Electrical and Microstructural Changes of β-PVDF under Uniaxial Stress Studied by Scanning Force Microscopy

Abstract

Abstract. Chain reorientation may be induced in polyvinylidene fluoride (PVDF) in its β-phase by applying a deformation perpendicular to the pre-oriented polymeric chains. This reorientation begins right after the yielding point and seems to be completed when the stress-strain curve stabilizes. As the deformation process plays an important role in the processing and optimisation properties of the material for practical applications, different deformation stress was applied to the PVDF lamellas and their topographic change and piezoelectric response were studied by means of scanning force microscopy in a piezo-response mode. The experimental results confirm the previously observed chain reorientation that occurs right after the yielding point and that is completed when the yielding region is passed. This reorientation is accompanied by a stretching of the granular structures observed in the topographical images and variations in the domain response. The observed results help to explain the variations in the macroscopic response of the material.

In situ monitored stretching induced α to β allotropic transformation of flexible poly(vinylidene fluoride)-CoFe2O4 hybrid films: The role of nanoparticles inclusion

“…These changes are well-illustrated by the optical images captured for each stretched sample state (Figure 1a,b,c), before engaging the AFM tip: an evolution from a spherulitic structure to a fibrillar one is unambiguously observed. So in the 6% elongated film well-defined large spherulites, assigned to the non-electroactive α phase [47][48][49], are present (Figure 1a), while in the 28% elongated one (Figure 1b), the spherulites are destabilized and start to align along the uniaxial traction direction giving rise to the fibrillar morphology. Darker transversal "belts" between the reorganized spherulite zones also appear (Figure 1g).…”

Electroforming free high resistance resistive switching of graphene oxide modified polar-PVDF

“…An application of a positive E-eld in the direction of the poled sample shrinks the device and hence provides a favorable path to ow the charge carriers abruptly across the heterostructure. [46][47][48][49] Shrink conditions and enough potential for the small oxygen diffusion length lead to the abrupt change in the charge carriers near the SET E-elds as shown in Fig. 5(a-c).…”