ABSTRACT
Polyvinylidene fluoride (PVDF)/Polyacrilonitrile (PAN)/Multiwalled nanotubes functionalized COOH (MWNT-COOH) nanocomposites with different contents of MWNTs were fabricated by using electrospinning and solution cast methods. The interaction of the MWNTs with the polymer blend was confirmed by a Fourier transform infrared (FTIR) spectroscopy study. The dispersion of the MWNTs in the polymer blend was studied by scanning electron microscopy. The impedance and electrical conductivity of PVDF-PAN/CNTs in a wide frequency range at different temperatures have been studied. The effect of the concentration of the filler on the conductivity of the polymer composite was discussed. Nanocomposites based on PVDF/PAN and MWNTs as filler, show a significant enhancement in the electrical conductivity as a function of temperature.
ABSTRACT
Multifunctional materials have attracted many interests from both fundamental and practical aspects, such as field-effect transistor, electric protection, transducers and biosensor. Here we demonstrated the first superior hydrophobic piezoelectric surface based on the polymer blend of polyvinylidene fluoride (PVDF)-polyacrilonitrile (PAN) assisted with functionalized multiwalled nanotubes (MWNTs), by a modified electrospinning method. Typically the ß-phase polyvinylidene fluoride (PVDF) was considered as the excellent piezoelectric and pyroelectric materials. However, polar ß-phase of PVDF exhibited a natural high hydrophilicity. As a well-known fact, the wettability of the surface is dominated by two major factors: surface composition and surface roughness. The significant conversions derived by the incorporation of MWNTs, from nonpolar α-phase to highly polar ß-phase of PVDF, were confirmed by FTIR. Meanwhile, the effects of MWNTs on the improvement of the roughness and the hydrophobicity of polymer blend were evaluated by atomic force microscopy (AFM) and contact angle (CA). Molar free energy of wetting of the polymer nanocomposite decreases with increasing the wt.% of MWNTs. All molar free energy of wetting of PVDF-PAN/MWNTs were negative, which means the non-wettability of film. The combination of surface roughness and low-surface-energy modification in nanostructured composites leads to high hydrophobicity. Particularly, fabrication of superior hydrophobic surfaces not only has fundamental interest but also various possible functional applications in micro- and nano-materials and devices.
ABSTRACT
Poly(vinyl pyrrolidone)/Poly(acrylonitrile)/multi-walled carbon nanotubes composites (PVP/PAN/MWNTs) were fabricated by a simple solution cast technique with a wide composition range from 0 to 3.12 wt% of MWNTs. The nanocomposites were characterized by fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). A percolated MWNTs network structure and relatively good dispersion of MWNTs are evident in PVP/PAN/MWNTs nanocomposites with 3.12 wt% of MWNTs. The thermal properties of the polymer blend with MWNTs were carried out by means of different scanning calorimetry (DSC). It indicated that the incorporation of MWNTs had a significant influence on crystallization and melting behaviors for the polymer nanocomposites. The four point probe method was used to measure the electrical conductivity, and the result showed ionic conductivity of the order of 2.87 × 10-4 S/cm to 1.91 × 10-2 S/cm. The effect of the concentration of the filler on the conductivity of the polymer nanocomposite was discussed. Nanocomposites based on PVP/PAN and MWNTs as filler show a significant enhancement in the electrical conductivity as a function of temperature. The low percolation threshold in PVP/PAN/MWNTs nanocomposites was explained by high aspect ratio of the nanotubes and their distribution inside the polymer blend.
