We report the results of studies on two series of polyaniline (PANI), doped with dichloroacetic (DCA) and trichloroacetic (TCA) acids, respectively, at various doping rates and obtained by the in situ polymerization method. Samples were characterized by x-ray diffraction, scanning electron microscopy and conductivity measurements. The direct current (dc) and alternating current (ac) electrical conductivities of PANI salts have been investigated in the temperature range 100–310 K and frequency range 7–106 Hz. The results of this study indicate better chain ordering and higher conductivity for PANI doped with TCA. The dc conductivity of all samples is suitably fitted to Mott’s three-dimensional variable-range hopping (VRH) model. Different Mott parameters such as characteristic temperature T0, density of states at the Fermi level (N(EF)), average hopping energy (W) and the average hopping distance (R) have been evaluated. The dependence of such values on the dopant acid used is discussed. At high frequencies, the ac conductivity follows the power law σac(ω,T) = A(T)ωs(T,ω), which is characteristic for charge transport in disordered materials by hopping or tunnelling processes. The observed increase in the frequency exponent s with temperature suggests that the small-polaron tunnelling model best describes the dominant ac conduction mechanism. A direct correlation between conductivity, structure and morphology was obtained in our systems.

We report the results of dielectric measurements over the frequency range10 Hz–1 MHz and the temperature range 150–300 K on polyaniline subjected to doping with dichloroacetic acid (DCA) and trichloroacetic acid (TCA) with various doping levels (6.1%, 8.2%, 13.3% and 4.1%, 6.15%, 13.5%, respectively). Conductivity is increased when the doping level or temperature is increased and samples doped with TCA are more conductive than those doped with DCA. A high frequency relaxation peak is observed in the loss factor curves attributed to the motion of charge carriers in the bulk polymer. A second loss peak appears in the low frequency range when we use the dielectric modulus representation and is attributed to electrode polarization. Both relaxations are well fitted by the Havriliak–Negami function, and the fitting parameters are determined. The characteristic relaxation frequency is described by the Arrhenius law. The activation energy for both relaxations is decreased by increasing the doping level and it is lower in the case of TCA doping acid.

Two spices trivalent transition metal ions, nonmagnetic Al 3+ , Bi 3+ and magnetic Cr 3+ , Mn 3+ substituted barium hexaferrite powders are synthesised via dynamic hydrothermal method then calcinated at different temperatures. Powder XRD patterns analysis and Rietveld refinement indicate magnetoplumbite-type crystalline phase. The crystallite size calculated using Scherer's formula varies from 153 to 248 nm as it is affected by the ionic radius of trivalent metal ions and calcination temperatures. The morphological features show agglomerations of spherical-shaped particles with an average size of 400 ± 50 nm for BaBiFe 11 O 19 and hexagonal-shaped particles 1-2µm for the other substitutions. Magnetic studies show a ferromagnetic behaviour for all samples. The nonmagnetic Al 3+ , Bi 3+ substituted materials have lower saturation magnetization Ms and remanence Mr than the magnetic substitutions Cr 3+ , Mn 3+. These results reveal that Ms and Mr are related to the magnetic moment of each metallic ion and its distribution in the lattice. For magnetic substitution, Ms of manganese substitution (61.10 emu/g) is found higher than that of chromium (60.33 emu/g) since Mn 3+ has a magnetic moment of 5µ B greater than Cr 3+ with 3µ B. Coercivity Hc and maximum energy product (BH) max determined from M-H loops exhibit an increasing trend with calcination temperature as they are related to the crystallite size. Hc and (BH) max of BaMnFe 11 O 19 are found maximum 0.426 T and 7.47 kJ.m-3 , respectively.

DGEBA‐DDM (diglycicyl ether of bisphenol‐A‐diamino diphenyl methane) networks of various epoxide/amine molar ratios ranging from 0.7 to 1.4, were studied by density, quasi static (10−4 s−1), and ultrasonic (5 106 s−1) modulus, and thermostimulated creep measurements. Any step aside stoichiometry leads to an antiplasticization, e.g. an increase of the quasi static modulus, whereas Tg decreases. The previous interpretations (based on volumetric property considerations), of this phenomenon are questionable. The only common feature of all the antiplasticized systems is an unexplained decrease of the population of macro‐molecular segments involved in beta motions.