In this study, different morphologies of polyaniline (PAni) nanostructures were obtained via interfacial polymerization. The influence of the time and temperature of polymerization on morphology was investigated. At room temperature the growth of nanosheets and nanoflowers with long polymerization time (1-5 days) was observed. In the syntheses carried out at 50°C the same nanostructures were obtained with only a few hours of polymerization, which illustrates that the increase in temperature considerably reduced the synthesis time and also provided the growth of nanofibers, morphology not found in the syntheses performed at room temperature. The characterization by XRD indicated the presence of diffraction peaks characteristic of PAni nanostructures with high crystallinity. As the conductivity of PAni is directly related to its crystallinity, it is expected that the nanostructures obtained have high conductivity, which may represent a greater potential for diverse applications. It can be concluded that the proposed synthesis presents a simple alternative for obtaining PAni nanostructures with different morphologies and high crystallinity.
Composite films made of poly(vinylidene fluoride) (PVDF) and conducting particles of carbon black (CB) were prepared using a hot press. Using different volume fractions of CB filler, electrical properties of the samples were analyzed with current-voltage (I 9 V) measurements and impedance spectroscopy. To help the discussion, percolation theory and simulation circuits based on Colie diagrams were used. The percolation threshold was found at 3 vol% of CB. At these volume fractions of filler, scanning electron microscopy (SEM) images showed connected particles in the polymer matrix, while in the higher volume content of filler, the particles started to form clusters. Furthermore, it was observed that increasing volume fractions up to 3 vol%, the Young's modulus and the tensile strength of the composite film were higher than that of the pure polymer, although the rupture strain was decreased. Composite films with 3 vol% of CB showed optimized electrical and mechanical properties and may be useful as an electrostatic dissipater.
Films made of a blend of polyaniline (PAni) and a nonpolar polyvinylidene fluoride (PVDF) polymer matrix were obtained by the mechanical mixing of both, with subsequent melting and quenching. Using the current versus voltage (IxV) measurements, the percolation threshold (concentration in which some conducting particles are connected to form at least one conductor path, related to one direction of the film) was determined to be between 40 and 45 % in volume along the surface. Related to the film thickness, a small amount of PAni (0.5 % in volume) was enough to transform the blend in a conducting material. Strain-stress tests indicated that a small amount of PAni can reinforce the polymer matrix. Furthermore, the immiscible blend obtained changes in its electrical conductivity, according to the pH of the solution in which it was immersed, indicating the possibility of the real application of that material as a resistor with variable electrical resistance.
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