Joint experimental and computational investigation of the structural and spectroscopic properties of poly(vinylidene fluoride) polymorphs.

State-of-the-art density functional theory calculations are here adopted for the investigation of the crystal structure and of the vibrational properties of α, β, γ, and δ phases of poly(vinylidene fluoride) (PVDF), in comparison with IR and Raman measurements. DFT calculations allowed a detailed interpretation of the IR and Raman spectra of α and β phases, giving vibrational assignments useful for qualitative and quantitative characterization of these systems. From a molecular perspective, the computational investigation of the crystal structure and the spectra of PVDF polymorphs helped in clarifying the role of supramolecular dipole-dipole interactions, which indeed modulate the vibrational properties of these systems, indicating also that intermolecular interaction could play a significant role in the modulation of ferroelectric properties. Furthermore, the combined experimental and computational approach allowed us to identify and characterize the thermally and mechanically induced γ phase, shedding light on the far-IR marker bands of this elusive phase of PVDF.