SPring-8, the large synchrotron radiation facility

A research group of Kyoto University (President, Hiroshi Matsumoto) and JASRI (President, Tetsuhisa Shirakawa) has succeeded in developing a method to measure the dynamic behavior of molecules in soft matters^*1 with a time scale of around 100 ns using the unique properties of γ-rays scattered from a nucleus that is resonantly excited using high-brilliance synchrotron radiation. Using this method, the dynamics of molecules in liquid crystals was examined and their state of association was clarified for the first time in the world.

The speed of motion of molecules in soft matters, such as liquid crystals, is lower than that in liquids; this low mobility, with a time scale of greater than nanosecond order, has been attracting attention. In particular, various types of motion are considered to occur in soft matters with complicated compositions, such as those in human bodies. Therefore, the development of a measurement method that can simultaneously specify the size of a moving area and observe the motion is especially important because it should significantly help us microscopically understand the fundamentals of soft materials. However, with conventional methods, the rapid microscopic measurement of the motions of atoms and molecules with a size of 0.1 – 6 nm in a time scale of 1 ns - 10 µs while specifying their length has been impossible. The research group produced highly directional and highly monochromatic γ-rays using synchrotron radiation generated by the Nuclear Resonant Scattering Beamline (BL09XU) of SPring-8.^*2 By observing the temporal changes in the intensity of γ-rays scattered upon irradiation onto a soft matter, they found that the dynamic behavior of molecules in the intralayer motion was equivalent to that in the interlayer motion for an amphiphilic liquid crystal (samples were provided by Isa Nishiyama, DIC Corporation) whose molecules were designed to associate with those of typical crystals. The result indicates that no strong microscopic molecular association was induced in the amphiphilic liquid crystal-based material. This study was the first to demonstrate that such a method can be applied to soft matters. This method is expected to lead to advances in research on microscopic dynamics in soft matters and to clarification of the dynamic behavior of molecules in living organisms.

This study was carried out by Makina Saito (Graduate Student) and Jun Yamamoto (Professor) of the Graduate School of Science, Kyoto University; Makoto Seto (Professor) of Kyoto University Research Reactor Institute; Yoshitaka Yoda (Senior Scientist) of JASRI, and other members. It was carried out as part of research with the theme "Studies on Nuclear Resonant Scattering Methods for Material Science" (Research Director: Makoto Seto) in the research field "Novel Measuring and Analytical Technology Contributions to the Elucidation and Application of Material" (Research Supervisor: Michiyoshi Tanaka, Professor Emeritus, Tohoku University) as part of the Core Research for Evolutional Science and Technology (CREST) project supported by JST. It was also supported by JASRI as a SPring-8 power user proposal with the theme "Studies on advanced nuclear resonant scattering methods for materials science" (Leader: Makoto Seto). The results of this study were published online in the international journal Journal of the Physical Society of Japan (JPSJ), published by the Physical Society of Japan, on 11 January 2012. It was also chosen as one of the "Papers of Editor's Choice" recommended by the JPSJ Editorial Committee.

Publication:
"Small and Large Angle Quasi-Elastic Scattering Experiments by Using Nuclear Resonant Scattering on Typical and Amphiphilic Liquid Crystals"
M. Saito, M. Seto, S. Kitao, Y. Kobayashi, M. Kurokuzu, Y. Yoda, and J. Yamamoto
Journal of the Physical Society of Japan 81(2012) 023001