Nanoconfinement: an Effective Way to Enhance PVDF Piezoelectric Properties

Abstract

The dimensional confinement and oriented crystallization are both key factors in determining the piezoelectric properties of a polymeric nanostructured material. Here we prepare arrays of one-dimensional polymeric nanowires showing piezoelectric features by template-wetting two distinct polymers into anodic porous alumina (APA) membranes. In particular, poly(vinylidene fluoride), PVDF, and its copolymer poly(vinylidene fluoride-trifluoroethylene), PVTF, are obtained in commercially available APA, showing a final diameter of about 200 nm and several micrometers in length, reflecting the templating matrix features. We show that the crystallization of both polymers into a ferroelectric phase is directed by the nanotemplate confinement. Interestingly, the PVDF nanowires mainly crystallize into the β-phase in the nanoporous matrix, whereas the reference thin film of PVDF crystallizes in the α nonpolar phase. In the case of the PVTF nanowires, needle-like crystals oriented perpendicularly to the APA channel walls are observed, giving insight on the molecular orientation of the polymer within the nanowire structure. A remarkable piezoelectric behavior of both 1-D polymeric nanowires is observed, upon recording ferroelectric polarization, hysteresis, and displacement loops. In particular, an outstanding piezoelectric effect is observed for the PVDF nanowires with respect to the polymeric thin film, considering that no poling was carried out. Current versus voltage (I-V) characteristics showed a consistent switching behavior of the ferroelectric polar domains, thus revealing the importance of the confined and oriented crystallization of the polymer in monodimensional nanoarchitectures.

Nanostructured polymer-based piezoelectric and triboelectric materials and devices for energy harvesting applications

“…NGs made from PVDF films present good robustness, reliability and flexibility [17,18]. However, the ability to control the required piezoelectric crystalline phase in confined geometries [19,20] has received considerable attention in recent times. In general, typical thin film fabrication often results in α phase PVDF (shown in figure 1(a)) which does not behave exhibit piezoelectricity due to net cancellation of dipoles along the chain [16].…”

Microstructured organic ferroelectric thin film capacitors by solution micromolding

“…piezo-response force microscopy, 7,8,13,16,21,27 but scarcely in actual devices. 17,18,[21][22][23]27,31,32 Careful analysis is required, as both the characterization method and the device geometry can influence the measured ferroelectric characteristics. Here we investigate for the first time the device physics of capacitors based on linear gratings of P(VDF-TrFE).…”

Electrical characterization of poly(vinylidene fluoride-trifluoroethylene) nanocrystals embedded in porous alumina matrix

“…21 Also, it was found the domain switching behavior through PFM hysteresis loop measurements. Figure 2(e) shows PFM amplitude image and corresponding piezoelectric hysteresis loops.…”

“…The alumina matrix due to restricted geometry of the pores makes it possible to increase the polar -phase fraction in the copolymer. 21 It leads to the polarization growth in the single copolymer nanocrystal compared to the bulk film. The total polarization of the composite samples can be increased by more complete filling of the pores in the AAO matrix, as well as by various treatments, such as hightemperature annealing and high electric field applying.…”

“…Piezoelectric behavior of one-dimensional polymer nanowires was observed, upon recording ferroelectric polarization, hysteresis, and displacement loops. 20,21 In this work, we propose to fill the aluminum oxide pores with the melted P(VDF-TrFE) copolymer for increasing the pore fillability. Also, complex studies of electrical properties of P(VDF-TrFE) nanowires were carried out in this research.…”