A study of the relationship between the rheo-dielectric effect and the elasticity of viscoelastic materials

Dielectrostriction is a rheo-dielectric phenomenon that relates the variation of dielectric properties of a material to deformation. For an initially isotropic material, two independent material parameters, called the strain-dielectric coefficients, α₁ and α₂, are required to describe dielectrostriction in terms of strain. Deformation affects a material's dielectric properties in two ways: (a) by introducing anisotropy in the material, which is characterized by α₁, and (b) by changing the volume density of the polarizable species, which is associated with (1 3 α₁ + α₂). Purely viscous fluids remain isotropic during any flow-induced deformation, and therefore the coefficient α₁ is always zero. In this paper, the dielectrostriction effect is studied in viscoelastic materials that are formulated to possess different degrees of elasticity. A special planar capacitance sensor rosette was employed to measure the coefficients α₁ and α₂ for these viscoelastic materials. The relationship between the material's elasticity and the coefficient α₁ is discussed, together with some potential applications based on this relationship in the conclusion.