A team led by Professor Hyo-Jae Yoon presents the possibility of developing polymers responding to mechanical forces with robust molecules.

Discovery of new reaction pathways for aziridine molecules using mechanical force.

▲ From left, Korea University Professor Hyo-Jae Yoon, Department of Chemistry, College of Science, 

Sang-Min Jung, Korea University

Professor Hyo-Jae Yoon, a professor of chemistry at the College of Science, reports his team discovered a new chemical reaction pathway for aziridine molecules by synthesizing new polymers that are sensitive to mechanical forces. The use of inactive aziridine molecules has shown that even molecules with a robust structure can respond to mechanical forces.

The research, supported by the National Research Foundation of Korea (Individual Basic Research Program and Priority Research Institute Support Program), was published in the January 12 issue of Angewandte Chemie (Impact factor: 12.257), a leading international journal in chemistry published by Gesellschaft Deutscher Chemiker (GDCh).

※ Paper Title: “Mechanical Force Induces Ylide-Free Cycloaddition of Nonscissible Aziridines”

※ Author Information: Sang-Min Jung (Korea University, lead author), Professor Hyo-Jae Yoon (Korea University, corresponding author)

Almost all chemical reactions used industrially depend on heat or light energy. On the other hand, chemical reactions to mechanical forces, especially those using ultrasound, are challenging problems that have been little studied.

Prof. Yoon's team has been working for years to overcome the shortcomings of the most used epoxies in the polymer industry. In particular, while attempting to solve the problem by replacing the epoxide functional group, the core of epoxy materials, with an aziridine functional group having a similar structure, a new polymer containing aziridine was synthesized and its chemical reactions in response to ultrasound were studied. It was found that the reactions proceed along a different reaction pathway from the cycloaddition reaction pathway of general aziridine, which proceeds in heat and light. The general cycloaddition reaction proceeds after the formation of ylide, but in the case of the reaction by mechanical force, it was observed to proceed without forming ylide.

Discovering new organic chemical pathways is a method for studying the mechanisms of chemical reactions. The discovery of new reaction pathways can have significant ramifications in that it enables the synthesis of various functional organic molecules that cannot be produced by existing synthetic methods. Observing and studying reaction pathways that could not be reached by conventional methods can be of great academic significance.

Shows that molecular structures can also be used in mechanochemistry.

Mechanochemistry research in the past has largely relied on high-energy chemical structures that are often brittle. The aziridine used in this research is regarded as a very robust and inert molecule. Thus, the study showed that even molecules with robust structures can be used to develop functional polymers that respond to mechanical forces.

In recognition of the importance and novelty of this research, the findings were approved for publication by Angewandte Chemie, the world's leading chemical authority. Professor Yoon said, “If we consider the possibility that the path of the mechanochemical reaction can be changed by the change of the structure of aziridine, a new additional chemical reaction route can be explored in the future.”

[Terminology]

1. Mechanochemistry

◯ Mechanochemistry refers to the field of studying chemical reactions driven by mechanical forces. The development of environmentally friendly chemical reactions, as well as the development of new chemical reaction pathways that could not be reached in the general chemical reactions conducted by heat and light energy, has attracted much attention, but the research itself is very difficult.

2. Cycloaddition reaction

◯ Cycloaddition refers to a reaction in which two molecules with pi bonds, when in close proximity to each other, transition to form new sigma bonds and create a ring. As the reaction proceeds according to the Woodward-Hoffman rules, the reaction mechanism may vary depending on the external energy of heat and light. In this study, we observed that different mechanisms are implemented when using mechanical forces.