Ikuo Taniguchi

Phase diagrams of diblock copolymers as functions of pressure and composition, essential for the molecular design of energy-efficient polymeric materials with pressure processability, are presented. While pressure-dependent modifications of temperature–composition phase diagrams have been investigated in relation to temperature-induced transitions, diagrams explicitly displayed on the pressure–composition plane remain largely underexplored. To establish a fundamental understanding of pressure-induced phase transitions, we construct pressure–composition phase diagrams using compressible random phase approximation theory and self-consistent field theory. The contrast in block compressibility is shown to govern pressure-responsive phase behavior: a large contrast enhances miscibility under pressure, whereas a small contrast reduces it. In highly asymmetric systems with more compressible soft segments, voids preferentially accumulate in soft domains, stabilizing ordered phases and skewing phase boundaries. These results provide a theoretical basis for the rational design of pressure-responsive polymeric systems.

Advancing sustainable plastics is crucial to achieving a circular plastic economy. Baroplastics, block copolymers exhibiting order-disorder transitions under pressure, allow polymer processing at ambient temperatures, reducing energy use and avoiding thermal degradation. Their application, however, has been limited by structural constraints. This study introduces poly(ε-caproclactone-random-5-ethyleneketal ε-caprolactone)-block-poly(l-lactide) (PmCL-b-PLLA) as a "baroplasticizer" for nonbaroplastic PLLA. Blending with the block polymers lowered PLLA's flow temperature by up to 100 °C (160 to 60 °C at 50 MPa) while preserving molecular weight after repeated pressure cycles, ensuring recyclability. The improved formability would arise from a pressure-induced ordered (solid)-to-disordered (melt/solid) phase transition. This work eliminates structural constraints in baroplastics, enabling broader low-temperature processing applications and advancing sustainable polymer technologies.

The dynamics of pressure‐induced order–disorder transitions in diblock copolymer systems and their effect on the flow properties are investigated. A dynamically extended compressible self‐consistent field theory allows us to study nonequilibrium copolymer systems under high pressure. The theory reveals that the differential reduction of free volume across different polymer segments drives the order–disorder transition upon pressure. The pressure‐induced transitions lower the energy required for deformations, supporting experimental observations on the low‐temperature processability of diblock copolymer materials as a sustainable solution. These findings advance the fundamental understanding of nonequilibrium phase behavior in block copolymers and provide valuable insights for designing polymeric materials with tailored low‐temperature processability, based on a clear physical picture of pressure‐induced phase transitions.

The pressure-responsive phase behavior of block copolymers, which is crucial for energy-efficient processing of certain polymeric materials, is systematically studied using a compressible self-consistent field theory based on a simple lattice vacancy model. To date, predictions of the phase behavior have been based mainly on qualitative assessments. In this study, we quantitatively show that large differences in the self-interaction energy between blocks lead to disordering with increasing pressure, while small differences lead to ordering. We discuss the molecular mechanisms underlying the phase behavior with a focus on voids, which account for the compressibility. The results from our theory agrees with the effective Flory–Huggins interaction parameter calculated by the compressible random phase approximation theory. Additionally, extending the theory to multicomponent systems, we investigate the effect of gas absorption on phase behavior, focusing on the balance of interaction parameters. Our results predict that gas absorption enhances pressure-induced ordering.

Although thin-film composite membranes have achieved great success in CO₂ separation, further improvements in the CO₂ permeance are required to reduce the size and cost of the CO₂ separation process. Herein, we report the fabrication of composite membranes with high CO₂ permeability using a laser-patterned porous membrane as the support membrane. High-aspect-ratio micropatterns with well-defined micropores on their surface were carved on microporous polymer supports by a direct laser writing process using a short-pulsed laser. By using a Galvano scanner and optimizing the laser conditions and target materials, in-plane micropatterns, such as microhole arrays, microline grating, microlattices, and out-of-plane hierarchical micropatterns, were created on porous membranes. An aqueous suspension of hydrogel microparticles doped with an amine-based mobile carrier was sprayed onto the patterned surface to form a defect-free thin separation layer. The surface area of the separation layer on the patterned support is up to 80% larger than that of flat pristine membranes, resulting in a 52% higher CO₂ permeance (1106 GPU) with a CO₂/N₂ selectivity of 172. The laser-patterned porous membranes allow the development of inexpensive and high-performance functional membranes not only for CO₂ separation but also for other applications, such as water treatment, cell culture, micro-TAS, and membrane reactors.

A theory based on a simple lattice vacancy model provides quantitative physical insights into pressure-induced order–disorder transitions of block copolymers.

The ocean constitutes approximately 70% of Earth's surface. Its average depth is 3688 m, of which depths beyond 200 m are classified as the deep sea. The deep sea is distinct from the surface of the ocean in terms of pressure, temperature, and sunlight. The unique physicochemical processes under the extreme environment of the deep sea and the specialized biochemical mechanisms developed by organisms to survive in the deep sea can serve as a vast source of inspiration for scientific and technological advancements. In this Perspective, we discuss three examples of deep-sea-inspired chemistry: (1) soft materials that respond to high pressures such as those observed in the deep sea; (2) molecular self-assembly inspired by the chemistry of hot and compressed water in deep-sea hydrothermal vents; and (3) nanobiotechnology and biomimetics inspired by survival strategies of deep-sea organisms. Finally, we provide an outlook on deep-sea-inspired chemistry. This Perspective aims to promote the sustainable utilization of the ocean based on knowledge, as opposed to the conventional utilization of the ocean solely based on resources. We hope that this Perspective will encourage chemists to harness their inspiration gleaned from the deep sea.