ atomic force microscopy (AFM) analysis along with surface energy considerations suggest that upon cooling from the polymer melt, the PE‐b‐PEO first forms a segregated horizontal lamellar morphology. AFM analysis indicates that the PEO crystallization triggers a morphological transition involving a rotation of the forming extended chain crystals in edge‐on orientation. Exposing their crystal side facets to the top surface permits to minimize their interfacial energy and form vertical nanostructures. Moreover, the edge‐on lamellae can be macroscopically aligned by directed self‐assembly (DSA), one necessity for various nanotechnological applications. It is believed that the observed mechanism to form stable edge‐on lamellae can be transferred to other crystallizable short chain BCPs, providing potential pathways for sub‐10 nm nanotechnology.