A critical analysis of the α, β and γ phases in poly(vinylidene fluoride) using FTIR

Abstract

Poly(vinylidene fluoride) (PVDF) has been widely utilized in scientific research and the manufacturing industry for its unique piezoelectric properties. In the past few decades, the vibrational spectra of PVDF polymorphic polymers via FTIR (Fourier transform infrared spectroscopy) have been extensively investigated and documented. However, reports on the analysis of α, β and γ phases often have conflicting views based on measured data. In this work, we analyze the FTIR vibrational bands of PVDF materials fabricated by different processes with detailed XRD (X-ray diffraction) characterization to identify the structural α, β and γ phases. By examining the results in this work and extensively reviewing published research reports in the literature, a universal phase identification procedure using only the FTIR results is proposed and validated. Specifically, this procedure can differentiate the three phases by checking the bands around 763 and/or 614, 1275, and 1234 cm⁻¹ for the α, β and γ phases, respectively. The rule for assignment of the 840* and 510* cm⁻¹ bands is provided for the first time and an integrated quantification methodology for individual β and γ phase in mixed systems is also demonstrated.