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

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 (mu CNTs) with different unzipping degrees were obtained through controlling the amounts of oxidant (KMnO4). Due to the increased available interface area and specific interaction between the oxygen-containing groups (such as >C=O) in mu CNTs and the >CF2 group of PVDF, the dispersion of mu CNTs in PVDF matrix is tremendously improved. The resulting PVDF/mu CNTs 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 mu CNTs nucleate PVDF crystallization and enhance piezoelectric beta phase with a concomitant decrease of alpha phase. This is particularly true for the nanocomposites including the mu CNTs with higher unzipping degree, in which the mass crystallinity and content of beta phase (F-beta) were enhanced, implied by the increased piezoelectric constant d(33). In addition, the increased storage modulus (E') tested by dynamic mechanical analysis confirmed that mu CNTs were more effective than pristine MWNTs in terms of reinforcing polymers. (C) 2012 Elsevier Inc. All rights reserved.