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.

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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Two groups of polymer nanocomposite samples were synthesized. One of them was Poly(vinyl chloride) (PVC) loaded with different concentrations of carbon nanopowder (CNP), while the other was PVC loaded with different concentrations of carbon nanotubes (CNTs). The dependence of the tensile mechanical parameters, rheological properties and the dc electrical conductivity on the concentration of either filler was investigated. Results revealed a lower electrical and mechanical percolation threshold of CNTs than CNP. Concentration of CNTs of 1 wt% increases the elastic modulus 2.3 times greater than CNP at a concentration of 2 wt%. The storage modulus and the complex viscosity studied at a frequency of 0.1 Hz had the same behavior as the elastic modulus. The glass transition temperature was slightly changed with the addition of either nanofiller. The behavior of the temperature dependence of the electrical conductivity was found to be temperature independent in the studied range for composites containing CNTs, while composites containing CNP showed an activated one at relatively high temperatures. At concentrations in the percolation region of either CNP or CNTs, a jump region in the I-V characteristics was observed with a highest slope of 36.35 at 1 wt% of CNTs. Otherwise the conduction mechanism of the charge carriers was determined and found to be Ohmic.

Polymer nanocomposites consisting of single-walled carbon nanotubes (SWCNTs) and poly(3-octylthiophene-2,5-diyl) (P3OT) were prepared at different SWCNT loadings to investigate the influence of SWCNT content on the structure, dielectric and rheological properties of P3OT host. The dielectric parameters and dielectric relaxation behavior were investigated as a function of SWCNT loadings and frequency. Dielectric results reveal that SWCNTs enhance the polar character of P3OT host, shift the peak maximum of loss tangent toward higher frequency values and increase the alternating current conductivity especially above the percolation threshold point. Besides, the rheological properties of SWCNT-P3OT composites were also investigated to realize the effect of SWCNT content on the complex viscosity, storage and loss moduli at different frequency values. The obtained results reveal that nanocomposites become electrically percolated at 0.44 wt% SWCNTs, while the rheological percolation threshold was found at 0.5 wt%. Additionally, this study showed that the relaxation behavior in SWCNT-P3OT composites is mainly due to the viscoelastic relaxation process. Moreover, at high level of SWCNT loadings, the nanotubes became more interconnected to form network like structures in the P3OT host. Finally, results obtained from structure-property analysis reveal that the addition of SWCNTs to P3OT host reduced the vibrational freedom of the polymer chains as a consequence of the intercalation of the polymer matrix into the nanotubes.

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In this study, series of nanolayered structures of Zn-Al LDHs were prepared by urea hydrolysis. Nanofibers and nanonets of the Al-doped ZnO were formed via the decomposition of the nanolayers under high pressure and temperature. Nanospheres were also prepared for comparison. The different morphologies of the prepared nanomaterials were confirmed by several techniques. An improvement for the optical properties of the doped zinc oxides was observed through narrowing of their band gap energies because of transforming the nanolayers to nanonets and nanofibers. The photocatalytic activities of the prepared nanomaterials were studied through photocatalytic degradation of the pollutants of acid green dyes. Complete decolorization and mineralization of green dyes happened in the presence of the nanolayers and nanospheres within 4-6 h, while the nanonets and the nanofibers achieved the complete decolorization and degradation of the dyes at shorter time 1.3 h. These results could be explained though the kinetic study of the photocatalytic degradation of dyes. It was concluded that the nanonets and the nanofibers were very effective for the photocatalytic degradation of pollutants.Keywords Al-doped ZnO nanolayers Á Nanofibers Á Nanonets Á Band gap energy Á Photocatalytic degradation Á Acid green dyes pollutants

Polymer nanocomposites consisting of single-walled carbon nanotubes (SWCNTs) and poly(vinyl chloride) were prepared by casting technique. The complex viscosity increased with increasing SWCNTs content, and it had a percolation concentration threshold equal to 0.45 wt % of SWCNTs. The storage modulus, G 0 , increased with increasing either SWCNTs content or frequency. A gradual decrease in the terminal zone slope of G 0 for the nanocomposites with increasing SWCNTs content may be explained by the fact that the nanotube-nanotube interactions will be dominant at higher CNTs content, and lead to the formation of the interconnected or network-like structures of SWCNTs in the polymer nanocomposites. The rheological loss factor indicates two relaxation peaks at frequencies of 0.11 and 12.8 Hz due to the interaction between SWCNTs and polymer chains and glass transition, respectively. Dynamic mechanical properties were measured for the prepared composites. The results indicate that the storage modulus changes steadily, and the tand peaks are less intense for high SWCNTs content. Tensile tests were measured and depicted by an increase in the elastic modulus with increasing SWCNTs content, but it decreases for all composites as the testing temperature increased.