Plumber's nightmare structure in block polymers

Professor Moon Jeong Park and PhD candidate Hojun Lee from POSTECH's Department of Chemistry brought to life nanostructures of block copolymers (hereafter BCPs), which were previously only envisioned. This study was featured in Science and published on the fifth of January 2024.

BCPs represent polymers constructed by linking blocks of one monomer with blocks of another. Capable of self-assembly, BCP's craft diverse nanoscale structures, finding widespread applications across fields covering semiconductor and medicine. Recent studies have been vigorously exploring comparisons in optical and mechanical properties based on BCP structure. However, as structures grow more intricate, their thermodynamic stability diminishes, posing considerable challenges in their production.

Among these structures, the plumber's nightmare, exhibiting medial packing of polymer chain ends, stands as an immensely complex and distinctive formation. While real-life instances of its manifestation were absent, it was hypothesized to possess unique optical and mechanical traits due to its distinctive channel structure, setting it apart from other nanostructures.

In this groundbreaking research, the team defied expectations by turning the impossible into possible. While most research has focused on the main polymer chains constituting BCPs, the researchers shift their focus to the inconspicuous, less than one percent, chain ends. They crafted di-end-functionalized BCPs by linking different molecules to each end of the polymer chain. Consequently, the polymer chain ends exhibited robust mutual attraction, causing all the polymer tails to coalesce inward, marking the team's successful realization of the plumber's nightmare structure, a world's first achievement.

Furthermore, the team successfully produced a range of BCP structures that had hitherto remained enigmatic, including gyroid and diamond structures. This accomplishment in materializing BCP structures previously confined to the realms of imagination and theory stands as a significant feat.

Of particular note, this study's significance lies in the conclusion that complex structures can be stably realized when potent forces exist at the ends, despite diverse adjustments made in BCP polymer composition and the main chain's chemical properties. This suggests the universal applicability and adaptability of this research for future studies focused on developing diverse composite-structure polymer nanostructures.

Professor Alisyn J. Nedoma from the University of Sheffield, an expert in the BCP field, remarked in the Science commentary, "It lays the groundwork for designing novel BCP nanostructures," assessing the potential cost-effectiveness in creating nanostructures with desired characteristics (see the Perspective by Nedoma).

The study's lead, Professor Moon Jeong Park explained, "This research has enabled us to establish a method for developing tailored network structures in polymer BCP. It will serve as a platform for crafting polymer BCPs with diverse properties in nano-technology applications."

This work was conducted with support from the following programs under the National Research Foundation of Korea: Mid-Career Researcher Program, Creative Materials Discovery Program, and Science Research Center Program.