Reviews & Analysis

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.