Close relationship between bending-electrostrictive response and space charge distribution in a polyurethane film

The object of our study was to clarify the mechanism of the bending-electrostrictive response of a polyurethane film. We investigated the mechanism using the pulsed electroacoustic method for measuring the space charge distribution in the film. The measurements revealed a similarity between the time courses of the bending-electrostrictive response and the space charge accumulation. That is, the film gradually bent to the cathode side during the first electric-field application to a virgin sample. However, it quickly bent during the succeeding second application. On the other hand, the measurement of the space charge showed that a negative space charge gradually accumulated inside the anode during the first application. However, it quickly accumulated during the second application. Time plots of the bending deformation and the space charge density clearly showed the above similarity in the response profile. Such a similarity suggests that the space charge is closely related to the bending electrostriction mechanism.