Unzipped multiwalled carbon nanotubes-incorporated poly(vinylidene fluoride) nanocomposites with enhanced interface and piezoelectric ß phase.

ABSTRACT

An improved method is described for the fabrication of poly(vinylidene fluoride) (PVDF)/carbon nanotubes (CNTs) hybrid materials to solve intrinsic limitation of CNTs. In this study, multiwalled carbon nanotubes (MWCNTs) were unzipped by an oxidative unzipping process before dispersing in PVDF matrix, and unzipped MWCNTs (µCNTs) with different unzipping degrees were obtained through controlling the amounts of oxidant (KMnO(4)). Due to the increased available interface area and specific interaction between the oxygen-containing groups (such as >C=O) in µCNTs and the >CF(2) group of PVDF, the dispersion of µCNTs in PVDF matrix is tremendously improved. The resulting PVDF/µCNTs nanocomposites were characterized by wide angle X-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry, scanning electron microscopy, and transmission electron microscopy. It is found that µCNTs nucleate PVDF crystallization and enhance piezoelectric ß phase with a concomitant decrease of α phase. This is particularly true for the nanocomposites including the µCNTs with higher unzipping degree, in which the mass crystallinity and content of ß phase (F(ß)) were enhanced, implied by the increased piezoelectric constant d(33). In addition, the increased storage modulus (E') tested by dynamic mechanical analysis confirmed that µCNTs were more effective than pristine MWNTs in terms of reinforcing polymers.