Measuring true electromechanical strain of electroactive thermoplastic elastomer gels using synchrotron SAXS

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.