Research Activities

In our laboratory, we are developing polymeric materials using topological supramolecules. Among these, materials based on rotaxane and polyrotaxane—composed of cyclic and axial molecules—have attracted significant attention 1). This is because cyclic molecules slide along axial polymers, resulting in structures, properties, and functions that differ from those of conventional polymer materials. Slide-Ring Materials and quasi-polyrotaxane nanosheets, both invented in our laboratory, are currently under active research and development. Our laboratory is also participating in several large national projects aimed at using these innovative materials to address global environmental problems.

1) Slide-Ring Materials
By cross-linking cyclic molecules in polyrotaxane, we have developed Slide-Ring Materials in which the cross-linking points can move freely 2). In conventional crosslinked polymers, the length of the polymer chains between crosslink points is not uniform, causing stress and tension to concentrate easily, which results in low toughness. Since the cross-linking points of Slide-Ring Materials move freely, they act like dynamic pulleys (known as the pulley effect), dispersing the concentration of stress and tension within the polymeric materials. This greatly improves toughness, elongation at break, durability, and other mechanical properties. The entropy of the rings also brings about characteristic dynamic properties due to the sliding motion of the rings, such as sliding transition, which is not seen in conventional polymeric materials. Although the Slide-Ring Materials were first developed as gels, the concept has proven effective for elastomers and resins as well 3). In particular, the addition of a small amount of polyrotaxane to usual elastomers and resins can significantly improve their toughness. The application and development of Slide-Ring Materials are progressing in various fields and have been put into practical use.

2) Pseudo-polyrotaxane nanosheet
Substances and materials in the form of nanoscale thickness sheets are called nanosheets. Many inorganic materials, such as graphene and titanium dioxide, are recognized as nanosheets and have attracted significant attention as two-dimensional materials. We recently discovered that isolated nanosheets about 16 nm thick and several micrometers in size can be synthesized in large quantities through a self-assembly process by mixing β-cyclodextrin and a triblock copolymer of poly(ethylene glycol)-poly(propylene glycol)-poly(ethylene glycol) in water 4). These nanosheets exhibit excellent biosafety and biocompatibility, adsorb onto various organic, inorganic, and biomaterials regardless of surface roughness, and form relatively dense polymer brushes in water. They are expected to have applications in medicine and healthcare.

3) Research Projects
Our laboratory is involved in the following national projects in the role of management and/or research.
- Moonshot Program
Microplastics in the ocean are currently a global issue. We are leading a project entitled "Research and Development of Marine Degradable Multi-Loc biopolymers from Inedible Biomass" under Goal 4 of the Moonshot Program by the New Energy and Industrial Technology Development Organization (NEDO), which started in 2020. We are developing innovative biopolymers having toughness and marine biodegradability at the same tome in collaboration with industry and academia.

http://www.moonshot.k.u-tokyo.ac.jp/

- Cross-Ministerial Strategic Innovation Program (SIP)
The transition from the current linear economy of mass production, mass consumption, and mass disposal to a circular economy that uses resources sustainably while satisfying economic rationality is a global challenge. Under the SIP Program launched by the Cabinet Office in fiscal year 2023, I lead the "Building a Circular Economy" program, collaborating with industry and academia to address the challenges of plastic recycling.
https://www.erca.go.jp/erca/sip/ce.html

- JST-Mirai Project, Large-scale type
Participating in the "Construction of Innovative Adhesion Technology by 4-Dimensional Analysis of Interface Multiscale" supervised by Distinguished Professor Keiji Tanaka (Kyushu University) and working on the development of molecular adhesion technology using the Slide-Ring Materials.
https://crea.kyushu-u.ac.jp/

Literature

1) L. F. Hart, et al., Nat. Rev. Mater., 6(6), 1-23(2021).
2) Y. Okumura and K. Ito, Adv. Mater. 13(7), 485-487(2001).
3) Y. Noda, et al., J. Appl. Polym. Sci., 131, 40509(2014).
4) S. Uenuma, et al., ACS Macro Lett., 10(2), 237-242 (2021).

Other Activities

Academic Societies：The Society of Polymer Science, Japan, The Chemical Society of Japan, The Cyclodextrin Society of Japan

Future Plan

Polymeric materials have become ubiquitous in our daily lives due to their lightweight and convenience. However, various challenges have become apparent, exemplified by issues like microplastics. In our laboratory, we collaborate with industry and academia to tackle social issues using proprietary technologies we have invented. We aim to develop innovative polymeric materials that are environmentally friendly, durable, long-lasting, recyclable, and capable of biodegrading if released into the environment.

URL

http://www.molle.k.u-tokyo.ac.jp/index_e.html