Exploration of Complex Morphologies in Block Copolymers through End-Group Chemistry

Block copolymers can self-assemble into various nanostructures, such as lamellae, cylinders, spheres, and gyroids, influenced by block compositions and thermodynamic incompatibility of two blocks. The gyroid structure, however, occupies a narrow stability window in phase diagram due to packing frustration arising from the thickness mismatch between channels and intersections. Consequently, thermodynamically stable network structures with tetrapod, hexapod, or more complex intersections have been extremely rare in block copolymers. While developing diverse network morphologies from block copolymers is a challenging task, it has received significant attention as a promising strategy to enhance mechanical, transport and optical properties across three-dimensionally interconnected networks. In this study, we propose using end-group chemistry as a method to alleviate packing frustration and stabilize network structures over a wide phase window in block copolymers. Particularly, the introduction of different di-end-functional groups into block copolymers to induce different strengths of end-end interactions through controlled linkages has resulted in the emergence of rich network morphologies. This enables the development of thermodynamically stable plumber's nightmare structures in block copolymers, which is unprecedented The underlying mechanisms for this is end-end interaction-driven manipulation of interfacial curvature, which can be broadly applied to block copolymers with diverse backbone structures, molecular weights, and block compositions. This study highlights the crucial role of end-group chemistry in influencing the self-assembly behavior of block copolymers, offering new opportunities for morphology control without the need for complicated synthetic procedures.