Focus Review

Artificial nanocelluloses are produced via the self-assembly of low-molecular-weight (LMW) cellulose in vitro and represent an emerging class of nanocelluloses developed over the past decade. Most artificial nanocelluloses reported to date are particulates. We have developed two types of nanostructured macroscopic materials through the self-assembly of LMW cellulose: nanoribbon network hydrogels and nanospiked microfibrous materials. This Focus Review summarizes our work along with related studies on these novel nanostructured cellulose materials.

The selective capture of heavy metal ions is a major challenge due to the need for materials with high affinity, selectivity, and capacity. Nature uses proteins to manage metal ions via specific structural motifs. This focus review summarizes recent advances in bioinspired and biosynthetic integrated strategies for the capture of heavy metal ions. The topics discussed include (1) the structural and thermodynamic features of metal-binding proteins, (2) synthetic polymers that mimic the biological functions of proteins, and (3) hybrid materials that integrate biological (macro)molecules with synthetic polymers.

Time-resolved small-angle X-ray scattering (TR-SAXS) is crucial for real-time monitoring of soft matter kinetics, offering nanometer-to-micrometer structural insights and revealing complex kinetic pathways and mechanisms. This review highlights its power in understanding block copolymer self-assembly kinetics in solution, covering micelle formation driven by non-covalent interactions, polyelectrolyte complex micelles via electrostatic interactions, and polymerization-induced self-assembly (PISA).

Structural and steric restrictions in polymer chains resulted in significant differences between cyclic polymers and their linear counterparts in the interfacial properties. The topological influences on the air–water interfacial activity and aggregation behavior of PEG and Pluronic surfactants were investigated. Silver nanoparticles adsorbed with cyclic PEG exhibited high dispersion stability under physiological and various conditions. This study successfully combined the biocompatibility of PEG with the antibacterial activity of silver nanoparticles. These results demonstrate that utilizing polymer topology can serve as a useful tool for designing new functional materials.

Harnessing the plasmonic properties of gold nanorods (AuNRs) requires proper control of their arrangement and assembly. However, although the assembly of AuNRs into ordered structures has been achieved, active control over them remains challenging. The author and colleagues have developed methods to control the arrangement and assembly of AuNRs based on complex formation via electrostatic interactions with DNA, a polymer with unique properties, structure and excellent functionality. This Focus Review presents our work on the arrangement and assembly of AuNRs by DNA.

In this study, we developed starch-based films with tunable disintegration and dissolution rates in freshwater and seawater. The modified starch was mixed with oxidized cellulose or a water-soluble polymer to produce transparent, homogeneous films. Hydrogen bonding stabilized the films in freshwater, while in seawater, the hydrogen bond crosslinks dissociated, causing the film to dissolve rapidly. This technology offers a strategic balance between water resistance in everyday environments and controlled disintegration in marine conditions, presenting a sustainable alternative to petrochemical plastics with potential applications across various industrial sectors.

This paper reviews the degradation of polyesters and polycarbonates, including degradable aliphatic polymers. Organic catalysts enable efficient degradation and recycling of these condensation polymers, promoting a circular economy and reduction of waste and CO₂ emissions. Although super engineering plastics are difficult to recycle, recent studies show organocatalysts can facilitate their depolymerization and monomer recovery. Advances in monomer synthesis and controlled ring-opening polymerization allow for functional, sustainable, and degradable polymers. Moreover, side-chain engineering in aliphatic polymers enables controlled degradation. Future work should emphasize greener synthesis and comprehensive analysis of degradation impacts.

Emerging from DNA/RNA nanoengineering, synthetic nucleic-acid liquid condensates, forming via phase separation of nanostructures, have attracted increasing attention as a powerful platform for synthetic biology and molecular computing. Base-sequence specificity allows for molecular encoding for their organization, functions, and droplet interactions. Authors overview key topics of these programmable droplets, from dynamics programmability to numerical modeling. Additionally, this review highlights cross-linker modules, which enable dynamic compartmentalization and division of droplets triggered by specific molecular input. These modules allow the condensate phase behavior to represent Boolean logic operation.

Simple coacervates formed from low-molecular-weight molecules offer unique dynamic features, including stimulus-responsive phase transitions and reversible assembly/disassembly. This Focus Review highlights molecular design strategies, from historical perspectives to recent advancements. The sophisticated design of coacervates provides new opportunities in protocell models, biosensing, and drug delivery systems.

This review highlights recent advances in engineering artificial enzyme condensates in vitro using charged polymers. Based on our recent findings, we describe strategies for designing condensates through interactions between polymers and enzymes or coenzymes. We then summarize enzyme activation mechanisms triggered by enzyme condensates, including size-dependent effects and conformational changes in enzymes. We also discuss potential applications and future directions, including multienzyme systems, integration with solid surfaces, and combination with rational enzyme design.

The process of spider silk assembly is a concerted, transitional process that combines liquid‒liquid phase separation (LLPS), liquid‒crystal (LC) and liquid‒solid phase separation (LSP), yielding fibers with outstanding mechanical properties. Spider silk proteins form micelle-like assemblies that undergo LLPS to form larger droplets, which are highly relevant for preorientation and permit intra- and intermolecular interactions, leading to a dimerized protein network and a nematic crystal phase of β-sheet-rich nanofibrils. The final solid fiber is drawn via LSP.

Ribonucleoprotein (RNP) granules are membraneless organelles formed through the condensation of RNA and proteins, which serve critical functions in diverse biological processes and disease contexts. Identifying their RNA composition is vital for understanding their molecular functions and mechanisms of formation, yet conventional approaches often fail to fully capture the complexity of these granules. This review highlights recent advances in transcriptome profiling of RNP granules using biochemical purification and proximity labeling, offering new insights into their molecular roles.

Carrier-free nano-prodrugs (NPDs) were developed for selective drug release in cancer cells using stimulus-responsive systems: esterases, reactive oxygen species (ROS), and glutathione (GSH). Esterase-activated NPDs showed hydrophobicity-dependent drug release through SN-38 modification. ROS-responsive NPDs with trimethyl lock groups demonstrated selective activation by intracellular H₂O₂. GSH-responsive dimeric SN-38 prodrugs exhibited enhanced antitumor effects with reduced side effects. These NPDs achieved high drug loading and excellent stimulus responsiveness without using carriers, providing a promising platform for safer and more effective cancer therapy.

Elastin-like polypeptides (ELPs) typically undergo liquid‒liquid phase separation to form coacervates. This focus review presents a molecular design strategy for novel ELPs to obtain self-assembled nanofibers via coacervation. In this molecular design, various functional motifs can be presented on the nanofiber surface, allowing cell-selective growth and differentiation control. In addition, unique viscoelastic properties of hydrogels composed of the nanofibers are discussed. These nanofibers and hydrogels could serve as platforms for small-diameter artificial blood vessels and scaffold materials for regenerative medicine.

Research on composite electrolyte membranes composed of polymer nanofibers and a polymer matrix has attracted significant interest because of their improved ion conductivity, excellent membrane durability, and ability to fabricate thinner membranes. Polymeric nanofiber-containing polymer electrolyte membranes are expected to be applied not only to electrolyte membranes for fuel cells and water electrolysis but also to all-solid-state Li-ion batteries. This focus review presents the latest information on these topics.

We have discovered that strain-induced crystallization (SIC) of the polymer chains occurs in homogeneous polymer gels, such as slide-ring gels and Tri-/Tetra-PEG gels, with sufficiently high polymer concentrations. SIC significantly improves the mechanical toughness of homogeneous gels. Polymer crystals form and dissolve immediately after the polymer gels are stretched and unstretched. The quick formation and dissolution of the strain-induced crystals leads to elastic mechanical responses with minimal hysteresis under cyclic stretching. Tough and elastic polymer gels have potential applications in biomedical materials and soft electric devices under repeated deformation.

This review highlights recent MD simulation studies focusing on subcontinuum heterogeneities in polymers from the perspective of their mechanical properties. The theoretical framework for rationally distributing the stress tensor to individual molecular components is revisited, and the key achievements made via this approach are summarized.

Polymer surfaces have notably different properties and dynamic behaviors from bulk materials. The properties and structure at the polymer surface and interface strongly depend on the chemical structure, conformation and dynamics of the polymer chains. In this review, the impacts of the structure and dynamics of designed polymer side chains on the surface and interface properties and their mechanism are described. In particular, the control of the molecular conformation and dynamics leads to their characteristic surface and interface properties.

Our recent studies on the anionic polymerization achieved using flow microreactors are reviewed. Using flow microreactors, with features such as precise temperature control, rapid mixing, and precise time control, otherwise impossible polymer synthesis reactions can occur. Some typical examples synthesizing polymers with reactive functional groups and heterotelechelic polymers are described. This review also highlights the in-line analyses of the polymer living end, helping a deeper insights of the reaction and its conditions. The continuous operation of the flow microreactors demonstrated their potential for industrial applications.

Our recent study on the property modification of composite materials where polymer blends are used as matrices were summarized. Polymer blends have good scalability; however, poor material design criteria is a critical defect in polymer blending. To address this problem, we focused on the multiscale phase separation in polymer blends. We propose a novel material design concept to combine polymers with different phase morphologies to obtain a combination of modification mechanisms, and hygrothermal resistant CFRP and transparent GFRP using polymer blends as matrix were obtained.