Why is the melting point of ionic liquid low? -Investigation of role of conformational entropy-

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K05393
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 32010:Fundamental physical chemistry-related
• Research Institution: Doshisha University
• Principal Investigator: Endo Takatsugu 同志社大学, 理工学部, 准教授 (50743837)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: イオン液体 / 融点 / 融解エントロピー / 配座

Outline of Final Research Achievements

The purpose of this work is understanding why ionic liquids have such an extremely low melting point. The important results obtained here are: (1) Contrary to previous discussion that focuses on enthalpic contributions, it has been revealed that entropic contributions played a dominant role in lowering melting point of ionic liquids. (2) A computational procedure that enables the decomposition of fusion entropy has been developed, and applied to representative ionic liquids. It has been demonstrated that the configurational entropy change during melting is the largest, and subsequently, the conformational entropy change is important. (3) Conformational entropy of ionic liquids has been estimated with both computational and experimental methods.

Free Research Field

物理化学

Academic Significance and Societal Importance of the Research Achievements

イオン液体は、塩でありながら、室温付近で液体になる物質のことである。そのユニークな性質から、極めて広範囲の応用展開がなされている次世代の液体である。イオン液体の定義から考えて、「イオン液体はなぜ異常に融点が低いか」を明らかにしたことは、イオン液体の本質に迫る重要な成果と言える。更に、本研究で得られた成果は、新しいイオン液体を創出するための分子設計に大いに役立つと期待できる。