Amphiphilic polymers and supramolecules, as well as natural bio(macro)molecules such as proteins and phospholipids, self-organize into molecular assemblies in water or specific environments. These molecules not only form precision aggregates in pure media in the absence of others but also afford selective self-assembly, called self-sorting, even in complex media including other molecules, depending on the molecular design. In this issue, the authors introduce cutting-edge (macro)molecular self-assemblies, focusing on the design of (macro)molecules for controlled self-assembly, characterization of structure, dynamic behavior, and hydration of molecular assemblies, self-assembly and self-sorting systems in complex or specific environments, and development of functional materials.

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SPSJ PMF Poster Awards 2025

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[in Japanese]

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Polymer self-assembly in aqueous media provides versatile platforms for functional materials in biomedical, interfacial, environmental, and energy-related applications. Recent progress has shifted the field from descriptive observation toward a design-oriented framework that emphasizes reproducibility and functional integration. This advance is supported by three key factors: precise control of polymer primary structures enabled by controlled radical polymerization, improved understanding of nonequilibrium assembly processes, and rational design of hydration at polymer-water interfaces. In particular, electrostatically driven assemblies such as polyion complex (PIC) micelles offer tunable structures, while also highlighting challenges in reproducibility and stability. Incorporation of zwitterionic polymers has emerged as an effective strategy to stabilize assemblies through strong hydration rather than simple charge neutralization. Recent studies further demonstrate that sequence information embedded in polymer architectures governs selective association and self-sorting behavior in mixed systems. These developments indicate that integrating polymer chemistry with interfacial hydration dynamics and process control is essential for translating complex self-assembled structures into reliable functional materials.

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In recent years, research and development into the medical application of nano-sized molecular self-assemblies, i.e., nanomedicine, has been accelerating. One of the main reasons is that nanomedicine can efficiently deliver gene and nucleic acid drugs to the target site, dramatically improving their efficacy. This article describes the outlook for nanomedicine based on molecular self-assemblies.

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Supramolecular gels are soft materials formed through the hierarchical self-assembly of low-molecular-weight gelators driven by non-covalent interactions. Recent advances in analytical techniques, including high-speed atomic force microscopy, confocal laser scanning microscopy, small-angle scattering, and theoretical and computational approaches, have provided unprecedented insights into dynamic self-assembly processes. Emerging strategies to regulate macroscopic properties focus on controlling bundling and network structures through secondary nucleation and fiber-surface functionalization, thereby enabling precise tuning of the mechanical strength of supramolecular gels. In addition, solvent effects play a crucial role in determining higher-order structures and assembly pathways. The range of solvents used for supramolecular gel formation has recently expanded to include deep eutectic solvents and π-conjugated liquids. Alongside these developments, supramolecular gels are increasingly regarded as dynamic and non-equilibrium materials inspired by living systems.

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[in Japanese]

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In solution chemistry, the reaction vessel has traditionally been one of the primary tools. Using porphyrin nanofiber formation as a model system, this article introduces the potential of microfluidic devices as an active platform for supramolecular chemistry. The application of flow offers several advantages in supramolecular systems. Microfluidic devices enable precise and reproducible control of reaction environments with short residence times, which are well suited to fast supramolecular assembly processes. Furthermore, reactions between nanofiber termini and monomeric species proceed selectively in microfluidic channels, even when such associations do not occur under conventional batch conditions. The resulting supramolecular structures are also unique: supramolecular growth is consistently observed to occur from a single terminus, leading to asymmetric nanofibers. This symmetry-breaking behavior implies that microfluidic flow provides a nonequilibrium reaction field at the molecular scale. Such asymmetric growth becomes more pronounced at higher flow rates, indicating that hydrodynamic forces actively promote supramolecular bond formation. These results highlight microfluidic devices not only as tools for sequence control, but also as systems that convert macroscopic flow energy into molecular-scale non-covalent bond formation.

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Self-assembling peptides (SAPs) form well-defined nanostructures through multiple intermolecular interactions in water, enabling the creation of biofunctional materials with diverse and complex structures and functions from relatively simple molecular designs. Here we highlight the crucial role of the mixed or connected states of multiple SAPs and/or SAPs and other functional molecules as a key design principle in biofunctional materials. The first topic addresses the control of self-sorting and co-assembly based on molecular immiscibility, demonstrating that the selective formation of self-sorted or co-assembled SAP structures alters the function of cell-adhesive motifs incorporated into the assemblies. The second topic focuses on the enzyme-mediated surface modification of SAP assemblies, where the oriented, multiple display of antigenic proteins leads to highly effective vaccine materials. These examples demonstrate that controlling the modes of mixing and binding in SAP systems is a powerful strategy for advanced biofunctional materials. Incorporating dynamic control under biocompatible conditions could further expand their potential in biological and biomedical applications.

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By measuring long-range hydration states using terahertz spectroscopy, it has become clear that water actively participates in the functions of soft matter and biomolecules, such as the thermoresponsive property of polymers, protein stability, and enzyme activity. These results suggest that by appropriately controlling the state of water (hydration and the mobility of water molecules), it will be possible to control or enhance the functionality of these materials.

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We developed sample preparation techniques for transmission electron microscopy that enable the observation of complex hierarchical structures formed by self-assembly of (macro)molecules, unraveling these structures at atomic or molecular-level resolution. We demonstrated that de-hierarchization approaches for the target materials, such as encapsulation of a single strand of polymer chains in a single-walled carbon nanotube and extraction of anisotropic structural components in liquid crystals through dilute solution dispersion, are effective for high-resolution observation by transmission electron microscopy.

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I grew up fascinated by polymers and advanced my work from university to Toyota Central R&D Labs., developing novel polymer blends and composites. Through interdisciplinary collaboration, I achieved both academic and practical outcomes and continue striving for impactful innovations bridging fundamental science and engineering.

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[in Japanese]

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This review highlights recent advances in electrochemical post-functionalization of polymers, a methodology that utilizes electrochemical electron transfer to modify polymer structures without hazardous oxidizing or reducing reagents. For π-conjugated polymer films, solid-state anodic and cathodic reactions generate reactive species via electrochemical doping, enabling nucleophilic substitution, halogenation, cyanation, phosphonylation, and skeletal transformations such as cyclization and carbonyl reduction. Key progress includes the design of soluble conjugated polymers enabling detailed NMR characterization and quantitative evaluation of the degree of functionalization (DOF), as well as paired electrolysis achieving simultaneous oxidative and reductive transformations in a single electrochemical cell. The review further covers solution-phase electrochemical post-functionalization applicable to commodity polymers such as polystyrene and polyolefins, encompassing cation-pool electrophilic substitution, electrochemical iodination, Birch-type dearomatization, manganese-catalyzed C-H azidation, and cathodic decarboxylation. The versatility of electrochemical approaches, including mild conditions, tunable selectivity, and applicability to waste upcycling, underscores their potential contribution to sustainable polymer chemistry.

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The spatial linking of polymer chains can provide an attractive fundamental motif for the creation of dynamic functions. In particular, systems that enable the reversible interconversion of polymer topologies between linear and cyclic, or linear and branched forms without breaking or forming of covalent bonds, as well as movable crosslink systems, have the potential to offer novel materials that stand distinctly apart from conventional ones. In this article, with the aim of contributing to new design proposals for stimuli-responsive polymers, specific examples of function emergence achieved through the linking of polymer chains to rotaxane skeletons are introduced to discuss their significance.

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