Solvent effects on the synthesis of piezoelectric membranes, based on nanofibers of the polyvinylidene polyfluoride polymer

Abstract

The qualitative and quantitative characteristics of piezoelectric membranes manufactured with the polymer polyvinylidene fluoride, through the electrospinning (TEH) technique were compared. We fabricated microfiber membranes of polyvinylidene fluoride (PVDF) using the electrospinning technique in Methyl Ethyl Ketone (MEK) solution at a ratio of 2:1 and compared them with those manufactured by other authors, who used Dimethylformamide (DMF) as a solvent. During the process, a potential difference of 15.0 kV was applied and the viscoelastic solution of PVDF was maintained at a temperature of 60$^{\circ} \mathrm{C}$. The working hypothesis was based on analyzing the influence of the polymer solute on two specific properties: (1) the diameter of the microfibers of the PVDF polymeric material, synthesized through TEH and; (2) the formation of the rotational crystalline structure of the polymer, specifically in the beta ( $\beta$ ) piezoelectric phase. The following techniques were used to characterize the synthesized samples: (1) Scanning electron microscopy (SEM), with which we were able to record the diameter of the microfibers between 85 and 113 nm . (2) X-ray diffraction (XRD), where the samples generated dispersions at 2 $\theta$=18.3$^{\circ}$, 19.9$^{\circ}$ and 20.6$^{\circ}$ , which indicated that the crystalline structure obtained is typical of the alpha ( $\alpha$ ) and beta ( $\beta$ ) piezoelectric phases. (3) Raman spectroscopy, with which a spectrum with wave number (k) between 800 $\mathrm{~cm}^{-1}$ and 840 $\mathrm{~cm}^{-1}$ was determined, which supported the changes we caused in the internal structure of the polymer, using the DMF/MEC mixture as the polymer solvent. The characterization of the samples obtained allowed us to discover that the properties of PVDF microfiber membranes are affected by the solvent used in the synthesis process. When comparing membranes that used only DMF as a solvent with our membranes manufactured with the DMF/MEC solvent, a higher concentration of the piezoelectric beta ($\beta$) structural phase was generated in the latter, which have greater application in power-generating devices.