Newswise — Supramolecular polymers represent a novel category of polymers currently undergoing evaluation for various material applications. These compounds possess intriguing characteristics and also play a significant role in cellular activities within the body. The prefix "supra" reflects their distinctive properties that surpass those of traditional polymers. Unlike conventional polymers, which rely on strong and irreversible covalent bonds for stability, supramolecular polymers are held together by weaker yet reversible hydrogen bonds. This unique feature enables them to undergo reversible assembly and disassembly processes, making them highly versatile. Consequently, they find applications in targeted drug delivery therapies, pollutant detection sensors, diagnostic markers, energy storage devices, personal care products, and self-repairing and recyclable materials. Due to their exceptional recyclability, they hold great promise for sustainable applications. However, a significant challenge remains: researchers have yet to comprehend how to precisely control the growth of these polymers.
Fortunately, recent advancements have emerged in this area. Researchers have successfully constructed "unlikely" polymers by triggering their assembly using "seeds," thereby gaining control over their growth. Seed-induced self-assembly occurs through two primary mechanisms: primary nucleation or elongation, where the polymer extends from its end, and secondary nucleation, where additional molecules adhere to the polymer's surface. Understanding the distinction between these processes is crucial as it enables researchers to exert better control and manipulation over the growth of these exceptional polymers. Unfortunately, in most instances of seeded self-assembly, differentiating between primary and secondary nucleation can be challenging.
Addressing this challenge, a team of researchers led by Professor Shiki Yagai from Chiba University embarked on a study to investigate and compare the influence of primary and secondary nucleation in the context of precisely controlled "seeded supramolecular polymerization." Their objective was to explore how different seed shapes impact the formation of new supramolecular polymers. The team's findings were initially published on May 10, 2023, and subsequently appeared in Volume 59, Issue 48 of Chemical Communications on June 18, 2023. Professor Yagai explains the team's motivation for pursuing this research topic: "Despite three decades since the concept of supramolecular polymers was established, practical applications have been hindered by the difficulty in controlling polymerization." Nevertheless, he firmly believes that due to the versatility of these self-organizing polymers, further research in this domain has the potential to yield widespread applications in our daily lives.
To conduct their experiments, the researchers utilized two different types of supramolecular polymers as "seeds." Whereas a previously studied seed had a closed-ended ring shape, a newly prepared seed featured an open-ended, helicoidal structure. The team observed that when the open-ended, helicoidal seed was employed, it acted as a template for the attachment and elongation of target molecules, facilitating their growth. Conversely, when the closed-ended ring-shaped seed was employed, it did not elongate itself but instead served as a surface where new molecules could adhere and form clusters, resembling a platform for the generation of novel structures.
This study highlights the significant influence of seed type on the assembly and final structure of self-assembling supramolecular polymers. This discovery paves the way for exciting possibilities in various applications, including the development of self-repairing materials, improved recyclability, advanced drug delivery systems, sensing technologies, and energy storage devices. Professor Yagai emphasizes the potential impact, stating, "By comprehending these assembly processes, we can design and produce the next generation of precise and eco-friendly polymers with tailored structures and properties. The practical implementation of supramolecular polymers will enable us to manufacture plastic materials with reduced energy consumption and lower recycling energy requirements."
The ability to manipulate these versatile and self-assembling polymers at the molecular level holds immense potential for addressing complex challenges and creating innovative, sustainable solutions across diverse fields such as healthcare and environmental sustainability.
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