High Electromechanical Deformation Based on Structural Beta-Phase Content and Electrostrictive Properties of Electrospun Poly(vinylidene fluoride- hexafluoropropylene) Nanofibers

Abstract

The poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)) polymer based on electrostrictive polymers is essential in smart materials applications such as actuators, transducers, microelectromechanical systems, storage memory devices, energy harvesting, and biomedical sensors. The key factors for increasing the capability of electrostrictive materials are stronger dielectric properties and an increased electroactive β-phase and crystallinity of the material. In this work, the dielectric properties and microstructural β-phase in the P(VDF-HFP) polymer were improved by electrospinning conditions and thermal compression. The P(VDF-HFP) fibers from the single-step electrospinning process had a self-induced orientation and electrical poling which increased both the electroactive β-crystal phase and the spontaneous dipolar orientation simultaneously. Moreover, the P(VDF-HFP) fibers from the combined electrospinning and thermal compression achieved significantly enhanced dielectric properties and microstructural β-phase. Thermal compression clearly induced interfacial polarization by the accumulation of interfacial surface charges among two β-phase regions in the P(VDF-HFP) fibers. The grain boundaries of nanofibers frequently have high interfacial polarization, as they can trap charges migrating in an applied field. This work showed that the combination of electrospinning and thermal compression for electrostrictive P(VDF-HFP) polymers can potentially offer improved electrostriction behavior based on the dielectric permittivity and interfacial surface charge distributions for application in actuator devices, textile sensors, and nanogenerators.

Tunable Mechanical and Electrical Properties of Coaxial Electrospun Composite Nanofibers of P(VDF-TrFE) and P(VDF-TrFE-CTFE)

“…A similar decreasing tendency in the dielectric loss was observed within the low frequency region from 12 to 100 Hz, as shown in Figure 7 b. The dielectric loss then increased with the increasing frequency above 103 Hz due to the polarization loss and DC conduction loss [ 61 , 62 ].…”

Towards Poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene)-Based Soft Actuators: Films and Electrospun Aligned Nanofiber Mats

“…In general, the electrostriction of a dielectric material can be increased by increasing its dielectric permittivity [ 32 ]. Electrospinning is a process that enhances the dielectric properties of the material for the following main reasons: (i) the mechanical stretching enforced by the electrospinning process enables for the alignment of the polymeric chains in the amorphous phase; (ii) the nanofibers have dipoles with a self-induced orientation; (iii) the electrical poling also enforced by the electrospinning process enables the spontaneous dipolar orientation [ 33 ] inside the nanofibers; and (iv) the nanofibers have a larger surface area to volume ratio than a bulk, which also increases the dielectric constant [ 34 ]. Furthermore, nanofibers allow for a better alignment of the dipoles because of the smaller amount of material that has to be reorganized around each dipole.…”

Phase and Structure Behavior vs. Electromechanical Performance of Electrostrictive P(VDF-HFP)/ZnO Composite Nanofibers

“…In consideration of the fact that the electrostrictive P(VDF-HFP) can produce both sizeable mechanical deformation and electrical polarizations, it can convert between electrical and mechanical energy forms. It can be used in actuators and energy-harvesting applications [ 10 , 11 ]. Moreover, the P(VDF-HFP) copolymer exhibits good chemical resistance, higher solubility, flexibility, durability, lightweight, and strong hydrophobicity [ 6 ].…”