Review

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.

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.

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.

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.

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.

Stimulus-responsive hydrogels are highly attractive as the surrogate materials that can simulate dynamic mechanical microenvironments surrounding biological cells in vivo. This review tries to provide with comprehensive overviews on the previous achievements, present pitfalls and challenges, and future perspectives on the recent development on stimulus-responsive hydrogel materials for the dynamic control of cell behaviors.

Hydrogels as biocompatible polymer have been attracted materials researchers for mimicking biological systems. One efficient approach to preparing hydrogels is using host–guest interactions between cyclodextrins (CDs) as host units and suitable guest units. The hydrogels formed by CD and guest unit reversible bonds show several biofunctionalities, such as self-healing ability, stimuli responsiveness, the ability to function as soft actuators for use in artificial muscles, and conductive responsiveness.

Graphene derivatives (e.g., graphene oxide (GO)) have been incorporated in hydrogels to improve the properties (e.g., mechanical strength) of conventional hydrogels and/or develop new functions (e.g., electrical conductivity and drug loading/delivery) for various biomedical applications.

Hydrogels have been used in vascular engineering owing to their mechanical properties and tissue-like characteristics. Hydrogel-based blood vessels can be constructed from natural or synthetic materials alone, or require a combination of both. The manufacturing methods play an important role in constructing vascular engineering to induce the vascular endothelial cells function driven by shear stress and biomechanical force. The different components and methods of engineered vascular hydrogels described in this review would provide useful information for the desired applications of in vitro tissue models.

Recent progresses in the developments of luminescent polymer films with stimuli responsiveness are illustrated. In particular, the influence of the alteration of connecting points in polymers on luminescent behaviors is explained. It is demonstrated that polymerization is a versatile strategy not only for transforming a class of nonemissive flexible boron complexes to luminescent dyes but also for precisely regulating optical properties of film materials that are promised to be applied as a scaffold for advanced chemical sensors.

Recent progress in ring-opening (co)polymerization of γ-butyrolactone (γBL) in the presence of various initiating/catalyst systems has been reviewed. Low reaction temperatures and high monomer concentrations are critical for the success of such polymerization, regardless of the different initiating/catalyst systems.

Water desalination through a reverse osmosis (RO) membrane is an important technology for producing pure water from seawater. High-performance membrane materials have been extensively developed because these materials are useful as core elements in practical water separation processes. Bridged polysilsesquioxane (PSQ)-derived membranes are promising candidates for robust RO membranes because they exhibit high thermal stability and chlorine resistance compared to conventional aromatic polyamide membranes. This review reports on our recent studies involving the development of RO membranes based on bridged PSQs.

There is increasing interest in solid particle-stabilized soft dispersed systems, including bubbles/foams (a gas-in-liquid dispersed system) and liquid marbles (a liquid-in-gas dispersed system). Synthetic colloidal polymer particles are attractive stabilizers, as their hydrophilic–hydrophobic character and surface chemistries can be designed and controlled on demand via polymerization with various functional monomers and post polymer reactions. In this review article, bubbles/foams and liquid marbles stabilized solely with stimulus-responsive polymer particles will be reviewed. The stabilities, structures, and motions of these dispersed systems can be controlled by external stimuli.

The cationic comb-type copolymers, which consisted of a polycation backbone grafted with high density of hydrophilic chains, form soluble and soft interpolyelectrolyte complexes with biopolymers and act as an artificial chaperone to assist in the folding of nucleic acids and peptides. The copolymers stabilize DNA duplex, triplex, and quadruplex structures and accelerate strand exchange reactions as well as assist in the folding of functional peptides into the active conformation.

Self-organization in nonequilibrium systems composed of a bulk filler powder and a bulk polymer melt as an initial state (i) into a final ordered state (f) in applied mechanical field occurs via cascade evolution of the dissipative structures (a) to (e) accompanied by the cascade energy dissipation processes [Process (I) and Process (II)]. These processes also induce the relevant cascade changes in free energy and stress level.

Designer supramolecular polymers are a growing field of polymer materials. The designability and flexibility in their structures and functionality have attracted a great deal of attention in polymer science, as well as in supramolecular chemistry. These polymeric structures are formed from one or more molecular components via reversible bonds; therefore, monomeric and polymeric states are in equilibrium on the relevant experimental timescale. The dynamic nature of supramolecular polymers in terms of chain lifetime and conformational flexibility are determined by external conditions. This adaptivity can result in stimuli-responsive structures and properties. This article describes the use of our host–guest structures based on a calix[5]arene, a bisporphyrin, and a self-assembled capsule in the synthesis of supramolecular polymers.

Among various approaches to create self-healing polymers, the introduction of dynamic bonds to polymers is one of the most powerful approaches. However, since the reformation of dynamic bonds requires molecular mobility, mechanical strength usually conflicts with an autonomous healing ability. In this review, we overview recent successful approaches to overcome this limitation, as well as attempts to design mechanically robust polymers that can heal with the assistance of ubiquitous stimuli. These approaches include combining careful dynamic bond chemistry choices and smart designs of the environment around the dynamic bonds.

Recent works revealed that protein and cell resistance of bioinert self-assembled monolayers originates in the physical barrier of the interfacial water. We review the history of the previous works that attempted to clarify the underlying mechanism and discuss prospects to apply the findings to design new biomaterials.