A dielectric study of poly(vinyl acetate) using a pulse-probe technique

There is considerable literature available that describes our understanding of the viscoelastic properties of polymers subjected to mechanical stresses or deformations. What we refer to here as a pulse-probe technique is one method that is commonly used to study the time-dependent behavior of materials in histories, e.g., temperature-jump or step-deformations, that exhibit fading memory responses. In the linear case the behavior is well understood in the context of Boltzmann superposition ideas. However, there is only limited work available that investigates the dielectric response of materials within this same context. In the present study, we present an investigation of the dielectric behavior of poly(vinyl acetate) (PVAc) using a two-step pulse-probe technique. Time domain dielectric experiments were performed in the vicinity of the glass transition temperature. After establishing the linear response function in single-step experiments, two types of pulse-probe experiments were performed. In one, the time duration t ₁ of the first step in the probe was varied. In the second case, the magnitude of the field E ₁ applied to the sample for the first step was varied. We not only demonstrate the existence of the memory effect in the dielectric response, but also find that the responses are consistent with the linear Boltzmann superposition principle. Evidence of deviations from linear superposition at the highest electric fields is also presented.