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

The purpose of this work is to promote and optimize the formation of the beta poly(vinylidene fluoride) (PVDF) phase, known to exhibit the maximum piezoelectric and ferroelectric properties, in free PVDF film as well as in hybrid one containing ferrimagnetic cobalt ferrite nanoparticles inclusions (CoFe2O4 NPs). In practice, uniaxial stretching was applied on both alpha-neat PVDF and alpha/beta PVDF hybrid films, and the alpha to beta transformation was followed by in situ near-field AFM observations and ex situ XRD, FTIR and DSC experiments. A strong influence of the nano-inclusions was observed on the mechanically induced allotropic transformation. They clearly promote the growth of the electroactive beta phase in the PVDF matrix and favour the improvement of the whole film crystallinity. The proposed flexible material processing is easy-to-achieve and low cost. It is very promising for architecting original and smart magnetoelectric devices, in which the piezoelectric phases (beta-PVDF) could be well interfaced with the magnetostrictive ones (CoFe2O4). (C) 2016 Elsevier Ltd. All rights reserved.