Stress dielectric response in liquid polymers

Deformation-induced dielectric response of dielectric materials, called dielectrostriction, provides a new approach to study properties and structure of liquid polymers. The dielectrostriction effect resembles the well-known birefringence phenomenon. While birefringence in liquid polymers is described by the stress-optic relationship, a stress-dielectric relationship applies to dielectrostriction. However, dielectrostriction measurements can be performed on both transparent and opaque materials, require a much simpler data acquisition technique, are capable of local measuring stresses, and can be implemented for in-line monitoring of polymer processing. In this study, a planar capacitor sensor technique has been developed to detect the dielectrostriction effect in shear flow of liquid polymers. Experimental evidences of the dielectrostriction effect and the stress-dielectric relationship in liquid polymers are presented for both silicone elastomer and poly(ε-caprolactone). Mechanisms contributing to the similarity between the stress-dielectric and the stress-optic relationship are discussed.