Vibrational spectrum of PVDF and its interpretation

IR spectra of poled and non-poled PVDF films were studied. Non-poled extruded samples were annealed and cooled at different cooling rates. Then, FTIR spectra of all samples were taken under scanning with different diaphragms. It was found that the spectra and their interpretation depend strongly on the scale of the scanning procedure for both poled and non-poled films. Scanning by a diaphragm with a diameter D close to the size of β-phase domains d reveals the presence of the β-phase in the annealed non-poled PVDF, whereas spectra obtained with a "large" diaphragm (D⪢d) do not show discernable peaks inherent to the β-phase. Cooling rate influence on the β-phase contents is strong. When the diameter of the diaphragm D and size of crystalline γ inclusions are of the same magnitude, peak splitting is observed in the poled PVDF.