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.

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Zinc oxide-Barium titanate-Polycarbonate (ZnOÀBaTiO 3 ÀPC) nanocomposites were prepared to investigate effect of ZnO-BaTiO 3 mixed nanoparticles on the optical, electrical, and thermal properties of polycarbonate (PC). The UV-visible absorption spectra was measured for the nanocomposites at room temperature between 200 and 800 nm and the optical energy gap was determined from the measured absorption coefficient data. Optical results reveal that BaTiO 3 ceramic has a strong absorption below 300 nm while ZnO has a strong absorption peak at 367 nm and the UV absorption in these regions depends on the ZnO and BaTiO 3 concentration. This indicates that the PC UV shielding region can be controlled through the mixed BaTiO 3-ZnO nanoparticle weigh ratios. Also, 10 wt% BaTiO 3 nanoparticles in PC insignificantly affects the optical energy gap whereas 10 wt% ZnO nanoparticles in PC decreases the optical gap from 4.14 to 3.9 eV. Results obtained from DC conductivity and thermal analysis reveal that adding BaTiO 3 nanoparticles into PC will decrease DC conductivity, restrict chain mobility, and increase thermal stability while, adding ZnO nanoparticles to PC increases DC conductivity, enhances chain mobility, and decreases the thermal stability. The optical, electrical, and thermal properties of these nanocomposites can be controlled by adjusting the ZnO to BaTiO 3 nanoparticles weight ratios in the PC matrix.

ABSTRACT:The influence of ZnO nanoparticles on the dielectric properties, dielectric relaxation behavior, and thermal stability of PC host was investigated at different ZnO nanoparticles concentration. The dielectric study was carried out over a frequency range from 500 Hz up to 1 MHz as a function of ZnO concentration. Results obtained from the best fitting of relative permittivity data with Yan and Rhodes model reveal that the dielectric relaxation is not a single relaxation process and there are two values of relaxation time for each nanocomposite at room temperature and domain frequency range. Furthermore, addition of ZnO nanoparticles to PC host changes the dielectric properties of PC, mainly, increases relative permittivity, dielectric loss, and AC conductivity while decreases the impedance values of PC host. Moreover, effect of temperature on AC conductivity of ZnO-PC nanocomposites at 1 kHz was also considered. Besides, dielectric relaxation behavior of PC was investigated at 1658C (above the glass transition temperature of PC) in the domain frequency range. At this elevated temperature (1658C), dielectric loss data shows a single relaxation peak (a-relaxation) in the domain frequency range and was successfully fitted with Debye equation. Also, it was found that as the content of ZnO nanoparticles increases in the PC host the frequency of the peak maximum (f max ) shifts toward higher frequency value and as a result decreases the value of relaxation time. Additionally, this study shows that the isothermal effect of ZnO nano particles on the a-relaxation of PC host is similar to the effect of temperature. Both of them have a linear dependence with ln(f max ). Furthermore, addition of ZnO nanoparticles to PC host will decrease the thermal stability and glass transition temperature of PC host. Finally, there is a strong evidence from the obtained dielectric and thermal results that addition of ZnO nanoparticles to PC host sagepub.co.uk/journalsPermissions.nav *Author to whom correspondence should be addressed. E-mail: aaljaafari@kfu.edu.sa Figure 1 and 12 appear in color online http://jtc.sagepub.com will highly enhance the chain mobility and also increase the polar character of PC host.

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