Role of nanoparticle surface charge on the nucleation of the electroactive β-poly(vinylidene fluoride) nanocomposites for sensor and actuator applications

The electroactive β-phase of poly(vinylidene fluoride) (PVDF) can be nucleated by introducing CoFe2O4 nanoparticles within the polymer matrix, leading to electroactive materials with large potential for sensor and actuator applications. The effects of the CoFe2O4 nanoparticle electrostatic charge on the phase crystallization of PVDF polymer is reported. For this purpose, the CoFe2O4 nanoparticles were coated with anionic (SDS), non-anionic (Triton X-100) and cationic (CTAB) surfactants and the obtained coated nanoparticles were used as fillers. It is found that the piezoelectric β-form of the polymer increases when CoFe2O4 nanoparticles with higher negative electrostatic charge are added. This behavior is attributed to the interaction between the magnetic particles negatively charged and the polymer CH2 groups, having a positive charge density. Further the relationship between the β-phase content and the piezoelectric response has been demonstrated. The magnetostriction of the ferrite nanoparticles and the proven piezoelectricity of the polymer allows the use of the material for piezoelectric and magnetoelectic sensors or/and actuators.We acknowledge the Foundation for Science and Technology (FCT) for financial support through PTDC/CTM/69316/2006, NANO/NMed-SD/0156/2007, and PTDC/CTM-NAN/112574/2009 projects. The authors are also thankfull for the support from the COST Action MP1003, 2010 "European Scientific Network for Artificial Muscles". P.M. thank the support of the FCT (Grant SFRH/BD/45265/2008). M.B. thanks the FCT for support under the "Compromisso corn a Ciencia" program