Development of leading-edge organic polymer materials toward emerging energy technologies and organic electronics has been addressed as a keen subject in chemical science and technology. Prof. Nishide has evoked renewed attention on organic radical molecules, which were known as intractable molecules in view of materials science. Through extension to their polymeric analogues, he has successfully developed rational design and syntheses of markedly robust organic radical polymers, which evolved a new field of "organic radical polymers in materials science" such as magnetic, electro-active materials. With in-depth understanding of exchanging and transporting phenomena of electric spins and charges, he has demonstrated ferromagnetic spin alignment and rapid charge-transport and -storage in the polymeric materials. His perspectives on organic radical polymers envisioned a new frontier of functional polymer chemistry and materials science, in particular, advances in energy-related materials. Some of his outstanding accomplishments are listed below:

1. Design of Conjugated Polyradicals for Magnetic Polymers
He has established the molecular designing and synthetic chemistry of high-spin magnetic polymers via precision poly-condensation and -addition reactions for head-to-tail connectivity of π -monomers, and precise introduction of multiple pendant radical groups in a non-Kekulé and non-disjoint fashion, which enabled through-bond, intramolecular ferromagnetic interaction or high-spin alignment in π-conjugated polyradicals. Extension of linear to branched and/or dendritic p-conjugated pathway lead to high-spin alignment in the quasi-multi-dimensional framework. Magnetic force microscopy clearly detected the durable and high-spin organic polyradical single molecule with a nanometer-sized, designable molecular shape, and tunable radical concentration. For instance, self-assembled array of polyradicals on the pre-patterned substrates via hydrophilic/phobic interaction has been demonstrated as a magneto-responsive nano-dot array.

2. Synthetic Chemistry of Organic Radical Polymers and Their Charge-Transport and -Storage
He has focused on redox reactions of robust radical molecules to yield the corresponding cation/anion and initiated the utilization of such reversible one-electron exchange process for charge-transport and -storage. The polymer designing strategy for charge-transport and -storage materials with high charge propagating capability, high charging rate, and long cycle life has been established. In general, radical molecules cannot be polymerized via conventional radical chain-growth polymerization. He challenged direct polymerization of radical monomers systematically, and successfully established synthetic chemistry of so-called "radical polymers", aliphatic polymers bearing redox-active stable radical pendant groups, by using new catalysts and polymerization techniques. Along the design criteria, he has developed organic radical polymers with facile polymer processing and large-scale production.
Electron self-exchange reactions between radicals were extremely rapid, and successive electron exchange among densely accumulated radicals along the polymeric backbone resulted in reversible and quantitative charge-transport and -storage in the polymer. He demonstrated that radical polymers served as electrode-active materials based on rapid heterogeneous electron transfer at interface of current collectors, and electron self-exchange / homogeneous electron transfer kinetics of radicals. Concentration-driven charge-transport in a long-distance was electrochemically analyzed and described as macroscopic current generation based on a sort of chemical reactions.
Radical polymer-based electrode-active materials were characterized by quantitative charge storage based on radical amounts and rapid charging capability. A (semi-)transparent, flexible and thin film configuration ensured their utilization to all plastic-based rechargeable batteries. Photo-current conversion devices by radical polymers has been investigated as organic solar cells, especially coupled with charge-storage toward a cord-less power source assisted by interior lighting.

3. Functional Polymers Based on Exchanging Reactions
Inspired by hemoglobin molecule as an oxygen carrier, he developed macromolecular metal complex membranes for selective and facilitated oxygen transport from air to yield oxygen-enriched gas production. Based on reversible and rapid binding/releasing of oxygen molecule by the metal complexes of cyclic conjugated ligands such as porphyrin, he prepared a solid membrane with rapid oxygen interaction, where oxygen permeated selectively by exchanging reaction among porphyrin sites. He described concentration-driven, selective permeation of oxygen quantitatively. Based on exchange rate constant and concentration-driven enhancement of flux, he has verified ultimately enhanced oxygen/nitrogen selectivity.

As shown above, his accomplishments were summarized on new exploration of organic radical chemistry in materials science. Especially, in view of exchanging phenomena of spins and charges, he has developed organic radical polymers, which were believed to be intractable, as robust as conventional polymeric materials at ambient conditions, and established a new area on these materials for practical use. Organic radical polymers he developed are practically useful in various organic-based devices, and are expanding their use in wide applications. All his significant contributions covering fundamentals to applications deserves for the Chemical Society of Japan (CSJ) Award.