Focus Review in 2024

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.

There are many barriers to gene and protein delivery to plant mitochondria, such as cell walls, cell membranes, and cytosolic localization. Functional peptides have been used to overcome these barriers. Peptides have a characteristic function depending on their sequence and high-order structure. The cytotoxicity of these peptides is also low. Therefore, functional peptides have attracted attention for their ability to improve gene and protein delivery efficiency to plant mitochondria.

Crystalline polysaccharides, which are abundant in nature, can be transformed into highly functional materials. However, the molecular basis for the formation of higher-order structures remains incompletely understood. Computer simulation is an advanced tool for modeling macromolecular structures, with atomistic simulations providing valuable information on crystalline polysaccharides. This focus review covers theoretical and computational studies, including atomistic simulations, performed by our research group on the crystallographic properties and novel nanostructures of cellulose, crystal structure of amylose analog polysaccharides, and dissolution mechanism of cellulose and chitin crystalline fibers.

This focus review presents our recent research on enhancing the mechanical properties of gel electrolytes and their application in lithium secondary batteries. It discusses the efforts made to achieve self-healing ion gels, which utilize ionic liquids as the electrolyte solutions. Additionally, the review covers the application of functional gel electrolytes in next-generation lithium secondary batteries. It focuses particularly on improving the cycling performance of lithium metal anodes, which are considered the very promising anode material.

This focus review describes two types of thermoplastic films developed via formulation design technology for mmWave communication. The first type is a crystalline polyaryletherketone (PAEK)-based film, which is improved with plate-like fillers and miscible noncrystalline polymers. This film exhibits low dielectric properties, heat resistance, low thermal expansion, and excellent multilayer processing capabilities. The second type is a specialized polyolefin resin-based film, which achieves ultralow dielectric properties comparable to those of PTFE and combines excellent copper adhesion with customizable functionalities such as laser processability, transparency, and flame retardancy.

Solid-state NMR with dynamic nuclear polarization (DNP-NMR) has recently attracted attention as a highly sensitive NMR measurement method for analyzing polymers. We recently investigated DNP-NMR for insoluble polymers, particularly cross-linked polymers, engineering plastics, and polymer-supported catalysts, and achieved high NMR signal sensitivity at a routinely accessible level. In this focus review, we present case studies on DNP-NMR measurements for a wide range of polymers.

Functional dyes offer fascinating properties in response to external stimuli and enable unique stimuli-responsive functions in materials by chemical incorporation into polymers. In this review, we highlight our recent studies conducted in the last half decade on stimuli-responsive smart polymers and polymeric materials offering, for example, switchable adhesion, mechanical actuation, and chemical sensing based on functional dyes that are chemically incorporated into the structures, with a particular focus on the stimuli of light, force, electric fields, and chemicals including water.

The review highlights the author’s recent discovery of the radical (co)polymerization ability of alkenylboronic acid derivatives and C–B bond-cleaving side-chain replacement in polymer reaction. The polymerization ability is attributed to the vacant p-orbital of boron, which can stabilize chain-growth radical species. In copolymerization and controlled polymerization, the boron monomer behaves as a relatively electron-rich and conjugated monomer. The boron attached to the polymer main chain was replaceable with other elements, providing access to various polymers of which synthesis is not straightforward, such as poly(α-methyl vinyl alcohol), poly(vinyl alcohol-co-styrene), and poly(ethylene-co-acrylate).

Injectable hydrogels hold promise as cell delivery carriers for cell transplantation therapy in regenerative medicine. Injectable hydrogels possess various benefits, including biocompatibility, biodegradability, tissue adhesive properties, scaffold functions, and minimal invasiveness. To overcome the barriers in clinical translation, biological and physicochemical functionalization, which can improve delivery efficacy to the target and graft survival posttransplantation, is desirable. This review discusses the strategies to design injectable hydrogels for cell delivery and summarizes the approaches available to improve the biological and physicochemical features of hydrogels.

Optical resonators have attracted renewed attention in chemistry and biology as minute and highly sensitive sensors that work in the environment and inside biological tissues and cells without any connected wires. Optical resonators should be functional for facilitating molecular interactions and biological compatibility, which is, however, challenging with conventional materials and processing techniques. In contrast, the authors have been tackling this issue by using supramolecular chemistry. This article reviews our recent progress on the methodologies for making organic optical resonators and their emergent optical properties.

Soft interfaces formed by polymer materials are important interfaces for biological systems (biointerfaces). Controlled radical polymerization (CRP) is highly suited for designing biointerfaces composed of polymer chains because it enables precise control of the polymer architecture at the nanoscale. This focus review describes the design of functional soft interfaces based on investigations of the structure-property relationships of CRPs. In particular, polymer brush surfaces showing autonomous property changes, comb-type copolymer-driven 2D/3D transformations of lipid bilayers, and molecular interactions in bactericidal cationic polymer brushes are depicted.

In this short review, we focus on the development of CO₂ separation materials consisting of hydrogel particles. The review starts with development of stimuli responsive micro- and nano-gel particles that reversibly absorb CO₂ isn response. The next chapter focuses on the development of temperature-responsive hydrogel films consisting of gel particles that reversibly absorb CO₂ and the importance of optimizing the pK_a values of the amines in the particles. In the end, assembly of defect-free nano-meter-thick CO₂ separation membranes consisting of the amine containing hydrogel particles are introduced.

Photochemically adaptable polymer materials are widely used in the fields of medicine, electronics, and engineering due to their precise and remote processability. Diverse designs of light-responsive units have been developed to fabricate various photocontrollable materials with low-energy, rapid, and reversible photoreactivity. Recently, multiple stimuli-responsive materials have been demonstrated to further control their photoreactivity by combining light with another stimulus, leading to advanced photocontrollable capabilities. This Focus Review summarizes the recent progress in developing photochemically adaptable polymer network materials by designing photoresponsive units, focusing on the chemical structures of cleavable moieties.

Our recent studies on the synthesis, characterization, degradation and applications of vinyl polyperoxides are reviewed. Primarily, the recent achievements in the design, biocompatibility, thermal and enzymatic degradation of water-soluble vinyl polyperoxides and copolyperoxides are described. Finally, future development possibilities and challenges of vinyl polyperoxides for various potential applications are summarised.