A series of polycarbonate films loaded with different concentrations of UV-ozone pretreated single-walled carbon nanotubes were prepared. The electrical and mechanical properties of these composites were investigated. The improvement of the single-walled carbon nanotubes dispersion in polycarbonate (PC) matrix leads to a dramatic enhancement in the electrical conductivity with low percolation threshold (0.5 wt% of single-walled carbon nanotubes loading). Results obtained from the analysis of the dielectric parameters at room temperature and domain frequency range reveal that single-walled carbon nanotubes increases the dielectric constant, dielectric loss, and AC conductivity of the composites. The dielectric relaxation behavior of these composites is mostly due to polymer molecular relaxation when the single-walled carbon nanotubes content is below the percolation threshold whereas it is almost due to the charge conductivity relaxation above 0.8 wt% single-walled carbon nanotubes. The calculated values of the elastic modulus obtained from the stress-strain curves also show a percolation behavior with a threshold of 0.08 wt% single-walled carbon nanotube.

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Polycarbonate (PC)/MnCl2 composites have been prepared in order to study the influence of MnCl2 salt on the dielectric properties (resistivity ρ, permittivity ε', dielectric loss ε '', dielectric relaxation time `τ' and dielectric relaxation process) and thermal stability of PC/MnCl2 composites. The dielectric study was carried out over a frequency range from 10 Hz to 306 kHz at room temperature as a function of frequency and salt concentration. Permittivity data was fitted in the frequency domain using Yan and Rhodes model in order to estimate the relaxation times for PC composites. As expected, the resistivity of the composites decreases with increasing of salt concentration and frequency. Also, it was found that, addition of MnCl2 salt to PC host changes the dielectric properties of PC, mainly, broadening dielectric spectra, increases permittivity and dielectric loss, shortening relaxation time and reduces thermal stability of PC and PC composites. Results reveal that the relaxation process of these composites is due to ionic conductivity relaxation with a single relaxation time and not due to viscoelastic relaxation, while in case of pure PC is due to viscoelastic relaxation.

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Carbon nanotubes (CNTs) were prepared using Alcholic Catalyst Chemical Vapor Deposition (ACCVD) technique in order to investigate the effects of their addition on the optical, electrical and mechanical properties of Poly (3-octylthiophene-2,5-diyl) (P3OT) matrix. The absorption spectra of the prepared CNTs and CNT-P3OT nanocomposites were measured in the spectral range 200 nm-3,000 nm at room temperature. The optical energy gap was determined from the obtained UV/Vis absorption spectrum. Optical results reveal that the prepared CNTs are almost single walled. Besides, the addition of CNTs to P3OT polymer matrix will decrease the optical energy gap and enhance the optical absorbance of P3OT matrix. On the other hand, the addition of CNTs to P3OT matrix will increase the electrical conductivity of P3OT matrix up to four orders of magnitude above the percolation threshold (0.44 wt% CNTs). Additionally, I-V characteristics indicate that the conduction mechanism is Ohmic at low applied voltage range while it is due to the trap charge limited at high applied voltage range. Furthermore, the behavior of dc conductivity with temperature was also investigated and the obtained results reveal that the activation energy decreases with CNTs content. Finally, mechanical results reveal that the elastic modulus values increase with the increasing of CNTs content in P3OT matrix.