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This focus review introduces recent progress made in microphase-separated structures under three-dimensional (3D) confinement. Block copolymers spontaneously form unique structures when the polymer molecules are assembled in confined spaces. The polymers are frustrated because of the limited space for phase separation, resulting in morphologies that are more complex than those of bulk films. In addition to conventional parameters such as block ratio, molecular weight and interactions of constituent polymers, the confinement effect is a significant parameter for controlling the morphologies. Here I give an overview of experimental and theoretical results for spherical 3D confinement and discuss the prospects for this area of research.
Although conventional polymer gels are known as mechanically weak materials, their fracture toughness can be effectively improved by introducing weak and brittle bonds into soft and stretchy polymer networks. This toughening method, denoted as the ‘sacrificial bond principle’, has been recently proposed. In this focus review, I describe some extremely tough gels prepared using this principle, e.g., double- or multiple-network gels with high water content featuring covalent sacrificial bonds, self-healing polyampholyte gels containing ionic sacrificial bonds and PDGI/PAAm gels based on hydrophobic sacrificial bonds exhibiting stress-responsive structural colors.
The recent progress of our research on proton exchange membranes for fuel cell applications is reviewed. In particular, we have focused on the effect of the molecular structures of fluorine-free sulfonated aromatic polymers on membrane properties (e.g., proton conductivity, chemical and mechanical stability). We identified an optimized hydrophilic molecular design (sulfophenylene as SPP), that is, SPP simultaneously exhibited the highest proton conductivity and excellent mechanical stability over a wide range of humidities.
Effect of viscosity ratio of the outer/inner solutions on the morphology of core–shell fibers was studied by altering the concentrations of two polymer solutions, poly(methyl methacrylate) and poly(acrylonitrile), as a role model. Nonuniform core–shell structures were observed at low viscosity ratio of PAN/PMMA. By increasing the viscosity ratio of PAN/PMMA, the total diameter and the wall thickness were increased, while the core diameter seems to be gradually decreased. Rheology aspects and suitable ranges of viscosity ratios were discussed and suggested in this work.
We developed advanced cellulose-based resin composites consisting of cardanol-bonded cellulose diacetate (CDA), polyester resins and glass fiber, which have high impact strength and bending strength suitable for durable products. By testing the addition of various polyester resins to the PAA-bonded CDA, we found that poly(butylene succinate adipate) (PBSA), which has flexibility and high compatibility with the PAA-bonded CDA, greatly increased its impact strength. Furthermore, adding glass fiber to the PAA-bonded CDA composites with PBSA enhanced its bending strength and impact strength.
The dielectric relaxation process of uncrystallized water (UCW) has been investigated for poly(ethylene glycol) (PEG)–water mixtures. The relaxation strength, Δɛ, of UCW for all PEG–water mixtures increased because of melting of the eutectic. For 10–40 wt% PEG–water mixtures, Δɛ increased again because of the melting of ice, whereas 50wt % PEG–water mixture did not show any additional increase because it did not contain enough water to form ice crystals.
We report experimental results of an attempt to control the orientation of cylindrical microdomains using the directional coalescence of non-equilibrium spheres along the stretching direction of a triblock copolymer film specimen. Thermal annealing, which induced the sphere-to-cylinder transition, was performed on the triblock copolymer film under a uniaxially stretched state. Unlike the application of shear flow, cylinder orientation with its long axis parallel to the stretching direction was not achieved by uniaxial stretching.
