Professor Yoshiki Chujo is widely considered today as one of the most creative and productive chemists in the world. The main remarkable achievements in the field of the chemistry should be noted as the following points.
1. Organic-Inorganic Nano-Hybrid Materials
Professor Chujo has been developing very new hybrid materials based on sol-gel reaction. Nano-ordered composite materials consisting of organic polymers and inorganic materials have been attracting attention for the purpose of the creation of high-performance or high-functional polymeric materials. Especially, the word of "polymer nanohybrid materials" claims the blends of organic and inorganic components at nano-level dispersion. By using this idea, he demonstrated the importance of the design of specific interactions between organic polymers and inorganic matrix. The precise design of such interactions made possible to produce molecular level hybrid materials. Such examples include hydrogen bonding, π-π interaction, ionic interaction, charge-transfer complex formation, hydrophobic interaction, CH-π interaction, CH-halogen interaction, stereo-complex formation, crystalline phase formation, and metal-ligand coordination. These hybrid materials exhibit an enhancement of mechanical strength and thermal stability of organic polymers and also high transparency.
2. Advanced Functional Materials Based on POSS (Polyhedral Oligomeric Silsesquioxanes)
Professor Chujo focused on the rigidity and versatility of the cubic polyhedral oligomeric silsesquioxanes (POSS). Based on the POSS structure, he discovered new functional materials such as low refractive materials, excellent fillers for polymers, POSS ionic liquids, POSS liquid crystals, effective and low-toxic MRI agents based on POSS.
3. New Hybrid Materials Based on Metal Nanoparticles
Professor Chujo also prepared new hybrid materials based on metal nanoparticles. Various types of these hybrid materials were discovered by his new idea. Such remarkable example is the formation of transparent electron-conducting films consisting of metal nanoparticles. The controlled self-assemblies of metal nanoparticles assisted by the functional polymers were demonstrated in one-, two- and three-dimensional structures. Especially, one-dimensional assembly was noted for the use of electrical nano-wires. He applied these metal nanoparticles hybrid materials to the optical and electronic materials. He also utilized these materials in the bio-medical field as MRI imaging materials.
4. Controlled Mineralization of Carcium Carbonate by Means of Polymer Matrix
It should be also noted that the nucleation and growth of calcium carbonate was successfully controlled by Professor Chujo. By using in-situ delayed polymerization method, the crystal morphology of calcium carbonate, calcite, vaterite, or aragonite, was selectively controlled.
5. New Stimuli-Responsive Hydrogels Based on Polyoxazoline
New stimuli-responsive hydrogels based on polyoxazoline were developed by Professor Chujo. Hydrophilic polyoxazolines produced non-ionic hydrogel. In these materials, he demonstrated the reversible gelation by using photo-dimerization, Diels-Alder reaction, redox reaction of thiol, and metal complexation. As a result, the swelling property was easily controlled by outer stimuli. It is also noted that the idea of reversible formation of gel makes possible to create a recycling thermosetting hydrogels.
6. New Luminescent Organoboron Materials Based on Conjugated Polymers
He explored the first example of the mainchain-type organoboron conjugated polymers. And then, a huge number of the luminescent organoboron polymers (e.g., poly(cyclodiborazane)s, poly(pyrazabole)s, poly(boron quinolate)s, poly(boron diketonate)s, BODIPY polymers, or carborane polymers) were discovered by Professor Chujo. These polymers showed very interesting luminescent properties (various tuned colors including white-light emission, aggregation-induced emission, crystal-induced emission, and so on).
7. New Polymeric Materials Based on Element-Blocks
It should be pointed out that Professor Chujo prepared new polymers having various types of inorganic elements or their blocks in the main chain. Such examples are consisting of the elements of B, Al, Ga, In, Si, Ge, P, As, Sb, Bi, S, Se, and others. Most of these polymers are the first examples of such elements-containing mainchain-type ones, and he proposed a new idea of "Element-Blocks". These polymers are strongly expected to show unique and interesting properties as new optic, electronic, magnetic and biomedical materials. For the preparation of these new materials, he discovered new polymerization methods. This would be very important point to explore the new chemistry for the functional materials.
The impact of Professor Chujo's work is manifested in the discovery of new organic-inorganic hybrid materials at the molecular level. These hybrid materials show very unique optical and electrical properties. Under this line, he has just started the national project (Scientific Research on Innovative Areas) in Japan titled "New Polymeric Materials Based on Element-Blocks".
In summary, the works of Professor Yoshiki Chujo in the field of chemistry stand out as pioneering. It is, therefore, with the outmost enthusiasm that he should be awarded for "the Chemical Society of Japan (CSJ) Award" for his brilliant contributions to chemistry.