Theory of the Spontaneous Polarization and the Pyroelectric Coefficient of Linear Chain Polymers

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Abstract
Polyvinylidene fluoride (PVF2) films consist of two crystalline phases; their relative abundance is determined by the draw temperature. One phase has a chain repeat of two monomer units, the other a planar zig‐zag conformation. We assume that the latter phase is responsible for the spontaneous polarization, and present a model, which should be applicable to linear chain polymers in general, of the polarization state of such a phase, in which the temperature dependence of the polarization arises from the torsional oscillations of the macromolecules. Three torques are taken into account: a phenomenological one due to nearest neighbor interaction, one due to the torsional stiffness of the macromolecule, and one due to the interaction of the permanent dipole moment with the local electric field. Numerical calculations show that this model can account for all the experimental data known so far, and the calculations also clearly demonstrate the dynamics of the poling process.

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