Plasticized relaxor ferroelectric terpolymer: Toward giant electrostriction, high mechanical energy and low electric field actuators

• A new all organic composite based on ferroelectric relaxor polymer matrix and bis (2-ethylhexyl) phthalate (DEHP) has been elaborated and characterized.
• P(VDF-TrFE-CFE) composite doped with DEHP shows a 28-fold increase of the longitudinal electrostrictive strain and a 235-fold increase of the mechanical energy density.
• This easy and low cost modification allows a 6 times reduction of the electric field compared to the neat terpolymer.
• Experimental results have been compared to classical models and the increase attributed to large interfacial effects caused by charges trapped at the structural heterogeneities of the polymer.

Enhancing the electrostrictive strain under low electric field of a dielectric electroactive polymer (EAP) is essential in soft actuators applications. Conventional electrostrictive polymers suffer of the high electric fields usually required to reach sufficient strain. Here we report a new approach that greatly enhanced the strain under electric field and the mechanical energy density of fluorinated terpolymer EAP. A new all organic composite based on poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) terpolymer (P(VDF-TrFE-CFE)) doped with bis(2-ethylhexyl) phthalate (DEHP) was synthesized. DEHP molecule acts as a plasticizer that leads to large dipolar interfacial effects. This chemical modification allows a 28-fold increase of the electrostrictive strain and a 215-fold increase of the mechanical energy density. As a consequence, this new approach permits the uses of the exceptional properties of the fluorinated terpolymer for an electric field nearly 5 times lower and represents a simple and effective solution to this technological barrier.