Yuji Higaki

Aqueous mesoscopic compartments produced by the microphase separation of double hydrophilic block copolymers serve as adaptive molecular compartments driven by thermodynamic imbalances. The impact of the inter-zwitterion interaction strength, modulated by the charge separation length (CSL) in zwitterions, on the microphase separation behavior of poly(carboxybetaine methacrylate)-block-poly(sulfobetaine methacrylate) (PCB2-b-PSBX) aqueous solutions was investigated. We demonstrate that longer CSLs significantly enhance the cohesive energy between sulfobetaine pairs, effectively deepening the thermodynamic potential well for phase separation. This enhancement reduces the threshold degree of polymerization required for ordering and promotes the formation of an ordered lattice at lower concentrations. Conversely, the resulting increase in the effective transient crosslink density led to the suppression of the water-uptake capacity of the PSBX-rich phase and the promotion of selective water partitioning into the PCB2-rich phase. The associated increase in interfacial stiffness and elastic constraint facilitates phase separation but can also lead to a kinetically arrested disordered state by inhibiting structural relaxation towards ordered lattices at high polymer concentrations. These findings highlight the importance of precise control of the inter-zwitterion interaction energies and the resulting interfacial mechanics for designing molecular systems with programmable, adaptive mesoscopic architectures.

The growing demand for flexible conductors in wearable electronics and soft robotics drives the need for elastomeric substrates with multiple functions, including robust mechanical properties, strong interfacial adhesion, and autonomous self-healing. Herein, we report a new class of polyolefin-based elastomers that address these multifaceted requirements. These materials are synthesized via a one-pot, scandium-catalyzed copolymerization of ethylene with thiophenyl-substituted propylenes in a sequence-controlled manner. By varying the substituents on the sulfur atom and the commoner feed ratio, the mechanical properties of the resulting copolymers can be finely tuned across a wide range. Remarkably, phenylthio-substituted copolymers exhibit high toughness, excellent elasticity, and intrinsic self-healing capability. Furthermore, these copolymers exhibit strong adhesion to gold nanoparticles due to the unique affinity between sulfur and gold. This interaction significantly enhances the durability of gold-coated copolymer conductors. This work underscores the potential of catalyst-controlled copolymerization of functionalized olefins for creating multifunctional polyolefin materials for flexible electronic applications.

This study explores the development of thermosensitive nanostructured coacervates formed by mixing ABA and AB block copolymers. Coacervates are liquid–liquid phase separation systems that can concentrate specific biomolecules, making them useful for biomedical applications such as sustained drug release. This study focuses on creating complex coacervates using ABA-type triblock copolymers that can bridge isolated polyion complex (PIC) domains, enabling the formation of well-ordered assemblies of polyethylene glycol (PEG)-conjugated PIC nanoparticles. These coacervates exhibit reversible responses to temperature changes and morphological hysteresis upon cooling, allowing for the controlled release of PIC micelles at physiological temperatures in the zero-order kinetics. This study demonstrates that the degree of bridging of PIC domains can be tuned simply by adjusting the blend ratio of diblock to triblock copolymers, which affects their physical properties and responsiveness. Real-time and snapshot observations of the assembling behaviors upon heating clarify the formation process of coacervates from both nano- and microscale viewpoints. The successful sustained release of a model protein, green fluorescent protein, is also confirmed to occur in a zero-order manner. These findings suggest that these coacervates are promising depot formulations for nanomedicine, offering a novel model for studying intracellular biomolecular condensates and an intervention method for condensates.

Advanced materials leveraging water control are garnering considerable interest, with the state of water emerging as a critical aspect of material design. This study explored the impact of microphase separation on water using aqueous solutions of double zwitterionic diblock copolymers, specifically poly(carboxybetaine methacrylate) and poly(sulfobetaine methacrylate) (PCB2-b-PSB4). These copolymers form a mesoscale periodic ordered lattice structure consisting of two distinct aqueous phases. Through differential scanning calorimetry and X-ray emission spectroscopy, it was found that water in these PCB2-b-PSB4 aqueous solutions exhibits pronounced cold crystallization and subtle distortions in hydrogen-bonding configurations.

Molecular assemblies that transform in response to pH and saccharide concentration are promising nanomaterials in the field of biomedicine, and polymeric micelles of amphiphilic polymers with phenylboronic acids (PBAs) have been studied. Herein, we report the impact of zwitterions on the acidity constant for the collapse and the glucose sensitivity of a polymeric micelle produced from a diblock copolymer comprising polyacrylamides with PBA and zwitterionic carboxybetaine (PAEBB-b-PCBAAm). The diblock copolymer was synthesized through reversible addition-fragmentation chain-transfer polymerization followed by deprotection. PAEBB-b-PCBAAm produced micellar aggregates in aqueous solutions at a neutral pH, and the polymeric micelles collapsed at a pH of 11.0 because the PBA transformed into a hydroxyboronate anion. The pK_a decreased in the presence of glucose owing to boronate ester formation. The PCBAAm chain significantly increased the pH at which the molecular assemblies dissociated. This is probably because the pK_a of boronic acid increased through the dipolar interaction of zwitterions, and/or the zwitterionic polymer corona is valid for screening of PBA ionization and electrostatic repulsion of boronate anions. This study on the modulation of pK_a through the zwitterionic interaction can facilitate the molecular design of pH- and saccharide-responsive biomaterials.