Control of polar phases of PVDF through electrospraying

Poly(vinylidene fluoride) (PVDF) is a thermoplastic fluoropolymer with wide applications in industry ranging from antifouling filtration membranes to lithium-ion battery cathodes. However, films with thicknesses on the order of micro- to nano-meters form the beta (chain conformation TTTT) and gamma (chain conformation TTTGTTTG’) crystallographic phases [1]. Here, we create thin mats of PVDF through an alternative method of processing, using solution electrospraying. We used the solvent N,N-dimethylacetamide (DMAc) to create electrospinning solutions with concentrations on a PVDF weight to DMAc volume basis ranging from 3% to 12%. The resultant films were analyzed with Fourier-Transform Infrared spectroscopy and wide-angle X-ray diffraction in order to observe and quantify the crystalline phases of the samples. The phases were identified using the methodology of Cai, et al. [2]. The specific ratios of crystallographic phases in the samples were found using Fourier Self Deconvolution of the FTIR absorbance spectra. [3]. We observed that solution concentration influenced the relative amounts of beta and gamma phases. A high ratio of electroactive gamma to beta phase (84/16) was found in the 12% weight-to-volume sample, and through this study we reinforce the link between thin films and existence of higher percentages of the electroactive crystalline phases in PVDF.

References

[1] Andrew J. Lovinger. Poly(Vinylidene Fluoride). Developments in Crystalline Polymers, Chapter 1. (Springer, Dordrecht, Netherlands, 1982, vol 33, pp. 196-273)

[2] Anuja S. Jayasekara, Peggy Cebe. Quantitative analysis of polar crystalline fractions in poly(vinylidene fluoride) electrospun fibers and electrosprayed films. Polymer (2023) 281, 2-7

[3] Xiomei Cai, Tingping Lei, Daoheng Sun, Liwei Lin. A Critical Analysis of the α, β and γ phases in poly(vinylidene fluoride) using FTIR. RSC Advances (2017) 7, 1-2