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This study deals with the preparation and characterization of novel composites accomplished by filling hydroxyethylcellulose with several amounts of bentonite. Molecular modeling enabled understanding the conformational and physicochemical features, which are responsible for the chemical reactivity parameters. Rheological analyses are made to investigate the effect of the polymer loading on the shear flow behavior. The morphology and homogeneity of each system is explored via optical microscopy. The band gap of the samples is slightly reduced by the addition of the bio-filler in the cellulosic medium, as indicated by UV-VIS spectral data. The dielectric response of these materials is extracted from refractometry experiments at several wavelengths. The electric energy density was achieved based on the dielectric properties determined at high and low frequencies. The outcome of this study offers new ways to produce alternative dielectric eco-materials having a good potential of accumulating electrical energy, as demanded for capacitor devices.

By using broadband dielectric spectroscopy over a wide frequency and temperature range, the effect of the chain extender and cross‐linkers on molecular dynamics of polyurethanes based on piperazine as a heterocyclic compound was assessed. Three relaxations attributed to local motions of polar side groups and small segments of the polyurethane chain (β, γ‐mode) and glass transition (α‐mode) were detected with the increase in temperature from −120 to 100 °C, along with the conductivity process at high temperatures and low frequencies. Experimental data were examined using the impedance and electric modulus for the conductivity study. Due to the presence of dipole polarization of functional groups in the hard segments, cross‐linked polyurethanes are characterized by higher dielectric constant value (≈11 at 1 kHz and 25 °C) compared to the linear ones (≈6–7 at 1 kHz and 25 °C). High conductivity was achieved for the Tween 20‐cross‐linked polyurethanes. The activation energy for the secondary γ relaxation was in the range of 34–37 kJ mol−1 for all polyurethanes, regardless of the chain extender or cross‐linker used. Piperazine‐based polyurethanes had lower activation energies for α relaxation and high conductivity compared to cyclohexane‐based polyurethanes. This indicates that α relaxation is more vulnerable to structural alterations. [ABSTRACT FROM AUTHOR]

Highly thermostable low-k polymer films with potential applications as dielectric materials in microelectronic industry were synthesized starting from 9,9-bis [4-(3,4-dicarboxyphenoxy)phenyl]fluorene dianhydride and various diamines. A polyetherimide/silica nanocomposite film was obtained using methyltriethoxysilane as precursor of inorganic phase. The chemical structure was confirmed by FTIR and [sup.1] NMR spectroscopy. Water vapor's sorption capacity, thermal stability, glass transition temperature, thermal diffusivity, specific heat, thermal conductivity, and dielectric characteristics of the films were determined. All the films exhibited excellent thermal stability, with an initial decomposition temperature in the range of 500-530[degrees]C. They showed low dielectric constant of 1.98-2.86 and low dielectric loss of 0.0037-0.011, at a frequency of 1 Hz and room temperature. The subglass [gamma]- and [beta]-relaxations, primary [alpha]-relaxation, and conductivity relaxation processes were discussed according to the chemical structure of the samples. Quantitative structure-property relationship (QSPR) study was conducted, and linear regression models were formulated to describe the causal relationships between different parameters and polyetherimide properties. KEYWORDS dielectric properties, fluorene groups, polyetherimides, QSPR study, thermal characteristics, 1 | INTRODUCTION Low dielectric constant (low-k) aromatic polyimides represent an important class of thermostable heterocyclic polymers that can be used in electronic industry as dielectrics between layers in thin [...]

In the present study, lead-free KTa0.65Nb0.35O3 ceramics were prepared by solid state reaction method using successive calcination steps in order to ensure the complete reaction of the system. The X-ray diffraction analyses of the prepared ceramics have shown the formation of a perovskite structure without any secondary phases. The increase of sintering temperature from 1150 to 1200°C leads to a better densification and decreasing of the Curie temperature (associated with tetragonal-cubic phase transition) closer to the room temperature, i.e. to 290K. The ceramics sintered at 1200°C exhibits a high tunability (n = 1.6) and a reduced hysteretic behaviour. Due to its moderate permittivity, low losses and field dependence permittivity, the KTa0.65Nb0.35O3 ceramics is suitable candidate for application as tunable capacitors.

Polymers play a crucial role in multiple industries; however, surface modification is necessary for certain applications. Exposure to non-thermal plasma provides a viable and environmentally beneficial option. Fused deposition molding utilizes biodegradable polylactic acid, although it encounters constraints in biomedical applications as a result of inadequate mechanical characteristics. This study investigates the effects of atmospheric pressure plasma generated by a dielectric barrier discharge system using helium and/or argon on the modification of polylactic acid surfaces, changes in their wettability properties, and alterations in their chemical composition. The plasma source was ignited in either He or Ar and was tailored to fit the best operational conditions for polymer exposure. The results demonstrated the enhanced wettability of the polymer surface following plasma treatment (up to 40% in He and 20% in Ar), with a marginal variation observed among treatments utilizing different gases. The plasma treatments also caused changes in the surface topography, morphology, roughness, and hydrophilicity. Plasma exposure also resulted in observable modifications in the dielectric characteristics, phase transition, and structure. The experimental findings endorse the utilization of plasma technologies at normal air pressure for environmentally friendly processing of polymer materials, specifically for applications that necessitate enhanced adhesion and have carefully selected prerequisites. [ABSTRACT FROM AUTHOR]