J. Appl. Cryst.の発刊に際して

Microemulsion-based media as novel drug delivery systems

Double-network (DN) gels have drawn much attention as an innovative material having both high water content (ca. 90 wt%) and high mechanical strength and toughness. DN gels are characterized by a special network structure consisting of two types of polymer components with opposite physical natures: the minor component is abundantly cross-linked polyelectrolytes (rigid skeleton) and the major component comprises of poorly cross-linked neutral polymers (ductile substance). The former and the latter components are referred to as the first network and the second network, respectively, since the synthesis should be done in this order to realize high mechanical strength. For DN gels synthesized under suitable conditions (choice of polymers, feed compositions, atmosphere for reaction, etc.), they possess hardness (elastic modulus of 0.1–1.0 MPa), strength (failure tensile nominal stress 1–10 MPa, strain 1000–2000%; failure compressive nominal stress 20–60 MPa, strain 90–95%), and toughness (tearing fracture energy of 100∼1000 J m−2). These excellent mechanical performances are comparable to that of rubbers and soft load-bearing bio-tissues. The mechanical behaviors of DN gels are inconsistent with general mechanisms that enhance the toughness of soft polymeric materials. Thus, DN gels present an interesting and challenging problem in polymer mechanics. Extensive experimental and theoretical studies have shown that the toughening of DN gel is based on a local yielding mechanism, which has some common features with other brittle and ductile nano-composite materials, such as bones and dentins.

Why are double network hydrogels so tough

The electrostriction of elastomeric polymer dielectrics with compliant electrodes is potentially useful as a small-scale, solid-state actuator technology. Electrostrictive polymer (EP) materials are capable of efficient and fast response with high strains (> 30%), good actuation pressures (up to 1.9 MPa), and high specific energy densities (up to 0.1 J g−1). In this article, the mechanism of electrostriction is shown to be due to the electrostatic attraction of free charges on the electrodes. Although EP actuators are electrostatics based, they are shown to produce 5–20 times the effective actuation pressure of conventional air-gap electrostatics at the same electric field strength. The thin uniform dielectric films necessary for fabrication of EP actuators have been fabricated by techniques such as spin coating, casting, and dipping. A variety of materials and techniques have been used to produce the compliant electrodes, including lift-off stenciling techniques for powdered graphite, selective wetting of ionically conductive polymers, and spray coating of carbon blacks and fibrils in polymeric binders. Prototype actuators have been demonstrated in a variety of configurations such as stretched films, stacks, rolls, tubes, and unimorphs. Potential applications of the technology in areas such as microrobots, sound generators, and displays are discussed in this article.

Electrostriction of polymer dielectrics with compliant electrodes as a means of actuation

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Studies in Surface Science and Catalysis

A gel of poly(vinyl alcohol) highly swollen with dimethyl sulfoxide was demonstrated to actuate at a much faster rate (more than 1000 times) than those reported on conventional gel actuators in air and to flap a wing of 12.5 cm at a rate of 2 Hz with a span of 10 cm by periodically applying electric field. The action (8% in length) induced by the electric field reached several hundreds times larger than those reported on the conventional ferroelectric solid materials. The electrostrictive gel was, thus, found to be a promising candidate material as a novel type of actuator or artificial muscle by having overcome some difficulties in responding time, electrochemical reactions on the electrodes, and magnitude of action in conventional methods or materials. © 1994 John Wiley & Sons, Inc.

Electrostriction of highly swollen polymer gel: Possible application for gel actuator

By using synchrotron radiation small-angle X-ray scattering (SR-SAXS), we have studied the structural properties of reversed micellar systems depending on hydrocarbon chains of apolar solvents, where we have treated water/bis(2-ethylhexyl)sulfosuccinate (AOT)/n-hexane, n-heptane, n-octane, and isooctane systems With increasing water/surfactant molar ratio w0 (= [H2O]/[AOT]), we have found that three different phases (oligomeric phase, transient phase, monomeric phase) appear successively in the above systems the same as in the water/AOT/isooctane system In the present experiments we have found other features of the reversed micellar structure depending on apolar solvents Thus, the w0 region of the transient phase broadens with increasing the hydrocarbon chain length The slope of the linear relation between micellar radius and w0 changes systematically depending on the length of linear hydrocarbon chain of apolar solvent, which clearly suggests that the penetration of the solvent molecules into the sur

Characteristics of AOT Microemulsion Structure Depending on Apolar Solvents

Reversibility and Hierarchy of Thermal Transition of Hen Egg-White Lysozyme Studied by Small-Angle X-Ray Scattering

https://www.cell.com/biophysj/pdf/S0006-3495(03)74591-3.pdf

Mitsuhiro Hirai

Papers

Electrostriction of highly swollen polymer gel: Possible application for gel actuator

Characteristics of AOT Microemulsion Structure Depending on Apolar Solvents

Reversibility and Hierarchy of Thermal Transition of Hen Egg-White Lysozyme Studied by Small-Angle X-Ray Scattering

Determination of Asymmetric Structure of Ganglioside-DPPC Mixed Vesicle Using SANS, SAXS, and DLS

Aerosol-OT Reversed Micellar Formation at Low Water-Surfactant Ratio Studied by Synchrotron Radiation Small-Angle X-ray Scattering