electric fi elds (above 50 V mm − 1 ), which poses the greatest obstacle to their practical application.When an electric fi eld is applied across a fi lm thickness, a fi lm of electrostrictive materials is compressed in the longitudinal direction, and spreads in the lateral planar direction. Unlike piezoelectricity, which has a linear relationship with applied fi eld, this electrostriction behavior demonstrates that the total thickness strain, s z has a quadratic relationship with the applied electric fi eld ( E ), as delineated by the following equation:where R 33 represents the sensitivity of the strain response of a material to the applied electric fi eld.In general, the electric actuation of dielectric elastomers is driven by the two mechanisms of Maxwell stress and a true electrostrictive effect, as illustrated in Figure 1 . [ 13 , 14 ] The electrostriction of a dielectric elastomer is usually dominated by Maxwell stress, which is caused by the Coulomb interaction between oppositely charged compliant electrodes, expressed as Equation 2 . Electric Actuation of Nanostructured Thermoplastic Elastomer Gels with Ultralarge Electrostriction Coeffi cientsElectrostriction facilitates the electric fi eld-stimulated mechanical actuation of dielectric materials. This work demonstrates that introduction of dielectric mismatched nanodomains to a dielectric elastomer results in an unexpected ultralarge electrostriction coeffi cient, enabling a large electromechanical strain response at a low electric fi eld. This strong electrostrictive effect is attributed to the development of an inhomogeneous electric fi eld across the fi lm thickness due to the high density of interfaces between dielectric mismatched periodic nanoscale domains. The periodic nanostructure of the nanostructured gel also makes it possible to measure the true electromechanical strain from the dimensional change monitored via in situ synchrotron small angle X-ray scattering. The work offers a promising pathway to design novel high performance dielectric elastomers as well as to understand the underlying operational mechanism of nanostructured multiphase electrostrictive systems.

The true electric actuation thickness strain of poly (styrene-b-ethylbutylene-b-styrene) (SEBS) gel was measured using an in situ synchrotron SAXS. The thermoplastic elastomer SEBS gel was microphase-separated to form a disordered styrene micelle nanostructure in an oil-swollen ethylbutylene matrix. The SEBS gel showed reversible cyclic load-unload compression behavior without permanent residual strain. The electromechanical strain of the SEBS gel with carbon paste electrodes could be evaluated by means of a nanostructure dimensional change traced by using the in situ synchrotron SAXS during actuation. The strain measured with SAXS was compared with the strain measured using conventional laser displacement sensor systems. The optical laser sensor method was likely to overestimate the thickness strain due to the bending movement of the dielectric elastomer. To our knowledge, the thickness strain value measured by the synchrotron SAXS is the closest to the true strain ever measured in the field of dielectric elastomer studies, because the nanostructure dimensional change depends on the thickness dimension change, not on the translational movement like the bending motion.

Without any contact with electrodes, nanostructured elastomers can electrically actuate, as reported by Sang Ouk Kim, Chong Min Koo, and co‐workers . The cover image illustrates the electric actuation of nanostructured materials, dominated by a true electrostriction mechanism. The degree of surface polarization on the interface between mismatched dielectrics is expressed by the surface color of the dispersion phases.

Mechanical properties, thermal stability and optical properties of triacetyl cellulose (TAC) films plasticized by three types of plasticizer, triphenyl phosphate (TPP), biphenyldiphenyl phosphate (BDP) and a mixture of TPP and BDP have been investigated in order to find the optimum plasticization condition for a protective film application in LCD. Mechanical properties such as modulus, tensile strength and elongation at break, and thermal property were significantly distinguished according to the type of plasticizer. TPP worked as the most effective plasticizer for TAC in the viewpoint of the mechanical properties. TAC=TPP showed the largest increase in elongation at break and the biggest reduction in the glass transition temperature at the same plasticizer level. However, TPP had the worst thermal stability. A mixture of TPP and BDP achieved the compromising plasticization to produce the moderate mechanical properties and thermal stability of TAC films for protective film application in LCD.