Fawzy Hamed Abd El-Kader

Cast thin films of Poly (methyl methacrylate)/Poly (vinyl acetate) blends of different concentrations undoped and doped with malachite green have been prepared and subjected to both dc electrical conduction and dielectric spectroscopy measurements. The analysis of dc electrical conduction data showed that the space charge limited current mechanism has been dominant for Poly (vinyl acetate) while Schottky–Richardson conduction mechanism prevailed for the Poly (methyl methacrylate) and blended samples. The values of field lowering constant β and the thermal activation energy ΔE involved in the dc conduction were reported, which provide another support for the suggested Schottky–Richardson mechanism. The increase in current for the blend sample doped with malachite green has been attributed to the formation of charge transfer complexes inside the polyblend matrix. The dielectric constant as a function of temperature for all samples have been calculated which are affected by the composition ratio and the addition of dye. The relaxation peak that appeared in the dielectric loss curve at 347 K for the doped blend sample is related to local dipoles that are present in the dye material. The obtained relaxation process spectra present in the investigated samples were analyzed with the well-known model of Havriliak–Negami.

Blend films based on PEO/PVA (50/50 wt%) undoped and doped with different concentration of TiO2 nanoparticles are prepared by casting technique. Characteristic properties of the blend films are investigated using Fourier transform infrared, X-ray diffraction (XRD), ultraviolet–visible spectra (UV-Vis), scanning electron microscope (SEM), differential scanning calorimetry (DSC) and thermogravimetric analysis. On the basis of results obtained from IR and DSC data, blends appear to be immiscible. XRD, UV-Vis and TG reveal that 1.0 wt% TiO2 is most ordered concentration. SEM reveals that the presence of TiO2 leads to changes in the surface morphology and gives rise to crystalline domains with coarse spherulitic structure. It has been seen that spherulites increases with addition of TiO2 nanoparticles. TG studies conclude that this concentration has low E*, ΔS* and ΔH*. So, it is more ordering and has low thermal motion. Kinetic thermodynamic parameters such as activation energy, enthalpy, entropy and Gibb’s free energy are evaluated from TG data using Coat’s–Redfern model.

X-ray diffraction, infrared (IR), and electrical properties for pure and Er (NO3)3-doped methyl-2-hydroxyethyl cellulose (MHEC) with concentrations of 0.5, 1, 2, 5, 7, and 10 wt % were studied. X-ray analysis indicates that the addition of Er (NO3)3, which is a crystalline material, to MHEC at concentrations 10 and 13 wt % leads to the formation of crystalline phases in the amorphous polymeric matrix. The appearance of the bending mode ν2 and the combination mode (ν1 + ν4) of Er (NO3)3 in the IR spectra of composite samples indicates the coordination of nitro group in the chains of MHEC. From the I–V characteristics, it was found that the charge transport mechanism in MHEC appears to be essentially space charge limited conduction, while the predominant mechanism in the composite samples is Poole–Frenkel. Values of both drift mobility (μ) and the charge carrier density (n) has been reported. The temperature dependence conductivity data has been analyzed in terms of the Arrhenius and Mott's variable range hopping models. Different Mott's parameters such as the density of states, N(EF), hopping distance (R), and average hopping energy (W) have been evaluated.