Polymeric Nanofibers with Ultrahigh Piezoelectricity via Self-Orientation of Nanocrystals.

Liu, Xia; Ma, Jing; Wu, Xiaoming; Lin, Liwei; Wang, Xiaohong · ACS Nano · 2017

basic_science · Level V

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Abstract

Piezoelectricity in macromolecule polymers has been gaining immense attention, particularly for applications in biocompatible, implantable, and flexible electronic devices. This paper introduces core-shell-structured piezoelectric polyvinylidene fluoride (PVDF) nanofibers chemically wrapped by graphene oxide (GO) lamellae (PVDF/GO nanofibers), in which the polar β-phase nanocrystals are formed and uniaxially self-oriented by the synergistic effect of mechanical stretching, high-voltage alignment, and chemical interactions. The β-phase orientation of the PVDF/GO nanofibers along their axes is observed at atomic scale through high resolution transmission electron microscopy, and the β-phase content is found to be 88.5%. The piezoelectric properties of the PVDF/GO nanofibers are investigated in terms of piezoresponse mapping, local hysteresis loops, and polarization reversal by advanced piezoresponse force microscopy. The PVDF/GO nanofibers show a desirable out-of-plane piezoelectric constant (d<sub>33</sub>) of -93.75 pm V<sup>-1</sup> (at 1.0 wt % GO addition), which is 426% higher than that of the conventional pure PVDF nanofibers. The mechanism behind this dramatic enhancement in piezoelectricity is elucidated by three-dimensional molecular modeling.