Correlation between crystallization kinetics and electroactive polymer phase nucleation in ferrite/poly(vinylidene fluoride) magnetoelectric nanocomposites

Abstract

Poly(vinylidene fluoride) (PVDF) nanocomposites with different ferrite nanoparticle loadings are interesting as, depending on ferrite type and content, the electroactive β-phase of the polymer is nucleated and the magnetoelectric coupling is induced. The isothermal crystallization behavior of ferrite/PVDF nanocomposites is studied using Polarized Optical Microscopy and the crystallization kinetic is analyzed by the Avrami theory in order to understand the crystallization conditions leading to the nucleation of the electroactive polymer phase. It is found that the nucleation kinetics is enhanced by the presence of ferrite nanoparticles, as evidenced by the increasing number of spherulites with increasing nanoparticle content and by the variations of the Avrami exponent. The crystallization velocity is intimately related to the polymer α- or β−phase formation in the nanocomposites and follows the order: NiFe2O4/PVDF > CoFe2O4/PVDF> Ni0.5Zn0.5Fe2O4/PVDF for a given temperature and nanoparticle loading, which results in larger amounts of β-phase for CoFe2O4/PVDF and Ni0.5Zn0.5Fe2O4/PVDF nanocomposites.