Far‐infrared spectra of piezoelectric polyvinylidene fluoride

Abstract

Poly(vinylidene fluoride) (PVF₂) is currently used to form piezoelectric films. The PVF₂ molecule can exist in more than one stable conformation and it has electrically polar groups making the polymer amenable to the electrification processes involved in the formation of the piezoelectric film. The two crystalline forms of PVF₂ are distinguishable by far‐infrared spectroscopy. Polarized far‐infrared spectra (1000‐50 cm⁻¹) of uniaxially oriented PVF₂ show changes in the strong perpendicular dichroism in a number of absorptions before and after being made piezoelectric. The dichroism is attributed to a structural rearrangement from a staggered trans‐gauche‐trans‐gauché conformation to a planar zig zag conformation. In the latter conformation the permanent dipoles are oriented approximately at right angles to the surfaces of the film and result in an electrically polarized film.