Metastable network phases from controlled self-assembly of high- χ block copolymers

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Well-ordered nanonetwork materials with triply periodic minimal surface texture are appealing and promising for innovative properties such as optical and mechanical metamaterials as inspired by nature (e.g., the photonic property from the wing structure of a butterfly and the high-impact property from the dactyl club of a mantis shrimp). Network structures possess self-supporting frameworks, open-cell character, high porosity, and large specific surface area, giving specific functions and complexity for practical applications. Here, a facile approach with simple routes for acquiring of metastable network phases beyond conventional phase diagrams is proposed and examined. By taking advantage of controlled self-assembly for high-interaction-parameter () block copolymers (BCPs), it is feasible to acquire network phases from the use of a selective solvent for self-assembly under controlled evaporation of the solvent. In contrast with the thermodynamically stable equilibrium phases from intrinsic BCPs and their blends with conventional network phases, a variety of kinetically trapped network phases with a high degree of ordering can be obtained from a single-composition lamellar phase, giving an easy method to acquire metastable network phases even for a primitive phase with large packing frustration (i.e., entropic penalty). Furthermore, the windows for network phases can even be expanded through controlled self-assembly of star-BCPs as compared with the linear-conformation diblocks. As a result, the topological architecture of BCPs could be another controlling factor to vary the phase behaviors, which may provide easy access to a variety of metastable network phases from thermodynamically stable phases through a kinetically controlled process for self-assembly. Published by the American Physical Society 2024