Reviews & Analysis

A supramolecular complex termed “hemoCD1” was constructed as the aqueous synthetic Hb/Mb model using a 1:1 inclusion complex of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphinatoiron(II) with a per-O-methylated β-cyclodextrin dimer with a pyridine linker. HemoCD1 was used as a selective CO scavenger in vivo due to its extremely high binding affinity to CO. In addition, hemoCD1 was utilized to quantify the accumulation of endogenous and exogenous CO in organs/tissues. Finally, hemoCD1 was employed as an antidote for CO poisoning in animals.

Regenerated fibers of β-1,3-glucan (curdlan) and α-1,3-glucan were fabricated by dry-jet wet spinning, and the fiber properties and structures are summarized in this review. The flexible and water-absorbent curdlan and the stiff and strong α-1,3-glucan would be utilized in different applications from conventional cellulose. As a new type of post-treatment, a two-step stretching method in water was developed for α-1,3-glucan by utilizing its crystal transition. This can be applied to various polysaccharides for future production of high-performance fibers.

Relationship between the primary structures and their properties is recognized as an important research subject for polymer chemists. To make progress in this academic field, innovative synthetic procedures of cyclic polymers are essential. The synthetic strategy has two typical pathways: one is the ring closure of functional linear polymers and the other is ring expansion polymerization using cyclic monomers, an initiator, or a catalyst. This focus review deals with the recent synthetic evolution of cyclic polymers, focusing on our new strategy: ring closing without highly dilute conditions.

The recent advances of the novel signal-amplification method, “supramolecular allosteric signal-amplification sensing” (SASS), are shown and summarized in this review. The SASS using polymers, polythiophenes and glucans introduced herein will be expandable to further smart polymeric systems, i.e., dynamic supramolecular assemblies.

Acidic pH is identified for various types of tumors, whereby it can be employed for crafting tumor-targeted nanomaterials. Cationic net charge of the nanomaterials at tumorous pH achieves selective interaction with anionic tissue constituents at tumor sites, for the effective tumor accumulation. However, tumorous pH is ca. 6.5, whereas pH of normal tissues is 7.4, and therefore responsiveness to the small pH window is the key toward the success for tumor delivery. The present manuscript highlights the polymer designs that recognize tumorous pH to make tumor-targeted nanomaterials.

The structural characterization of DDS carriers, including transdermal DDS, is one of the essential factors in the understanding of the biological properties and useful for the development of new carriers. This review introduces a quantitative evaluation of the surface coating on a carrier with the contrast variation technique of SAXS in the first section and the localization determination of drug molecules in liposomes in the second section. The final section describes the microemulsions containing deep eutectic solvents in the inner phase for use in transdermal DDS.

Silk fibroin (SF) is a natural protein polymer material and has been fabricated and studied as a scaffold for tissue engineering and regenerative medicine. To append new functions to SF scaffolds and understand their in vivo behaviors, researchers have addressed modifications of SF scaffolds by using transgenic silkworm and peptide modification technologies. These modified SF scaffolds had on-target functions and showed their potential as a material for tissue engineering applications. This review summarizes the methodologies and characteristics of functionalized SF scaffolds.

Water-gated polymer thin-film transistors (WG-PTFTs) fabricated by a simple procedure can be operated at an ultralow voltage, whereby the WG-PTFTs with molecular recognition units allow chemical sensing. Upon the addition of analytes, the electric double layer capacitance of the WG-PTFTs can be changed by accumulation and desorption of charged species at the interface of the semiconductor and electrolytes. For example, the WG-PTFTs have successfully detected biogenic amines and a herbicide glyphosate. In short, our proposed WG-PTFTs are among the most promising platforms for sensing applications based on π-conjugated polymer materials.

Boronic acids (BA) are known for their ability to reversibly interact with the diol groups, a common motif of biomolecules including sugars, ribose, and catechols. One can tailor BAs to elicit a divergent profile of binding strength and specificity on the basis of stereochemistry and controlled electronic effects. This focus review provides an overview of a phenylboronic acid (PBA)-based, totally synthetic platform for insulin delivery applications developed in our group, with focuses on the development of new PBA derivatives, glucose-responsive gels, and the gel-combined medical devices.

Electrospinning (ES) is a technique that can produce nanofiber mats from arbitrary polymers. We prepared actuators consisting of nanofiber mat electrodes and ionic liquid gel using three methods, and examined the effect of the preparation method on actuator performance. The results showed that actuators with nanofiber mat electrodes spun from the lowest spinning solution concentration showed a larger strain against an applied voltage. Furthermore, we prepared two types of actuators with different fiber directions and examined the effect of nanofiber alignment on actuator performance.

Strategic design and synthesis of semiconducting polymers with intrinsic ductility and/or stretchability are introduced in this review. The best polymer films show high charge mobilities over 1 cm²V⁻¹s⁻¹ even at 100% tensile strain. On the other hand, their mechanical properties remain inadequate, with high elastic moduli over 0.1 GPa. For semiconducting polymers to be promising candidates in applications such as wearable electronics, electronic skins, and bioelectronics, the trade-off relationship between their electronic and mechanical performance must be prevented by further developing and combining versatile and efficient approaches.

This focused review introduces our rheological studies on static and dynamic polymer networks using Tetra gel, host-guest gel, and telechelic associative polymer networks. Although the characteristics of crosslinks strongly influence the rheological properties of polymer networks, the understanding of the molecular origin of these properties remains incomplete owing to structural complexity. Our multiple experimental characterizations, including multiaxial stretching and the combination of dynamic viscoelastic and spectroscopic measurements, will add to the molecular understanding and further provide important information on the design of novel polymer network materials.

Our recent studies on the development of semiconducting polymers based on three novel π-extended heteropolycyclic aromatic frameworks, using phenanthro[1,2-b:8,7-b’]dithiophene (PDT) as a weak donor and alkoxy-substituted anthra[1,2‑c:5,6‑c’]bis([1,2,5]thiadiazole) (ATz) and vinylene-bridged 5,6-difluorobenzo[c][1,2,5]thiadiazole (FBTzE) as new thiadiazole-based acceptor units are described. Furthermore, their detailed relationships between the thin-film structure and device performance in organic field-effect transistors (OFETs) and organic photovoltaic cells (OPVs) were investigated. These results demonstrated that these novel π-extended heteropolycyclic aromatic frameworks have great potential as building units for high-performance OFETs and OPVs.

Ferroelectric polymers, poly(vinylidene fluoride) (PVDF), and its copolymers have been exploited for various applications, including nonvolatile memories, energy harvesters, and piezoelectric/pyroelectric sensors. To achieve better performance in PVDF-based devices, crystallization manipulation and controllable nanostructure formation are unavoidable and are of crucial importance. For this review, recent exploitation of the control of PVDF ferroelectric polymer crystallization at the nanoscale was specifically examined and summarized to provide insight into the future development of ferroelectric polymer nanomaterials.

Recently, controlled/living supramolecular polymerization has been evolved by many research groups; however, the principles of monomer design remain elusive. In this focused review, I present a case study of a series of porphyrin-based monomers that we have investigated over the past 10 years. By systematically designing monomers, we have been able to gain deep insights into the mechanisms of controlled/living supramolecular polymerization, and we have even been able to apply the developed method to synthesize two-dimensional supramolecular nanosheets with controlled areas and aspect ratios.

This focused review provides an overview of our recent work and related research regarding the precise anionic ring-opening polymerization (AROP) of substituted epoxides, including alkylene oxides, glycidyl ethers, and glycidyl amines, using t-Bu-P₄ as the phosphazene base catalyst to produce functional polyethers, such as homopolymers, block copolymers (BCPs), and topologically unique polymers. First, the fundamental aspects and applicable monomer scope of the t-Bu-P₄-catalyzed AROP are discussed. Subsequently, the applications of the AROP system for synthesizing functional materials and architectural polymers are presented.

Despite the tremendous efforts made in recent decades to remove imperfections from gels, discernible signs of spatial defects have been persistently observed in gels. Researchers believe that gels are inherently heterogeneous. In this focus review, I briefly introduce a recent finding from our research group’s efforts to fabricate polymer gels free of spatial heterogeneities via “bond percolation”. The commonly observed scattering profiles for the spatial defects disappeared in the homogeneous gels. The newly observed scattering profiles are a benchmark for gel structures.

Our recent development on healable soft materials that utilize block copolymer self-assembly in ionic liquids is reviewed. We begin by discussing photohealable ion gels that respond to specific wavelength of light irradiation by forming and collapsing stimuli-responsive networks. Then, we highlight on the self-healing ion gels based on synergetic combination of supramolecular interaction and block copolymer self-assembly, which realize high mechanical strength and fast self-healing ability in the absence of any external stimuli.

The functionalization methods of polymeric materials using various types of cross-links, such as supramolecular cross-links, photo cross-links, and associative dynamic covalent bonded cross-links, were described. First, the enhancement and precise tuning of the thermal and mechanical properties are demonstrated in the supramolecular cross-link-based and photo cross-link-based designs. In the latter section, the design and physical property tuning of functional materials based on a special type of cross-linked materials with associative dynamic covalent bonded cross-links, known as vitrimers, are demonstrated.