Reviews & Analysis

Water-soluble Naphthalene diimide (NDI) binds to the DNA duplex via threading intercalation mode. This has provided unique DNA analytical techniques, functional DNA polymers, and supramolecular polymers. Especially the ferrocene-containing NDIs, having electrochemically active sites, has been applied to an electrochemical gene detection system and also utilized in the precision analysis of genes and single nucleotide polymorphisms. Recently, NDI derivatives have been recognizing as potential candidate for anticancer therapeutics and for designing a unique cancer-detection system.

This focus review describes the synthetic routes to cyclic compounds and cyclic polymers via spontaneously occurring cyclization processes using (1) rotaxane chemistry and (2) dynamic covalent chemistry. Systems with rotaxane-based structures proceed via the spontaneous and selective cyclization of two self-complementary molecules and a macromolecular rotaxane switch, which results in a topology change from linear to cyclic. Systems based on dynamic covalent chemistry use exchange reactions of bis(2,2,6,6-tetramethylpiperidin-1-yl)disulfide (BiTEMPS) units. Controlling the dynamic nature of BiTEMPS-based molecules provides cyclic topologies via spontaneously and selectively occurring cyclization processes.

Direct CO₂ capture from the air (DAC), is inevitable to reduce the concentration of CO₂ in the atmosphere. Recent reports of ultrahigh CO₂ permeances in gas separation membranes indicate a potential of new technology for DAC (m-DAC). In this paper, we use chemical process simulation to discuss the potential of m-DAC considering the state-of-the-art performance of organic polymer membranes. Based on the analysis, we propose the target properties for separation membranes required for m-DAC with competitive energy expenses as well as the direction of future membrane development for DAC.

Polyhydroxyalkanoates (PHAs) are biobased and biodegradable materials. The artificial PHAs, such as lactate-based polymers, synthesized by engineered platforms expand the range of physical properties. The artificial polymers with superior properties are produced mainly from CO₂-derived biomass using microbial platform with engineered enzymes. The oligomers can be secreted from cells and derivatized into high-molecular-weight polymers through assembling with other segments. The review summaries recent advances in the biosynthesis and biodegradation of artificial PHAs and oligomers.

To shift from a petroleum-dependent society to a sustainable society using eco-friendly materials, polysaccharides from natural products are important candidates as alternative materials. We have researched one of the cyanobacterial polysaccharides, “sacran,” which is extracted from Aphanothece sacrum. In this review, the unique characteristics, structures, and preparation of sacran LC gels are introduced. These matters are discussed especially from the perspectives of polymer science, colloidal science, gel science, etc. We hope that sacran will be used in a variety of fields, such as tissue engineering, pharmacodynamics, and biomedical materials, with possible contributions to the development of a sustainable material society.

Our recent studies on the cellulose nanofibrils (CNFs)/polymer nanocomposites prepared via Pickering emulsion templating are reviewed. CNF-stabilized monomer-in-water emulsions were used as starting materials to design the composite structures. In the first part of this review, we summarize the preparation of transparent films. The second part describes the approaches to prepare a composite microparticles having CNF shells.

To establish a sustainable material production system and preserve the Earth’s environment, “biomass plastics” that are made from renewable biomass instead of petroleum and “biodegradable plastics” that are completely degraded into carbon dioxide and water by enzymes secreted by microorganisms in the environment are desirable products. This miniature review describes a series of studies on microbial polyesters and polysaccharide ester derivatives, including the synthesis of novel polymers, development of new processing techniques for high-performance films and fibers, elucidation of the relationship between structure and properties using synchrotron radiation, and control of the rate of enzymatic degradation.

Our recent studies on how nanostructures can be self-assembled in discotic liquid crystals to create self-organizing functional systems of discotics with tuned physical properties are reviewed. In the first part of the article, charge carrier and semiconducting properties of discotic liquid crystals in the form of 1-D molecular wires are described. The second part of this report summarized our recent results on self-assembly of Ag, Au, Cu, and graphene nanoparticles, carbon dots, CdTe and CdSe quantum dots, gold nanorods, CdS nanoribbons, silver nanodisks, and graphene sheets in discotics.

Recent studies on exploration of mechanical deformation of microtubules under tensile and compressive stress, using a newly developed methodology, have been reviewed. In the first part of this review article, development of the methodology and its utility in studying the mechanoresponsiveness of microtubules have been described. In the second part, applications of the recently developed methodology in studying dynamic soft interfaces have been elaborately discussed.

Our recent studies on the zincate complex dilithium tetra-tert-butylzincate-catalyzed transesterification and polymerization are reviewed. In the first part of this report, the ROP of ε-caprolactone catalyzed by TBZL is described. In the second part of this report, the acylation and transesterification of alcohols with vinyl acetate and carboxylic esters catalyzed by TBZL are summarized. Next, TBZL-catalyzed polycondensations of diphenyl carbonate (DPC) with diols are discussed. In the last part of this report, the transesterifications of poly(phenyl methacrylate) (PPhMA) side chains with alcohols catalyzed by TBZL are described.

We reviewed our recent studies on optical manipulation techniques for microspectroscopic analysis of optically trapped polymers. A focused laser beam exerts an optical force on polymer chains, leading to the microassembly formation of them. We applied the conventional optical tweezers for the concentration determination techniques of phase-separated thermoresponsive polymer chains by combining with microspectroscopies. To overcome the limitations of the conventional optical tweezers, localized surface plasmon has attracted much attention. Finally, we introduced our original manipulation technique based on nanostructured semiconductor-assisted optical tweezers; NASSCA optical tweezers.

The chain-growth polymerization mechanism is essentially unsuitable for sequence control due to its statistical propagation feature. However, the development of reversible-deactivation radical polymerization has opened the door to the sequence control. Our group has developed some methodologies and concepts for the synthesis of sequence-controlled oligomers/polymers via radical polymerization: it is crucial to introduce some additional components into the initiator and/or the monomer for reversible-deactivation radical polymerization and in most cases these components are designed to be removed or transformable afterward.

Biodegradable plastics are gaining attention as one of the solutions to marine plastic wastes, which are increasing every year. Among them, polyhydroxyalkanoate (PHA) and polycaprolactone (PCL) are known to exhibit particularly good marine biodegradability. In this review, to understand their excellent marine biodegradability, the biosynthesis of PHA and cutin, a natural analog of PCL, and the biodegradation of PHA and PCL in the carbon cycle in marine ecosystems are described.

Carbon dioxide capture and storage (CCS) technology has become important due to the threat of global warming and climate change. Furthermore, the development of carbon dioxide capture and utilization (CCU) technology, which reuses the captured CO₂, has been prioritized in recent years to accelerate the deployment of “CCUS.” Amine-based CO₂ capture is a key process for realizing a carbon neutral society.

This article reviews an evaluation-oriented exploration of photo energy conversion systems including organic photovoltaics, perovskite solar cells, photocatalysts, and photodetectors. A time-resolved spectroscopy using a gigahertz electromagnetic wave enables rapid screening of potential optoelectronics of organic/inorganic semiconductors and fast finding of their optimal film processing conditions. This approach is further empowered by machine learning that provides a high-throughput virtual screening in the large molecular space. The author discusses a perspective on this evaluation (from fundamental to application) and its effective combination with data science.

The use of iron catalysts in CO₂/epoxide chemistry has been less explored compared with zinc, cobalt, and chromium catalysts. This review highlights recent examples including iron complexes that deoxygenate epoxides in situ and geometry-dependent selectivity towards either polycarbonate or cyclic carbonate production. Reaction conditions (temperature, CO₂ pressure, and amount of nucleophilic cocatalyst) and catalyst structure are all critical in accessing efficient catalysis for polycarbonate formation.

Drying-induced patterns, “meniscus splitting,” are introduced through a series of demonstrations using self-assembled polysaccharides as a method for the preparation of advanced biomimetic materials. Under the control of physicochemical factors, the depositing polymer bridges the gap between two substrates to make multiple nuclei at specific positions for membrane growth. By developing interfacial instability, meniscus splitting causes partitioning of a space, similar to dissipative structures seen in nature, from one space into multiple spaces.

The nucleophilic conjugate substitution of α-(substituted methyl)acrylate is a very convenient reaction that occurs at ambient temperature with a variety of nucleophiles, such as amines, thiols, phenols, enols and carboxylic acids. The reaction is quantitative when the nucleophile and leaving group have distinctly different acidities, whereas it becomes dynamic and reversible if their acidities are similar. This review describes the fundamentals and applications of conjugate substitution reactions in polymer chemistry, particularly in monomer synthesis, end-group incorporation, end-functionalization, polycondensation, and main chain scission.

A variety of catalysts including zinc, cobalt and chromium complexes were reviewed for the copolymerization of epoxides and CO₂ with cyclic anhydrides and/or cyclic esters to synthesize CO₂-based poly(ester-co-carbonate)s. The structure and structure-performance relationship of the as-prepared copolymers were discussed in detailed.

Macroscopic deformable materials controlled by light have been the subject of growing research interest in the last few decades due to both their fundamental properties and their wide applicability. In this review, examples of photomechanical effects in crystals, polymers, and CLCPs based on photoisomerization and photodimerization are reviewed.