Spectroscopic Investigations on Polyvinylidene Fluoride Nanofibers

Polyvinylidene fluoride (PVDF) is a polymer with good mechanical properties, high thermal stability, and limited solubility in strong polar solvents. PVDF has a simple chemical formula (C₂H₂F₂)_n, where n is the degree of polymerization, and exhibits several conformations that induce up to 5 crystalline phases. The beta phase is the most attractive due to its ferroelectric features, triggered by the all-planar zigzag conformation. The processability of PVDF and the possibility of further enhancing the ferroelectric features of PVDF through crystallization from solutions with different solvents, high field poling (preferable in the melted state), and blending with other polymers are under investigation. This study focuses on the preparation and characterization of PVDF nanofibers by using the force-spinning method, aiming to achieve an enhancement of the beta phase content. The polymer and the solvent (dimethylacetamide DMAC) were purchased from Sigma and used as received. Solutions of PVDF in DMAC have been obtained and homogenized by stirring. The solvent was thermally evaporated. The homogeneous solutions of PVDF were then subjected to the force spinning at various spinning rates ranging from 4,000 to 10,000 rotations per minute. The phase content of the as-obtained mats was determined by X-ray diffraction using a Bruker Discovery 8 spectrometer. Complementary data have been obtained by Raman spectroscopy by using a Renishaw spectrometer equipped with a laser emitting at a wavelength of 785 nm.