Flexoelectricity in Soft Polymer Films

International audienceFlexoelectricity in matter is a two-way linear electromechanical coupling, like piezoelectricity, but direct flexoelectric effect corresponds to the electric polarization induced by a strain gradient, whereas piezoelectric polarization is related to the strain itself. Similarly, converse flexoelectric effect is defined as an electric field gradient-induced strain or stress and piezoelectric effect is a coupling between strain or stress and electric field. Thus, due to the symmetry-breaking effect of the strain gradient, flexoelectricity may be observed in all dielectrics, while piezoelectricity can only be found in non-centrosymmetric materials. Besides, as strain gradients may dramatically increase when feature scale shrink down to the micro/nano range, flexoelectric response may become large and consequently has been widely studied in oxide thin films. However, strain gradients also inversely scale with elastic stiffness that may make flexoelectricity competitive with piezoelectricity in flexible soft polymer films. Thus, the purpose of the study is to present the experimental determination of thickness dependent flexoelectric coefficients in thermoplastic films and large flexoelectric-like effect in moderately conducting polymer blends